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 TRANSVERSE VERTICAL SECTION OF THE GAS WO 
 
 Lo 
 
 
 
 C-7hatory, deL h 
 
 to the Otteen' 
 
A 
 
 PRACTICAL TREATISE 
 
 ON 
 
 GAS - LIGHTING; 
 
 IN WHICH THE 
 
 GAS-APPARATUS GENERALLY IN USE IS EXPLAINED 
 AND ILLUSTRATED 
 
 BY 
 
 TWENTY-TWO APPROPRIATE PLATES. 
 
 THE THIRD EDITION , 
 
 CAREFULLY CORRECTED AND ADAPTED TO THE PRESENT IMPROVED 
 STATE OF THE MANUFACTURE OF GAS. 
 
 BY 
 
 THOMAS S. PECKSTON, R.N., 
 
 CIVIL ENGINEER, 
 
 LATE A VICE-PRESIDENT OF THE LONDON MECHANICS’ INSTITUTION, AND 
 PRESIDENT OF THE MECHANICS’ INSTITUTION, DUBLIN, 
 
 &C. &C. &C. 
 
 LONDON : 
 
 HEBERT, CHE APSIDE. 
 
 1841 . 
 
LONDON : 
 
 Printed by William Clowes and Sons, 
 Stamford Street. 
 
(otfE.'T 
 
 TO THE HONOURABLE 
 
 SIR COURTENAY BOYLE, K.C.IL, 
 
 VICE-ADMIRAL OF THE WHITE, &c. &c. &c. 
 
 Dear Sir, 
 
 To you I dedicate this, I trust, very much 
 improved Edition of “A Practical Treatise on 
 Gas-Lighting ,” in the same spirit in which I had 
 the pleasure of dedicating to you the two former 
 Editions, as a testimonial of my most grateful ac- 
 knowledgments for the kindness and attention 
 which you have on all occasions evinced towards 
 me. 
 
 I am 
 
 Dear Sir, 
 
 With the greatest respect. 
 
 Your most obliged 
 
 and devoted Servant, 
 THOMAS SNOWDON PECKSTON. 
 
 10, Arundel Street , Strand , London , 
 22nd March, 1841. 
 
 a 2 
 
V 
 
 PREFACE. 
 
 Since the former editions of this work were laid 
 before the public, the author has (almost without 
 intermission) been practically engaged in giving plans 
 for gas-works, and superintending their erection in 
 England, Ireland, the Channel Islands, &c. During 
 the progress of his labours, many things suggested 
 themselves to him, having a tendency to simplify and 
 amend the apparatus used for the manufacture of 
 coal-gas, which he considered might be useful to the 
 practical engineer. He therefore determined to in- 
 troduce the results of his own experience into any 
 future impression of this work that might be called 
 for, and therein not to overlook such improvements 
 as have fallen beneath his notice. 
 
 The time has now arrived for his again appearing 
 before the public, and as he has spared no pains to 
 make the following treatise as complete as he pos- 
 sibly could, he trusts it will be favourably received 
 by all classes of readers. 
 
 In treating of the Theory of Artificial Light, he 
 has, to a very considerable extent, remodelled his 
 
VI 
 
 PREFACE. 
 
 former plan, and added much new matter, the result 
 of his own practice, as well as of that of others. 
 In treating of the apparatus used in the gas manu- 
 factory, he has dwelt very fully upon the leading 
 improvements which have been made in the retorts 
 and modes of setting them, in the condensing (or 
 refrigerating) vessels, in the purifier and the gas- 
 holder. On the laying down of main-pipes in the 
 streets, for matter which appears to him now re- 
 dundant, he has added much of a practical nature 
 which he expects will be found useful. He has also 
 noticed the latest improvements in the fitting up of 
 houses and shops, &c., and in the construction of 
 gas-burners. On the governor, regulator, and gas- 
 moderator, he has so fully written as to make the 
 construction and operation of each fully intelligible. 
 He has also dwelt at somewhat more length upon 
 the subject of tests, in order that due precaution 
 may be taken at the manufactory to prevent the 
 possibility of impure gas being supplied to the 
 public. He has almost entirely re-written the 
 chapter on the Chemical Constitution of Coal-gas, 
 and he trusts, thereby, rendered it more valuable. 
 As oil-gas and gas from turf are not likely to be 
 used for illuminating purposes, and as the manu- 
 facture of carbonate and muriate of ammonia be- 
 longs more properly to the manufacturing chemist 
 than to the gas-light manufacturer, he has but 
 briefly mentioned them. He trusts, however, the 
 
PREFACE. 
 
 Vll 
 
 pages taken up in treating upon those subjects in 
 the former editions are employed to better pur- 
 poses in this, by his furnishing therein a description 
 of the gas-regenerators, and an account of other 
 apparatus, devised for most effectually converting 
 into carburetted-hydrogen gas the tar and ammo- 
 niacal liquor produced from the coal in the re- 
 tort as they, in a state of vapour, are on their 
 passage to the hydraulic main, and by his giving a 
 method for correctly ascertaining the specific gra- 
 vity of coal or other gases, and also by his explain- 
 ing in great detail the arrangement of a coal gas- 
 light establishment, as recently erected by him, from 
 a ground-plan, section, and elevations (drawn to a 
 a scale). 
 
 1 0 , Arundel Street , Strand , London , 
 
 22nd March, 1841. 
 
A 
 
 PRACTICAL TREATISE ON GAS- 
 LIGHTING. 
 
 CHAPTER I. 
 
 Theory of the Production of Artificial Light, and of the Action of 
 Candles and Lamps ; with Directions for ascertaining the compa- 
 rative illuminating Power of Candles, Lamps, and Gas Lights ; 
 and for computing the relative Cost of Light afforded by each. 
 
 It is not improbable but tbis chapter may appear to 
 some readers as redundant, and they may turn away 
 from it with a remark that every one is aware of the 
 theories it treats of ; and, therefore, why load a work 
 professedly explanatory of gas apparatus with such 
 matter ? Should such remark be made, the reply is 
 simple. The work is intended for all classes of 
 readers who are in any way interested in gas con- 
 cerns, and few, it is supposed, would be bold enough 
 to affirm that, taking such readers in the gross, all 
 are acquainted with either the theory of artificial 
 light or with that of combustion. 
 
 The author of this work is well aware that there 
 are very few books upon any one art or science 
 which can be said to be complete in themselves ; 
 authors taking it for granted that readers take them 
 
 B 
 
2 
 
 THEORY OF THE PRODUCTION 
 
 up with a knowledge of many things of which 
 indeed they literally know nothing. The same 
 thing occurs too frequently at the lecture table, 
 whereas, if the lecturer or the author adopted a 
 different course, both hearers and readers would 
 probably receive more benefit. With such ideas im- 
 pressed upon the mind, it is intended, in this 
 instance, to begin at the beginning and to proceed 
 step by step to the end, so that when the work is 
 completed it may not, at all events, belie its title-page ; 
 and, as it is divided into chapters, those who have no 
 relish for theory can turn to practice, wdiere it is ex- 
 pected they will find matter worthy their perusal. 
 
 In treating of the theory of artificial light, if we 
 give the matter due consideration, we cannot fail to 
 perceive that, when usefully employed, it is procured 
 by the agency of fire ; and if we follow up our in- 
 quiries, we shall find that in all ages of the world, 
 even from the time of our first parents, fire has been 
 known ; we shall also find in newly discovered 
 countries that the aboriginal inhabitants were in- 
 variably acquainted with that agent. It was di- 
 rected by the Jewish law that the fire upon the altar 
 should burn continually. In some countries it was 
 considered as the image of life, and hence lighted 
 torches were emblematically placed in the hands of 
 the newly married ; extinguished torches placed upon 
 the tombs of the dead. The fable of Prometheus 
 having stolen fire from heaven furnished (some have 
 
OF ARTIFICIAL LIGHT. 
 
 3 
 
 thought) an idea to the early philosophers of its 
 being the soul of the world and the visible symbol 
 of an invisible deity ; as such it has been and is still 
 worshipped by heathen nations. 
 
 As to the origin of fire, it is of little consequence 
 to us whether, for ordinary purposes, we procure it 
 by rubbing two dry sticks briskly one against the 
 other, or by the use of flint and steel ; but, we can- 
 not reflect upon the powerful effects of this agent, 
 obtained by other means, without emotions of 
 astonishment and almost reverential awe, being, as it 
 were, simultaneously produced. By a combination 
 of mirrors we can so concentrate the sun’s rays as 
 thereby to fuse, almost instantaneously, the most ob- 
 durate metal : the mode of arranging such mirrors 
 appears to have been well known in the time of 
 Archimedes ; for, from the walls of Syracuse, it is 
 said, by such means he destroyed the fleet of Mar- 
 cellus, when acting against that city ; and, notwith- 
 standing this piece of history has frequently been 
 considered as bordering upon the marvellous, the 
 experiments of Father Kircher, and his pupil 
 Schottus, made at Syracuse ( vide Philos. Trans., 
 vol. xlviii., page 621), have proved that by a com- 
 bination of mirrors he might easily have done so. 
 
 Fire £an be produced by electricity and by gal- 
 vanism, and it is from the effects of the latter agent 
 that such amazing discoveries have been made in 
 several branches of chemical science. It is also 
 
 b 2 
 
4 
 
 THEORY OF THE PRODUCTION 
 
 attainable by compression, by percussion, and by 
 several chemical preparations. 
 
 Spontaneous combustion frequently occurs by the 
 decomposition of water, as, for instance, when hay or 
 other vegetable matters are put up in ricks before 
 being properly dried : such also occurs when sub- 
 stances impregnated with oil are laid up in large 
 heaps in a damp state. Peat laid up in very large 
 heaps is subject to the same ; as is also pyritous coal, 
 when piled in the open air, or where water has ac- 
 cess to it, the effect of which is sufficient to set fire 
 to the whole mass. 
 
 Having now briefly adverted to the mode of pro- 
 curing fire, and the natural causes by which it is 
 sometimes spontaneously produced, we come next to 
 consider the nature of flame ; and, in doing so, we 
 must set out by observing that such flame as issues 
 from any body submitted to the action of fire, con- 
 sists of matter which, if collected, would universally 
 possess hydrogen gas as one of its component parts. 
 More, if the flame yielded but little light, and less 
 as it increased in brilliancy. Such gas is more or 
 less pure as the matter used for its production is 
 more or less free from impurities : its purity, there- 
 fore, and consequent brilliancy, when exhibited as 
 flame, vary with the circumstances under which it 
 was generated. When the circumstances under 
 which the combustion of inflammable matter is car- 
 ried on are favourable, the flame is perfect and bril- 
 
OF ARTIFICIAL LIGHT. 
 
 5 
 
 liant ; on the contrary, should the combustion be 
 incomplete, part of the matter capable of furnishing 
 light and heat will pass off in smoke ; hence, 
 wherever much soot is found, we may conclude the 
 body producing it had not been used to the greatest 
 advantage. 
 
 It seldom happens when coals are used that com- 
 bustion is carried on advantageously ; for to produce 
 a complete combustion, a very small quantity of coals 
 should be supplied to the fire at one time, an ar- 
 rangement too tedious to be generally adopted. 
 Coals are heaped upon the fire in such a way, that 
 it requires much time to elapse before they are burnt 
 through, and whilst this is going on a dense smoke 
 is continually thrown out which answers no pro- 
 fitable purpose. 
 
 The artificial light afforded by an inflammable 
 body, whether it be a candle, lamp, or any other sub- 
 stance, arises from the flame such body may exhibit 
 when in the act of combustion ; and as, from what 
 has been premised, it may be concluded that com- 
 plete combustion is necessary to the economical pro- 
 duction of light, therefore the question will be, how 
 are we to produce the greatest quantity of light at 
 the least expense ? 
 
 Perhaps the best rule to be adopted for the pur- 
 pose would be to allow no more of the inflammable 
 matter to mix with the surrounding atmospheric air 
 than could be consumed. If it be allowed to exhibit 
 
6 
 
 THEORY OF THE PRODUCTION 
 
 itself in bulky diameters, much of its effect will be 
 lost ; for, under such circumstances, the interior of 
 the flame cannot be completely burnt, for want of its 
 being supplied with that due proportion of oxygen 
 which is necessary to produce complete combustion. 
 If the matter submitted to combustion be thrown 
 out at a very low temperature, it will not burn in 
 the open air ; it is, therefore, of consequence that the 
 matter for producing flame should have attained a 
 proper heat, and be thrown into the atmosphere with 
 that velocity which will allow it to be wholly de- 
 composed by its burning, so that no smoke may arise 
 from it. If the stream of air acting upon the com- 
 bustible matter be too great, it will defeat the effect 
 desired ; whilst the contrary will so tend to weaken 
 the flame as to render it nearly useless. 
 
 The necessity of a proper supply of air for sup- 
 porting combustion to advantage suggested the idea 
 of the argand lamp, the ingenious inventor of which 
 proceeded upon two principles ; the first of which 
 was to increase to the greatest extent the surface of 
 the wick, the second to increase the quantity of air 
 applied to it, and in this way to produce the com- 
 bustion of all the material absorbed. It is well 
 known that the wick in the argand lamp is thin and 
 circular, and that there are in its wick as many 
 cotton capillary tubes for absorbing the oil as in a 
 common thick wick. By this arrangement the whole 
 of the matter applied, that can be burnt, is consumed 
 
OF ARTIFICIAL LIGHT. 
 
 7 
 
 in consequence of the wick being spread through a 
 large surface, and a current of air, produced by the 
 glass chimney, being applied both to the inside and 
 outside of this wick. If the apertures beneath the 
 lamp be stopped, it immediately smokes, in conse- 
 quence of the heat increasing to such a degree as to 
 distil off the oil more rapidly than the air can effect 
 its combustion ; as soon, however, as the current of 
 air is restored, the combustion becomes again com- 
 plete and the production of smoke terminates. 
 
 Every one who reads or writes much by candle- 
 light must have observed that a small flame is 
 always brighter and more luminous than a large 
 one ; and that when a candle has been newly snuffed 
 it yields from six to eight times the quantity of light 
 which is afforded by it when the wick becomes so 
 lengthened as to make the application of the snuffers 
 again necessary. It is from this variability of the 
 light, as afforded by candles and ordinary lamps, 
 that persons accustomed to read or work long by 
 such lights have their eyes injured; and this injury 
 is not so much from the light itself as from its fluc- 
 tuation, which compels the optic nerves to be con- 
 tinually adjusting their action, in order that the eye 
 may be adapted to the light under all its changes. 
 
 To remedy the inconvenience arising from the 
 variability of light as just referred to, Mr. Ezekiel 
 Walker proposed that tallow candles should be 
 placed in such a direction as to recline thirty degrees 
 
8 
 
 THEORY OF THE PRODUCTION 
 
 from the perpendicular : for doing this, candlesticks 
 may he easily constructed, or they may be made to 
 hold the candle at any angle which may be desired. 
 When a candle is placed at thirty degrees from the 
 perpendicular, there will be no necessity for snuffing 
 it ; for when it burns thus the flame rises vertically 
 from the upper side of the wick, exposing the top of 
 it, which projects beyond the flame, to the action of 
 the air. By this mode of causing the candle to snuff 
 itself that part of the wick which is acted upon by 
 the flame must necessarily remain of nearly the 
 same length ; and, if the wick is uniformly twisted 
 throughout, the flame will remain of the same 
 strength and dimensions. This can never be ef- 
 fected when candles are snuffed by an instrument ; 
 but when a candle is so placed as to snuff itself, the 
 light is steady, and at the same time so invariable in 
 its intensity, that the eye feels no pain or uneasiness 
 in performing its office. 
 
 What Mr. Walker proposed to effect is spoken 
 of as of a thing probably not universally known ; 
 but the elegant contrivances of Mr. Palmer for 
 burning tallow candles with what he terms metallic 
 wicks answer precisely the same purpose — that is to 
 say, his candles, so to speak, snuff themselves, from 
 the wicks as they untwist themselves spreading out 
 in such a manner that the apex of each projects 
 beyond the body of the flame, is acted upon by the 
 oxygen of the atmosphere and gradually consumed. 
 
OF ARTIFICIAL LIGHT. 
 
 9 
 
 His candlesticks are generally elegant in appearance, 
 the light afforded from his candles, quantum of light 
 for quantum of light, cheaper than from ordinary 
 tallow candles, and the comfort of reading, writing* 
 or working by them greater beyond all compa- 
 rison. 
 
 The improvements in table lamps have within the 
 last few years been great beyond all comprehension. 
 Amongst the best of these are the “ shadowless over - 
 flowing lamp” and the “ solar -lamp” The former, 
 from its producing a constant supply of oil to the wick, 
 will burn with a uniform flame for seven or eight 
 hours without adjustment, so that the light from it 
 is nearly as intense as that produced from gas, quite 
 as regular as to the quantity of light supplied, and 
 not half the expense of common tallow candles light 
 for light. As these are constructed so as to burn 
 common oil, the expense of one which yields as much 
 light as five mould candles of six to the pound, is 
 not so much as it would be for using two such 
 candles in the ordinary way ; thus producing a great 
 saving of expense whilst it affords much additional 
 comfort. 
 
 The observations just made relative to the im- 
 provements of candles and lamps it is to be hoped 
 will not be considered as entirely out of place, as 
 they have for their objects economy and comfort. 
 Our next business will be to observe that it cannot 
 be doubted but bodies which are capable of producing 
 
10 
 
 THEORY OF THE PRODUCTION 
 
 flame contain such latent matter as supports com- 
 bustion. Indeed, it is well known that light forms 
 a constituent part of some bodies, for from them it 
 is disengaged as they form neW combinations. That 
 the light evolved by artificial means is derived from 
 the matter submitted to combustion is clear to de- 
 monstration ; for we need but observe the change of 
 colour which flame exhibits during the process of 
 burning to be certified of the fact. Such variation 
 does not depend upon the medium which supports 
 combustion, but is to be solely attributed to the 
 matter of the combustible body. By considering 
 this matter we can easily comprehend the possibility 
 of tinging the colour of the purest kind of flame, 
 by mixing the body producing it with substances for 
 that purpose : thus — 
 
 Spirits of wine burn with a bluish flame, and 
 sulphur with nearly the same tinge. 
 
 Zinc burns with a bright greenish white flame. 
 
 Preparations of copper, or of the substances with 
 which they are mixed, burn with a bright vivid 
 green flame. 
 
 Spirits of wine mixed with common salt, when 
 set on fire, burn with a very unpleasant effect. 
 
 Spirits of wine and a little boracic acid, or nitrate 
 of copper, stirred together and set fire to, burn with 
 a beautiful green flame. 
 
 Spirits of wine mixed with nitrate of strontia, 
 burn with a carmine red colour. 
 
OF ARTIFICIAL LIGHT. 
 
 11 
 
 Muriate of lime tinges the flame of burning spirits 
 of wine of an orange colour. 
 
 As for the colours of flame exhibited when coals, 
 wood, and other combustibles are used, their dif- 
 ferent shades amount but to a few of red, purple, 
 and yellow. These, doubtless, arise from the greater 
 or lesser quantity of watery vapour, or smoke, which 
 passes through the flame unburnt, with the other 
 incombustible products. 
 
 By observing the flame of a common candle care- 
 fully, we shall perceive that the colour of it is not 
 uniformly alike; the lower part next to the cup 
 formed in the tallow is always blue, the part con- 
 tiguous to the wick is opake ; the exterior to the 
 height of the wick bright and luminous, as it is also 
 to the top of the flame immediately after the candle 
 is snuffed ; but, when the flame becomes lengthened 
 and the top of the wick assumes a fungus-like ap- 
 pearance, the apex of the flame will then be of a 
 reddish or brownish colour. 
 
 In proceeding to illustrate the theory of the action 
 of candles, lamps, &c., we are to observe that when- 
 ever light is to be procured, for ordinary purposes, 
 the most ready means of obtaining it is by the process 
 of combustion. The most common method of ob- 
 taining artificial light, where the use of candles and 
 lamps is unknown, is, by burning masses of wood or 
 other matter in their solid state; but where im- 
 provements have gained footing, artificial light has 
 
12 
 
 THEORY OF THE PRODUCTION 
 
 for most purposes, till within the last thirty-five 
 years, been obtained by the means of lamps and 
 candles. About the period just alluded to, public 
 attention was called to Gas, procured from coal, as a 
 substitute for candles and lamps, as being a much 
 cheaper and far more effective mode of procuring 
 light ; and, although the progress made in that great 
 improvement was but slow in the beginning, the 
 almost universal adoption of Gas for street and shop 
 lighting since, points out to us that it has perhaps 
 spread its usefulness throughout the British Empire 
 as well as upon the continents of Europe and Ame- 
 rica, with equal if not greater rapidity than has 
 fallen to the lot of any modern improvement. 
 
 When lamps are used, it is necessary that the 
 combustible material should be such as will remain 
 in a fluid state at the usual temperature of the at- 
 mosphere. In the use of candles the case is different, 
 for the matter of which they are formed does not 
 become fluid but by a very considerable application 
 of heat. Of whatever substance, however, the in- 
 strument for yielding light is composed, it is required 
 to be rendered volatile before flame can be produced ; 
 and, for this purpose it is not necessary to volatilize 
 much of the matter at a time, as a very small por- 
 tion of it will be sufficient for affording a useful 
 light. A candle or lamp contains sufficient combus- 
 tible matter to last several hours ; and it is by the 
 operation of the wick that the operation of generat- 
 
OF ARTIFICIAL LIGHT. 
 
 13 
 
 ing light is effected. In using a lamp, the oil 
 should be such as will readily inflame, and the wick 
 of sufficient capacity to convey to the place of com- 
 bustion, by capillary attraction, such quantity of oil 
 as by admixture with the oxygen of the air, will be 
 completely consumed. By this attraction, the oil 
 continually flows to the laboratory, where the de- 
 composing process is carried on. 
 
 On a candle being first lighted, such a degree of 
 heat is given to the wick as is sufficient to melt the 
 tallow, which is formed into a kind of cup where it 
 is decomposed. It is in this part that the carburetted 
 hydrogen gas and vapour are mixed with the air, 
 and yield a bluish flame. This, however, commu- 
 nicates so much heat to the higher part of the gas 
 evolved as to give it a yellowish tinge. As the tallow 
 melts, and becomes decomposed by the action of the 
 wick, a fresh supply continues to be given. The 
 upper part of the wick, which is surrounded by the 
 flame, becomes black, owing to part of the carbon 
 and hydrogen produced by combustion entering into 
 its composition, the wick being defended from the 
 action of the air by the flame which surrounds it. 
 There cannot be a doubt but to this circumstance 
 the wick owes its protection ; for, when by the con- 
 sumption of the tallow the wick becomes too long 
 to support itself vertically, the top projects beyond 
 the flame (which will invariably be the case when 
 
14 
 
 THEORY OF THE PRODUCTION 
 
 the wick deviates from a perpendicular line), and 
 being thus exposed to the action of the air, burns 
 off and is soon converted to ashes. 
 
 As part of the tallow which is volatilized is not 
 burnt, owing to its passing through the centre of 
 the flame, and not being acted upon by the oxygen 
 of the surrounding air, it passes off in smoke ; hence 
 it follows, when the wick and flame are large, there 
 is proportion ably greater waste of combustible ma- 
 terial than when the wick and flame are small. In- 
 deed, when a candle is made with a wick of a single 
 thread, though it yields but a very small flame, yet 
 such flame is not only particularly bright but free 
 from smoke, whilst, on the contrary, in common 
 lamps, where a very large wick is used, the smoke is 
 considerable, and tends to lessen the strength of 
 light which, from the quantity of matter used, might 
 naturally be expected. 
 
 As in the process of combustion of candles the 
 fluid tallow is contained in the cup formed at their 
 top, it follows that the thickness of the wick is a 
 circumstance requiring attention ; for, if the wick 
 be not of sufficient capacity for carrying off the fused 
 material as rapidly as it enters into a state of fusion, 
 it will run down the sides of the candles ; or, as we 
 familiarly express it, “ the candle gutters.” This 
 inconvenience, arising from the nature of the mate- 
 rial of which the candle is formed, it appears, that 
 
OF ARTIFICIAL LIGHT. 
 
 15 
 
 as wax is not so fusible as tallow, the wick of the 
 latter description of candle may be made much 
 slighter than the wick of the former. 
 
 A candle with a thick wick, when first lighted 
 and snuffed short, yields a flame perfect and lumi- 
 nous, unless the diameter of the wick be very great ; 
 in such case the middle of the flame will be opake, 
 as for want of a proper supply of oxygen the com- 
 bustion cannot be completely effected. But when 
 the wick becomes lengthened, the distance between 
 its top and the top of the flame given out will be 
 shortened; and the tallow which is decomposed, 
 having a shorter distance of flame to pass through, 
 is not entirely burnt, and that part which is not so 
 passes off in smoke. The wick, if not snuffed, con- 
 tinues to lengthen till, unable to support the accu- 
 mulation of soot formed round the top of it, it falls 
 on one side, allowing the air to act upon it; or, 
 otherwise, the upper part of the flame given out is 
 so shortened as to expose the top of the wick to the 
 air; in the latter case, however, spontaneous snuff- 
 ing is not effected. The portion of the tallow carried 
 off by the lengthened wick is too great to be entirely 
 burnt, and it takes off a considerable portion of the 
 heat of the flame as it assumes a state of elasticity. 
 This process tends to diminish combustion, whilst a 
 greater supply of tallow, in a fluid state, produces 
 an accumulation of soot at the top of the wick ; 
 and, when much soot has been there deposited, the 
 
If) 
 
 THEORY OF THE PRODUCTION 
 
 candle does not give more than from a sixth to an 
 eighth of the light which the materials submitted 
 to combustion, if properly managed, would produce : 
 it is from this circumstance that ordinary tallow 
 candles so frequently require snuffing. 
 
 When wax candles are used, it is found that as 
 the wick lengthens the intensity of light decreases ; 
 but then, as the wick is very thin in comparison 
 with the wick of a tallow candle, it sooner falls from 
 the middle of the flame, and, the top becoming ex- 
 posed to the air, is burnt off. When the wick of a 
 wax candle is in the centre of the flame, it is not of 
 sufficient magnitude to cause the diameter of that 
 flame to he so enlarged as to prevent the air having 
 access to it. It follows, from what has been said, 
 that as wax is with difficulty fused, a large quantity 
 of it may he burnt by means of a very small wick. 
 It is from this circumstance the wick, of course, is 
 pliant, and soon becomes unable to support itself in 
 a vertical position ; on its losing that position, the 
 action of snuffing is spontaneously performed in the 
 manner already noticed, and with much greater pre- 
 cision than it could have been by any mechanical 
 operation. 
 
 If we take into consideration what has been said 
 relative to wax and tallow candles, it will appear 
 that the making of the latter so as to be equal to the 
 former cannot be effected, unless by some contrivance 
 we can render tallow as difficult of fusion as wax ; 
 
OF ARTIFICIAL LIGHT. 
 
 17 
 
 for the advantage which a wax candle has over one 
 of tallow arises from wax requiring a higher tem- 
 perature to fuse it, consequently the fusion is not so 
 rapid and the cup formed by the action of the flame 
 not so soon destroyed. Therefore, to render tallow 
 when used for generating light equal to wax, it 
 must either he burnt in a lamp, or to prevent the 
 melted material running to waste, the wick must be 
 made of a more pliant material than is at present 
 used, or the tallow itself must, by some chemical ar- 
 rangement, be rendered less fusible. 
 
 When we are desirous of ascertaining the illumi- 
 nating power of candles or other luminous substances, 
 we must have recourse to some method different 
 from that of simply viewing the lights themselves, 
 and by the eye forming a comparison between one 
 light and another ; the organs of human vision are 
 not adapted to ascertain with sufficient accuracy the 
 exact proportion which one light may hear to ano- 
 ther placed near it, by first looking at one light and 
 then at the other. But, though from such examin- 
 ation of different lights their intensities cannot be 
 ascertained accurately, yet the eye is peculiarly 
 adapted for judging of the strength of shadows ; so 
 much so, that by proper arrangements the propor- 
 tional quantities of light, emitted by two or more 
 candles, lamps, or gas-lights, may be determined 
 with almost mathematical correctness, and the com- 
 parative strength of light afforded by a gas-burner 
 
 c 
 
18 
 
 THEORY OF THE PRODUCTION 
 
 compared with what is given out by one or more 
 candles of certain dimensions. 
 
 Light always travels in straight lines, and in every 
 direction from the body yielding it, therefore its 
 strength must decrease in proportion to the distance 
 from the point of divergency. Therefore, by suppos- 
 ing two or more lights to be placed at such distances 
 from an interposing opaque object, as to cause sha- 
 dows of equal intensity to be cast upon something 
 white fixed to a wall behind it, if we measure the 
 distance of each light from its respective shadow, 
 we obtain data for ascertaining the proportionate 
 illuminating power of each ; for whatever light falls 
 upon any body would have fallen upon the place oc- 
 cupied by its shadow had there been no interposing 
 object; and this position may be established in the 
 following manner : — 
 
 Let the light (suppose of a candle) which flows 
 from a point A, plate I, fig. 1, and passes through a 
 square hole, B, be received upon a plane, C, parallel 
 to the plane of the hole ; or let the figure C be the 
 shadow of the plane B, and when the distance C is 
 double of B, the length and breadth of the shadow 
 C will be each double the length and breadth of the 
 plane B, and treble when A D is treble of A B and 
 so on, which may easily be examined by the light of 
 a candle placed at A. Therefore, the surface of the 
 shadow C, at the distance A C, double of A B is 
 divisible into four squares, each equal in area to the 
 
r 
 
 siafo i. 
 
 -FvcJ. 9. Jvg. 10- 
 
 27io s S. Tecfastoiv .■ 
 
 J^orulojv. Tul?bu57i£cL by JT Hetefb 20 ?yjFe2>? 1&41 
 
 C. BvTbarv, 1&/1' 
 
OF ARTIFICIAL LIGHT. 
 
 19 
 
 square B, at a treble distance into nine squares, each 
 equal to the square B, as represented in the figure. 
 The light, then, which falls upon the plane B, being 
 suffered to pass to double that distance, will be uni- 
 formly spread over four times the surface, and con- 
 sequently will be four times fainter in every part of 
 that space ; at a treble distance it will be nine times 
 fainter, and at a quadruple distance sixteen times 
 fainter than at B, and so on, according to the in- 
 crease of the square surfaces B, C, D, E, built upon 
 the distances A B, A C, A D, A E. Consequently, 
 the quantities of this rarefied light, received upon a 
 surface of any given size and shape whatever, re- 
 moved successively to these several distances, will be 
 but one-fourth, one-ninth, one-sixteenth of the whole 
 quantity received by it at the first distance, A B ; or, 
 in other words, the densities and quantities of light 
 received upon any plane are diminished in the same 
 proportion as the squares of the distances of that 
 plane from the luminous body are increased ; and, on 
 the contrary, are increased in the same proportion as 
 these squares are diminished. 
 
 From what has been said, it follows, that as the 
 shadow of any body, at twice the distance of the sur- 
 face from the point of illumination, will occupy a 
 space four times the area of the interposing object, 
 consequently the strength of light will decrease as 
 the square of the distance is increased. Therefore, 
 by placing two lights in such situations as to throw 
 
 c 2 
 
20 
 
 THEORY OF THE PRODUCTION 
 
 shadows of equal densities upon a white wall or 
 screen, from some opaque substance placed between 
 them and that wall or screen, the intensity of light 
 afforded by each will be inversely as the squares of 
 their distances from the shadows. When two lights 
 of unequal illuminating powers are so placed as to 
 produce shadows contiguous to each other, from an 
 opaque interposing body, the stronger light will yield 
 the deepest shadow, and the weaker light the faintest 
 shadow. In making experiments for ascertaining 
 the intensity of different illuminating bodies, it is 
 necessary that they should he so placed as to produce 
 shadows contiguous to and partly impinging upon 
 each other, and of equal intensity. 
 
 When it is required to compare the intensities of 
 light produced by candles of different sizes, the fol- 
 lowing mode may be adopted. Fix a sheet of paper 
 against the wall of your room at a convenient height, 
 and place a small fire screen at a few feet distant 
 from it, taking care to fix the part intended to throw 
 a shadow upon the paper, at a proper height for 
 doing so. Then let one of your assistants take the 
 candle which yields the smallest quantity of light, 
 and proceed to such a distance from the screen as 
 may he convenient, but so as to allow the shadow to 
 be produced to fall upon the paper. Next, let him 
 who holds the candle yielding the strongest light 
 proceed in nearly the same direction from the screen 
 as the former, till the shadow from his candle falls 
 
OF ARTIFICIAL LIGHT. 
 
 21 
 
 nearly upon the same part of the paper as that pro- 
 duced by the weakest light. Should the darkness 
 of shadow from the strongest light be greater than 
 that produced by the weaker, let your second assist- 
 ant increase his distance from the interposing ob- 
 ject till the shadow from each candle is equally 
 dark ; this being done, measure the distance of each 
 light from the paper receiving their respective sha- 
 dows ; then say, 
 
 As the square of the distance of the weakest light 
 from the shadow. 
 
 Is to the square of the distance of the strongest 
 light from the shadow. 
 
 So is unity, (or 1) 
 
 To a fourth number, and that number shows the 
 proportion of light yielded by the strongest light 
 as compared with that yielded by the weakest one. 
 
 The same result will be produced by dividing the 
 square of the distance of the strongest light from . 
 the shadow by the square of the distance of the 
 weakest light therefrom. 
 
 But, by way of example, let us suppose we have 
 proceeded agreeably to the plan already pointed out, 
 with two candles of different illuminating powers, 
 and have measured the distances of each from 
 the shadows, and found the weaker light to be at 
 six feet distance from the shadows, and the stronger 
 light at twelve feet ; and desire to know how many 
 candles of the least illuminating power, if placed 
 
22 THEORY OF THE PRODUCTION 
 
 close together and in the same situation, as to dis- 
 tance from the interposing object as the stronger 
 light, would produce a shadow equally strong, and 
 consequently the same quantity of light. 
 
 The square of 6 is equal to 36 
 12 „ 144 
 
 therefore, as 36 : 144 : : 1 : 4 or 144 4 . 36 == 4, the 
 number of candles of the smaller illuminating power 
 which would be required to be all lighted at one 
 time, and placed close to each other, to produce the 
 same intensity of light as the larger candle. 
 
 This method may be adopted whenever the illu- 
 minating bodies are such as can be moved ; cases, 
 however, occur sometimes which render a trifling 
 deviation therefrom needful. For instance, when 
 one of the bodies emitting light is stationary, as in 
 the case of a gas-burner. Then in making the ex- 
 periment it will require but one candle to be used, 
 which must be moved backwards and forwards be- 
 tween the interposing body and the burner, till the 
 shadows from each upon the paper against the wall 
 are equally dark. To judge accurately of the 
 strength of each shadow, the candle should be held 
 in such a position as will allow the shadows from it 
 and from the gas-burner to be shown upon the 
 paper contiguous to, or rather impinging upon each 
 other. (See plate I. fig. 2 .) Measure the distances 
 from the gas-burner, and from the candle to the 
 shadow, and then proceed as already directed ; the 
 
OF ARTIFICIAL LIGHT. 
 
 23 
 
 following example will more fully explain the mat- 
 ter : — Having adjusted the flame of a gas-burner to 
 two inches in height, and placed an opaque body 
 between it and a sheet of white paper attached to a 
 wall twelve feet distant from the burner, a mould 
 candle of six to the pound was introduced between 
 the burner and the body producing the shadow, and 
 moved backwards and forwards till the shadows pro- 
 duced by the gas-burner and the candle were equally 
 dark ; on their being so, the candle was found by 
 admeasurement to be four nine-tenths feet from the 
 shadow produced ; the number of such candles to 
 produce as much light as is given by the burner, are 
 required, 
 
 The square of 4*9“ 24*01 
 „ „ 12*0= 144 * 00 
 
 Then as 24 * 01 : 144 :: 1 : 6, or 144 ~ 24 * 01 = 6 
 nearly, the number of candles necessary to produce 
 the same intensity of light as is afforded by the gas- 
 burner. 
 
 From experiments made in this way, without the 
 aid of any description of photometer, although the 
 more scientific reader may prefer the use of such de- 
 scription of instrument as that invented by Professor 
 Leslie, it may be determined, whether more or less light 
 is obtained by burning several small candles, or one 
 or more of greater dimensions, during a given time, 
 at the same expense ; for, by such, the intensity of 
 light afforded by each is ascertained : and, the quan- 
 
24 
 
 THEORY OF THE PRODUCTION 
 
 tity of matter consumed for obtaining it is easily 
 ascertainable. The same thing bolds good with re- 
 spect to lamps and gas-burners, and nothing is more 
 easy than to compare the illuminating power of each, 
 and to ascertain the relative cost of any substance 
 which may be employed for furnishing light. 
 
 As by turning the stop-cock which supplies a gas- 
 burner, the light afforded by it can be adjusted to that 
 of a well-snuffed tallow candle ; if then the experi- 
 ment be carried on for some specific time, and the 
 candle be weighed before the experiment is com- 
 menced, and again immediately after it is ended, 
 (the price per pound of candles being known,) the 
 person making the experiment will ascertain the cost 
 of procuring light by such candle for the said time. 
 The quantity of gas consumed by the burner, as 
 pointed out by the index to the experimental gas- 
 holder, or gas-meter, will enable him to ascertain 
 the cost of procuring a similar light by the use of 
 gas. To enable him to do this he must, however, 
 inform himself at what cost a specific number of 
 cubic feet of gas can be generated. 
 
 Although what has been just stated holds per- 
 fectly good when the comparison is made between 
 a single jet gas-burner when adjusted so as to emit 
 the same quantity of light as a tallow candle of six 
 to the pound, and which in that case would consume 
 about seven-tenths of a cubic foot of gas per hour, it 
 by no means shows the saving effected by the use 
 
OF ARTIFICIAL LIGHT. 
 
 25 
 
 of gas when burners of a larger size are used. It is 
 very well known that supposing we use candles for 
 obtaining the light we require, should we not find 
 one sufficient, if we lighted two it must be at twice 
 the expense, if three at thrice the expense, and so 
 on. The case is similar with oil lamps, at all events 
 to a considerable extent ; but w T ith gas the case is 
 altogether different. No one would think, who 
 uses gas now, of putting five or six single jet lights 
 (unless for some specific purpose as to situation) for 
 obtaining five or six times the quantity of light ; he 
 would see that such mode would be very injudicious 
 and anything but economical. He would argue thus 
 from what in all probability he had heard from his 
 neighbours, or from his own observations, as to the 
 effects produced by gas-burners of different sizes. 
 The burners affording the greatest quantity of light 
 from the least quantity of gas are the argands of 
 -f-f- of an inch diameter with twelve holes, and of -f-f- 
 of an inch diameter having fifteen holes; in each 
 size the holes are of an inch in diameter. A 
 burner of this description, consuming five cubic feet 
 of gas per hour, gives as much light as twelve mould 
 candles of six to the pound. Now, as it was re- 
 marked before that a single jet light adjusted so as 
 to be equal to one such candle, consumed T 7 -o 
 of a cubic foot of gas per hour, it follows of conse- 
 quence that twelve such lights would consume 
 xt r X 12 = 8*4 cubic feet of gas, whereas one 
 
26 
 
 THEORY OF THE PRODUCTION 
 
 argand burner, consuming but five cubic feet per 
 hour, would afford as much light. A saving, there- 
 fore, arises to the consumer of 3*4 feet per hour by 
 using one argand instead of twelve single jet 
 burners. 
 
 It was long since determined, from experiments 
 made by Count Rumford for ascertaining the quan- 
 tity of materials necessary to produce a light of a 
 certain intensity, for a given time, that there must 
 be burnt by weight : 
 
 Of wax 100 pounds, of tallow* 101 pounds, of oil 
 in an argand lamp 129 pounds, and of an ill-snuffed 
 tallow candle 229 pounds; and from an immense 
 number of experiments made upon coal gas by 
 various persons, at different places, and under a 
 variety of circumstances, we may reckon that to pro- 
 cure as much light as is afforded by 100 pounds of 
 wax candles 5,500 cubic feet of coal gas (at an 
 average) would require to be consumed. If we take 
 the present price of wax, tallow, oil, and coal gas, (at 
 the price charged in London,) we shall find that the 
 comparative cost of the different modes of lighting 
 
 will stand thus : — £ 5 j 
 
 72 J lbs. of wax candles, at 2 s. 6d. 
 
 per lb. - -- -- -- 9 1 3 
 
 101 lbs. of best Kensington mould 
 
 candles, at 8 d. per lb. - - 3 7 4 
 
 * 724 lbs. of wax candles will burn as long as 100 lbs. of tallow 
 candles of the same size and number to the pound. 
 
OF ARTIFICIAL LIGHT. 
 
 27 
 
 £. s. d. 
 
 129 lbs. of oil (spermaceti), at Is. 
 
 per lb., or 9 s. per gallon - - 6 9 0 
 
 229 lbs. of ill-snuffed tallow candles 
 
 (dips), at per lb. ■ - 6 4 0| 
 
 5,500 cubic feet of coal gas, at 9s. per 
 
 thousand cubic feet - - - 2 9 6 
 
 In pursuing our inquiries relative to the com- 
 parative cost of obtaining light from materials of 
 different description, we shall find we are indebted 
 to Mr. Ezekiel Walker for some valuable matter 
 communicated to the public through the medium of 
 the 8vo. series of Nicholsons Journal, from which 
 the following is extracted : — “ A mould candle of 
 six to the pound, in two instances, consumed 15 
 drams in three hours ; in a third instance, 1 ounce 
 in three hours ; and in a fourth, 17-^- drams ; so that, 
 taking the average, one pound of such candles would 
 last about fifty hours, or equal to fifty such candles, 
 each burning an hour, cost, as above, 8 d” 
 
 An imperial gallon of sperm oil burnt in an 
 argand lamp which yields light equal to five candles, 
 will burn somewhere about 100 hours, or equal to 
 500 candles, each burning one hour; the expense 
 per hour, when sperm oil is 9s. per gallon, will be a 
 little more than a penny for such lamp ; but when 
 whale or seed oil, which are now very much used in 
 the late invented “ overflowing shadowless lamp,” 
 and also in the “ solar lamp,” supply the place of 
 
28 
 
 THEORY OF THE PRODUCTION 
 
 sperm oil, as these oils can be purchased at from 3s. 
 to 3s. 6d. per gallon, we find that an imperial 
 gallon will burn about ninety hours, and furnish 
 light equal to 4f mould candles of six to the pound, 
 or equal to 427^ candles, each burning one hour. 
 These lamps, with whale or seed oil, will cost not 
 quite one halfpenny per hour. 
 
 It is generally admitted that an argand burner of 
 fifteen holes will consume about five cubic feet of gas 
 per hour, and yield a light equal to twelve mould 
 candles of six to the pound. 
 
 Hence we may put the comparative cost of dif- 
 ferent modes of procuring light in a somewhat 
 different shape to what has been already done, 
 thus : — £ m 
 
 A quantity of light equal to that pro- 
 duced by 500 candles of six to 
 the pound, if obtained from wax 
 candles, at 2s. 6J. per lb., will re- 
 quire 7J lbs., and cost - - - - 
 
 An equal quantity of light, when ob- 
 tained from sperm oil, costs - - 
 
 An equal quantity of light from 
 10 lbs. of short six tallow candles, 
 costs- - -- -- -- -- 0 
 
 An equal quantity of light from whale 
 or seed oil costs ------ 0 
 
 An equal quantity of light from 210 
 cubic feet of coal gas costs - - - 0 
 
 s. 
 
 d. 
 
 0 18 4 
 
 0 9 0 
 
 6 8 
 
 4 3 
 
 9 * 
 
 1 
 
OF ARTIFICIAL LIGHT. 
 
 29 
 
 £. s. d . 
 
 And if an equal quantity of light were 
 to be procured by the use of ill- 
 snuffed dip candles, it would hardly 
 be obtained for less than the price 
 given for sperm oil, that is to say - 0 9 0 
 
 We may, however, perhaps put the above in a still 
 plainer point of comparison by making the cost of 
 wax candles the standard, and subsequently letting 
 the others follow, decimally expressed, thus : — 
 
 Wax candles - -- -- -- -- 1-000 
 Sperm oil burnt in argand lamps - - - *496 
 
 Ill-snuffed tallow candles ----- -496 
 
 Tallow candles (mould) six to the pound - *368 
 Whale or seed oil, burnt in the “ over- 
 flowing shadowless lamp,” or the 
 
 “ solar lamp - '234 
 
 Coal gas - -- -- -- -- - -100 
 
 Or, if the cost of wax candles be Is., the cost of 
 these other means of equal illumination will be as 
 under : — 
 
 £. s. d. 
 
 Wax 0 1 0 
 
 Sperm oil - -- -- -- 006 
 
 Ill-snuffed tallow candles - - 0 0 6 
 
 Tallow candles- - - - - - 0 0 4J 
 
 Whale or seed oil ----- 0 0 2| 
 
 Coal gas- - - - - -nearly 0 0 1| 
 
 The experiments which have been made for the 
 
30 
 
 THEORY OF THE PRODUCTION 
 
 purpose of coming at the above results give evidence 
 that the quantities of light produced by tallow 
 candles are in such proportion to each other as 
 would be expressed by multiplying the time that the 
 candle is burnt by the quantity of matter consumed. 
 This law being established, we have a standard given 
 by which we may compare the strength of various 
 lights ; for, if a small mould candle he lighted, and 
 so placed as neither to produce smoke nor require 
 snuffing, it will lose in weight a little over five 
 drams in an hour, or about one ounce in three hours. 
 The quantity of light so produced may be expressed 
 by 1 ; should it, however, at any other time lose 
 more or less weight in three hours than an ounce, 
 the quantity of light it yields may be ascertained, for 
 the quantity of light produced in a given time (the 
 combustion being perfect) is always in a direct pro- 
 portion to the quantity of matter consumed. 
 
 From what has been said on the subject arise the 
 two following theorems : — 
 
 First. When the quantities of matter of two or 
 more bodies consumed are equal, and times of burn- 
 ing the same, they will give equal quantities of 
 light. 
 
 Second. When the times of burning of two or 
 more bodies are equal, the quantities of light emitted 
 by each will be in direct proportion to the respective 
 weights of matter consumed. 
 
 Corollary. It follows, as has been before observed, 
 
OF ARTIFICIAL LIGHT. 
 
 31 
 
 that, the light produced by any number of bodies 
 used for the purpose of generating it, is always in 
 the compound ratio of the time of burning and 
 weight of material burnt. 
 
 Hence we are able to lay down the following 
 rules for investigating such subjects : — 
 
 Let M represent the mould candle ; 
 
 d its distance from the wall on which the 
 shadows were compared ; 
 m its quantity of matter consumed in a given 
 time; 
 
 t express that time ; and 
 Q the quantity of light emitted by M in the 
 same time. 
 
 Let C represent any other candle ; 
 
 8 its distance from the wall; 
 q its quantity of matter consumed in a given 
 time; 
 
 t that time ; and 
 
 g the quantity of light emitted by C in the 
 same time. 
 
 The intensity of light being directly as the squares 
 of the distances of the two candles from the wall, 
 we have — 
 
 As d 2 : 8 2 : : Q : g, the quantity of light emitted 
 by C in the same time as that emitted by M. 
 
 Then, supposing the quantities of light to be in 
 direct proportion to the quantities of matter con- 
 sumed in the time t , we have — 
 
32 
 
 THEORY OF THE PRODUCTION 
 
 As nx • • Q • g, tiifc quantity of light emitted 
 
 by C in that time. 
 
 Therefore — — — and the quantities 
 
 d 2 m 
 
 of light of M and C are in proportion to the 
 quantities of matter consumed by each in any specific 
 time. To make this matter quite easy to every 
 reader, the two following rules are subjoined for 
 solving questions of this description. 
 
 Proposition 1st. — Given the distance of one candle 
 from the wall where the strength of shadow is ob- 
 served, the quantity of light emitted by the same in 
 a given time, and the distance of another candle or 
 other luminous body throwing a similar shadow 
 upon the same wall from it ; to find the quantity of 
 light which will be produced by the latter in the 
 same time as the former. 
 
 Rule. — As the square of the first candle’s distance 
 from the w^all is to the square of the second candle’s 
 (or other luminous body’s) distance from the said wall, 
 so is the quantity of light emitted by the first candle 
 to the quantity of light emitted by the second in the 
 same time. 
 
 Proposition 2nd. — The weight of one candle con- 
 sumed in a given time, the quantity of light emitted 
 by the same, and the weight of another candle con- 
 sumed in a like time being given (the candles being 
 so placed as to throw shadows of equal intensity 
 upon the same wall) ; to find the quantity of light 
 
OF ARTIFICIAL LIGHT. 
 
 33 
 
 which will be produced by the latter in the same 
 time as the former. 
 
 Rule. — As the quantity of matter consumed by 
 one candle in a given time is to the quantity of 
 matter consumed by the other in a like time, so is 
 the quantity of light emitted by the first candle to 
 the quantity of light which is emitted by the second. 
 
 These rules may be followed for comparing the 
 strength of the light of candles of different sizes 
 with each other, and for ascertaining their relative 
 cost. They are, by transposition, capable of pro- 
 ducing various statings, and are easily applied to 
 practice. 
 
 The rules, &e. relative to ascertaining the 
 quantity and cost of light procured from luminous 
 bodies, and for comparing the expense at which a 
 given quantity of light may be procured by divers 
 methods, to some may appear of little use ; but it 
 may be observed to such, that the author considers 
 he is writing for practical men as well as for 
 men of science. From upwards of twenty years’ 
 experience in the lighting of towns with gas, he is 
 enabled to state that without such rules many a 
 practical engineer (perhaps possessing no other work 
 which treats upon the same subject) who might be 
 called upon to light a town with gas, where such 
 light had not been before used, would find con- 
 siderable difficulties arise to prevent his making his 
 arrangements advantageously ; and which a judi- 
 
34 
 
 THEORY OF THE PRODUCTION 
 
 cious application of the matter given in this chapter, 
 relative to comparing one description of light with 
 another, will tend to prevent. 
 
 It may not be uninteresting to some readers to 
 know that a taper lamp fitted with a wick of eight 
 threads of cotton will consume in one hour 0*50775 
 ounces of spermaceti oil, and that such a lamp yields 
 about -f the quantity of light as a mould candle of 
 six to the pound. It requires snuffing hut seldom, 
 and casts a steady and strong light, and, when oil is 
 sold at 9s. per gallon, the expense of burning it 
 twelve hours is rather more than h\d. 
 
 A chamber lamp, with a wick of four ordinary 
 threads of cotton, consumes in an hour 0 22283 
 ounces of spermaceti oil, and, when oil is sold at 9s. 
 per gallon, it can be kept burning for twelve hours 
 at an expense of 2 \d. nearly. 
 
 One pint and a quarter of whale oil, when used 
 for the purpose of generating light by means of a 
 lamp, is found to be equal in illuminating power to 
 a pound of tallow candles, eight to the pound, set 
 up and burnt out one after the other. 
 
 The suggestions of Dr. Franklin relative to a 
 greater proportion of light being obtained by using 
 two candles in such a position as allows the flames 
 to touch each other than when they are burnt 
 separately, has been proved by many experiments to 
 extend to the flames of gas-lights ; for these when 
 combined yield a much stronger light than they 
 
OF ARTIFICIAL LIGHT. 
 
 35 
 
 would afford if used in a separate state ; and when- 
 ever flames are placed near to each other, the illu- 
 minating consequences are always most beneficial, 
 inasmuch as thereby the heat of the respective flames 
 are preserved, for they act in mutual defence against 
 the cooling influence of the surrounding air. 
 
 As the argand lamp, from whence the idea of the 
 argand burner was evidently taken, is superior in its 
 effect, and at the same time more economical than 
 any other ; so also great advantages arise from 
 burning gas upon a similar principle ; for by the use 
 of the argand burner the junction of many flames is 
 effected without any fear of the light being deterio- 
 rated from its not being exhibited in a thin surface. 
 If we reflect that flame is transparent, there can- 
 not arise an apprehension of the strength of light 
 afforded by a burner or a lamp (in which the flame 
 is exhibited between two concentric circles), where 
 the outer surface is the surface of a cylinder, being 
 diminished on account of one part of the flame being 
 covered by the other. 
 
 We have endeavoured to explain the modes by 
 which a comparison as to intensity between one light 
 and another may he made, and also how* the cost of 
 each may be ascertained ; and have also stated the 
 cost of a given quantity of light obtained from wax 
 and tallow candles, from spermaceti and other oils, 
 and from coal gas, in order that our readers may 
 have those things brought immediately before their 
 
36 
 
 THEORY OF THE PRODUCTION 
 
 notice ; and as we expect gas consumers will be 
 benefited by one or two remarks resulting from 
 long experience relative to the most economical 
 mode of using gas, we propose with such, and a 
 table of comparative costs of obtaining light, to 
 bring this chapter to a conclusion. 
 
 It will be seen from what has been already said 
 that small burners, such for instance as single jets, 
 are not so economical as large ones ; for by the 
 former it would require about 8 \ cubic feet of gas to 
 obtain the same quantity of light as would be 
 afforded from 5 cubic feet consumed by means of an 
 argand burner. It may, therefore, be taken for 
 granted that the twelve and fifteen-hole argand 
 burners are the most economical ; and, of the two, 
 the fifteen-hole burner, quantum of light for quantum 
 of light, is superior to the twelve. In using argand 
 burners, however, the consumer should always do so 
 with chimney glasses, and be careful that the flame 
 should never on any account rise higher than from 
 3 inches to 3J inches. If it be allowed to rise 
 higher more gas will find its way through the 
 burner than can be consumed, and consequently a 
 portion of it will pass off in smoke to the injury of 
 his ceilings or goods, or both. 
 
Compara i ive Statement of the Illuminating Power, and Expense per Annum, of Gas, Candles, and Spermaceti Oil. 
 
 OF ARTIFICIAL LIGHT. 37 
 
 « ° 
 <5 be 
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 £ -o 
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 ^ O 
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 v a 
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 Po M 
 CO 2 
 
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 05 o 
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 rt 1 
 
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 ^ rC W 
 
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 3 a. 
 
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 ill 1 1 
 
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 aj — « 03 
 
 ®.S rt ® — 
 5s «f£b 
 g| §B g 
 
 -a S o d 5 
 
 M h o qj P. 
 
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 JJ'g Sog 
 
 _o a> •—* cs 
 
 p3 3 ^£< u 
 
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 o cd ® ts !> 
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 ra -h 3 o to 
 Hi O g D JH 
 
 ^3 ‘-is o^J-d 
 
 t*< 'S ^5 H 3 
 
 CX,.^ OJ 
 
38 
 
 NATURAL HISTORY 
 
 CHAPTER II. 
 
 On the Natural History of Pit-Coal, and its component Parts, as 
 ascertained by Analysis : also accounts of the quantities of Gas 
 generally obtained by the Manufacturer from Coals of different 
 Species. 
 
 Coal, or pit-coal , as it is called in mineralogy, is a 
 solid inflammable substance, somewhat shining, dry, 
 and light, compared with the strata in which it is 
 found. In this country it is very abundant, and 
 may be considered almost inexhaustible. It is pe- 
 culiarly adapted for domestic purposes, as well as 
 various uses in the arts. It is found chiefly in the 
 countries lying nearly in the same latitude as Great 
 Britain. It is likewise said to be found in the 
 northern parts of China. In the southern hemisphere 
 it is stated to be very abundant in New Holland ; 
 but we have no distinct account of coal in the conti- 
 nent of Africa. Of this substance there are several 
 species. 
 
 1st. Jet. This substance is found in France, 
 Spain, Germany, Great Britain, and other countries, 
 in detached kidney form masses of various sizes, 
 from one inch to seven or eight feet in length. The 
 colour is a deep black ; internal, glossy opaque ; not so 
 brittle as asphaltum ; texture striated ; fracture con- 
 choidal ; specific gravity 1*259. It has no smell. 
 
OF PIT-COAL. 
 
 39 
 
 except when heated, and then it resembles asphaltum 
 in its odour. It melts in a strong heat, burns with 
 a greenish flame, and leaves an earthy residuum. It 
 becomes electric by friction, and when distilled yields 
 a peculiar acid. 
 
 2nd. Cannel coal. This is found in Lancashire 
 and in different parts of Scotland. It is of a bright 
 black colour ; opaque ; structure sometimes slaty ; 
 texture compact; it breaks easily in all directions, 
 and, if broken transversely, presents a smooth con- 
 choidal surface. 
 
 It burns with a lively flame, like a candle, as per- 
 haps its name implies, but is very apt in burning to 
 throw splinters to a great distance ; it is said, how- 
 ever, to be deprived of this property by being im- 
 mersed in water for some hours previous to being 
 used. In the coal-field at Wigan, there is a stratum 
 of this coal, unmixed, nearly four feet in thickness. 
 Cannel coal is susceptible of polish, and, like jet, is 
 often wrought into trinkets. 
 
 A specimen of Lancashire cannel coal, analyzed 
 by Mr. Kirwan, contained 75*20 charcoal, 21*68 
 maltha, and 3*10 alumina and silica, or together 
 99*98. A specimen of the slaty kind, from Ayrshire, 
 called splent coal, was composed of 47*62 charcoal, 
 32*52 maltha, and 20*00 earths, or together 100*14. 
 The specific gravity of cannel coal is from 1*282 to 
 1*426. This coal does not soil or stain the fingers 
 when handled. 
 
40 
 
 NATURAL HISTORY 
 
 3rd. Common coal. This very useful combustible 
 is never found in the primitive mountains, but only 
 in the secondary mountains, or in plains formed of 
 the same materials with them. It is always in strata, 
 and generally alternates with clay, sandstone, or 
 limestone. The colour is black, more or less perfect ; 
 lustre usually greasy or metallic ; opaque ; structure 
 generally slaty ; specific gravity 1-25 to 1*37 ; usually 
 stains the fingers, takes fire more slowly, and burns 
 longer than cannel coal ; cakes more or less during 
 combustion. Of this species there are many varieties 
 in Great Britain, distinguished by the names of 
 caking coal, rock coal, &c. Mr. Kirwan analyzed a 
 variety of different kinds of coal of this species. The 
 results of some of bis experiments are exhibited in 
 the following table: — 
 
 Whitehaven. 
 
 Newcastle. 
 
 Wigan. 
 
 Swansea. 
 
 Leitrim. 
 
 
 57- 
 
 58 
 
 61-73 
 
 73-53 
 
 71-43 
 
 Charcoal. 
 
 41-3 
 
 40 
 
 36*7 
 
 23-14 
 
 23-37 
 
 Maltha and Asphalt. 
 
 1*7 
 
 2* 
 
 1-57 
 
 3-33 
 
 5-20 
 
 Earths. 
 
 100-0 
 
 100 
 
 100-00 
 
 100-00 
 
 100-00 
 
 
 4th. Spurious coal. This species is generally found 
 amidst strata of genuine coal : it is also called parrot- 
 coal in Scotland. The colour is greyish black ; 
 structure usually slaty ; texture earthy ; specific gra- 
 vity T5 to 1*6; generally explodes and bursts when 
 heated. It is composed of charcoal, maltha, and 
 asphalt, and above 20 per cent, of stony matter. 
 
 * Earth and metallic matter and sulphur. 
 
OF PIT-COAL. 
 
 41 
 
 5th. Anthracite. This substance, as we are in- 
 formed by Dolomieu, is found exclusively in the 
 primitive mountains. It is commonly amorphous ; 
 sometimes crystallized in short hexagonal prisms; 
 colour black or brownish black ; structure slaty ; 
 fragments rhomhoidal ; specific gravity T3 ; often 
 stains the finger s» This species burns precisely like 
 the spurious coal,leaving 40 per cent, of white ashes. 
 According to Dolomieu it is composed of about 64’0 
 charcoal, 32*5 silica, and 35 iron, or together 1000. 
 
 6th. Kilkenny coal. This mineral has been found 
 in Hungary, Italy, France, Ireland, and Wales. It 
 occurs in stratified masses, or in lumps nested in 
 clay ; the colour is black ; opaque ; texture foliated ; 
 specific gravity T4 to T526 ; often stains the fingers; 
 insoluble in acids ; deflagrates with nitre ; does not 
 burn till wholly ignited, and then consumes slowly 
 without emitting flame or smoke. It consists almost 
 entirely of charcoal and sulphur ; the latter is in a 
 very large proportion, which sends out while burning 
 a suffocating effluvia. It does not produce any soot, but 
 whitens the places where the fumes are condensed. 
 
 7th. Culm coal. This species of coal has nearly 
 the same appearance as that of common coal, but its 
 texture is more dull. In Sweden it is considered a 
 distinct species ; but what is commonly denominated 
 culm in England is the refuse or dust produced by 
 working the different kinds of coal. It is difficult 
 to kindle except in furnaces where there is a great 
 draught of air. 
 
42 
 
 NATURAL HISTORY 
 
 8th. Sulphureous coal. This is a dull and heavy 
 species of coal ; it contains a very considerable por- 
 tion of pyrites, and produces a great quantity of 
 ashes. There is a great danger attends the working 
 of this coal ; for, if any considerable quantity is left 
 together, it generates heat and will set the mine on 
 fire. Specific gravity 1*5. 
 
 9th. Bovey coal. This coal consists of wood pe- 
 netrated with petroleum or bitumen, and combina- 
 tions of sulphuric acid. It is found in many parts 
 of the Continent, but is most abundant in England 
 at Bovey, near Exeter, from whence it derives its 
 name. 
 
 The foregoing are the kinds of coal commonly 
 known ; but the different qualities and proportions 
 of their ingredients make a number of other varieties 
 used for different purposes. Thus various kinds of 
 coals are often found mixed with one another under 
 ground, and some of the finer sorts run like veins 
 between those of a coarse kind. On submitting pit- 
 coal of any kind to distillation, it first yields a watery 
 liquor, then a volatile oil, afterwards a volatile alkali, 
 and lastly, a thick oil ; but it is remarkable, that by 
 rectifying this last oil, a transparent and light oil is 
 produced, which, being exposed to the air, becomes 
 black like animal oils. 
 
 Perhaps, by dividing the different kinds of pit-coal 
 into fewer classes than those already noticed, the 
 practical gas-light manufacturer’s object will be more 
 easily obtained; we shall, therefore, consider that 
 
OF PIT-COAL, 
 
 43 
 
 pit-coal may be divided into three classes according 
 to the proportions of its component parts. 
 
 Such coals as are chiefly composed of bitumen, 
 are to be considered as belonging to the first class. 
 
 Those which contain a lesser proportion of bitu- 
 men, and more charcoal, comprehend the varieties of 
 the second class. 
 
 The third class are such as contain very little 
 bitumen, but are chiefly composed of charcoal, che- 
 mically combined with different earths. 
 
 Remarks upon Coals of the First Class. 
 
 Those coals which come under the first class light 
 without difficulty, burn with a bright and yellowish 
 white blaze during the whole process of combustion. 
 They do not cake nor require stirring ; neither do 
 they produce cinders, but are reduced to white ashes. 
 Coals of this class are apt to throw out splinters 
 whilst burning; but, as has been before observed, 
 that may in a great measure be obviated by wetting 
 them before they are used. At the head of this 
 class is to be placed cannel coal. Those of Lanca- 
 shire, and such as are obtained on the north-western 
 coast of England, belong to it. It sometimes occurs 
 in the coal pits of Durham and Northumberland. 
 Most of the varieties of Scotch coal may also be 
 considered as forming part of it, and more particu- 
 larly the splent , which is an inferior kind of cannel 
 coal. 
 
 Notwithstanding what has been remarked by some 
 
44 
 
 NATURAL HISTORY 
 
 about the quantity of gas obtained from a given 
 quantity of coals by the practical gas engineer, and 
 in the large way too, not being much to be depended 
 upon, as it has from time to time been given to the 
 public either in a tabular form or otherwise, I shall 
 not be deterred from following precisely the same 
 track as was pursued in a former edition of this 
 work, by throwing into a tabular form the results 
 of various experiments made in the large way, under 
 my own particular direction, and which seventeen 
 years of additional experience have tended rather to 
 confirm than otherwise. I shall not stop here to 
 inquire by whom such remarks have been made, 
 that is to say, whether by the mere theorist or by 
 the practical man ; but, I may remark that in gas- 
 lighting, as well as in every other art, theory with- 
 out practice avails little — let them act together, they 
 are most important. For the truth of this remark, 
 all persons wdio have considered the subject at all 
 will be apt to agree with me, and more particularly 
 such of my readers as are conversant with matters 
 connected with gas ; for, every one who has read 
 the evidence of scientific men (theorists only) as 
 given from time to time before various Committees 
 of the House of Commons, when different gas-light 
 Bills were under consideration, must have seen how 
 vastly superior was the evidence given by the prac- 
 tical man on those occasions, though he might be of 
 very inferior scientific attainments. 
 
 The following table shows the quantity of gas 
 
OF PIT-COAL 
 
 45 
 
 obtainable in the manufactory, or in the large way, 
 from several of the different varieties of th e first class 
 of coals, when ellipsoidal retorts are used and kept 
 at a bright cherry-red heat by day-light ; the charge 
 to each retort being about 126 pounds of coal. 
 
 Names of Coals. 
 
 Number of 
 hours in 
 ■which one 
 charge is 
 worked off. 
 
 Cubic feet of 
 Gas obtained 
 from a Ton 
 of Coals. 
 
 Cannel Coal, Scotch 
 
 4 
 
 11,850 
 
 Ditto, Lancashire 
 
 4 
 
 11,680 
 
 Ditto, Yorkshire 
 
 4 
 
 11,240 
 
 Newcastle Coal, Tanfield Moor . . . 
 
 6 
 
 10,070 
 
 Gloucestershire Coal, Forest of Dean, High 
 
 
 
 Delph 
 
 6 
 
 9,880 
 
 Newcastle Coal, Hartley’s 
 
 6 
 
 9,600 
 
 Ditto, Cowper’s High Main . 
 
 6 
 
 9,460 
 
 Ditto, Pontops 
 
 6 
 
 9,040 
 
 Gloucestershire Coal, Low Delph .... 
 
 6 
 
 7,660 
 
 Ditto, Middle Delph . 
 
 6 
 
 7,260 
 
 Staffordshire Coal, first kind 
 
 6 
 
 6,474 
 
 Ditto, second kind .... 
 
 6 
 
 6,090 
 
 Ditto, third kind 
 
 6 
 
 5,840 
 
 Ditto, fourth kind 
 
 6 
 
 5,807 
 
 It will be seen on inspecting the foregoing table, 
 that the three species of cannel coal are very pro- 
 ductive of gas, and that the charges are worked off 
 in less time than when any of the other coals therein 
 described are used; but the product of coke is of 
 little or no value, it being not only small in quantity 
 but inferior in quality, exceedingly light, and some- 
 what resembling an indifferent kind of charcoal. 
 When gas procured from this coal is used, it is re- 
 quisite that the gas-holder should be worked at a 
 very light pressure, and that the flame of the burner 
 
46 
 
 NATURAL HISTORY 
 
 should never be allowed to be more than from an 
 inch and a quarter to an inch and a half in height ; 
 for, if these precautions are not taken (as the gas is 
 much richer in bi-carburetted hydrogen than the 
 gas obtained from other descriptions of coal, and 
 thence requiring more oxygen for effecting complete 
 combustion) a considerable portion of it will pass 
 through the burner without being consumed, pro- 
 ducing an offensive odour and abundance of smoke, 
 to the annoyance of the parties to whom it is sup- 
 plied. The holes of the argand burner, with which 
 such gas is used, should be of smaller diameter also 
 than those used where gas is made from the other 
 descriptions of coals. 
 
 The gas procured from cannel coal, when used 
 with judgment, has a very rich appearance; and, 
 in manufactories where coals are used which are not 
 very productive of gas, it would be highly desirable, 
 when the retorts are worked with 126 pounds of 
 coals for one charge, that one-third of such quantity 
 should be cannel coal , which would very much add 
 to the illuminating power of the gas ; and, in some 
 cases a greater proportion might be used with ad- 
 vantage. 
 
 Of this class of coals. Hartley’s are well adapted 
 for heating retorts when set on the furnace plan ; 
 but the Tanfield Moor, though generating a very 
 large proportion of heat, is not so, it being very 
 subject to clinker and to burn out the furnace bars 
 
OF PIT-COAL. 
 
 47 
 
 as well as the retorts and the surrounding brick- 
 work. 
 
 From various experiments made on the different 
 kinds of Staffordshire coal it is found necessary, for 
 extracting the gas advantageously, to work the re- 
 torts at a considerably higher temperature than 
 would have been required, had any of the varieties 
 of the Newcastle coal been submitted to the distil- 
 latory process. These coals, as well as the coals from 
 Gloucestershire, when used for making gas, produce 
 a light and porous cake, very inferior in quality to 
 that which is obtained from each of the varieties of 
 the second class of coals. 
 
 Remarks upon Coals of the Second Class. 
 
 Coals of the second class do not burn with so 
 bright a flame as the former. The flame of these 
 coals is of a yellowish tinge. After laying some 
 time upon the fire they become soft and swell ; they 
 then cake and produce tubercles, from whence issue 
 small jets of flame. When coals of this kind are 
 burnt in an open grate, the passage of the air 
 through them is prevented by the top of the fire 
 caking, and closely adhering ; in consequence, the 
 lower part of the coal contained in the grate is con- 
 sumed and leaves a hollow, whence, if the upper 
 part were not occasionally broken through, the fire 
 would go out. These coals produce a smaller pro- 
 portion of ashes than coals of the first class. The 
 
48 
 
 NATURAL HISTORY 
 
 ashes are of a greyish or reddish colour, according 
 to the quality of the earthy part of which the coal is 
 partly formed. They produce hard grey cinders, which, 
 when burnt over again with fresh coals, produce a 
 very strong heat. The colour of the flame produced 
 from this class of coal is not so white and brilliant 
 as that emitted by cannel coals and those of similar 
 properties; and that portion of it which is given 
 out after the bitumen it contains is disengaged, is of 
 a pale blue colour. The gas which they produce 
 during this part of the process of combustion, is a 
 mixture of oxide of carbon, hydrogen, and carbonic 
 acid. The coke produced from this class of coal 
 during the process of generating gas therefrom, 
 when carbonization is properly carried on, is well 
 adapted for domestic and culinary purposes; and 
 when such coal is manufactured into coke by means 
 of coke ovens by some gas companies, and in some 
 private gas establishments adopted for heating re- 
 torts instead of furnaces, in the ordinary way, it is 
 calculated to be used in the furnaces of iron-founders 
 and for other metallurgical operations. Coals of 
 this class are denominated in the market strong 
 burning coals. Smiths prefer the smaller kind of 
 this class of coals before any other, in consequence 
 of its affording the greatest heat, the best cinders, 
 and standing a strong blast. Some of the varieties 
 contain pyrites, others thin layers of limestone and 
 shells; these are found amongst the ashes they 
 
OF PIT-COAL. 
 
 49 
 
 afford as slates and stones. When submitted to dis- 
 tillation, a greater heat is required than is necessary 
 for decomposing cannel coal , and some other coals 
 of the first class. The aqueous fluid, which passes 
 over during the process, contains sulphate, carbonate, 
 and hydro-sulphuret of ammonia. When coals of 
 this kind are mixed with those of the first class in 
 the proportion of two-thirds of the former with 
 one-third of the latter, an excellent fuel is thereby 
 formed ; and, if on making the mixture the propor- 
 tion of coals of the first class be increased, the fuel 
 will be more easily managed, and will burn with 
 greater cheerfulness ; but its durability will decrease 
 in a like proportion. 
 
 The following table shows the quantity of gas 
 obtainable in the manufactory, or in the large way, 
 from several of the different species of this class of 
 coals, when ellipsoidal retorts are used and kept at a 
 heat rather above cherry red by day-light, the charge 
 to each retort being 126 pounds of coal, which will 
 be well worked off in six hours. 
 
 Names of Coals. 
 
 Bewicke and Craister’s Wallsend 
 Russell’s Wallsend 
 Bewicke’s Wallsend 
 Bell’s Wallsend 
 Heaton Main . 
 
 Killingworth Main 
 Benton Main . 
 
 Wigan Orall . 
 
 Wear Wallsend 
 Burdon Main . 
 
 Cubic feet of Gas 
 obtained from a Ton. 
 
 10,370 
 10,360 
 10,130 
 9,963 
 9,740 
 9,393 
 9,082 
 9,000 
 8,652 
 8,341 
 
 E 
 
50 
 
 NATURAL HISTORY 
 
 Names of Coals. 
 
 
 Cubic feet of Gas 
 obtained from a Ton. 
 
 Brown’s Wallsend . 
 
 
 8,336 
 
 Wellington Main 
 
 
 8,270 
 
 Temple Main . 
 
 
 8,180 
 
 Headsworth 
 
 
 8,052 
 
 Hebburn Seam 
 
 
 7,896 
 
 Hutton Seam . 
 
 
 7,785 
 
 Nesham .... 
 
 
 7,763 
 
 Manor Wallsend 
 
 
 7,700 
 
 Bleyth .... 
 
 
 7,420 
 
 Eden Main 
 
 
 6,670 
 
 Primrose Main 
 
 
 6,220 
 
 Pembry .... 
 
 
 4,200 
 
 Remarks upon Coals of the Third Class . 
 
 Coals of this class require a very high temperature 
 to bring them into ignition ; they do not burn till 
 wholly ignited, and then some of the varieties pro- 
 duce a very weak flame ; others neither yield flame 
 nor smoke, and merely produce a red heat, like that 
 which is generated by charcoal when undergoing 
 combustion. They contain a very considerable por- 
 tion of charcoal ; they produce only a small quantity 
 of ashes, but these are generally very heavy. Some 
 of the varieties of this class of coals, when distilled 
 in close vessels, produce but very little tar, and the 
 portion which is disengaged is of the consistency of 
 melted pitch : the Kilkenny coal, however, being 
 altogether void of bitumen, produces no tar. Under 
 the distillatory process, most varieties of coals of this 
 class yield a gaseous fluid, composed of gaseous oxide 
 of carbon, hydrogen gas, and a considerable portion 
 of sulphuretted hydrogen. 
 
OF PIT-COAL. 
 
 51 
 
 As it appears by some experiments made on six 
 different species of Welch coal that the best pro- 
 duced, at the maximum, but 1,567 cubic feet of gas 
 from a ton ; it is evident that the different varieties 
 of the third class of coals cannot be used profitably 
 for making gas. Amongst the varieties of this class 
 of coals are those found near Kilkenny, the Welch, 
 and the stone coal. 
 
 The following table is introduced for the purpose 
 of showing the relative proportions of gas obtainable 
 from the different species of coals enumerated in the 
 two preceding tables, the Scotch cannel being con- 
 sidered the standard, and estimated at 1,000. 
 
 Scotch Cannel 
 
 
 
 1,000 
 
 Lancashire Cannel 
 
 
 
 986 
 
 Yorkshire Cannel 
 
 
 
 949 
 
 Bewicke and Craister's Wallsend 
 
 
 
 875 
 
 Russell’s Wallsend 
 
 
 
 861 
 
 Bewicke’s Wallsend 
 
 
 
 855 
 
 Tanfield Moor 
 
 
 
 850 
 
 Bell’s Wallsend . 
 
 
 
 841 
 
 Forest of Dean, High Delph. 
 
 
 
 834 
 
 Heaton Main 
 
 
 
 822 
 
 Hartley’s .... 
 
 
 
 810 
 
 Cowper’s High Main . 
 
 
 
 798 
 
 Killingworth Main 
 
 
 
 792 
 
 Benton Main 
 
 
 
 766 
 
 Pontops .... 
 
 
 
 762 
 
 Wigan Orall 
 
 
 
 759 
 
 Wear Wallsend . 
 
 
 
 730 
 
 Burdon Main 
 
 
 
 704 
 
 Brown’s Wallsend 
 
 
 
 703 
 
 Wellington Main. 
 
 
 
 697 
 
 Temple Main 
 
 
 
 690 
 
 Headsworth 
 
 
 
 679 
 
 Hehburn Seam 
 
 
 
 666 
 
 e 2 
 
52 
 
 NATURAL HISTORY 
 
 Hutton Seam 
 
 657 
 
 Nesham ..... 
 
 655 
 
 Manor Wallsend .... 
 
 650 
 
 Forest of Dean, Low Delph . 
 
 646 
 
 Bleyth 
 
 624 
 
 Forest of Dean, Middle Delph 
 
 612 
 
 Eden Main 
 
 562 
 
 Staffordshire Coal, first kind . 
 
 546 
 
 Primrose Main .... 
 
 525 
 
 Staffordshire Coal, second kind 
 
 514 
 
 Ditto, third kind 
 
 492 
 
 Ditto, fourth kind 
 
 . 490 
 
 Pembry ..... 
 
 354 
 
 The author trusts the general reader will not find 
 the tables introduced into this chapter uninterest- 
 ing. To the practical man he knows they must be 
 of importance, for they exhibit the results of a long 
 series of experiments, carefully made, the greater 
 part of them in the large way and all to such an 
 extent as was quite sufficient for obtaining what 
 might be considered as practical results. He is 
 aware that in infant establishments for manufac- 
 turing coal-gas, and more particularly in those 
 which have within the last ten years sprung up in 
 all directions in provincial towns, some of very small 
 magnitude, every one concerned in their manage- 
 ment cannot be expected to understand, in detail, 
 the operations required, and generally speaking gen- 
 tlemen forming directories and committees of ma- 
 nagement do not consider it needful that they 
 should trouble themselves with more than the very 
 outlines of the manufacture ; being content with the 
 management of the financial concerns of the esta- 
 
OF PIT-COAL. 
 
 53 
 
 blishment only ; and leaving the more laborious part 
 attendant upon the carrying on of the works to well- 
 informed servants ; themselves, occasionally, inspect- 
 ing the apparatus, &c., for the purpose of ascertain- 
 ing whether there be an appearance of neglect on 
 the part of any one employed. It is thought no one 
 will dispute the necessity which exists for directors 
 and committee men being acquainted fully with 
 everything connected with the works of which they 
 may have the management ; for, if they are not, 
 they must, to a very great extent, be at the mercy 
 of their servants, and be able to form but a very in- 
 different judgment as to whether every means are 
 laid hold of for carrying on their business on the 
 most economical plan, which the energies of prac- 
 tical and scientific men are continually endeavour- 
 ing to effect. For instance they may have their 
 retorts so set as to burn out and become useless in 
 a very few months, whereas by a different mode of 
 setting, the retorts still heating as well, and at no 
 increased expense for fuel for heating them, they 
 might last a year or longer ; or the retorts might 
 be so set as either to render it next to impos- 
 sible to get them to a proper working heat ; or, 
 if such heat could be gained at all, at an enormous 
 expense of fuel, which difficulties might be obviated 
 by their own suggestions, if they informed them- 
 selves as to what had been done elsewhere. The 
 same argument would hold good through every part 
 
54 
 
 NATURAL HISTORY 
 
 of the process of generating, washing, condensing, 
 purifying and storing the gas, as well as in its dis- 
 tribution to public or street lamps, or to the private 
 consumer. If they are not acquainted with all these 
 things, they are in a somewhat similar position to 
 a person carrying on any other business with which 
 he is unacquainted — its success must mainly depend 
 upon the persons (therewith acquainted) whom he 
 may employ, and so he must rely upon their judg- 
 ment instead of his own, to his inconvenience and 
 probable disadvantage. To meet this contingency as 
 well as for other reasons, the author has been in- 
 duced to bring out this new edition of his work, (the 
 former editions having been long out of print,) and 
 it is his intention so to remodel his matter, where it 
 may require it, as to bring down the information 
 which has been accumulating for some years back 
 relative to the manufacture of gas, to the present 
 time, so that the work may be safely consulted, as 
 one which describes all real improvements of recent 
 date. He has thus far, for reasons already named, 
 been very explicit ; and it is his intention as he pro- 
 ceeds to be equally so, divesting his matter as much 
 as possible from all technical phraseology, in order 
 that all who read may clearly comprehend the appa- 
 ratus he purposes to describe, and as clearly under- 
 stand all the details relative to the working thereof. 
 In going so fully into the properties of different 
 kinds of coal, he trusts the reader will find some 
 
OF PIT-COAL. 
 
 55 
 
 advantage, inasmuch as it will show him that every 
 description of coal is not equally productive of gas, 
 and should he happen to be a director of a gas com- 
 pany, or a member of the committee of management, 
 it will induce him to pause before large orders are 
 given, and thus prevent what has heretofore occurred, 
 that is to say, the stores of an establishment filled 
 with coals unproductive of gas, and, too late, found 
 to be totally unfit for the purpose intended. 
 
 To prevent a recurrence of such an oversight has 
 been the author’s motive in furnishing the preceding 
 tables, in addition to which he suggests that gen- 
 tlemen who are entrusted by the proprietary to 
 manage gas establishments, and who may be about to 
 purchase coals for stock, (whether the coals be named 
 in the tables here given, or otherwise,) to make it an 
 invariable rule not to purchase to any extent, till 
 they have, by experiments upon a few tons at their 
 own works, ascertained the quantity and quality of 
 the gas which may be procured from the coals about 
 to be purchased, as well as the nature of the coke 
 they will produce, and the degree of heat which is 
 necessary for extracting the gaseous matter from 
 them. 
 
 I shall conclude this chapter with a few remarks 
 on the probable time that Great Britain may be 
 supplied with coal from the mines of Durham and 
 Northumberland, (independent of the various mines 
 in Yorkshire, Staffordshire, Worcestershire and 
 
56 
 
 NATURAL HISTORY 
 
 other counties,) for the purpose of showing that, 
 however extensive the practice of supplying light by 
 the gas procured from pit-coal may be, there cannot 
 in this country be any apprehension of a scarcity of 
 that material for some centuries yet to come ; and 
 may we not presume that before the coal mines are 
 worked out, the All-wise Disposer of events will en- 
 able men to provide some other method for obtaining 
 artificial light, which would to us be equally extra- 
 ordinary, (could we live to witness it,) as a gas-light 
 or a locomotive engine would have been to our an- 
 cestors in the fifteenth century, or, without going 
 back so far, to those living less than half a century 
 ago. 
 
 In the first edition of this work, (published in the 
 year 1819,) it was stated that the seams of coal 
 worked in Durham and Northumberland, were then 
 equal to a bed twenty miles in length by fifteen in 
 breadth, and the average thickness of the bed was 
 stated to be one yard and a half ; also, that from 
 one-fourth to one-sixth would be sufficient to be 
 left as props for supporting the tops of the mines. 
 This being premised, if we make our calculation 
 that one-fifth should be left for the last mentioned 
 purpose; then as 15 miles are equal to 26,400 yards, 
 and 20 miles are equal to 35,200 yards, and the 
 average thickness of the stratum is one yard and 
 a-half ; if we multiply 26,400 by 35,200 and again 
 by H, we shall have for the last product 1,393,920,000 
 
OF PIT-COAL. 
 
 57 
 
 cubic yards of coal contained in the mines above- 
 mentioned ; from this we are to deduct one-fifth 
 for pillars to support the roof, the remainder 
 
 1.115.136.000 expresses the cubic yards of coal 
 which may, in process of time, be brought to market ; 
 and, as each cubic yard of the various species of coal 
 produced from these mines, may be estimated as 
 equal to one ton, consequently the number of cubic 
 yards and of tons are equal. Now as it appears 
 from the Register, that the total annual consump- 
 tion of coals from Newcastle and Sunderland is about 
 
 3.105.000 tons, and as the total quantity of coals 
 which these mines were capable of supplying in the 
 year 1819, was then stated to be 1,115,136,000 tons ; 
 therefore if that number be divided by the tons an- 
 nually consumed, the quotient will express the num- 
 ber of years such supply could then have been given ; 
 and taking into consideration that twenty-two years 
 have since elapsed, we may set it down as tolerably 
 near the truth, that those mines will afford a supply 
 of coals for 337 years from this period. 
 
 Should objections be made to the above statement, 
 on the ground that a much greater quantity of coal 
 must be used annually since the new mode of pro- 
 curing light, by means of coal-gas, has been so 
 widely extended, than was consumed heretofore, the 
 author’s reply would be that, although many hun- 
 dred thousand tons of coal are now used every year 
 for making gas ; yet in point of fact it would be 
 
58 
 
 NATURAL HISTORY 
 
 altogether incorrect to suppose even one-half of the 
 coal so used, was an additional drain, to that extent 
 even, upon the mines ; for every one knowing any 
 thing about coal-gas making, must be aware that the 
 coke produced in the retorts is capable of giving out 
 more heat after the gas is extracted from the coal 
 than before it underwent such operation ; and that 
 such coke is well adapted for almost every culinary 
 and domestic purpose to which coal itself is appli- 
 cable. It is hardly needful to add, in support of our 
 position, that the coke produced at the different gas 
 establishments in the metropolis, and elsewhere, is 
 now so well known and so much approved of for use 
 in the kitchen, laundry, &c., that the demand for it 
 is quite commensurate with the quantity produced ; 
 and as whatever coke may be used by the public as 
 fuel, must necessarily equally diminish the quantity 
 of coals which would otherwise be consumed, we 
 can hardly reckon upon a very increased annual con- 
 sumption since the adoption of gas-lights. The 
 quantity of coal, however, used for fuel in the gas- 
 manufactories, must as a matter of course add to the 
 consumption considerably ; and there has recently 
 been another drain upon the coal mines, by the de- 
 mand for coke for working locomotive engines upon 
 the numerous railways with which this country is 
 intersected ; still after all we may fairly reckon that 
 the mines we have referred to will not be exhausted 
 for three centuries yet to come — setting aside all 
 
OF PIT-COAL. 
 
 59 
 
 consideration as to the various and extensive coal 
 mines in various parts of this country. It may he 
 remarked further that in several gas establishments 
 there is no loss of coal for fuel ; for where the re- 
 torts are heated by means of coke ovens, the coals 
 therein used, instead of being burnt away to cinders 
 and ashes, are converted into a very valuable coke. 
 
60 
 
 THEORY OF THE 
 
 CHAPTER III. 
 
 The Theory of the Combustion of Coal considered, for the purpose 
 of explaining the nature of Gas-light and its production. 
 
 W hen pit-coal is burnt in an open fire-place it emits 
 flame, which is occasionally exhibited in streams of 
 peculiar brightness. This flame is coal-gas in a state 
 of combustion. But besides this gas, there are ex- 
 pelled from coal, by the action of heat, an aqueous 
 ammoniacal vapour, (which on being condensed forms 
 liquid ammonia,) a thick fluid nearly resembling tar, 
 and some non-inflammable gases. The wavering 
 and changing of the colour of flame proceeding from 
 a coal fire, is occasioned by the variety of products 
 which coal affords; and as these are evolved, we 
 have at one time streams of brilliant light, at ano- 
 ther clouds of dense and aqueous vapour thrown off 
 as smoke. Seeing, then, that when coals are burnt 
 in the ordinary way we have evident proofs that 
 they contain inflammable gas, which, if collected 
 and properly applied, would serve as a substitute for 
 the lights obtained by using candles or oil, together 
 with other valuable products, we must be aware that 
 whenever they are distilled in close vessels the 
 various parts of which they are formed may be col- 
 lected. Such part of the coal as is bituminous will 
 
COMBUSTION OF COAL. 
 
 61 
 
 melt out and be partly converted into gas as it is 
 evolved in a state of vapour, the residue will be ex- 
 hibited in the form of tar. That which contains 
 ammoniacal salts will he thrown off as vapour, and, 
 on condensation, will appear as an amber-coloured 
 fluid, more or less charged with ammonia, according 
 to the circumstances under which the distillation 
 may have been carried on, and the quality of the 
 coal. Whilst the above products are evolved, a con- 
 siderable quantity of carburetted hydrogen gas (or 
 more properly speaking coal-gas) and some unin- 
 flammable gases are also generated. These having 
 all been freed from the coal by the action of heat, 
 and collected in their respective reservoirs, its base, 
 which is a carbonaceous substance, known by the 
 name of coke, remains in the retort, or distillatory 
 vessel. The coal-gas, being freed from the sulphur- 
 etted hydrogen and non-inflammable gases, is fit for 
 use, and may be forced out of the gas-holder where 
 it is collected to any distance, by means of cast- 
 iron pipes laid under ground ; from whence 
 smaller pipes of wrought iron, of drawn tin, or of 
 copper, convey it to the respective burners in the 
 houses, &c., where gas is used. At the extremity 
 of the pipes are fixed the burners, to which, by 
 means of stop cocks, the gas is admitted, and through 
 orifices made in the burners it escapes and is ignited 
 for the purpose of affording light. Thus from pit- 
 coal, a mineral raised in considerable quantities 
 
62 
 
 THEORY OF THE 
 
 in this country, is obtained a substitute for such 
 lights as are afforded by using wax, tallow, or oil, 
 but of a far superior quality and at an immense 
 saving of expense. When this is considered, it 
 cannot but be gratifying to the feelings of every 
 Englishman to know that, within his native country, 
 there are abundant resources for generating arti- 
 ficial light ; and, that he is no longer entirely de- 
 pendent on the relations he holds with foreign 
 powers, or on the fisheries, for a supply of such 
 materials as were heretofore exclusively used for 
 producing it. 
 
 The early promoters of gas-lighting rested their 
 claims to public notice and encouragement on pre- 
 cisely the same grounds as the gas companies of the 
 present day ; that is to say, on the ease with which 
 the various products obtainable from coal are col- 
 lected and the cheap rate at which they can afford 
 to sell them, but more particularly the article of 
 gas. They considered the flame which pit-coal 
 yields when it is consumed in the ordinary way is 
 turned to very little advantage, being frequently 
 confined to one place and there of much less use 
 than a red heat would be. They noticed also that 
 it was often obscured and smothered by the quantity 
 of incombustible matter which was thrown off 
 with it, and from which a considerable portion of 
 the coal-gas generated is not applied to any useful 
 purpose. 
 
COMBUSTION OF COAL. 
 
 63 
 
 If we direct our attention to the process of the 
 combustion of coal, when burnt in a common grate, 
 we shall very frequently observe streams of flame 
 burst out of the clouds of smoke which are evolved ; 
 these suddenly disappear and fresh ones supply their 
 place as the quantity of inflammable gas preponde- 
 rates over the non-inflammable gases and aqueous pro- 
 ducts. Should we apply a lighted taper to the small 
 jets issuing from that part of the coal from whence 
 the tar oozes and which it points out as bituminous 
 they will ignite and burn with a brilliant flame. In 
 short, it is quite evident that a considerable quantity 
 of gaseous matter, which is capable of generating 
 both light and heat in open fire-places, must escape 
 up the chimney, leaving but a portion of it to be 
 exhibited as flame. 
 
 If we compare the theory of the production of 
 gas-light with the theory of the production of arti- 
 ficial light by means of candles or of lamps, we shall 
 instantly perceive that the principles are similar; 
 for, in candles or lamps, the wick bears a like situa- 
 tion to that of coal when submitted to distillation 
 in a close vessel. The wick of a candle serves to 
 convey the melted tallow by capillary attraction to 
 where it is to be consumed. It is there decomposed 
 and forms carburetted hydrogen gas ; as this is made 
 use of a fresh supply is constantly kept up, which 
 maintains the flame. By a parity of reasoning, it 
 appears that the burning of oil in a lamp depends 
 
64 
 
 THEORY OF THE 
 
 on similar circumstances. The oil of a lamp is 
 drawn up through the wick, and is formed as coal 
 in a retort into that carburetted hydrogen gas 
 from whence proceeds illumination. After con- 
 sidering these matters it may be asked, though 
 now rather late in the day to make such inquiry, 
 What do gas-light companies profess to accom- 
 plish? To such a question the following is an 
 answer. They profess to generate such quantities 
 of gas as may he wanted for supplying that district 
 or place where their works may be situated with a 
 very superior description of artificial light, by means 
 of a sufficient number of retorts, gas-holders, and 
 other necessary apparatus ; and that this gas is pre- 
 cisely the same sort of material as the flame of a 
 candle or lamp, being, however, more safe than 
 either, of higher illuminating power, capable of 
 forming various devices, and, quantum of light for 
 quantum of light, vastly cheaper. The difference 
 between obtaining light from candles and lamps 
 and from coal-gas is this : when coal-gas is used as 
 a substitute for light afforded by the combustion of 
 tallow or oil in the raw state, the distillatory process 
 for lighting streets and districts, nay whole towns 
 and large cities, is carried on in one place, perhaps 
 far from where the light may be wanted ; whilst, 
 by the action of candles or lamps, the process is 
 performed wherever such candle or lamp may be 
 used, namely, at their respective wicks. We may. 
 
COMBUSTION OF COAL. 
 
 65 
 
 perhaps elucidate this matter still more by observ- 
 ing, that the production of artificial light for illu- 
 minating purposes is brought about by one way or 
 another by the agency of heat. When gas for 
 illumination is to be obtained from coal, the retort, 
 or distillatory vessel, is first heated by the fire over 
 which it is placed till it becomes sufficiently hot for 
 decomposing the coal. When it is so, the coal is 
 introduced into it, and the atmospheric air being 
 excluded, the heat of the retort being kept up acts 
 upon the coal within it, and thereby the gaseous 
 and vaporous products are evolved, which pass off 
 through the different parts of the apparatus, the 
 useless and noxious constituents thereof being ar- 
 rested in their passage through them, and the car- 
 buretted hydrogen gas alone transmitted to the gas- 
 holder in a sufficiently pure state for the purposes of 
 illumination. From the gas-holder this is forced 
 by pressure through pipes at any time and to any 
 distance required for the use of the consumer. 
 
 In concluding this chapter, we are to observe that 
 the system of generating light from pit coal is sup- 
 ported not only by reason, but now by long ex- 
 perience also ; that the discovery ranks highly 
 amongst those which have within the last half 
 century been made in chemistry, and it appears cal- 
 culated to produce still more favourable results than 
 any we have yet witnessed from its use ; for from 
 its application we have learnt that those uses to 
 
 F 
 
66 
 
 THEORY OF THE 
 
 which we have been accustomed to put coals, tallow, 
 and oil, are not all to which it is applicable. The 
 production of artificial light from coal, as it relates 
 to our comforts, is of no small importance, and the 
 source afforded for obtaining it by means of gas is in 
 this country abundant. By the introduction of the 
 gas-lights the process of analyzing coals, which was 
 formerly confined to the laboratory of the chemist, 
 is now in the large way performed with the greatest 
 simplicity at any gas-light establishment. Indeed, 
 so much has the scheme extended itself, that there 
 are now in London, Westminster, Southwark, and 
 environs alone (as recently stated by Dr. Ure , in 
 his Dictionary of Arts , Manufactures , and Mines ) 
 eighteen public gas-works belonging to twelve dif- 
 ferent gas companies, with a capital employed in 
 works, pipes, tanks, gas-holders, apparatus, &c. 
 amounting to 2,800,000/., from whence is derived a 
 yearly revenue of 450,000/. It is further stated, 
 
 180.000 tons of coal are used annually for making 
 gas, and that such coal produces 1,460,000,000 cubic 
 feet of gas. The London Companies have about 
 
 40.000 private consumers to supply with gas, who 
 altogether use about 134,300 burners. There are 
 2,650 public or street lamps supplied with gas in the 
 city of London, and 27,750 in the city of West- 
 minster, the borough of Southwark, and the 
 environs. There are 380 lamp-lighters ; and, alto- 
 gether, about 2,500 persons are employed in the 
 
COMBUSTION OF COAL. 
 
 67 
 
 metropolis alone in this branch of manufacture. 
 The aggregate number of gas-holders is 176, several 
 of them telescopic, or double ones, which are capable 
 of storing 5,500,000 cubic feet. 890 tons of coals 
 are said to be used in the retorts on the shortest day 
 (say 24th December) in twenty-four hours, and 
 during the evening and night of that day there are 
 7,120,000 cubic feet of gas used. Between 1822 
 and 1827 the quantity of gas generated in one year 
 nearly doubled itself, and that in five years, and 
 between 1827 and 1837 it doubled itself again, and 
 the demand for it is still very rapidly increasing. 
 
68 
 
 STATEMENT OF DISCOVERIES 
 
 CHAPTER IV. 
 
 An Historical Statement of the successive Discoveries which have 
 been made in Decomposing Coal, and on the Rise and Progress 
 of the application of Coal-Gas as a substitute for Wax, Tallow, or 
 Oil, as a means of illumination. 
 
 Before we commence describing tlie different kinds 
 of apparatus and machinery used for the purpose of 
 generating coal gas, it is presumed some readers will 
 feel an interest in knowing when and in what way 
 the first idea of applying coal gas to the purpose of 
 affording light originated ; and also in having de- 
 scribed to them, in as concise a manner as the subject 
 will admit of, the gradations through which it has 
 risen till it reached its present pre-eminence over 
 every artificial light hitherto known, both as relates 
 to the quantity and quality of the light thereby 
 afforded and the cheap rate at which it can be sup- 
 plied. From this abridged history there will be 
 seen the necessity of a considerable lapse of time to 
 mature and introduce new systems, the difficulty 
 with which improvements in science are so esta- 
 blished as to become universally adopted, and the 
 slowness with which mankind follow after known 
 principles that forward something which may be 
 considered as an innovation upon former and long 
 established habits. 
 
IN DECOMPOSING COAL. 
 
 69 
 
 That a permanently elastic and inflammable aeri- 
 form fluid is evolved from pit-coal appears to have 
 been first experimentally ascertained by the Rev. Dr. 
 John Clayton, Dean of Kildare. With the exact 
 date of the discovery we are not acquainted : but, as 
 the communication made to the Earl of Egmont, 
 F.R.S., in 1739, by Dr. Robert Clayton, Bishop of 
 Cork and Orrery, purported to be an extract of a 
 letter from the discoverer to the Hon. Robert 
 Boyle, who died in 1691, the discovery must have 
 been made prior to that event, though not published 
 in the Philosophical Transactions of the Royal 
 Society till the year 1739. 
 
 The coal-evolved gases, however, were known to 
 miners even before the formation of the Royal 
 Society, from the direful effects they produced, and 
 were by them termed choke-damp (carbonic acid gas) 
 and fire-damp (carburetted hydrogen gas). The 
 earliest account which the Royal Society has pub- 
 lished relative to either is in their Transactions for 
 the year 1667 ; it is entitled, “ A Description of a 
 Well and Earth in Lancashire taking fire by a Candle 
 approached to it ; imparted by Thomas Shirley, Esq., 
 an eye witness,” and is as follows : — 
 
 “ About the latter end of February, 1659, return- 
 ing from a journey to my house in Wigan, I was 
 entertained with the relation of an odd spring 
 situated in one Mr. Hawkley’s ground (if I mistake 
 not), about a mile from the town, in that road which 
 
70 
 
 STATEMENT OF DISCOVERIES 
 
 leads to Warrington and Chester. The people of 
 this town did affirm that the water of this spring 
 did burn like oyle ; into which error they suffered 
 themselves to fall for want of due examination of 
 the following particulars ; for, when I came to the 
 said spring (being five or six in company together) 
 and applied a lighted candle to the surface of the 
 water, ’tis true there was suddenly a large flame 
 produced, which burnt vigorously ; at the sight of 
 which they began to laugh at me for denying what 
 they had positively asserted. But I, who did not 
 think myself confuted by laughter grounded upon 
 inadvertency, began to examine what I saw ; and 
 observing that this spring had its eruption at the 
 foot of a tree growing on the top of a neighbouring 
 bank, the water of which filled a ditch that was 
 there, and covered the burning place lately men- 
 tioned ; I then applied a lighted candle to divers 
 parts of the water contained in the said ditch, and 
 found, as I expected, that upon a touch of the candle 
 and the water the flame was extinct. Again, having 
 taken up a dish full of water at the flaming place 
 and held the lighted candle to it, it went out ; yet I 
 observed that the water at the burning place did 
 boyle and heave like water in a pot upon the fire, 
 though my hand put into it perceived it not so 
 much as warm. This boyling I conceived to pro- 
 ceed from the eruption of some bituminous or sul- 
 phureous fumes, considering this place was not above 
 
IN DECOMPOSING COAL. 
 
 71 
 
 thirty or forty yards distant from the mouth of a 
 coal-pit there. And, indeed, Wigan, Ashton, and 
 the whole country, for many miles’ compass, is 
 underlaid with coal. Then applying my hand to 
 the surface of the burning place of the water, I 
 found a strong breath, as it were a wind, to bear 
 against my hand. Then I caused a dam to be made, 
 and thereby hindering the recourse of fresh water to 
 the burning place ; I caused that which was already 
 there to be drained away ; and then applying the 
 burning candle to the surface of the dry earth at the 
 same point where the water burned before, the 
 fumes took fire and burned very bright and vigorous. 
 The cone of the flame ascended a foot and a half 
 from the superficies of the earth. The basis of it 
 was of the compass of a man’s hat about the brims. 
 I then caused a bucket full of water to be poured on 
 the fire, by which it was presently quenched, as well 
 as my companions’ laughter was stopped, who began 
 to think the water did not burn. I did not perceive 
 the flame to he discoloured like that of sulphureous 
 bodies, nor to have any manifest scent with it. The 
 fumes, when they broke out of the earth and prest 
 against my hand, were not, to my remembrance, at 
 all hot.” 
 
 The above extract has been made partly under an 
 idea that it may not be uninteresting to the general 
 reader, as being one of the most early records of the 
 action of what was, no doubt, carburetted hydrogen 
 
72 
 
 STATEMENT OF DISCOVERIES 
 
 gas generated from natural causes ; and it will be 
 seen in its proper place, when the experiments of Dr. 
 Clayton are given (which it is proposed to furnish 
 in the Doctors own words), that in all probability 
 his attention was directed to the matter by ob- 
 serving the very same spring which Mr. Shirley 
 speaks of. 
 
 Dr. Priestley states, in his Observations and Ex- 
 periments on Air, published in 1790, that “Mr. 
 Boyle was the first who discovered that what we 
 now call fixed air and inflammable air are really 
 elastic fluids, capable of being exhibited in a state 
 unmixed with common air.” There is no record, 
 however, of either having been obtained from coal 
 by distillation prior to the time of Dr. Stephen 
 Hales, the ingenious author of a work on Vegetable 
 Statics, published in 1726 ; yet, although there be 
 no positive record, Dr. Clayton’s letter, without 
 date, to Mr. Boyle, as already referred to, shows it 
 must have been written in Mr. Boyle’s life-time, 
 consequently antecedent to Dr. Hales’s experiments. 
 Dr. Hales states, that “ from the distillation of 158 
 grains of Newcastle coal he obtained 180 cubic 
 inches of air, which weighed 51 grains, being nearly 
 one-third of the whole.” His experiments were 
 made, however, for the purpose of ascertaining the 
 elasticity of air produced by the distillation of coal, 
 and consequently its inflammable and other pro- 
 perties were not inquired into. 
 
IN DECOMPOSING COAL. 
 
 73 
 
 Before we notice Dr. Clayton’s experiments, we 
 shall mention some circumstances relative to the 
 properties of coal gas as given in the Philosophical 
 Transactions for 1733. The paper is headed “ An 
 account of the damp air in a coal-pit of Sir James 
 Lowther, sunk within twenty yards of the sea,” 
 dated, “ Whitehaven, August 1st, 1733.” 
 
 “ Sir James Lowther having occasion to sink a 
 pit near the full sea-mark, for the draining of one of 
 his principal collieries near Whitehaven, in the 
 county of Cumberland, which was known would be 
 near eighty fathom in depth to the best seam of 
 coals, which is three yards thick. The work was 
 carried on day and night very successfully, through 
 several beds of hard stone, coal, and other minerals, 
 till the pit was sunk down forty-two fathom from 
 the surface, where they came to a bed of black stone, 
 about six inches thick, very full of joints and open 
 cliffs, which divided the stones into pieces of about 
 six inches square, the sides whereof were all spangled 
 with sulphur, and in the colour of gold. Under 
 this black stone lies a bed of coal, two feet thick. 
 When the workmen first pricked the black stone bed, 
 which was on the rise side of the pit, it afforded very 
 little water, contrary to what was expected ; but 
 instead thereof, a vast quantity of damp, corrupted 
 air, which bubbled through a quantity of water then 
 spread over that part of the pit, and made a great 
 hissing noise ; at which the workmen, being some- 
 
74 
 
 STATEMENT OF DISCOVERIES 
 
 what surprised, held a lighted candle towards it, and 
 it immediately took fire upon the surface of the 
 water and burned very fiercely, the flame being 
 about half a yard in diameter and near two yards 
 high, which frightened the workmen, so that they 
 took the rope and went up the pit, having first ex- 
 tinguished the flame by beating it out with their 
 hats. The steward of the works being made 
 acquainted with it, went down the pit with one of 
 the men, and holding a candle to the same place, it 
 immediately took fire again as before, and burnt 
 about the same bigness, the flame being blue at the 
 bottom and more white towards the top. They 
 suffered it to burn for nearly half an hour ; and no 
 water being drawn in the time, it rose and covered 
 the bottom of the pit near a yard deep, but that did 
 very little abate the violence or bulk of the flame, it 
 still continuing to burn upon the surface of the 
 water. They then extinguished the flame as before, 
 and opened the black stone bed near two feet broad, 
 that a greater quantity of air might issue forth, and 
 then fired it again ; it burned a full yard in diameter 
 and about three yards high, which soon heated the 
 pit to so great a degree that the men were in danger 
 of being stifled, and so were as expeditious as pos- 
 sible in extinguishing the flame, which was then too 
 strong to be beaten out with their hats ; but with 
 the assistance of a spout of water of four inches in 
 diameter, let down from a cistern above, they 
 
IN DECOMPOSING COAL. 
 
 75 
 
 happily got it extinguished without further harm. 
 After this no candles were suffered to come near it 
 till the pit was sunk down quite through the bed of 
 black stone, and the two foot coal underneath it ; and 
 all that part of the pit, for four or five feet high, 
 was framed quite round, and very close jointed, so as 
 to repel the damp air, which, nevertheless, it was 
 apprehended, would break out in some other ad- 
 joining part unless it was carried off as soon as pro- 
 duced out of the cliffs of the stone ; for which end a 
 small hollow was left behind the framing, in order 
 to collect all the damp air on one side of the pit, 
 where a tube of about two inches square was closely 
 fixed, one end of it into the hollow behind the 
 framing and the other carried up into the open air, 
 four yards above the top of the pit ; and through 
 this tube the said damp air has ever since discharged 
 itself without being sensibly diminished in its 
 strength or lessened in its quantity since it was first 
 opened, which is now two years and nine months 
 ago. It is just the same in summer as in winter, 
 and will fill a large bladder in a few seconds by 
 placing a funnel at the top of the tube, with the 
 small end of it put into the neck of the bladder, and 
 kept close with one’s hand. 
 
 “ The said air being put into a bladder, as is 
 above described, and tied close, may he carried away 
 and kept some days, and being afterwards pressed 
 gently through a small pipe into the flame of a 
 
76 
 
 STATEMENT OF DISCOVERIES 
 
 candle, will take fire and burn at the end of the 
 pipe as long as the bladder is gently pressed to feed 
 the flame, and when taken from the candle after it 
 is so lighted, it will continue burning till there is 
 no more air left in the bladder to supply the flame. 
 This succeeded in May last, before the Royal So- 
 ciety, after the air had been confined in the bladder 
 for near a month. 
 
 “ The air, when it comes out at the top of the 
 tube, is as cold as frosty air. 
 
 “ It is to be observed, that this sort of vapour or 
 damp air will not take fire except by flame ; sparks 
 do not affect it, and for that reason it is frequent to 
 use flint and steel in places affected with this sort 
 of damp, which will give a glimmering light that 
 is a great help to the workmen in difficult cases. 
 
 “ After the damp air was carried up in a tube, in 
 the manner above described, the pit was no more 
 annoyed with it, but was sunk very successfully 
 through several beds of stone and coal, without any 
 other accident or interruption, till it came to the 
 main seam of coals, which is three yards thick and 
 seventy-nine fathom deep from the surface ; and the 
 said pit being oval, viz., ten feet one way and eight 
 the other, it serves both for draining the water by 
 a fire-engine and also for raising the coals.” 
 
 Notwithstanding the preceding communication 
 to the Royal Society, and the exhibition of the gas 
 brought from Whitehaven before its members, it 
 
IN DECOMPOSING COAL. 
 
 77 
 
 does not appear that the scientific men of that day 
 made any effort whatever to ascertain how a similar 
 gas might be produced, or offered any suggestion as 
 to the gas itself being applied to any useful purpose. 
 The narrator describes with great precision some of 
 the properties of coal-gas, such, for instance, as its 
 elasticity and inflammability after being kept for 
 some time, and that it would not ignite by means of 
 sparks nor otherwise than by being brought into 
 contact with flame ; properties which it is well known 
 are characteristic of coal-gas. 
 
 Having spoken of Mr. Shirley’s observations, and 
 given the preceding narrative, we shall now give 
 Dr. Clayton’s account of what led him to think of 
 distilling pit-coal and the results which arose out 
 of that attempt ; and as no language of ours could 
 furnish a more clear, distinct, and intelligible ac- 
 count than what the Doctor gave himself, (see 
 Philosophical Transactions of the Royal Society for 
 the year 1739, Vol. XLI. ), we cannot do better 
 than transcribe the same for the perusal of our 
 readers : — 
 
 “ Having seen a ditch within two miles of Wigan, 
 in Lancashire, wherein the water would seemingly 
 burn like brandy, the flame of which was so fierce 
 that several strangers have boiled eggs over it, the 
 people thereabouts, indeed, affirmed that about 
 thirty years ago, it would have boiled a piece of beef ; 
 and that whereas much rain formerly made it burn 
 fiercer, now after rain it would scarcely burn at all. 
 
78 
 
 STATEMENT OF DISCOVERIES 
 
 It was after a long continued season of rain, that I 
 came to see the place, and make some experiments, 
 and found accordingly that a lighted paper, though 
 it were waved all over the ditch, the water would 
 not take fire. I then hired a person to make a dam 
 in the ditch and fling out the water, in order to try 
 whether the steam which arose out of the ditch 
 would then take fire, hut found it would not. I 
 still, however, pursued my experiment, and made 
 him dig deeper ; and when he had dug about the 
 depth of half a yard, we found a shelly coal, and the 
 candle being then put down into the hole, the air 
 catched fire and continued burning. 
 
 “ I got some coal, and distilled it in a retort in an 
 open fire. At first there came over only phlegm, 
 afterwards a black oil , and then likewise a spirit 
 arose, which I could no ways condense ; but it forced 
 my lute or broke my glasses. Once, when it had 
 forced my lute, coming close thereto in order to try 
 to repair it, I observed that the spirit which issued 
 out caught fire at the flame of the candle, and con- 
 tinued burning with violence as it issued out in a 
 stream, which I blew out and lighted again, alter- 
 nately, for several times. I then had a mind to try 
 if I could save any of this spirit ; in order to which, 
 I took a turbinated receiver, and putting a candle to 
 the pipe of the receiver, whilst the spirit arose, I 
 observed that it catched flame, and continued burn- 
 ing at the end of the pipe, though you could not 
 discern what fed the flame. I then blew it out 
 
IN DECOMPOSING COAL. 
 
 79 
 
 and lighted it again several times ; after which I 
 fixed a bladder, squeezed and void of air, to the pipe 
 of the receiver. The oil and phlegm descended into 
 the receiver, but the spirit, still ascending, blew up 
 the bladder. I then filled a good many bladders 
 therewith, and might have filled an inconceivable 
 number more, for the spirit continued to rise for 
 several hours, and filled the bladders almost as fast 
 as a man could have blown them with his mouth, 
 and yet the quantity of coals distilled was inconsi- 
 derable. 
 
 “ I kept this spirit in the bladders a considerable 
 time, and endeavoured several ways to condense it, 
 but in vain; and when I had a mind to divert 
 strangers or friends, I have frequently taken one of 
 these bladders and pricked a hole therein with a pin, 
 and compressing gently the bladder near the flame 
 of a candle till it once took fire, it would then con- 
 tinue flaming till all the spirit was compressed out 
 of the bladder ; which was the more surprising, be- 
 cause no one could discern any difference between 
 these bladders and those which are filled with com- 
 mon air. 
 
 “ But then, I found that this spirit must be kept 
 in good thick bladders, as in those of an ox, or the 
 like ; for, if I filled calves’ bladders therewith, it 
 would lose its inflammability in twenty-four hours, 
 though the bladders became not relaxed at all.” 
 
 Clear and intelligible as is the account which Dr. 
 
80 
 
 STATEMENT OF DISCOVERIES 
 
 Clayton gives of his discovery — a discovery in which 
 some of the most striking and valuable properties of 
 coal-gas must have arrested his attention — still it 
 would appear he himself had no idea as to how it 
 might be usefully employed. It would appear also 
 that the discovery did not, at the time of his pro- 
 mulgating it, attract any particular notice. 
 
 Dr. Richard Watson, (afterwards Bishop of Llan- 
 daff,) in the year 1767, published the result of his 
 researches on the subject of obtaining gas from coal, 
 in the second volume of his Chemical Essays, from 
 .which it would appear he examined the qualities of 
 the gaseous and other products, generated whilst 
 distilling pit-coal ; and observed, that the carbu- 
 retted hydrogen gas would not only inflame as pro- 
 duced, when allowed to issue from the distillatory 
 vessel, but that its inflammable property was re- 
 tained after passing it through water and allowing 
 it to ascend by means of curved tubes. The other 
 products obtained during the process were an am- 
 moniacal liquor, a thick oil resembling tar and 
 coke. 
 
 On taking a review of what has been already said 
 relative to the observations which had been made 
 upon gas naturally produced, and the experiments 
 which had been instituted for obtaining gas by dis- 
 tillation from pit-coal, we shall find that about a 
 century elapsed from the time of Mr. Shirley no- 
 ticing the burning ditch near Wigan, and that of 
 
IN DECOMPOSING COAL. 
 
 81 
 
 Dr. Watson making his experiments without any 
 useful results being produced. Another quarter of 
 a century passed away before the application of gas 
 obtained from coal and other substances was thought 
 of as a substitute for candles and lamps, for it was 
 not till the year 1792 that Mr. Murdoch, who then 
 resided at Redruth, in Cornwall, commenced a series 
 of experiments upon the quantity and quality of the 
 gases contained in different substances. The fol- 
 lowing account of his discovery is given by Dr. W. 
 Henry, of Manchester, in Thomson’s System of 
 Chemistry , vol. i., p. 52. 
 
 “ In the course of his experiments, he remarked 
 that the gas obtained by distillation from coal, peat, 
 wood, and other inflammable substances, burnt with 
 great brilliancy upon being set fire to ; and it oc- 
 curred to him , that by confining and conducting it 
 through tubes, it might be employed as an econo- 
 mical substitute for lamps and candles. The distil- 
 lation was performed in iron retorts, and the gas 
 conducted through tinned iron and copper tubes, to 
 the distance of seventy feet. At this termination, 
 as well as at intermediate points, the gas was set 
 fire to as it passed through apertures of different 
 diameters and forms, purposely varied with a view 
 of ascertaining which would answer best. In 
 some, the gas issued through a number of small 
 holes like the head of a watering pan, in others it 
 was thrown out in thin long sheets; and again, in 
 
 G 
 
82 
 
 STATEMENT OF DISCOVERIES 
 
 others in circular ones, upon the principle of Ar- 
 gand’s lamp. Bags of leather and of varnished silk, 
 bladders, and vessels of tinned iron, were filled with 
 the gas, which was set fire to and carried about 
 from room to room with a view of ascertaining how 
 far it could be made to answer the purpose of a 
 moveable or transferable light. Trials were like- 
 wise made of the different quantities and qualities 
 of gas produced by coals of various descriptions, 
 such as the Swansea, Haverfordwest, Newcastle, 
 Shropshire, Staffordshire, and some kinds of Scotch 
 coals. 
 
 “ Mr. Murdoch’s constant occupations prevented 
 his giving further attention to the subject at that 
 time ; but he again availed himself of a moment of 
 leisure to repeat his experiments upon coal and peat 
 at Old Cumnock, in Ayrshire, in 1797 ; and it may 
 be proper to notice, that both these and the former 
 ones were exhibited to numerous spectators, who, if 
 necessary, can attest them. In 1798, he constructed 
 an apparatus at Soho foundry, which was applied, 
 during many successive nights, to the lighting of 
 the building, when the experiments upon different 
 apertures were repeated and extended upon a larger 
 scale. Various methods were also practised of wash- 
 ing and purifying the air to get rid of the smoke 
 and smell. These experiments were continued, with 
 occasional interruptions, until the epoch of the 
 peace in 1802, when the illumination of the Soho 
 
IN DECOMPOSING COAL, 
 
 83 
 
 manufactory afforded an opportunity of making a 
 public display of the new lights ; and they were 
 made to constitute a principal feature in that exhi- 
 bition.” 
 
 Thus far we have followed Dr. Henry ; but, to 
 put the matter in a still clearer point of view as to 
 what induced Mr. Murdoch to think of substituting 
 gas so obtained for candles or lamps, we will take 
 his own account, as given in the Philosophical 
 Transactions for 1808, and in vol. xxi. of Nichol- 
 son’s Journal. He states : — 
 
 “ It is now nearly sixteen years since, in a course 
 of experiments I was making at Redruth, in Corn- 
 wall, upon the quantities and qualities of different 
 kinds of gases, produced by the distillation from 
 different mineral and vegetable substances, I was 
 induced , by some observations I had previously 
 made upon the burning of coal , to try the combus- 
 tible property of the gases produced from it, as 
 well as from peat, wood, and other inflammable sub- 
 stances ; and, being struck with the great quantities 
 of gas which they afforded , as well as with the bril- 
 liancy of the light , and the facility of its production, 
 I instituted several experiments with a view of as- 
 certaining the cost at which it might be obtained, 
 compared with that of equal quantities of light 
 yielded by oils and tallow .” 
 
 He then narrates the progress of his experiments 
 
 g 2 
 
84 
 
 STATEMENT OF DISCOVERIES 
 
 to the same effect as we have already given them, 
 and adds, — 
 
 “ At the time I commenced my experiments I 
 was certainly unacquainted with the circumstance 
 of the gas from coal having been observed by others 
 to be capable of combustion ; but I am since in- 
 formed that the current of gas escaping from Lord 
 Dundonald’s tar-ovens had been frequently fired ; 
 and I find that Dr. Clayton, in a paper in vol. xli. 
 of Transactions of the Royal Society, so long ago as 
 the year 1739, gave an account of some observations 
 and experiments made by him, which clearly mani- 
 fest his knowledge of the inflammable property of 
 the gas, which he denominates the spirit of coals ; 
 but the idea of applying it as an economical substi- 
 tute for oils and tallow does not appear to have oc- 
 curred to this gentleman ; and I believe I may, 
 without presuming too much , claim both the first 
 idea of applying , and the first application of this 
 gas to economical purposes .” 
 
 It has been considered expedient to be rather full 
 in explaining the steps which intervened between 
 the period of Mr. Shirley’s observations and that 
 when a new era began to dawn under the scientific 
 researches of Mr. Murdoch, who, in himself con- 
 necting the two great links of science and practice, 
 achieved what the theorist alone would perhaps 
 have scarcely thought of — at all events, what 
 
IN DECOMPOSING COAL. 
 
 85 
 
 scientific men during a period of one hundred and 
 twenty-five years had not effected. 
 
 Prior to the first edition of this work being pub- 
 lished, a popular author of the day (Mr. Accum) had 
 given the credit of the first application of coal gas as 
 a substitute for candles and lamps to Mr. F. A. 
 Winsor, who exhibited the general nature of gas- 
 light illumination at the Lyceum Theatre, London, 
 in the years 1803 and 1804; hut the apparatus by 
 the means of which he obtained coal gas, and the 
 mode of purification which he adopted, he kept a 
 secret. He showed the manner of conveying the 
 gas through the house, and exhibited various devices 
 for chandeliers and burners. Instead of copper 
 pipe, or, what is far superior, the drawn tin tubing, 
 now almost exclusively used, he proposed long 
 flexible tubes brought from the ceiling or the wall, 
 to the ends of which were attached different descrip- 
 tions of burners. He proved experimentally that 
 the flame of coal gas, when properly managed (by 
 allowing no more gas to pass through the burner 
 than can be entirely consumed), produces no smoke ; 
 and that it is not, as the flame from candles or 
 lamps, subject to emit sparks, and therefore not so 
 dangerous ; nor is it so liable to be put out by 
 sudden gusts of wind or by heavy rain. 
 
 It is expected that no one who is at all acquainted 
 with the rise and progress of this new branch of 
 manufacture would wish to deprive Mr. Winsor of 
 
86 
 
 STATEMENT OF DISCOVERIES 
 
 the credit he very justly claims of being highly 
 instrumental in bringing the utility of gas-lights 
 before the attention of the public ; for it must be 
 admitted that but for his persevering labours, both 
 as a lecturer and a writer, on the subject of gas, the 
 thing might have remained to this day as a philo- 
 sophical plaything, and rendered no real benefit to 
 the public ; it being probable that Mr. Murdoch 
 was too much occupied by other avocations to admit 
 of his devoting so much time to this matter as it 
 required for drawing towards it that public atten- 
 tion which was essentially necessary. It is, there- 
 fore, willingly admitted that Mr. Winsor did much 
 as a promulgator, having to overcome great dif- 
 ficulties whilst lecturing at the Lyceum Theatre, 
 partly from the circumstance of his being a 
 foreigner, which rendered it necessary that he 
 should employ a person to read his lectures to his 
 audience, and partly from the character of his me- 
 chanical assistants, who were generally such as were 
 unable to render him such services in his pursuits 
 as were required. Notwithstanding these un- 
 favourable circumstances, Mr. Winsor persevered in 
 endeavouring to carry out his plans, and removed 
 his exhibition to Pall-mall, where, early in 1807, he 
 lighted up a part of one side of the street with gas, 
 which was the first instance of that kind of light 
 being applied to such a purpose in London. He 
 projected a national light and heat company ; and, 
 
IN DECOMPOSING COAL. 
 
 87 
 
 having obtained a patent, he published some 
 pamphlets to recommend it. It is not our business 
 to enter into long inquiries as to how the statements 
 he made were fallacious ; but we may, as they ap- 
 pear curious, mention some of them. He informed 
 the public that a deposit of five pounds in the 
 National Light and Heat Company would secure to 
 the person subscribing it a handsome annual income. 
 We were not to have any more smoke in London, 
 or throughout the country, when once his plans 
 were carried out ; consequently, as he expressed 
 it, that unchristian-like employment of chimney- 
 sweeper would be at an end. But what was the 
 most attractive to many arose out of the immense 
 profits which were certain of being divided by the 
 shareholders ; for, if a single five pounds deposit 
 would secure to the depositor a handsome annual 
 income (we shall be more moderate in our calcula- 
 tions than was Mr. Winsor, and reckon it at only 
 20/. per annum), it might reasonably be expected 
 that many would be ready to make a venture, and 
 many did do so, but without ever realizing the ad- 
 vantages the patentee had held out, whose patent, 
 amongst other very desirable objects, was to effect 
 the paying off of the national debt, and afterwards 
 (besides enriching the proprietors of the company 
 he was desirous of seeing formed) the revenue was 
 to be increased by a tax upon the products obtained 
 from coal in the gas-manufactories more than com- 
 
88 
 
 STATEMENT OF DISCOVERIES 
 
 mensurate to that arising from the tax upon candles. 
 Plausible, however, as Mr. Winsor’s statements 
 were, none of the advantages he held out have as 
 yet been realized, nor is it very probable they ever 
 will be ; and, although nearly fifty thousand pounds 
 were subscribed in five pound shares, for establish- 
 ing his New Light and Heat Company, he was not 
 enriched, for he expended the whole in endeavouring 
 to carry out his projects. Sanguine in his expecta- 
 tions, indefatigable in his exertions, and zealous in 
 the cause, he directed all the talents and energies he 
 possessed towards one grand object, and thus 
 achieved much for the public good ; but, with all 
 his ardour, his skill, and his exertions, he, like 
 many others, achieved but little towards promoting 
 his own comforts or the comforts of his family. 
 The public, however, have been benefited to no 
 small extent by what he did ; and though we cannot 
 name him as the original discoverer of this new 
 mode of supplying light, we think his name ought 
 to be had in remembrance for having done much to 
 hasten its adoption. It is not necessary to say more 
 with respect to Mr. Winsor than that he kept his 
 position with the company which he had mainly 
 been the means of forming for some years, but 
 without forwarding his scheme very considerably. 
 
 Attention having been awakened, we find that in 
 1804, whilst Mr. Winsor was lecturing in London, 
 Mr. (afterwards Dr.) William Henry, in a course 
 
IN DECOMPOSING COAL. 
 
 89 
 
 of lectures on chemistry which he delivered in Man- 
 chester, showed the method of producing gas from 
 coal, and illustrated how readily and advantageously 
 it might be used as a means for affording light ; and 
 it is probable his lectures were the means of intro- 
 ducing gas-lighting into some large concerns in 
 Manchester and its immediate neighbourhood. He 
 was one of the first amongst the chemists of emi- 
 nence who analyzed the composition and investi- 
 gated the properties of coal-gas with scrupulous 
 accuracy ; and that his experiments, which were 
 numerous, and extended not only to gas procured 
 from coal, but also from wood, peat, oil, wax, &c. 
 (the results of which were published in 1805, and 
 various other papers written by him appeared after- 
 wards in the Philosophical Transactions, and also in 
 several periodicals) tended to make the subject of 
 gas-lighting a more frequent object of discussion 
 amongst scientific men, there is little doubt. 
 
 In the year 1805, Mr. Northern, of Leeds, called 
 the attention of the public to applying coal gas for 
 the purpose of producing light instead of candles, 
 &c. An account of what he did is extracted from 
 the Monthly Magazine for April, 1805 : — 
 
 “ I distilled,” he says, “ in a retort fifty-six ounces 
 of pit-coal in a red heat, which gave six ounces of a 
 liquid matter covered with oil, more or less fluid 
 as the heat was increased or diminished. About 
 twenty-six ounces of cinder remained in the retort ; 
 
90 
 
 STATEMENT OF DISCOVERIES 
 
 tlie rest came over in the form of air, as it was col- 
 lected in the pneumatic apparatus. I mixed part of 
 it with atmospherical air, and fired it with the 
 electric spark with a tolerable explosion, which 
 proves it to be hydrogen. Whether any other 
 gases were mixed with it I did not then determine. 
 In the receiver I found a fluid of an acid taste, with 
 a great quantity of oil, and at the bottom a substance 
 resembling tar. 
 
 “ The apparatus I make use of for producing 
 light is a refiner’s crucible, the top of which, after 
 filling with coal, I close with a metal cover, luted 
 with clay or other luting, so as to prevent the 
 escape of the gas ; a metal pipe is soldered into the 
 cover, bent so as to come under the shelf in the 
 pneumatic trough, over which I place a jar with a 
 stop-cock and a small tube, the jar being previously 
 filled with water ; the crucible I place on the com- 
 mon or other fire, as is most convenient ; and as the 
 heat increases in it, the gas is forced rapidly through 
 the water into the jar, and regularly displaces it. I 
 then open the cock and put fire to the gas, which 
 makes its escape through the small tube, and imme- 
 diately a most beautiful flame ensues, perfectly free 
 from smoke or smell of any kind. A larger light, 
 but not so vivid or clear, will be produced without 
 passing the gas through water, hut attended with a 
 smoke somewhat greater than that of a lamp charged 
 with common oil. 
 
IN DECOMPOSING COAL. 
 
 91 
 
 “ I have great hopes that some active mechanic 
 or chemist will, in the end, hit on a plan to produce 
 light for large factories and other purposes at a 
 much less expense, by the above or similar means, 
 than is at present produced from oil.” 
 
 As a preliminary step towards the hopes of Mr. 
 Northern being realized, Mr. Samuel Clegg, who 
 had at the works of Boulton and Watt, at Soho, 
 directed his attention to the construction of gas- 
 light apparatus, communicated to the Society of 
 Arts an account of his method of lighting up manu- 
 factories with gas, for which he received the silver 
 medal; which, although hut a small token of the 
 general estimation of this new branch of manufac- 
 ture, if we consider the rapid advances it has since 
 made, yet might at that time have been thought 
 sufficient for the information afforded. As to Mr. 
 Clegg the gas-light manufacturer is indebted for 
 various improvements in apparatus and machinery, 
 we shall give the account of his inventions between 
 1805 and 1817, given by himself in a small 
 pamphlet published several years ago. He says — 
 
 “ My attention was first directed to the prepara- 
 tion of gas for the purposes of illumination in the 
 year 1804. In 1805 I erected a gas apparatus at 
 the cotton-mill of Henry Lodge, Esq., near Halifax, 
 which was the first in the kingdom. In 1806 I 
 lighted his dwelling-house, where I first attempted 
 to purify the gas by lime introduced into the tank 
 
92 
 
 STATEMENT OF DISCOVERIES 
 
 in which the gasometer floated. In 1807 I lighted 
 the manufactory of Messrs. T. and S. Knight, of 
 Longsight, near Manchester. In 1809 I erected a 
 gas apparatus in a large manufactory at Coventry, 
 belonging to Mr. Harris, in which I introduced a 
 paddle at the bottom of the tank to agitate the lime. 
 In 1811 I lighted a large manufactory at Dolphin- 
 holme, near Lancaster, by means of an apparatus 
 similar to what I had erected at Coventry. In the 
 same year I erected an apparatus at Stonyhurst 
 College, Lancashire (here I exhibited the portable 
 lamps by condensing the gas in a copper globe), 
 where I introduced a lime-machine, the first ever 
 employed for that purpose* — a machine which has 
 been universally adopted, and which has rendered 
 the introduction of gas practicable in any situation. 
 In that year, also, I lighted a large cotton-mill in 
 Manchester, belonging to Mr. Greenway, where I 
 first introduced the hydraulic pipes for isolating the 
 retorts, a plan now in general use. In 1812, when 
 the extensive cotton-mills belonging to Mr. Samuel 
 Ashton and Brothers, at Hyde, near Stockport, were 
 lighted, I introduced the lime-machine and the 
 hydraulic mains with increased effect. Here the 
 twelve inch cylindrical retorts and improved mouth- 
 pieces were first introduced. Here also I first at- 
 tached to the gasometer the mechanism for regu- 
 lating its specific gravity. In the same year I 
 
 * The wet lime purifier. 
 
IN DECOMPOSING COAL. 
 
 93 
 
 lighted the premises of Mr. Akerman, in the 
 Strand. In 1813 I undertook the direction of the 
 different gas-works belonging to the Chartered Gas- 
 light Company in London and Westminster, and 
 during the four following years lighted a great part 
 of both cities. In the course of that period I in- 
 vented and adopted the rotative retorts, the semi- 
 fluid lime-machine, the rotative and reciprocating 
 gas-meter, the governor or regulator, and an appa- 
 ratus for the decomposition of oil, tar, &c. In 1817 
 I invented the colla psin g gas.-holder. In that year 
 also I erected a gas apparatus at His Majesty’s 
 Mint; and since that time I have lighted several 
 towns, including Bristol, Birmingham, Chester, 
 
 In giving Mr. Clegg’s statement of what he per- 
 formed during the first twelve years after the manu- 
 facture of gas had begun to claim the attention of 
 the public, we admit having passed over what others 
 were doing during the same period ; but we trust 
 we shall not be accused of neglecting others and 
 speaking of Mr. Clegg exclusively. Should we, 
 however, be so, our answer is, the undeniable pre- 
 ponderance of his claims to notice over those of 
 others, arising from his having erected the first gas- 
 works in the kingdom, put up the first purifier, and 
 been the first to introduce the mode of isolating the 
 retorts by means of the hydraulic main, dip and H 
 pipes. Had he done nothing more, his name must 
 
94 
 
 STATEMENT OF DISCOVERIES 
 
 stand high among those of engineers connected with 
 gas companies. 
 
 We must not, however, dwell longer upon Mr. 
 Clegg’s inventions here, but turn for a time towards 
 what others were meanwhile doing. We find that 
 in 1806 Mr. Josiah Pemberton, who had for some 
 time been contriving and constructing gas apparatus, 
 exhibited the gas-lights in a variety of forms and 
 with great effect at the front of his manufactory, in 
 one of the principal streets of Birmingham. His 
 apparatus was simple in construction and arrange- 
 ment, consisting of a cast iron vessel something 
 similar to an iron pot, which was set in brick-work 
 like a common boiler. It had a strong cover of the 
 same material fitted to its top, to which was attached 
 the pipe that conveyed the gas away as it was pro- 
 duced to a square cistern containing water, which 
 cistern was divided by several vertical partitions, 
 which obliged the gas to ascend and descend in its 
 passage through the water, so as to be well con- 
 densed and washed before it reached the gasometer, 
 which was suspended in a large wooden vat and 
 fitted with a counterpoise or weight to take off part 
 of its pressure. He erected gas apparatus in the 
 way of business for Mark Saunders, Esq., an eminent 
 button-manufacturer, for the purpose of lighting his 
 manufactory, and also for soldering the shanks of 
 buttons. It completely effected the objects for 
 
IN DECOMPOSING COAL. 
 
 95 
 
 which it was intended. In the same and the fol- 
 lowing year he erected several others on a similar 
 plan for different individuals in Birmingham and its 
 immediate neighbourhood. In 1808 he constructed 
 and fixed an apparatus applicable to several uses for 
 Mr. Benjamin Cook, a manufacturer of brass tubes, 
 gilt toys, and other articles in which a great deal of 
 ^soldering had to he done. This apparatus answered 
 the purpose for which it was intended so well, that 
 Mr. Cook furnished in Nicholson’s Journal, vol. xxi., 
 p. 291, and vol. xxii., p. 145, an account of it. He 
 did not, however, name the person who had con- 
 trived and erected it for him. We think that “ he 
 who wins the palm should wear it,” and would not, 
 as faithful historians, deprive merit of its reward, 
 although the person referred to, it would appear, 
 was not quite so scrupulous on the point, having in 
 1810 received from the Society of Arts the silver 
 medal for a drawing and description of Mr. Pem- 
 berton’s apparatus. 
 
 In 1808 Mr. Murdoch communicated to the 
 Royal Society an account of his having successfully 
 employed coal gas to lighting up the extensive 
 establishment of Messrs. Phillips and Lee, of Man- 
 chester; for which Count Rumford’s gold medal 
 was presented to him, and his paper was inserted in 
 their Transactions, and thence copied into several 
 periodicals, whence its contents were widely circu- 
 lated. It contained much useful and accurate in- 
 
96 
 
 STATEMENT OF DISCOVERIES 
 
 formation, attracted considerable attention, and led 
 to important consequences ; for it had a tendency to 
 show by facts as well as by calculations, not the 
 imaginary, but the real advantages attendant upon 
 the use of gas. We find what Mr. Murdoch says 
 in his subsequent statement very different, as to re- 
 sults, to what Mr. Winsor had but a short time 
 before been telling the public in his secret results of 
 his “ official experiments,” as he termed them ; for 
 he says, “ Official experiments proved one chaldron 
 of coal to contain 23/. 2s. in value, which gives 
 about two hundred and forty-two millions for the 
 yearly consumption of the realm. The estimated 
 savings are only rated at 114,845,294/., all costs of 
 carbonizing, &c. deducted ; and if the Company 
 only realize one-tenth of this reduced sum, each 5/. 
 deposit will secure to the subscribers 570/. per 
 annum. Wonderful as this may appear, the esti- 
 mates and experiments will stand the test of the 
 best calculators and chemists.” Another part of 
 Mr. Winsor’s scheme was to impose a tax upon 
 coals , in order to promote the use of his gas and 
 coke ; this he calculated would produce a revenue of 
 10,751,000/. per annum to the Government. Mr. 
 Murdoch, a practical man, holds forth no such 
 prospects ; on the contrary, in plain and intelligible 
 language, he says — 
 
 “ The whole of the rooms of the cotton-mill of 
 Mr. Lee, at Manchester, which is, I believe, the 
 
IN DECOMPOSING COAL. 
 
 97 
 
 most extensive in the United Kingdom, as well as 
 its counting-houses and store-rooms, and the ad- 
 jacent dwelling-house of Mr. Lee, are lighted with 
 gas from coal. The total quantity of light used 
 during the hours of burning has been ascertained, 
 by a comparison of shadows, to be about equal to the 
 light which 2,500 mould candles of six to the pound 
 would give ; each of the candles with which the 
 comparison was made consuming four-tenths of an 
 ounce (175 grains) of tallow per hour. 
 
 “ The gas-burners are of two kinds ; the one is 
 upon the principle of the argand lamp, and re- 
 sembles it in appearance ; the other is a small curved 
 tube with a conical end, having three circular aper- 
 tures or perforations of about a thirtieth of an inch 
 in diameter, one at the point of the cone and two 
 lateral ones, through which the gas issues, forming 
 three divergent jets of flame, somewhat like a fleur- 
 de-lis. The shape and general appearance of this 
 tube has procured it, among the workmen, the name 
 of the cockspur burner. 
 
 “ The number of burners employed in all the 
 buildings amounts to 271 argand and 653 cockspurs, 
 each of the former giving a light equal to that of 
 four candles of the description above mentioned, and 
 each of the latter a light equal to two and a quarter 
 of the same candles ; making, therefore, the total of 
 the gas-light a little more than equal to that of 
 2,500 candles, six to the pound. When thus regu- 
 
98 
 
 STATEMENT OF DISCOVERIES 
 
 lated, the whole of the above burners require an 
 hourly supply of 1,250 cubic feet of the gas pro- 
 duced from cannel-coal; the superior quality and 
 quantity of the gas produced from that material 
 having given it a decided preference in this situa- 
 tion over every other coal, notwithstanding its 
 higher price. 
 
 “ The time during which the gas-light is used 
 may, upon an average of the whole year, be stated at 
 least at two hours per day of twenty-four hours. In 
 some mills, where there is over-work, it will be 
 three hours ; and in the few where night-work is 
 still continued, nearly twelve hours. But taking 
 two hours per day as the common average through- 
 out the year, the consumption in Messrs. Phillips 
 and Lee’s mill will be 1,250 x 2 = 2,500 cubic 
 feet of gas per day ; to produce which seven hundred- 
 weight of cannel-coal is required in the retort. The 
 price of the best Wigan cannel-coal (the sort used) 
 is Is. 1 \d. per hundredweight (1/. 2s. 6 d. per ton) 
 delivered at the mill, or say about 8s. for the seven 
 hundredweight. Multiplying by the number of 
 working-days in the year (313), the annual con- 
 sumption of coal will be 110 tons, and its cost 125/. 
 
 “ About one-third of the above quantity, or say 
 forty tons of good common coal, value 10s. per ton, 
 is required for fuel to heat the retorts, the annual 
 amount of which is 20/. 
 
 “The 110 tons of cannel-coal, when distilled. 
 
IN DECOMPOSING COAL. 
 
 99 
 
 produced about seventy tons of good coke, which is 
 sold upon the spot at Is. 4 d. per cwt., and will 
 therefore amount annually to the sum of 93/. 
 
 “ The quantity of tar produced from each ton of 
 cannel-coal is from eleven to twelve ale gallons, 
 making a total annual produce of about 1,250 ale 
 gallons ; which, not having been yet sold, it cannot 
 yet be determined its value. 
 
 “ The interest of the capital expended in the 
 necessary apparatus and buildings, together with 
 what is considered as an ample allowance for wear 
 and tear, is stated by Mr. Lee at about 550/. per 
 annum, in which some allowance is made for this 
 apparatus being made upon a scale adequate to the 
 supply of a still greater quantity of light than he 
 has occasion to make use of. 
 
 “ Mr. Lee is of opinion that the cost of attend- 
 ance upon candles would be as much, if not more, 
 than upon the gas apparatus ; so that, in forming 
 the comparison, nothing need be stated upon that 
 score on either side. 
 
 “ The economical statement for one year then 
 stands thus : — 
 
100 
 
 STATEMENT OF DISCOVERIES 
 
 £. S. d. 
 
 Cost of 110 tons of cannel-coal - 125 0 0 
 
 Do. of 40 tons of common coal, to 
 
 carbonize 20 00 
 
 145 0 0 
 
 Deduct the value of 70 tons of 
 coke - -- -- -- -- 93 00 
 
 The annual expenditure in coal, 
 after deducting the value of the 
 coke, and without allowing any- 
 thing for the tar, is therefore - 52 0 0 
 
 And the interest of capital sunk, 
 
 and wear and tear of apparatus - 550 0 0 
 
 Making the total expense of the 
 
 gas apparatus per annum about - 600 0 0 
 
 “ That of candles to give the same light would be 
 about 2,000/. : for, each candle consuming at the 
 rate of four-tenths of an ounce of tallow per hour, 
 the 2,500 candles burning, upon an average of the 
 year, two hours per day, would, at Is. per pound, the 
 present price, amount to nearly the sum of money 
 above mentioned. 
 
 “ If the comparison were made upon an average of 
 three hours per day, as in most cases would perhaps 
 be nearer to the truth, and the wear and tear re- 
 maining nearly the same as in the former case, the 
 
IN DECOMPOSING COAL. 
 
 101 
 
 whole cost would not exceed 650/., while that of the 
 tallow would be 3,000/.” 
 
 From 1809 up to 1815 very considerable progress 
 was made in the erection of works for manufacturing 
 gas from coal in London and other places ; but about 
 the middle of that year Mr. John Taylor, then of 
 Stratford, in Essex, obtained a patent for an appa- 
 ratus for the purpose of producing an inflammable 
 air or olefiant gas, fit for yielding light of great 
 brilliancy, and free from any disagreeable smell, 
 from any kind of animal, vegetable, or mineral oil, 
 fat, bitumen, or resin which can be rendered fluid by 
 heat or otherwise. 
 
 Between the years 1815 and 1823 several com- 
 panies were formed in different parts of Great 
 Britain and Ireland, and also in other countries, for 
 the purpose of making gas from oil or from the 
 other materials named by Mr. Taylor in his patent ; 
 and in consequence many such gas-works were built 
 in towns where gas-light had not before been intro- 
 duced, and in several in opposition to existing coal 
 gas establishments. Such as were in favour of oil 
 gas held out to the public many reasons why it 
 should be preferred to gas obtained from coal. 
 
 1st. That the matter from which such gas is ex- 
 tracted does not contain any portion of sulphur ; 
 therefore, that oil gas could be used with greater 
 comfort in the house of the private consumer, and 
 in many shops, particularly those of silversmiths. 
 
102 
 
 STATEMENT OF DISCOVERIES 
 
 cutlers, braziers, &c., in which they asserted, when 
 coal gas was used, the goods were liable to tarnish, 
 rust, &c. Its superior purity was also particularly 
 dwelt upon : the most costly decorations were in no 
 danger from its use; it left no offensive residuum 
 whatever after combustion; was as cleanly as wax 
 candles, but afforded a far more brilliant light. 
 
 2nd. That the lighting of cities and towns with 
 oil gas would give great encouragement to the 
 fisheries ; and that in Ireland it would render incal- 
 culable advantages to the labouring poor (many of 
 whom might be advantageously employed on the coast 
 in the catching of sun-fish, &c.) whilst it would pro- 
 mote the farmers interests by finding him a market 
 for the offal fat, which was stated to be fully as 
 useful as oil in the production of gas. 
 
 3rd. That as about three cubic feet in bulk of oil 
 gas gave as much light as ten feet of coal gas, the 
 expense of erecting the apparatus, &c. in the first 
 instance was considerably diminished ; and the ex- 
 penses of carrying on an oil gas establishment, as far 
 as related to labour and wear and tear, when com- 
 pared with those for coal gas works, were very much 
 reduced. 
 
 If we admit these statements to be correct, we 
 still fall far short of the main point upon which any 
 new branch of manufacture depends for success, viz., 
 that the article manufactured shall be such as the 
 manufacturer can afford to sell at a fair price to the 
 
IN DECOMPOSING COAL. 
 
 103 
 
 public, and such as will at the same time afford him 
 a remunerating profit for the money he may have 
 invested. In the case of oil gas, it so happened that 
 neither of these ends were accomplished in any one 
 instance ; for the parties who used oil gas found it 
 exceedingly expensive, whilst those who had invested 
 their money in works and apparatus for generating 
 and distributing oil gas, after several years’ trial in 
 many cases, and for a sufficiently lengthened period 
 in all to see whether any profits would arise, found 
 invariably that they had not the remotest chance of 
 realizing any dividend worth naming by way of 
 paying interest upon their investments. 
 
 Finding no profits arising from the manufacture 
 of gas from oil, they had recourse to resin as a sub- 
 stitute ; but that produced no better results as to 
 profits than oil had done ; from that the companies 
 resorted, in the first instance, partially to the use of 
 coal, and ultimately all the splendid establishments 
 which had been built in the largest commercial and 
 manufacturing towns of the empire for manufac- 
 turing gas from oil were converted into coal gas 
 manufactories. Amongst the oil gas works more 
 likely, from local circumstances, to have answered 
 better than others, may be named those built in 
 Liverpool, Bristol, and Hull ; but in each of those 
 places the companies, after lengthened and expensive 
 trials, were glad to abandon the oil gas scheme 
 altogether, and to reconstruct their respective works 
 
104 
 
 STATEMENT OF DISCOVERIES 
 
 so as to be able to procure gas from coal. In short, 
 as oil gas, even when oil can be purchased at 20/. 
 per ton, cannot be brought into the market to com- 
 pete with coal gas ; and as very great care is now 
 taken to deprive the latter of all its impurities, coal 
 gas is now, generally speaking, quite as innocuous as 
 gas procured from oil can be. 
 
 In 1819, within the period of which we are now 
 speaking, Mr. David Gordon obtained a patent for 
 making vessels of great strength (fitted with peculiar 
 valves to regulate the emission of the gas), into 
 which it was proposed to compress the gas so as to 
 render it portable. His inventions led to the 
 formation of “ The London Portable Gas Company 
 which for some time supplied various consumers 
 with the portable gas ; but that speculation, like 
 the one upon gas procured from oil, failed, from its 
 not affording any source of profit to the parties who 
 had invested their money in works, machinery, ap- 
 paratus, and the necessary carriages for carrying to 
 their customers vessels filled with gas to supply 
 their demand for that article. 
 
 Whilst the oil gas and portable gas companies 
 were in existence, Professor Daniel, F.R.S., invented 
 an apparatus for converting resin into gas ; but that, 
 like the two others, it would appear, had never any 
 chance of competing with coal gas as a profitable 
 speculation, though adopted by oil gas companies 
 under a hope of realizing a profit. 
 
IN DECOMPOSING COAL. 
 
 105 
 
 As the manufacture of oil gas , of resin gas , and 
 of portable gas has long ceased to be carried on by 
 any gas company from the cause already named, and 
 as it is more than probable such manufacture will 
 not be again attempted, we do not propose to dwell 
 further upon them, nor to load the following pages 
 with descriptions of apparatus which could answer 
 no useful purpose. We have spoken of them as 
 warnings to deter others from running headlong 
 into vast speculations without first endeavouring to 
 establish, on a smaller scale, how far they promise 
 to be profitable. It was remarked in a former 
 edition of this work, that “ in this age of improve- 
 ment, we have almost daily brought before us inven- 
 tions exhibiting much contrivance, which sometimes 
 come forward with an importance appearing to the 
 superficial observer as real, but which, when sub- 
 mitted to cool and sober investigation, leave us 
 nothing to commend but the ingenuity of the 
 inventor : for, whenever we have submitted to our 
 consideration what is new in the practice of any art, 
 we are, amongst other things, to establish not only 
 its usefulness, but its economy also ; and unless the 
 invention be productive of the latter as well as of 
 the former of these requisites, it must be set down, 
 as far as it relates to the public good, of little in- 
 trinsic value, notwithstanding it may exhibit great 
 marks of ingenuity and science.” 
 
 In 1823, when a strenuous effort was being made 
 
106 
 
 STATEMENT OF DISCOVERIES 
 
 to obtain an Act of Parliament for lighting Bristol 
 with oil gas, the author of this work published a 
 second edition thereof, in which was an entire 
 chapter upon gas procured from oil : he did not 
 then attempt to say anything to the disparagement 
 of oil gas as a light, but, from his own practice, he 
 furnished estimates of the expense of erecting a coal 
 gas apparatus for generating gas for lighting 160 
 public and 500 private lights, to lay 7,500 yards of 
 main pipe, &c., the expenses of carrying it on, and 
 the annual receipts ; by which it appeared that upon 
 an outlay of 11,500/. the annual balance of profits 
 would be 1,142/. 12s. 8 d., or very little short of ten 
 per cent, per annum upon the capital invested. He 
 also furnished similar details for an oil gas establish- 
 ment of sufficient magnitude to supply an equal 
 number of lights, and having the same extent of 
 main pipe, the outlay for which amounted to but 
 little more than three-fourths of that for coal gas, 
 viz., 8,000/. ; but when he came to set the annual 
 expenditure (estimating the oil at something under 
 19/. per ton) against the annual receipts, he found 
 that the former exceeded the latter in the sum of 
 124/., so that the proprietors of such a company, 
 instead of receiving any dividend at all upon the 
 money they might have respectively invested, would 
 have been at the year’s end 124/. out of pocket. He 
 also furnished a similar statement to the proprietor 
 of the Monthly Magazine, in which publication it 
 
IN DECOMPOSING COAL. 
 
 107 
 
 appeared, during the time his work was in the press. 
 What he then said upon the matter, subsequent ex- 
 perience has fully borne him out in, as the entire 
 cessation of making gas from oil or from resin bears 
 convincing testimony. 
 
 In the spring of 1823 the author made a series of 
 experiments at the gas-works at Newry (Ireland), 
 for the purpose of ascertaining whether gas could be 
 procured from turf obtained from a bog about two 
 miles distant from that town, which led him to con- 
 clude that, in places where turf w^as plentiful, it 
 might be used advantageously instead of coals for 
 procuring gas for lighting towns, &c. These ex- 
 periments were made for the purpose of ascertaining 
 whether a new source of industry could not be 
 opened in Ireland by applying turf, which is in 
 many parts of that country so abundant, to the pur- 
 pose of making gas for illuminating purposes. 
 
 We have endeavoured to give a faithful account 
 of the labours of those who entered into the field 
 of gas-lighting during the very early stages of its 
 existence, and having traced its progress from its 
 birth up to a period when it was fast approaching 
 towards maturity, we shall conclude our historical 
 sketch ; for, if we were to attempt to speak of all 
 that has been achieved in improvements of gas 
 apparatus, and to enter into statistical details (which, 
 to furnish with any degree of accuracy for Great 
 Britain and Ireland only, would require returns 
 
108 
 
 STATEMENT OF DISCOVERIES. 
 
 stating the outlay, expenditure, receipts, and various 
 other particulars as to quantity of light, &c. fur- 
 nished from every gas establishment in the empire) 
 as to the number and magnitude of the gas works 
 which have been erected throughout this and other 
 countries, within the last seventeen years, we should 
 swell this chapter far beyond the hounds intended 
 or the nature of the work would allow. We have 
 shown many of the difficulties which the first 
 manufacturers of gas for illuminating purposes had 
 to overcome, and some of the prejudices they had to 
 contend with, and in viewing these we can hardly 
 fail of feeling surprise at what has been done in so 
 short a period. 
 
109 
 
 CHAPTER V. 
 
 On the Retorts, and various Modes of setting them. 
 
 The retorts used for the distillation of pit-coal are 
 of different shapes in different establishments, being 
 either circular, semicircular (or D shaped), ellip- 
 tical, kidney formed, or square. It must be under- 
 stood, that when adverting to their shape, a trans- 
 verse vertical section parallel to the mouth-piece is 
 spoken of. There was, however, a patent taken out 
 in 1815 for a retort differing widely from any of 
 the above — it was termed the “ rotary retort ,” but it 
 was never brought into general use. We propose 
 to speak of the different kinds of retorts as above 
 named, but shall be more particular in our observa- 
 tions upon those now generally adopted, and such as 
 seem most likely to answer the purpose of the ma- 
 nufacturer of gas. 
 
 The circular, or cylindrical, retorts have been tried 
 under my own particular observation, under various 
 modes of setting, during a lengthened period, so have 
 been the D shaped and the elliptical, as were also 
 the “ rotary retorts ,” so long as they were used at 
 the Westminster Gas Works. I can, therefore, state 
 such facts relative to each as I noticed myself, which 
 
110 
 
 ON THE RETORTS, 
 
 I expect will enable the gas manufacturer to form a 
 just conception of the comparative value of the cy- 
 lindrical to that of the D shaped, or the elliptical, 
 &c. &c. ; and having done so, I shall leave him to 
 choose that shape which he thinks most likely to 
 answer his purpose. 
 
 The circular, or cylindrical, retorts are from six to 
 seven, or eight feet in length, and generally about 
 twelve inches diameter inside. Those upon which 
 my observations were principally made were only 
 six feet in length, and were first set upon the flue 
 plan and subsequently upon what is now generally 
 called the oven plan. When set on the flue plan, 
 and two heated by one fire, carbonization was car- 
 ried on at about twenty per cent., that is to say, it 
 required twenty tons of coals to keep a sufficient 
 number of retorts so heated as to be capable of car- 
 bonizing 100 tons properly when the retorts were 
 worked at eight hours charges with 160 pounds of 
 coals to one retort for each charge. 
 
 When speaking of four, six, or eight hours 
 charges, it is to be understood that so many hours 
 elapse between the time of the coal being introduced 
 into the retort and the coke being withdrawn from 
 it, during which time the mouth-piece is closed by 
 its lid, consequently the different products evolved 
 must pass off through the connecting, H, and dip- 
 pipes to the hydraulic main, and thence to their 
 different reservoirs ; the base of the coal, or coke. 
 
AND MODES OF SETTING. 
 
 Ill 
 
 being all that should be left in the retort when the 
 lid is removed, preparatory to drawing out the 
 coke. 
 
 The fire-place for heating the retorts I am now 
 speaking of, set two over one fire, on the flue plan, 
 was on that side of the brickwork opposite to their 
 mouths ; and, under these circumstances, a retort 
 cast from iron of the second running, and weighing 
 about ten hundred weight, would last from eight to 
 ten months. 
 
 In tracing the steps which led towards the plans 
 upon which retorts are very generally set, and com- 
 paring the advantages arising to the manufacturer 
 by deviating from the plan of setting them as already 
 described, we naturally suppose that any deviation 
 therefrom would have in view the decreasing the 
 per centage of carbonization, or the expenses at- 
 tendant upon the wear and tear of retorts. In car- 
 rying out our inquiries we shall see how far either 
 has been effected. 
 
 The first step towards the present mode of setting 
 retorts was by heating three with one fire. On such 
 plan several were set at different gas-works ; and so 
 long ago as the year 1817, I had an opportunity of 
 making the most minute and particular observations 
 from the time of their being set till they were en- 
 tirely burnt out. The fire-places were in front of 
 the retorts. By adopting that mode of setting the 
 retorts, it was found in practice that it cost quite as 
 
112 
 
 ON THE RETORTS, 
 
 much to set a specific number on that plan as would 
 set a like number on the flue plan with two over 
 one fire. It was found also, that, instead of carbon- 
 ization being carried on at a lower per centage, it 
 was increased. The retorts I am now speaking of, 
 and upon which my observations were made, did not 
 heat uniformly : when the extreme end of them was 
 almost at a white heat, that part which was within 
 eighteen inches of the mouth-piece remained quite 
 black. The coals were not well carbonized, conse- 
 quently the proportion of gas procured from a ton 
 diminished ; and, to sum up the evils which resulted 
 from that mode of setting retorts, the retorts were 
 burnt out in about two-thirds of the time they had 
 lasted when set on the flue plan, two over one fire. 
 When all these things are considered, we shall not 
 be surprised to learn that the three to one fire plan 
 fell to the ground ; for, from it expenses and incon- 
 veniences were increased, whilst there was a less 
 return of products of all descriptions for meeting 
 either. 
 
 Experiment on a large scale having proved that 
 no desirable end was attained by setting three re- 
 torts to one fire, another mode was almost immedi- 
 ately tried, on which plan 100 retorts were put up 
 at one of the London gas establishments. They 
 were set four to one fire, but it was found impossible 
 to bring them up to a good working heat ; for one 
 part of the retort would have required a heat suffi- 
 
AND MODES OF SETTING THEM. 113 
 
 ciently strong to melt it before the other part had 
 attained to even a dull red heat. A failure in one 
 quarter did not prevent others from attempting to 
 get over the difficulty. A second setting of retorts, 
 in which four were to be heated by one fire, suc- 
 ceeded better than the first; for the retorts heated 
 very regularly, but carbonization was not carried on 
 at so low a per centage as when only two were 
 heated by one fire ; it was considerably increased, 
 and, what was still worse, the retorts were sooner 
 burnt out. The carbonization increased daily in its 
 expenses, till at last it rose as high as fifty per cent. 
 This was principally owing to fewer retorts being 
 worked than the fires necessary to be kept up would 
 have heated, had the retorts placed over each fire 
 that was kept lighted continued in a working con- 
 dition. It very frequently happened, that when 
 seventy or eighty retorts only were at work, as 
 many fires were kept lighted as actually heated 100, 
 from the cause we are about to mention. The 
 action of the fire not being uniformly directed to- 
 wards each retort in the series of four, one of them 
 frequently became burnt through, and was conse- 
 quently ineffective ; whenever such was the case, 
 only three out of the four could be used for making 
 gas ; soon afterwards a second would give way, and 
 then but two remained in use, and so on. Indeed, 
 it was no uncommon occurrence to work but two 
 retorts by means of that fire which was capable of 
 
 I 
 
114 
 
 ON THE RETORTS, 
 
 heating four, from two out of the four being burnt 
 out. This was a matter of necessity ; for, whenever 
 it became necessary to remove defective retorts over 
 one fire in order that they might be replaced by 
 such as were effective, the adjoining fires could not 
 be kept lighted ; for, if they remained so, the brick- 
 setters could not perform their work owing to the 
 heated state of the brick-work ; consequently, when 
 it became necessary to replace a series of four, the 
 use of twelve retorts was lost to the manufacturer 
 till such time as the defective ones over the fire- 
 place undergoing repair were removed and replaced 
 by new ones, and the brick-work all made good 
 preparatory to their being again brought into action. 
 The pulling down of the defective retorts and the 
 replacing of a series of four, so as to be again ready 
 for working, was seldom accomplished in less than 
 a week ; therefore, when the manufacturer was un- 
 able, from the quantity of gas he had to supply, to 
 dispense with the use of so many retorts, he was 
 compelled to work them under every disadvantage. 
 
 When retorts were set four to one fire the top 
 ones invariably failed first, and this led to a suppo- 
 sition that if the top ones were guarded by fire-tiles 
 from the action of the flame, in the same way that 
 the lower retorts were guarded, they would pro- 
 bably remain for a longer time effective. Retorts 
 were accordingly so set, and whilst the fire-places 
 were continued at the side of the retort bed oppo- 
 
AND MODES OF SETTING THEM. 
 
 115 
 
 site to that for charging and drawing the retorts, 
 they did last considerably longer ; but they were by 
 no means so effective as on the former plan. They 
 collapsed and fell out of all shape, and in consequence 
 could not contain such a quantity of coals as could 
 be profitably carbonized by the coal-gas manufac- 
 turer. A deviation from this mode was made by 
 placing the fires in front of the retorts, but it was a 
 complete failure. The bottom retorts were soon 
 destroyed, the flame from the fire-place playing so 
 forcibly upon their ends as literally to reduce them 
 into a state of fusion, although the flame was such 
 as only to keep the principal part of the retort at a 
 bright red heat. 
 
 Although retorts of various shapes had been used 
 at different gas establishments prior to the year 
 1817, we find no account of any having been set save 
 on the flue plan, that is, by the fire acting under 
 the retort and then returning over it on its way to 
 the main flue, till the spring of that year, when a 
 plan was adopted for heating cylindrical retorts set 
 in ovens, a plan then denominated the “ oven plan 
 it still bears the same name, but since its first adop- 
 tion has been very greatly modified and improved. 
 The first experiments were made at one of the 
 London gas-light establishments, by heating one 
 retort in an oven. It was reported to have heated 
 uniformly and at little expense. At the same esta- 
 blishment were next set two in one oven, then three, 
 
 i 2 
 
116 
 
 ON THE RETORTS, 
 
 and afterwards five. It may be observed here, that 
 retorts of almost every shape on different modifications 
 of the oven plan, each oven containing five, seven, 
 and in some cases a greater number of retorts, are 
 now generally so set at gas-light establishments. Of 
 the cylindrical retorts set in ovens in the year 1817, 
 I had only an opportunity of making my observa- 
 tions upon twenty. They were set in four ovens, 
 each oven being heated by three fires ; consequently, 
 when all the retorts were serviceable, twelve fires 
 were required to be kept up to heat twenty retorts. 
 By the adoption of the oven plan, as it was then 
 arranged, hardly any advantages could have been 
 expected to be gained ; on the contrary, it was de- 
 monstrated that the destruction of the retorts was 
 more rapid than when set on the flue plan, owing 
 to the lower ones being placed immediately over the 
 fire, from the action of which nothing whatever was 
 placed to guard them. The form of the retorts 
 precluded every hope of carbonization being accom- 
 plished in less time than by any others of a cylin- 
 drical shape ; and as to the per centage at which 
 carbonization might be carried on, what could be 
 expected favourable when, after the retorts (upon 
 which my observations were made) had been in 
 action six weeks only, it was necessary to keep up 
 twelve fires to enable the stokers to work twelve 
 retorts ? 
 
 The rapid destruction of the retorts when set on 
 
AND MODES OF SETTING THEM. 
 
 117 
 
 the oven plan immediately over the fire-places, and 
 without any protection from the action of the fire, 
 induced persons connected with gas manufactories 
 to turn their attention to the matter, so that the 
 retorts might he kept at a proper temperature by 
 reverberated heat and yet be so protected as not to 
 be rapidly destroyed, as had been the case in the plan 
 just spoken of. The first step towards using the 
 reverberatory furnace successfully, as applied to the 
 heating of retorts, was by having the fire-places 
 covered with fire-tiles or fire-humps, leaving occa- 
 sional openings at the sides for the flame to pass 
 through into the retort oven, by which the brick- 
 work became properly heated, as did also the retorts. 
 In ovens where five retorts were used, the three 
 lower ones rested upon the fire-tiles which covered 
 the fire-places, and the two upper ones were sup- 
 ported by means of pillars built of fire-bricks. To 
 protect the lower retorts from the action of the 
 flame which arose through the side openings, the 
 retort oven was made sufficiently wide to allow the 
 two outer bottom retorts to be cased with fire-bricks 
 made for the purpose, by which means a retort 
 would continue serviceable nearly double the time it 
 would have done without such protection ; for when 
 the retorts were left altogether unprotected from 
 the action of the fire, they were very rapidly de- 
 stroyed, and were quite as soon rendered unservice- 
 able if the retorts were left unprotected where the 
 
118 
 
 ON THE RETORTS, 
 
 side openings were placed, and more particularly so 
 if the retorts projected over a part of them. When 
 such was the case, the retorts would have holes 
 burnt through them opposite to each of the side 
 openings, by which they were rendered useless in 
 less than one half the time in which they would 
 have been so had they been properly protected. 
 
 Upon a plan nearly similar to what we have been 
 describing, cylindrical, ellipsoidal, kidney-formed, 
 and D-shaped retorts continued to be set for some 
 years subsequent to 1818. In that way elliptical 
 retorts were set in several gas works, and were 
 found to last for more than two years, though kept 
 constantly in use, when set in nests or ovens of five 
 and heated by two fires. In some instances, under 
 this improved arrangement, carbonization was said 
 to have been carried on at less than thirteen per 
 cent. The improvement was not, however, univer- 
 sally adopted ; many other modes were tried, several 
 of which led to a more rapid destruction of the re- 
 tort than had been the case when the flue plan was 
 followed, and consequently to increased expenses. 
 
 With cylindrical retorts, the manufacturer cannot 
 expect, by one mode of setting more than another 
 (provided the retorts can be kept at a good working 
 heat), to obtain a greater proportion of gas from a 
 given quantity of coal, and that in a shorter time ; 
 for, whenever coal may he submitted to distillation 
 in masses of twelve inches diameter, the operation 
 
AND MODES OF SETTING THEM. 
 
 119 
 
 will be very tedious and equally imperfect. The 
 heat passing through, and from the red hot retort 
 acting upon the outer surface of the coal within it, 
 will cause that outer surface to be speedily decom- 
 posed, consequently the gas generated will pass off 
 very rapidly during the first hour of the charge in 
 particular, during which hour one-fifth of the entire 
 quantity of gas the charge of coal contains will be 
 extracted, about three-fourths of the quantity made 
 during the first hour will be generated during the 
 second hour of the process, and about seven-tenths 
 of that amount during the third ; so that nearly one 
 half of the entire quantity of gas that can be ob- 
 tained from the coal within the retort will be ob- 
 tained during the first three hours of the distillatory 
 process. The reason of this is easily explained ; the 
 outer surface of the coal is first acted upon by the 
 heat, and, as that is the largest surface, it presents 
 the greatest surface of coal to be decomposed, and 
 consequently admits of a greater quantity of gas being 
 thence extracted ; but, so fast as the gaseous and other 
 matters are generated, it becomes more compact and 
 forms itself into a crust of hard and compact coke of 
 some thickness, which counteracts to a certain ex- 
 tent the process in the interior part of the cylinder 
 formed by the coal inside of the retort ; for the core 
 of the charge is deprived of much of the heat of the 
 fire by this outer case of compact coke, and the gas 
 thence evolved must force its way through the same 
 
120 
 
 ON THE RETORTS, 
 
 before it can extricate itself from the retort. When- 
 ever such is the case, carbonization cannot be carried 
 on to advantage, nor will it answer any one de- 
 sirable end. The great object which the manufac- 
 turer should ever keep in view, is to obtain the 
 greatest quantity of gas in the least time and at the 
 least expense; such can never be effected by means 
 of cylindrical retorts or by means of retorts of any 
 other shape into which the coal is of necessity in- 
 troduced in masses of considerable thickness: his 
 plan, therefore, must be to use retorts of such shape 
 as will admit of the coals proposed to be carbonized 
 being spread out in layers of from three to four 
 inches in thickness. For such mode of operation 
 the elliptical retort twenty inches by ten inches 
 inside, kidney-shaped twenty inches by ten inches 
 inside, or the D-shaped, with the straight part repre- 
 senting its bottom, twenty inches in width and ten 
 inches in height inside : a convenient length for any 
 of the retorts just named is from seven feet to seven 
 feet six inches. With any of the above shaped re- 
 torts, 120 pounds of any of the descriptions of 
 Newcastle coals will be well carbonized in from four 
 to five hours. 
 
 Before speaking of the more recent improvements 
 in the mode of setting and working retorts, we shall 
 say something relative to the “ rotary retort” 
 which we are induced to do from the action of that 
 retort bearing us out in what we have remarked 
 
AND MODES OF SETTING THEM. 
 
 121 
 
 relative to submitting coal in thin layers to the dis- 
 tillatory process. We first remark that Mr. Maiben, 
 of Perth, invented a retort for distilling coal by ex- 
 posing it to the action of heat in thin strata. From 
 his experience he learnt that the gas evolved during 
 the first part of the process of carbonization was of 
 too aqueous a quality to be fit for combustion, and 
 that evolved during the latter part of the process 
 was so strongly impregnated with sulphur as to be 
 highly objectionable. To remedy those evils, he 
 considered that, if the coal were spread in a thin 
 layer in the retort, the action of the heat thereupon 
 would be more instantaneous ; consequently, the bad 
 gas evolved in the beginning and towards the end of 
 the process might by means of a valve be prevented 
 from entering into the gas-holder. The retorts he 
 made use of were of a square shape, and of a size 
 sufficient to carbonize twenty-five pounds of coal 
 when spread out therein in a layer of about two 
 inches thick. The coal was introduced into the 
 retort by means of a sheet iron box, which was 
 charged and slided in whenever the gas had been 
 extracted from the former charge, which, under such 
 management, was generally accomplished in two 
 hours. This description of retort being much too 
 small to be serviceable in large establishments, led 
 Mr. Clegg to construct a retort on similar principles, 
 and of sufficient capacity for carbonizing about 
 twenty-seven hundred-weight of coals in twenty- 
 
122 
 
 ON THE RETORTS, 
 
 four hours. For this retort he took out a patent in 
 December, 1816; and in the Repertory of Arts for 
 that month. No. 175, and for January, 1817, No. 
 176, a particular desciption of the invention is to he 
 found. The first of them which was ever put up 
 (being eight feet six inches in diameter), as were also 
 the second and third (each of twelve feet six inches 
 diameter), were worked under my observation from 
 the time they were first brought into action, a period 
 of several months, till they were taken down to 
 make room for a new retort-house which was re- 
 quired to be built by the company. Each of these 
 retorts contained fifteen boxes, made of strong boiler 
 plate, riveted together, which slided into the retort 
 upon wrought iron arms, as described in the specifi- 
 cation published in the Repertory of Arts above 
 alluded to. Whilst the arms could be kept up they 
 were worked without much difficulty. The coal re- 
 mained in the retort six hours, but was only exposed 
 to the action of a red heat one-third of that time, or 
 two hours. Five boxes, having passed that, waited 
 in the retort for the coal in the five boxes over the 
 red heat being decomposed, which, on being effected, 
 the retort was opened, and those five boxes which 
 had passed the red heat were withdrawn from the 
 retort and fresh ones charged with coal introduced 
 upon the arms they had occupied. This process 
 brought the five boxes which had been over the red 
 heat into the situation which those just drawn had 
 
AND MODES OF SETTING THEM. 
 
 123 
 
 lately occupied, there to remain till the coal in the 
 five just brought over the red heat might be decom- 
 posed when the operation of change was again, as 
 already described, repeated ; so that there were con- 
 tinually five boxes charged with coal lately intro- 
 duced into the retort, gradually drying prior to 
 being brought over the red heat — five filled with well 
 dried coals over the red heat, and five others filled 
 with coke produced from the coal they contained 
 whilst over the red heat, ready for being withdrawn 
 from the retort. Had not the expense of erecting 
 retorts of this description been very considerable, 
 and the wear and tear enormous, they would in all 
 probability have been adopted in that establishment 
 where they were first tried ; but both were so much 
 against them, that every idea of using them there 
 was abandoned. It is but justice to state that the 
 “ rotary retorts ” produced gas at the rate of up- 
 wards of 11,000 cubic feet from one ton of coals, 
 which was full fifty per cent, more than what were 
 reckoned at that time very good results from cylin- 
 drical retorts, 7,400 cubic feet of gas from one ton 
 of coals being the maximum. I am now speaking 
 of results in 1817 and 1818, which the reader must 
 bear in mind ; for, from one step to another the 
 quantity of gas obtained from a ton of coals has 
 gradually increased to about 9,000 cubic feet, 
 although 8,500 has been set down by Mr. Joseph 
 Hedley as the London average in 1837. Under 
 
124 
 
 ON THE RETORTS, 
 
 some recent patented improvements in gas appa- 
 ratus, I have, during the year 1840, been^obtaining 
 at an average upwards of 12,000 cubic feet of gas 
 from a ton of Townley Main and other Newcastle 
 coals, which apparatus and the results therefrom I 
 propose hereafter to describe ; I shall not, therefore, 
 dwell further upon either here, but return to the 
 rotary retort , by means of which carbonization was 
 carried on at from sixteen to eighteen per cent. The 
 increase of coke on coal carbonized was about fifty 
 per cent., and the process of carbonizing under the 
 above circumstances was accomplished in about six 
 hours. During the time the rotary retorts were in 
 action, I had abundant opportunity for observing 
 that the statement of Mr. Maiben, which had ap- 
 peared so reasonable, was fully verified in practice, 
 even on a large scale ; and from thence learnt that 
 the more rapidly the decomposition of coal is effected, 
 exactly in the same ratio we are to expect an in- 
 crease in the quantity of gas generated from a given 
 quantity of coal ; for when cylindrical retorts, 
 charged with Bewicke and Craster’s Wallsend coals, 
 worked at a low temperature, and at six hours 
 charges, were producing but from 6,000 to 6,700 
 cubic feet of gas from one ton of coals, the rotary 
 retorts were producing from 11,100 to 11,850 cubic 
 feet of gas from the same quantity of coal ; three- 
 fourths of which was evolved in one-third of that 
 time, or in two hours. 
 
AND MODES OF SETTING THEM. 
 
 125 
 
 The distillation of coal when exposed in thin 
 strata to the action of the fire having been proved 
 by very extensive experience to be the most beneficial 
 to the manufacturer, as far as relates to the products 
 obtained ; therefore, if the expenses of setting retorts 
 proper for such a process, and keeping them in 
 repair, could have been accomplished at anything 
 near the sum requisite for working those of cylin- 
 drical form, it was but natural to expect to see some 
 mode adopted likely to produce the effect sought for. 
 Mr. Maiben’s retorts were much too small for ex- 
 tensive manufactories, and the rotary retorts were 
 so very expensive, it was not probable that either 
 could be brought into general use. To overcome 
 the difficulties arising from the use of retorts such 
 as I have just mentioned, it was proposed to use 
 ellipsoidal retorts about six feet six inches in length, 
 their major axis being twenty inches, and their 
 minor axis ten inches inside dimensions. From 
 retorts of this shape there was every probability that 
 the results, as far as related to the quantity of gas 
 and coke obtained from a ton of coals, would be very 
 similar to those from the rotary retort ; whilst the 
 expense of setting them would be but little more 
 than what was incurred by setting an equal number 
 of cylindrical retorts, and not near so much as the 
 cost of setting that number of cylindrical retorts 
 which was capable of carbonizing equal quantities of 
 coals in equal times. Upwards of twenty years of 
 
126 
 
 ON THE RETORTS, 
 
 extensive experience have fully demonstrated this to 
 me. The elliptical retorts, the kidney-formed, or 
 the large D retorts have great advantages over 
 cylindrical ones. The charge in them may be 
 worked off in half the time that it can be in cylin- 
 drical retorts ; and five of them in action, worked 
 with 120 pounds of coals to each, during a four 
 hours’ charge, will produce as much gas in twenty- 
 four hours as ten cylindrical retorts, worked at eight 
 hours’ charges, with 160 pounds of coal to each 
 retort every charge. The elliptical retorts on which 
 my observations have been made have generally been 
 set in these various ways, viz. : two to one fire, on 
 the furnace plan; three in one oven, heated by 
 means of a furnace ; five in one oven, heated by a 
 furnace ; three in an oven, and five in an oven, each 
 series being heated by means of coke-ovens. The 
 elliptical retorts on which my first observations 
 were made were set five in an oven, and were heated 
 by one fire. They were taken down after being 
 ninety-four days in action (to make room for some 
 alterations of buildings in the manufactory), so little 
 injured by the fire that two out of the five were but 
 barely discoloured, and the remaining three had not 
 at all fallen out of shape. At the very time that 
 those retorts were in action, cylindrical retorts set 
 on the oven plan were almost always entirely burnt 
 out in less than two months. 
 
 Having spoken of the cylindrical, rotary, and el- 
 
AND MODES OF SETTING THEM. 
 
 127 
 
 liptical retorts, I shall make a few observations upon 
 the semi-circular, or D-shaped, the kidney-formed, 
 and the square ones, preparatory to describing 
 several methods of setting retorts, as hereafter illus- 
 trated by the plates. The semi-circular, or small D 
 retort, from its form, when set with judgment, is ap- 
 plicable to small gas establishments, being easy to 
 charge and draw ; the lid of the mouth-piece being 
 much lighter and more easily taken off, luted, and 
 refixed than that of the larger D retort, of the 
 elliptical, or of the kidney-shaped. It is not, how- 
 ever, so well adapted for producing the best results 
 as to quantity of gas obtained as any of the above- 
 named ; for if 160 pounds of coal be introduced into 
 a small D retort, twelve inches across the bottom 
 and twelve inches in height, inside dimensions, and 
 length about seven feet, it will nearly fill it ; hence 
 the same objections to the use of it hold good, as 
 have been urged against the cylindrical retort of 
 about the same size. I have had abundant oppor- 
 tunities during the last ten years of noticing the 
 results from small sized D retorts, and am prepared 
 to say that the average quantity of gas from Felling 
 Main and other Newcastle coals did not exceed 
 7,800 cubic feet of gas to the ton. They were set 
 in ovens of three, two, and one nearly similar to the 
 oven of three D retorts, as shown in one of the plates, 
 the oven of two being the same width as that of 
 three, but with an elliptical arch over it, and the 
 
128 
 
 ON THE RETORTS, 
 
 oven of one being rather more than half the width 
 of either of the other two. The retorts were so set 
 that the proprietor for whom they were erected 
 might use one, two, three, four, five, or six, or any 
 greater number, as the nights gradually became 
 longer, or, contrariwise, leave off the use of one, 
 two, three, &c., as the nights became shorter — an 
 arrangement found advantageous in a small town 
 where, during two of the summer months, one such 
 retort was found sufficient to supply the quantity of 
 gas which was called for by the shop-keepers and 
 other private consumers. In most small towns such 
 an arrangement of retorts, whether they be D- 
 shaped or otherwise, is better, supposing six retorts 
 require to be put up, than fixing them in two ovens 
 of three each ; that is to say, an oven of three, an 
 oven of two, and an oven of one retort. At the 
 places where the small D retorts as above were 
 fixed there was not any great demand for coke ; in 
 consequence, that product was used as fuel for heat- 
 ing the retorts, and therewith carbonization was 
 carried on at an average of about thirty per cent, 
 upon the cost of the coals used for making gas. At 
 one of the establishments, where nine D retorts 
 were put up, a period of more than two years elapsed 
 before even one of them required to be replaced, 
 though the net annual income to the proprietors ex- 
 ceeded 500/. ; and at another, of about the same 
 magnitude, the results as to the per centage at 
 
AND MODES OF SETTING THEM. 
 
 129 
 
 which carbonization was carried on, and the wear 
 and tear of retorts were nearly similar to those 
 which have been just stated. 
 
 In some instances, D retorts have been set six in 
 a range, nearly similar to the square retorts (see 
 Plate VII., figures 4 and 5) ; but, instead of being 
 heated by a furnace, a coke oven was employed for 
 that purpose. That mode of setting has, however, 
 nearly gone out of use, and retorts so set are not to 
 be found now at many gas-light establishments. 
 
 The semi-cylindrical, or large D retort, with its 
 horizontal diameter from twenty to twenty-two 
 inches, and its vertical varying from nine inches 
 to twelve inches, inside dimensions and length, ex- 
 clusive of its mouth-piece, from seven feet six inches 
 to eight feet, is probably as good a shape for pro- 
 ducing high results as to gas obtained as any that 
 can he used ; for in it 160 pounds of coal can be 
 spread over the bottom in an uniform layer of between 
 three and four inches in thickness ; when so, if the 
 retort be kept at a bright-red heat, a charge of 160 
 pounds will be completely worked off in about four 
 hours, so that one such retort will carbonize, in 
 twenty-four hours, about 960 pounds of coal, and 
 produce nearly 4,000 cubic feet of gas from almost 
 any of the Newcastle unscreened coals. In practice 
 I should recommend, in works where more than six 
 retorts are required, that large D retorts should be 
 set in ovens, with three retorts in each, as here- 
 
 in 
 
130 
 
 ON THE RETORTS, 
 
 after described, with descending flues, where such 
 arrangement is practicable ; but, in those instances 
 where recent improvements may be adopted, and 
 from which we may expect to get 5,000 cubic feet 
 of gas from the same retort, the same quantity of 
 coals and in the like time, the descending flues 
 cannot be adopted. 
 
 The kidney-formed retorts possess very nearly 
 the same properties as the large D-shaped and 
 elliptical retorts — these may be set singly, in twos, 
 threes, or fives, as may be most convenient, and 
 either over furnaces or coke-ovens. Indeed any of 
 the descriptions of retorts may be heated by means 
 of coke-ovens, if in the place where they are used 
 there is a ready demand for coke, either for malting 
 or other purposes. The coke produced in the coke- 
 oven, as it is generally constructed, when applied to 
 the purpose of heating the retorts in a gas manu- 
 factory, is quite as good for malting as that which 
 the maltster prepares in ovens which he constructs 
 for the express purpose of making coke. Such coke 
 is also well adapted for the use of the iron-founder, 
 and when made in ovens sufficiently large for heating 
 three or five elliptical or large D-shaped retorts, 
 if such ovens be properly managed, the coke will 
 answer his purpose quite as well as if prepared in 
 the ordinary manner. Where, therefore, there 
 happens to be a demand for coke, the gas manu- 
 facturer will consult his own interest by using coke- 
 
AND MODES OF SETTING THEM. 
 
 131 
 
 ovens for heating his retorts, as by so doing, the 
 coke produced, from the coal from which the 
 gas is extracted and from the coke-oven, will more 
 than pay for all the coal he may use for both 
 purposes. But, if he cannot find a market for his 
 coke, then it will be to his interest to heat his 
 retort-ovens by means of furnaces arched over as 
 hereafter shown in our description of the different 
 kinds of retorts and the modes of setting them. 
 The furnace system possesses one very material ad- 
 vantage over the coke-oven mode of operating; for, 
 should circumstances require the retorts to be worked 
 at a higher temperature than usual, for hastening 
 the distillatory process, or for procuring more gas 
 in a shorter time, it would be found by the coke- 
 oven plan very difficult, if not impossible, to effect 
 either purpose ; but either might with ease be 
 accomplished by means of furnaces, so that when- 
 ever any contingent call for an extra supply of gas 
 may be expected, it would in such case always be 
 the wisest plan to have all the retorts heated by 
 furnaces, or, at all events, such a number as would 
 meet any extraordinary demand for gas called for at 
 a short notice. 
 
 The so-called square retort is generally about twenty 
 inches in breadth, thirteen inches high, and six feet 
 long inside. It has a rib cast along the middle, 
 on the inside of that part which is the bottom when 
 the retort is set. This rib rises to the height of 
 
 k 2 
 
132 
 
 ON THE RETORTS, 
 
 three inches, but does not approach nearer to the 
 mouth-piece than about eighteen inches. It is for 
 the purpose of strengthening the bottom of the 
 retort and preventing it from falling out of shape ; 
 hut when we consider the mode in which square 
 retorts are set, that is to say, side by side, with 
 the bottom of each resting upon a flat surface of 
 fire-humps or fire-tiles, (see mode of setting square 
 retorts in plates,) it does not appear to be necessary. 
 These retorts, when set six in one bed, and that 
 number heated by one fire, are placed close alongside 
 of each other. The fire is at one end of the range, 
 and is so contrived as to admit of the flue being 
 carried under the whole range towards the mouths 
 of the retorts ; it is then brought over the top of 
 them, and again under and over in the like way, 
 previous to its being allowed to enter into the 
 main flue. Under this arrangement, square retorts, 
 weighing about thirteen cwt., being worked at 
 six hours’ charges with 120 pounds of coals to each 
 as one charge at such a heat as causes 7,500 cubic 
 feet of gas to he generated from one ton of the best 
 description of Newcastle coals, are found to remain 
 serviceable one year. The carbonization (when they 
 are once brought to a working state) is carried on at 
 about twenty-five per cent. ; but they require good 
 fires to be kept up under them for a fortnight or 
 three weeks before they attain to a proper working 
 heat. These retorts are not so advantageously used 
 
AND MODES OF SETTING THEM. 
 
 133 
 
 as others we have been speaking of. They are more 
 expensive in the first instance than cylindrical retorts. 
 The length of the flues passing under and over them 
 being extensive and of but small dimensions, they 
 are frequently choked up, and require, for clearing 
 them out, various openings. When, therefore, it is 
 found necessary to examine those flues, it generally 
 happens that the heat of the retorts becomes very 
 considerably decreased ; and, when we consider the 
 time requisite for heating them in the first instance, 
 we must be aware that such a diminution cannot be 
 overcome but by a considerable expense of fuel, and 
 by carrying on the process very unfavourably and 
 imperfectly. Lastly, when the retort is burnt out, 
 the cost of replacing it is nearly equal to the first 
 cost of setting it ; whilst in using cylindrical, ellip- 
 tical, D, or kidney-formed retorts set in ovens, a 
 retort is generally replaced for about one-half of the 
 expense of its first setting ; for the arches over the 
 ovens which contain the retorts, if well constructed 
 in the first instance, will remain serviceable for many 
 years (several which have been up under my di- 
 rection have been in use for upwards of ten years, 
 and are still nearly as good as when first erected) ; 
 and when retorts so set are burnt out, all that is 
 required to be done is to remove the brick-work in 
 front from the soffit of the arch to the level of the 
 furnace bars should they be heated by furnaces ; or 
 to the crown of the arch of the coke-oven should 
 
134 
 
 ON THE RETORTS, 
 
 they be heated by means of coke-ovens ; and then 
 draw out the burnt-out retorts by means of proper 
 tackle. When the defective retorts are removed, 
 the bricklayer can repair the furnace, which, in 
 twelve months, if constantly in use, will be very 
 much burnt away, and turn the arch over it, upon 
 which the lower retorts will have to rest preparatory 
 to new ones being fixed. In such a case, a brick- 
 layer and labourer will be able to repair a furnace 
 for three or five elliptical or other large retorts in 
 a couple of days, provided they be not delayed by 
 waiting for the effective retorts being fixed. Where 
 a coke-oven is used, supposing the arch over it be not 
 injured, and which it will not be for several years 
 if turned with fire-bricks made for the purpose 
 (brick and brick) laid end wise, the work of the 
 bricklayer and his labourer for replacing five burnt- 
 out retorts will not exceed one day. 
 
 As on the proper mode of setting the retorts 
 the prosperity of a gas-light establishment mainly 
 depends, I trust the reader will not think me tedious 
 if in this place I furnish my own views upon the 
 subject. By mode of setting, I mean, first, that the 
 furnaces or coke-ovens should be so constructed as 
 to ensure at all times a sufficient quantity of heat 
 for raising the retorts to such a temperature as will 
 thoroughly decompose the coal submitted to dis- 
 tillation in a period of from four to six hours, when 
 charges of from 120 to 160 pounds of coals are used 
 
AND MODES OF SETTING THEM. 
 
 135 
 
 in each retort for one charge. I am now speaking 
 of elliptical or other retorts which admit of the 
 coals being spread over a large surface in thin 
 layers. Secondly. That where furnaces are used, 
 the expense of fuel should he as low as possible. 
 In my own practice, taking the average of five- 
 and-twenty years, I am prepared to say, the average 
 quantity of coke or coal used as fuel for heating 
 the retorts has not amounted to thirty per cent, on 
 the cost of coals used in the retorts for making gas. 
 On the coke-oven system, as has been before ob- 
 served, where there is a quick sale for the coke, the 
 coke produced sells for more than the coals cost. 
 There is another point beyond those already noticed ? 
 which is well worthy of attention, — it is, that the 
 brick-work which surrounds the furnaces, coke-ovens, 
 and retort-ovens should be well executed. My at- 
 tention has been drawn to this matter from finding 
 it is the practice with some of the retort setters of 
 the present day to use no lime mortar in any part of 
 their work, whereas in several parts of it such 
 mortar is very preferable to fire-clay. Where fire- 
 clay is used altogether, it will much increase the 
 expense of setting the retorts in the first instance ; 
 and having no bond, will, particularly in the filling 
 up between the arches over the retort-ovens, and in 
 the covering over the upper flues, &e., be apt to 
 crack and give way, so much so, that, by the time 
 the retorts are destroyed, it will be necessary to 
 
136 
 
 ON THE RETORTS, 
 
 take down and rebuild anew tlie entire of the work, 
 thus entailing an immense and altogether unnecessary 
 annual expense, an expense which might be saved if 
 all the parts which did not come into immediate 
 contact with the fire were laid in lime and sand- 
 mortar, and all the joints well filled in every course 
 with grout of a similar description. If the work 
 were so done, and fire-bricks were used for turning 
 the different arches made expressly from models to 
 suit the spring and sweep of the arch, so that when 
 placed upon the centres they lay brick and brick 
 so as not to admit of any fire-clay between them 
 (except a very thin grout poured over the arch 
 when turned to fill up any small interstices), and if 
 the fire-bricks of the furnaces and coke ovens were 
 so laid also, though even the first cost of erection 
 might be rather more than by a more unworkman- 
 like mode of procedure, still in the end the manu- 
 facturer would find by adopting it a very considerable 
 annual saving therefrom. 
 
 Another matter in the working of retorts is of 
 some moment ; that is to say, there ought to be 
 every facility afforded for drawing and re-charging 
 them ; for when the lid is removed from the retort 
 and the coke therein is withdrawn, the action of the 
 air upon the metal is apt to cool it before the coals 
 of the fresh charge can be thrown in in the ordinary 
 way. To remedy this evil at many of the large 
 gas-works, the coals are now introduced by means 
 
AND MODES OF SETTING THEM. 
 
 137 
 
 of a long tray or scoop, into which the proper quan- 
 tity of coals has been put. This scoop, so charged 
 with coal, is introduced into the retort, and then 
 turned over and withdrawn, leaving the coal uni- 
 formly spread over the bottom, and thus allowing 
 the lid to be replaced much sooner than it could be 
 supposing the charge had to he thrown into the 
 retort by means of a shovel. In very small works, 
 however, it cannot be adopted, as it requires more 
 than one man to manage the scoop or tray plan 
 properly. 
 
 Whilst speaking of the retorts and making such 
 suggestions relative to setting and working them, it 
 may not be out of place if we remark that the great 
 expense of heating them led some persons engaged 
 in the erection of gas-works, so early as the year 
 1819, to consider whether it was not possible to 
 adopt a system which would effectually answer the 
 purpose of heating retorts without that waste of 
 fuel which must ever arise when they are heated by 
 means of furnaces or fire-places, and it was then 
 considered practicable to obtain that end by making 
 a coke-oven for heating each nest, or batch of re- 
 torts, provided the heat generated during the car- 
 bonizing process could be applied so as to act upon 
 the retorts. This end has been fully attained, and 
 the consequence resulting from the use of coke-ovens 
 is, that the coal which is used under such circum- 
 stances (instead of being destroyed after performing 
 
138 
 
 ON THE RETORTS, 
 
 the heating process) is drawn from the oven in the 
 shape of a very valuable coke, equal in weight, at an 
 average, to one half of the weight of the coal used ; 
 and where there are iron foundries or malting esta- 
 blishments at hand to create a market, this coke is 
 of equal value to the coal which produced it, so that 
 the manufacturer heats his retorts for nothing, in- 
 stead of incurring an expense of from twenty-five to 
 thirty per cent, on the coals used for the production 
 of gas. This is all well when a market can be 
 found ; hut in places where there are neither founders 
 nor maltsters to take the coke so made, it becomes 
 a very expensive and wasteful process : it therefore 
 behoves all gas companies to satisfy themselves 
 whether, if they should adopt the coke-oven plan 
 for heating retorts, they can find a market for their 
 coke. The coke thus made is not of a quality fit for 
 ordinary purposes ; and hence some concerns where 
 the coking system has been followed have been 
 overstocked with coke to an enormous extent. By 
 placing a set of grate-bars, however, opposite the 
 coke-oven door, and making an ash-pit below, which 
 can be closed by a door made to fit air-tight (see 
 mode of converting a coke-oven into a furnace in 
 plate, and as described at the end of this Chapter), 
 a coke-oven may be worked as a furnace in a case 
 of emergency, or when the stock of coke on hand is 
 increasing. When used as a coke-oven, the door of 
 the ash-pit is kept shut so as to exclude any draught 
 
AND MODES OF SETTING THEM. 
 
 139 
 
 of air from passing through the fire-bars ; but when 
 as a furnace, it is kept open, and the coal or coke 
 used for heating the retorts thrown in so as to 
 occupy very little space beyond the range of the 
 fire-bars on the bottom of the oven. It will easily 
 be understood that the coke made in this oven will 
 be precisely similar as to quality to that made in an 
 oven without grate-bars, and it will as easily be 
 comprehended that it possesses the advantages 
 which the furnace-system offers. 
 
 Before we commence describing the different 
 modes of setting retorts, as exhibited in the plates 
 herewith furnished, we may make a few remarks 
 upon some of the descriptions of retorts which have 
 from time to time attracted the attention of gas 
 companies, but which, generally speaking, are either 
 entirely out of use or only to be found in few 
 places, and these in a comparatively small way. At 
 one time we had retorts made of fire-humps, fire- 
 bricks, and fire-clay, very large, heated at great 
 expense, and, in spite of the greatest care and skill, 
 soon becoming leaky. At another time we had 
 fire-clay retorts round and elliptical, and of other 
 shapes, moulded of the shape required before being 
 burnt : these were thought likely to be very durable, 
 and also to produce very extraordinary results ; but 
 on being tried, they were found neither to possess 
 durability nor to offer any other advantage over 
 cast-iron retorts of the same shape and size. We 
 
140 
 
 ON THE RETORTS, 
 
 have had and still have retorts which feed and dis- 
 charge themselves, and others again of as many 
 forms, descriptions, and sizes, as would take a 
 volume to describe, instead of a page or so, which 
 is all the consideration of the subject as to practical 
 utility requires. Retorts upon retorts have been 
 patented or laid before the public through the 
 medium of the periodical press ; some ingenious and 
 clever, others stupidly absurd. It has been our 
 constant endeavour, amidst such an abundant sup- 
 ply of materials, not to mislead or bewilder our 
 readers by noticing absurdities or by prolix details, 
 and therefore we do not propose to select from 
 patented inventions (unless in cases of obvious utility 
 and confirmed merit) any apparatus, whether it be 
 retort, condenser, purifier, gasometer, or anything 
 else used by the gas manufacturer. We shall con- 
 tent ourselves with describing such apparatus as we 
 think most likely to answer the manufacturers 
 purpose, and we trust that in doing so we shall 
 make ourselves perfectly intelligible. 
 
 Having made these remarks, we shall next de- 
 scribe the method of setting two cylindrical retorts 
 on the flue plan , so as to be heated by one fire , as 
 exhibited in Plate VII., figures 1, 2, and 3. 
 Figure 1 exhibits a longitudinal section of these 
 retorts. In it a is the fire-place, b a section of the 
 fire-bars, and c the ash-pit. The direction taken by 
 the flue is pointed out by small arrows. 
 
AND MODES OF SETTING THEM. 
 
 141 
 
 Figure 2 represents a front view of two cylin- 
 drical retorts set to one fire on the flue plan. In it 
 the manner in which the conducting pipes are con- 
 nected to the retorts is exhibited : these lead to the 
 hydraulic main in a similar way to what is shown 
 in Plate X., figures 1 and 2. 
 
 Figure 3 is a vertical section of the same retorts, 
 supposed to be drawn about midway of their lengths. 
 In this section a represents the end of that part of 
 the flue leading from the fire under the lower retort 
 which rises near the mouth-piece thereof through 
 the openings b b , and passing between the two re- 
 torts, rises over the end of the upper one ; and being 
 brought over the top of it, by means of an opening 
 c , about nine inches from the mouth-piece, enters 
 the upper flue, and thence passes into the main flue. 
 ddd are vertical sections of the fire-tiles ; on the 
 bottom and middle one the retorts are supported, 
 and the upper one forms the bottom of the top flue. 
 
 Description of the method of setting six square 
 retorts so as to be heated by one fire , as ex- 
 hibited in Plate FII., figures 4 and 5. 
 
 Figure 4 represents a transverse section of square 
 retorts, in which six are heated by one fire. These 
 retorts are twelve inches square inside, and six feet 
 in length. The fire-place a with the ash-pit b is 
 placed at one end of the series ; but so as when the 
 observer stands in front of the retorts he shall be in 
 
142 
 
 ON THE RETORTS, 
 
 front of the fire-place also. Under this arrangement 
 the retorts 1 and 6 heat the best, and 5 the worst. 
 If the reader compares the situation of the flues, as 
 exhibited in figure 5 of this plate, he will observe 
 that there are four which communicate with the 
 fire-place. These are divided by fire-humps laid 
 edgewise across the whole series of retorts, forming 
 the flues marked dddd , figure 5. This range of 
 flues is covered by fire-tiles, and upon them the re- 
 torts are placed close alongside of each other. Over 
 the top of the retorts is a range of flues eeee , 
 which corresponds with the lower ones, and these 
 are covered with fire-tiles and a course of fire-bricks. 
 Upon the latter is a third series of flues of about 
 two-thirds the depth of the former ones, and these 
 rise by the opening f, figure 5, into the main flue. 
 In figure 4 the transverse direction of the flues is 
 shown by the arrows leading from the fire-place. 
 The mouth-pieces of these retorts are circular, as 
 shown upon the retort marked 6. 
 
 Figure 5 represents a longitudinal section of 
 these retorts, in which the flues and action of the 
 fire have already been described. A is the retort, 
 a the fire-place, b the ash-pit, and c the fire-bars. 
 
 Figure 6. Five elliptical retorts heated by two 
 coke-ovens, exhibiting front view of one oven of 
 retorts, and transverse vertical section of another. 
 1, 2, 3, 4, 5, retorts, a , door and frame to coke-oven 
 A. b, opening to coke-oven B, without showing 
 
AND MODES OF SETTING THEM. 
 
 143 
 
 door and frame. C, a cast-iron plate, with a rib 
 along the back of it, built into the brick-work, to 
 prevent the pushing out of the arch E (figure 7) 
 over the coke-oven. The ends of the plate C fall 
 behind the upright cast-iron pilasters D D, which 
 are secured in their places by means of screw-bolts 
 passing entirely through the brick-work, with a 
 boss and nut at the back and nuts in front, as 
 shown at c c. # * # # * * 9 situation of sight-holes for 
 examining the heats of the retorts, and for removing 
 any deposit which may accumulate. A, transverse 
 vertical section of one of the ovens. B, transverse 
 vertical section of the other oven, e e e e, height at 
 which the arches E E E spring. E E E, section of 
 the arch E (figure 7). F F F, section of the fire- 
 blocks. F (figure 7), upon which the retorts 1, 2, 3 
 are laid. G G, pillars built of fire-brick (see also 
 figure 7), upon which the shields HH rest, for 
 guarding the two upper retorts 4 and 5. The 
 shields are made to pattern by the fire-brick manu- 
 facturer. The flues and the direction the flame 
 takes on its way to the main flue are both marked 
 by arrows, and more fully explained by figures 7 
 and 8. I, arch of fire-bricks over the retort-oven. 
 
 Figure 7. Longitudinal section of figure 6, in 
 which the corresponding parts are marked with 
 similar letters and figures of reference. 
 
 Figure 8. Plan of the flues above the arch I 
 (figures 6 and 7) which lead to the main flue. 
 
144 
 
 ON THE RETORTS, 
 
 Figure 9. Plan of the under side of the arch I 
 (figure 6), the situation of the front and back vents 
 to the flues, and the situation and dimensions of the 
 side flues * * * *. 
 
 Figures 6, 7, 8, and 9, are drawn from a scale of 
 a quarter of an inch to a foot. 
 
 Figure 10. Front view of sight-hole frame and lid. 
 
 Figure 11. Section of sight-hole frame and lid. 
 
 Figures 10 and 11 are drawn from a scale of 
 one inch and a half to a foot. 
 
 Plate VIII., Figure 1. Front elevation of one 
 retort with its connecting pipe, and sections of two 
 others similarly set ; each heated by one furnace, 
 drawn to a scale of a quarter of an inch to a foot. 
 Figures 2, 3, and 4 are also drawn to the same 
 scale. AAA, arches turned over the ovens in 
 which the retorts are placed. B B, sections of re- 
 tort-ovens. C C, transverse vertical sections of the 
 retorts. C *, front elevation of retort, showing 
 flange and upright connecting piece. D D, vertical 
 section of arches over the furnaces, upon the crown 
 of which the retorts are placed. ****, openings 
 in arches D D for allowing the flame from the 
 furnaces E E to rise into the retort-ovens B B (see 
 also figure 3, in which the corresponding openings 
 are similarly marked), a a a a, casing of fire- tiles 
 to prevent the flame from the furnaces striking upon 
 or against the retorts, so that they may be heated 
 by reverberation only. F F, sight-hole covers. 
 
AND MODES OF SETTING THEM. 
 
 145 
 
 which can be removed, for ascertaining the heat of 
 the retorts, or for clearing away any deposit which 
 may accumulate in the retort-ovens, b , opening in 
 the top of the retort-oven leading into the flue c , 
 which proceeds towards the main flue d. G, fur- 
 nace-door, sliding upon the plate HH, which is 
 partly bedded in the brick-work. I, opening in 
 front of fire-place, over which the fire-door slides 
 when it is necessary said opening should be closed. 
 J, section of the fire-place which is hopper-shaped, 
 as described in the figure, and also in figures 2 and 
 4. K K K, sections of ash-pits. 
 
 Figure 2. Longitudinal vertical section of re- 
 torts, described in figure 1, upon which correspond- 
 ing parts are marked with similar letters of refer- 
 ence. L, furnace-door, n , damper, mm , bearers. 
 o o , frame of damper. 
 
 Fig ure 3. Plan over the crown of the arch D, 
 showing the openings ***** for allowing the flame 
 from the furnace E (figures 1 and 2) to rise into 
 the retort-oven B, shown in aforesaid figures. C, a 
 longitudinal horizontal section of the retort, with 
 its mouth-piece. 
 
 Figure 4. Plan of the furnace, showing the 
 situation of the fire-bars L, and bearers m m m m. 
 This furnace is splayed off from the height of J 
 (figure 1) to the sides up to the springing of the 
 arch D, and at the extreme end to the soffit of said 
 
 L 
 
146 
 
 ON THE RETORTS, 
 
 arch, so as to form it into a shape similar to the 
 interior of a hopper. 
 
 Figure 5. Transverse vertical section of three 
 large D retorts set in one oven, and heated by either 
 a coke-oven or furnace, as may be most desirable. 
 A, arch turned over the oven in which the retorts 
 are placed. B B B, transverse vertical section of 
 the retort-oven. C, D, E, vertical transverse sec- 
 tions of the retorts. F F, transverse vertical sections 
 of brick-work carried up the entire length of the 
 retort-oven, leaving between them a space G, which 
 space, as well as the walls F F, is covered by the 
 fire-tiles HH, upon which the retort C is placed. 
 The walls F F have openings * * in them for allow- 
 ing the heat from the coke-oven, oven, or furnace, 
 which accumulates in the space G, to pass off into 
 the retort-oven in the direction of the arrows, as 
 more fully described by figure 7. I, one of the 
 openings through the arch J over the coke-oven, 
 for allowing the flame and heat therefrom to find 
 a way into the space marked G. J, the arch over 
 the coke-oven. K, transverse vertical section of the 
 coke-oven. L, opening to the coke-oven in front. 
 M, ends of the fire-bars. N, bearer. O, ash-pit. P 
 and Q, flues running underneath the retorts D and 
 E, from front to rear of them : see also figure 6, 
 where they are shown in section at the foot of the 
 back flues marked R and S. In this figure the 
 
AND MODES OF SETTING THEM. 
 
 147 
 
 direction which the flame takes is shown by the 
 arrows. This mode of setting retorts is denomi- 
 nated the descending flue 'plan. 
 
 Figure 6. A, arch turned over the oven in which 
 the retorts are placed. J, arch over the coke-oven. 
 K, section of the coke-oven. P and Q, vertical 
 sections of the flues which run underneath the 
 retorts D and E from front to rear ; see also figures 
 5 and 9, where the same flues are marked with 
 similar letters. RS, rising flues which lead into 
 the main flue UU. T, damper and frame. UU, 
 longitudinal vertical section of a part of the main 
 flue. 
 
 Figure 7. Longitudinal section of walls F F 
 (figure 5). * # *, openings for allowing the heat 
 
 received from the coke-oven into the space G 
 (figure 5) to pass off in the direction of the arrows 
 shown upon that figure. V, section of front wall, 
 see also figure 10. Ill, openings in the crown of 
 the arch J over the coke-oven. K, to allow the 
 flame and heat from said coke-oven to pass into the 
 space marked G (figure 5). 
 
 Figure 8. Plan of the coke-oven K, showing the 
 situation of the grate-bars put in for the purpose of 
 working it as a furnace when deemed needful. K, 
 floor of coke-oven. M M, fire-bars. N N N N, 
 bearers upon which the fire-bars rest. 
 
 Figure 9. Plan of the flues which run along 
 under the retorts D and E, (figure 5,) and of the 
 
 l 2 
 
148 
 
 ON THE RETORTS, 
 
 rising or back flues R S, and main flue U U, 
 (Figure 6,) and of the openings III through the 
 crown of the arch J (figures 5 and 7). The same 
 letters of reference being placed upon figure 9 as 
 are used for similar parts in figures 5, 6, and 7, 
 further explanatory remarks are not in this place 
 required. 
 
 Figure 10. Longitudinal and vertical section of 
 retorts C, D, E (figure 5). The same letters of 
 reference are placed upon figure 10 as upon figures 
 5, 6, and 7, to designate corresponding parts. In 
 addition, however, we have, V V, section of the front 
 wall. W, sliding door with the Plate X upon 
 which it slides, and the sliding cover Y to be placed 
 over the part Z, connected with the ash-pit O, when 
 K is to be worked as a coke-oven ; but to be removed 
 to allow a draft through the fire-bars when K is to 
 be worked as a furnace. 
 
 When these retorts are heated by K worked as a 
 coke-oven, the oven should be charged once in 
 twenty-four hours with half a ton of coals, which 
 will produce about sixteen bushels of very excellent 
 coke, together with something over a bushel of 
 small or inferior coke. When worked as a furnace, 
 the fire should not be allowed to extend further than 
 about six inches beyond the fire-bars, which must 
 always be kept covered, but on no occasion to a 
 greater thickness than from four to six inches. 
 
 It may be useful here to remark, that when the 
 
AND MODES OF SETTING THEM. 
 
 149 
 
 coke-oven K is first brought into use, the best way 
 to get it up to a good working heat is to work it as 
 a furnace, allowing it the benefit of all the draft 
 the uncovered ash-pit will afford. To effect this 
 will require two or three days, and whilst the heat 
 is getting up, (in this case,) it will be advisable that 
 the fire, as it burns up, should be spread over the 
 bottom of the oven till the whole of it be covered 
 to the depth of from nine inches to a foot in thick- 
 ness, letting the stoker be careful to remove all 
 burnt-out material so that the fire may be kept 
 lively. By such management, we will suppose the 
 entire of the brick-work, of which the coke-oven 
 and the retort-oven over it are composed, is raised 
 to nearly a white heat, and the retorts to something 
 higher than a bright cherry-red head visible by 
 daylight. When such is the case, let the whole of 
 the fire be raked out of the oven, and its place 
 supplied by ten cwt. of coals spread over the 
 bottom at a uniform thickness; when that is 
 done, close the opening L by the sliding door W, 
 and open the damper T to nearly its full extent, in 
 order that the smoke and vapour from the coals just 
 introduced may have a free course to the main flue 
 and thence to the chimney. Let the damper remain 
 in that state till the coal be thoroughly ignited, 
 which it will be in from one hour and a half to two 
 hours. During that time, leave the part Z leading 
 into the ash-pit O uncovered ; but so soon as the 
 
150 
 
 ON THE RETORTS, 
 
 coal is well lighted, let the iron cover or door Y 
 be placed over Z so as to prevent any external air 
 finding its way into the ash-pit, and let the damper 
 T be closed within about three inches. In such 
 situation, the remaining part of the process will 
 be accomplished in about twenty-two hours ; or, 
 twenty-four hours will elapse between the time of 
 the coals being thrown into the oven and the time 
 when such charge has been converted into coke and 
 is ready for being drawn. So soon as the coke is 
 drawn, charge again with the same weight of coals 
 and attend to the doors, dampers, &c., as just di- 
 rected, by which method there cannot arise any 
 difficulty in keeping the retorts at a proper working 
 heat or in producing an excellent coke. It will be 
 desirable, however, to arrange the charging of the 
 retorts when heated by means of coke-ovens, so that 
 the charging of the retorts and the charging of the 
 coke-oven may not come round at the same time. 
 The best way will be always to charge the coke- 
 oven when the charge in the retorts is about half 
 burnt off, as whenever coke-ovens are used, the heat 
 must of necessity be decreased during the process of 
 drawing out the coke and recharging with fresh 
 coals, which would be subject to a further decrease 
 were the retorts charged with fresh coals also at 
 the same time. We have endeavoured to give such 
 instructions for the working of coke-ovens as we 
 hope will be clearly understood, and which, if fol- 
 
AND MODES OF SETTING THEM. 
 
 151 
 
 lowed, we are, from our experience, prepared to say 
 will produce the effects the gas manufacturer wishes 
 to accomplish, that is to say, to keep his retorts at a 
 good working heat, and to produce from the coals 
 used for heating them a valuable coke. We do so, 
 from having known instances of coke-ovens having 
 been worked in such a way as neither to produce 
 one of the objects just mentioned nor the other. 
 If, for instance, the coke-oven should be entirely 
 closed by covering up the ash-pit, shutting the door 
 of the oven and plastering both up very soon after 
 it was charged, so as to prevent any access of air to 
 assist in the lighting up of the coal, and if, in ad- 
 dition to this, the damper should be entirely closed 
 or even partly so, hardly any one would expect that 
 the coal in the oven would burn, or the retorts be 
 heated ; yet, strange as it may seem, such mode of 
 operation has been resorted to. 
 
 Having made these remarks, we proceed to ex- 
 plain the remainder of the figures of Plate VIII. 
 
 Figure 1 1 is a front view of a sight hole, frame, 
 and lid. 
 
 Figure 12 is a section of a sight hole, frame, 
 and lid. 
 
 Figures 1 1 and 12 are drawn from a scale of one 
 inch to a foot. 
 
 Figure 13. Front view of sliding door from fur- 
 nace ; G, door ; H, cast-iron plate upon which the 
 door slides. 
 
152 
 
 ON THE RETORTS, 
 
 Figure 14. Side view of sliding door for furnace, 
 marked with the same letters of reference as figure 
 13. 
 
 Figures 13 and 14 are drawn from a scale of 
 half an inch to the foot. 
 
 Plate 9, Figure 1. Represents a front view of 
 five cylindrical retorts set in one oven, heated by 
 one fire with the hydraulic main, H and dip pipes. 
 A, A, A, A, A, the retorts as set and in a finished 
 state. In this view the two upper retorts are 
 shown with all the lids of their respective mouth- 
 pieces ; the two outer lower ones with the lids on, 
 but without their being secured by a cross-piece 
 similar to what is shown upon the middle one. The 
 bed of these retorts is supported by an arch of brick- 
 work B B. It is brought so far forward as to allow 
 room enough for the stokers to charge and draw 
 the retorts, and for a sufficient quantity of coals to 
 be kept for supplying two or three charges with 
 fuel for present use, luting, tools, &c. Immediately 
 in front of the retorts is introduced (and which 
 serves as the key-stone to the arch) a cast-iron 
 frame of about three feet and a half long and two 
 feet broad at the top, with an iron-door fitted to it. 
 The bottom of the frame is struck to the radius of 
 the arch, and of course the sides taper inwards in 
 proportion to that radius. The situation of this 
 opening is shown at C. This opening is for the 
 purpose of allowing the red-hot coke, when drawn 
 
AND MODES OF SETTING THEM. 
 
 153 
 
 from the retorts, to fall under the archway at D. 
 a, the door of the fire-place ; b , the door of the 
 ash-pit. These doors are furnished with three 
 perpendicular slits of about two-thirds of their 
 height and five-eighths of an inch wide, for allow- 
 ing a current of air to pass to the fire. The di- 
 mensions of these slits can be decreased by another 
 piece made with openings to correspond, which 
 slides horizontally in grooves in a line with the slits 
 on the door, so as to regulate the admission of air 
 to such an extent as the stoker may find needful. 
 c c c c c, are the conducting pipes which convey the 
 gas as it is evolved from the retorts towards the 
 hydraulic main, ddddd, front elevations of the 
 H pipes, e e e e c, front sections of the dip-pipes 
 with the saddles through which they are bolted to 
 the hydraulic main. E, the hydraulic main. F, 
 the main pipe for conveying the gaseous and other 
 products evolved towards their respective reservoirs. 
 G G G G, cast-iron columns fitted with crutches 
 at the tops of the upper ones for supporting the 
 hydraulic main. 
 
 Figure 2 is a section of the same retorts, which 
 supposes them to be cut through from the top to 
 the bottom about the middle. In this section the 
 hydraulic main, dip, H and conducting pipes are 
 not shown. A A A A A, the retorts, a a part of the 
 arch forming the retort-oven and brick-work con- 
 tiguous to the fire-place, all of which requires to be 
 
154 
 
 ON THE RETORTS, 
 
 constructed of fire and arch-bricks. The crown of 
 the oven is flattened by means of fire-tiles as at b. 
 At the extreme end of the retort-oven are two 
 openings which lead into the two small flues cc. 
 These flues (c c) pass above the top of the oven 
 towards the fronts of the retorts, and then each 
 turns towards the centre flue d , which having 
 entered, that one leads towards the main flue H, 
 which it enters through the opening e. f is the 
 fire-place, and g the ash-pit. a* arch turned 
 over the fire-place, upon which the three lowermost 
 retorts are bedded. There are three openings at 
 each side of this arch marked # , (see also figure 
 3 * * *,) for allowing the flame from the fire-place 
 to rise into the retort-oven, which flame striking 
 against the interior of the retort-oven, causes the 
 retorts to be heated by reverberation. The two 
 upper retorts may be supported by one or more 
 wrought-iron belts brought through the upper part 
 of the oven, and passing through a cast-iron bearing- 
 bar placed above it, where they may be secured by 
 means of screw-nuts in the situations wanted ; or 
 they may be supported by one or more pillars built 
 of fire-brick to the height required as may be deemed 
 most expedient. 
 
 Figure 3 is a longitudinal section of cylindrical 
 retorts set on the oven plan. A A are the retorts, 
 the mouth-piece of the lower one being secured by 
 the lid and cross-bar, the upper one is shown with- 
 
AND MODES OF SETTING THEM. 
 
 155 
 
 out the lid. f is the fire-place with the position of 
 the grate-bars, g is the ash-pit. The action of 
 the fire in this section is as has already been de- 
 scribed by figure 2 ; the flame from the fire-place 
 (which is hopper-shaped as described in Plate X 
 figures 1, 2, 4) passes through the openings marked 
 # * # ^ gee corresponding ones in the arch a* a*, 
 figure 2) into the oven where the retorts are placed, 
 and strikes against the sides and soffit of the 
 arch a a , (figure 2,) reverberating upon the retorts 
 A A A A A, by which reverberation they are uni- 
 formly heated. From the retort-oven the surplus 
 heat is carried off by the opening shown at the 
 extreme end of the retorts, and passes along the 
 flue c towards their mouths till it comes to d , when 
 it enters the middle flue lying parallel to the flue 
 c ; that leads into the rising part e, and thence into 
 the main flue H. h is the conducting pipe which 
 conveys the gaseous and other products from the 
 retorts to the H pipe i, and that carries them into 
 the dip pipe k, which enters into the hydraulic main 
 E. In this section of the hydraulic main, the 
 fluid by which the dip pipe is sealed is shown at /, 
 through which the gas bubbles up as it is evolved, 
 and passes along the upper part of the hydraulic 
 main towards the main pipe F, (as shown in figure 
 1,) on its way to the washer, condenser, &c. The 
 hydraulic main is represented in this section as 
 supported in a similar way to what was shown in 
 
156 
 
 ON THE RETORTS, 
 
 figure 1 ; but instead of a brick arch for supporting 
 the floor in front of the retorts, in the retort-house, 
 m is one of a range of cast-iron beams for supporting 
 a floor constructed of cast-iron plates, n is the 
 opening for allowing the coke, when drawn from 
 the retorts, or from the coke-ovens for heating the 
 retorts where such are used, to fall upon the floor 
 at o. This opening is covered by a cast-iron door 
 or lid, and kept closed at all times save when the 
 retorts or coke-ovens are being drawn. 
 
 Plate X. Figure 1 represents a front view of 
 three D retorts AAA, as set and in a finished state. 
 In it the upper retort is shown without its lid ; the 
 two lower ones are represented with their lids on 
 and as secured in their places by means of cross bars 
 and screws in the usual way. a, the door of the 
 fire-place, b, the door of the ash-pit, which may be 
 similar to those described at figure 1, plate IX. (see 
 page 153) ; in the references to which figure, so far 
 as regards the conducting pipes which lead from 
 the retorts to the H pipes, the H pipes and the dip 
 pipes are so particularly described as to render repe- 
 tition here not necessary. In this figure E repre- 
 sents the hydraulic main, and F the main pipe for 
 conveying the gaseous and other products evolved 
 towards their respective reservoirs. This figure 
 also represents a section of three D retorts AAA, 
 similar to those just mentioned, which supposes 
 them to be cut through from the top to the bottom 
 
AND MODES OF SETTING THEM. 
 
 157 
 
 about the middle. In this section, though the 
 hydraulic main, the dip pipes and H pipes be 
 shown, the connecting pipes are shown as if broken 
 off a little above the brick-work which covers the 
 arches and flues of the retort-oven. «, an arch 
 turned over the fire-place from front to rear, with 
 four openings left at each side, marked * * in this 
 figure, and # * * * in figure 2, for allowing the flame 
 from the fire-place to rise into the retort-oven, 
 which flame striking against the interior of the 
 retort-oven causes the retorts to be heated by rever- 
 beration. The parts between the crown of the 
 arch a and the walls of each side of the retort-oven 
 are filled in with fire-bricks (leaving, however, the 
 openings # * # * through such fillings in), so as to 
 form a perfectly horizontal bed for the two lower 
 retorts to rest upon ; and care should be taken in 
 forming said openings that the edges of them on 
 their upper surface should not approach nearer than 
 two inches, at the very least, to the outside of the 
 bottom retorts, in order that the flame may not 
 strike directly against them, for should it do so it 
 will very soon burn holes through each of the 
 bottom retorts, directly opposite to where these 
 openings are situated. Indeed it would protect the 
 bottom retorts very much if the sides of each con- 
 tiguous to the openings just referred to were cased 
 with fire-tiles their entire length, which might be 
 made for the purpose in lengths of about eighteen 
 
158 
 
 ON THE RETORTS, 
 
 inches, width six inches, and thickness two inches. 
 In the front of the retort-oven is the opening d , 
 which leads into the flue e, figure 2, and by it into 
 the main flue H. f is the fire-place, and g the 
 ash-pit. 
 
 Figure 2 is a longitudinal section of D retorts, 
 set as described in figure 1. A A are the retorts. 
 f is the fire-place, with the position of the grate- 
 bars. g is the ash-pit. The action of the fire in 
 this section is as has already been described by 
 figure 1 ; the flame from the fire-place (which is 
 hopper-shaped, as described in figures 1, and a 
 plan of which is given at figure 4 of this plate) 
 passes through the openings marked **** (see 
 corresponding ones in the arch marked a , figure 1) 
 into the oven where the retorts are placed, and 
 strikes against the sides and soffit of its arch 
 (figure 1), reverberating upon the retorts AAA, 
 by which reverberation they are uniformly heated. 
 From the retort-oven the surplus heat is carried off 
 by the opening d, and passes along the flue e to the 
 main flue H. The upper retort is supported by one 
 or more pillars (marked B, figure 1) built of fire- 
 brick, or by a wall, built of such material, its entire 
 length, as represented in this figure. 
 
 Figure 3 is a plan of the top flues e (figure 2) 
 which lead towards the main flue. In this plan 
 each retort-oven has its own separate flue, which 
 leads towards a short main flue that rises directly 
 
AND MODES OF SETTING THEM. 
 
 159 
 
 into the chimney, and merely crosses a portion of 
 the end of the retort-bed, instead of running the 
 entire length thereof, as is the more usual practice. 
 This arrangement of top flues will answer well 
 when only two or three ovens are required, but in 
 ranges of a greater number it becomes so compli- 
 cated as to render its adoption impracticable. 
 
 Figure 4 is a plan of the fire-place, in which the 
 situation of the door-way thereto and the fire-bars 
 are shown ; the brick-work round the fire-place is 
 to be carried up to the height shown in figures 1 
 and 2, and from that height it is to be splayed off 
 at the sides as shown in figure 1, and at the end as 
 shown in figure 2 ; so that when the work is entirely 
 completed, it will form a shape something similar 
 to a hopper. The filling in may be of common 
 bricks laid in lime and sand-mortar, but it must be 
 finished either with fire-bricks laid edgewise and 
 well grouted with fire-clay or with two courses of 
 fire-bricks, as may be most convenient. 
 
 Figure 5 is a front view of doors and frames for 
 the fire-place and ash-pit. The lower door, or that 
 for the ash-pit, is cast with three perpendicular slits, 
 each five-eighths of an inch wide and eight inches 
 long, for allowing a current of air to pass to the 
 fire. The dimensions of these slits can be decreased 
 by another piece (figure 7) cast with corresponding 
 openings, which slides in grooves horizontally, so 
 that thereby the admission of the air can be regu- 
 
160 
 
 ON THE RETORTS, 
 
 lated to such a degree as the person having charge 
 of the fire may deem needful. The grooves and 
 slide are shown in section at figure 6. 
 
 Figure 6. Vertical section of furnace-doors and 
 frames for showing the thickness of the metal (half 
 an inch) and distance which the frame is intended 
 to be brought within the brick- work (six and a half 
 inches) . 
 
 Figure 7. Front view of the piece which is in- 
 tended to slide over the ash-pit door, described in 
 figure 5. This may be made of boiler-plate one- 
 fifth of an inch thick, or of cast-iron three-eighths 
 of an inch in thickness, with the slits as shown. 
 
 Figure 8. Side view of a fire-bar for a retort 
 furnace of a very convenient length, and of the best 
 shape for ensuring durability. 
 
 Figure 9. Plan of the upper face of said fire- 
 bar ; its entire length is two feet six inches ; the 
 bearings at each end are three inches by three 
 inches, and depth three inches ; the width of the 
 upper face of the fire-bar between the bearings is 
 two inches and a quarter. 
 
 Figure 10 is a section of figure 8 at its greatest 
 depth ; width at the top two inches and a quarter ; 
 depth of the upper or square part of the bar two 
 inches ; of the lower or circular part, three inches : 
 the circular part of the bar is bevelled off at each 
 side, so as to leave the lower edge about three- 
 quarters of an inch broad. 
 
AND MODES OF SETTING THEM. 
 
 161 
 
 Figure 1 1 . Side view of one of the bearing bars, 
 upon which the fire-bars rest ; its extreme length is 
 one foot eight inches, and depth three inches. 
 
 Figure 12. Transverse section of the bearing 
 bar, figure 11, which shows that it is two inches in 
 thickness by three inches deep. 
 
 The reader is here informed that figures 1, 2, 3, 
 and 4, of Plate X., are drawn from a scale of a 
 quarter of an inch to a foot, and figures 5, 6, 7, 8, 
 9, 10, 11, and 12, from a scale of one inch to a foot ; 
 he can, therefore, from them prepare working draw- 
 ings for setting three D retorts as therein described ; 
 and whilst speaking of that particular plate it may 
 be observed, that the same remark is applicable to 
 all the plates in which different modes of setting 
 different kinds of retorts have been delineated. 
 
 Having now described such retorts and modes of 
 setting them as we think most applicable to the 
 purposes of the gas-light manufacturer, whether the 
 manufactory be upon a small or upon a large scale, 
 we shall draw this chapter to a conclusion by re- 
 marking, that we are well aware we have not given 
 drawings or descriptions of one half of the methods 
 which have been adopted at several gas manufac- 
 tories for setting retorts : we refrain from doing so 
 because we think no useful end would be thereby 
 attained, as all the plans in use at the present day 
 are but modifications of those we have described. 
 Whilst in some manufactories the flue plan, as we 
 
 M 
 
162 
 
 ON THE RETORTS. 
 
 have described it, is still adhered to ; in others the 
 heating of three, five, or seven (or even more) retorts 
 in one retort-oven, by means of one or more fires on 
 the furnace system, is the favourite practice ; and 
 whilst others, again, prefer heating three or five 
 large retorts in one retort-oven, by means of a coke- 
 oven ; whilst some, again, prefer ascending and some 
 descending flues, yet, as has already been observed, 
 all these methods arise out of plans we trust we have 
 so sufficiently described as to render them perfectly 
 intelligible to the practical reader, who, with our 
 plates and descriptions, we expect will find no diffi- 
 culty in constructing his retort-ovens, furnaces, and 
 coke-ovens, so as to answer for any number of retorts 
 he may deem it expedient to set in one batch or nest. 
 Our plates, we know from much experience (as they 
 are all made from working drawings of our own 
 made by ourselves, from which we have erected 
 apparatus at various places and to a very great 
 extent), are particularly applicable to all establish- 
 ments where from three to one hundred elliptical, 
 kidney-shaped, or large D retorts are required, and 
 more particularly those described by figures 1, 2, 6, 
 
 7, 8, and 9, Plate VII. ; figures 1, 2, 3, 4, 5, 6, 7, 
 
 8, 9, and 10, Plate VIII. ; figures 1, 2, and 3, Plate 
 IX. ; and figures 1, 2, 3, and 4, Plate X. 
 
163 
 
 CHAPTER VI. 
 
 On Carbonization, so far as relates to the most beneficial time for 
 working the retorts and the per centage at which it may be 
 carried on. 
 
 Experience has taught every gas manufacturer 
 that the well-being of every gas-light establishment 
 mainly depends upon the retorts being kept at a 
 good working heat, and upon the expense of coal or 
 other material used for the purpose of heating them 
 being at as low a per centage upon the cost of coals 
 used in the retorts as it is possible. These are 
 things of the utmost importance so far as the manu- 
 facture of gas is concerned ; we must admit, how- 
 ever, that occasionally other things occur which 
 militate against the proprietors of gas shares obtain- 
 ing a fair profit for their investment, which we 
 intend to notice in their proper place ; but, if the 
 retorts are not skilfully and economically worked, 
 no saving in any other department can make good 
 the loss which will thence inevitably arise. Hence 
 numerous have been the experiments made for the 
 purpose of decreasing the expenses which arise from 
 the destruction of the retorts ; for carrying on the 
 process of carbonization at a low per centage ; and 
 for obtaining the greatest quantity of gas in the 
 
 M 2 
 
164 
 
 ON CARBONIZATION. 
 
 least possible time, and that gas of the best 
 quality. 
 
 As the different shapes of the retorts, with the 
 general results arising from the use of each, have 
 been spoken of in the preceding chapter, we shall 
 now confine our inquiries more particularly to the 
 length of time in which the charge of coals in a 
 retort is most advantageously worked off, and the 
 per centage at which carbonization ought to be 
 carried on. 
 
 In the early period of this mode of obtaining light, 
 it was not at all uncommon to hear of attempts to 
 decompose coal in such prodigious masses as would 
 require more than twenty-four hours to work off at 
 one charge. When such was the case, more coal 
 was used for heating the retort than the quantity 
 it contained from which gas was to be extracted. 
 Retorts of as much as twenty inches in diameter 
 have been heard of, and the time alluded to is that 
 when such were used. When these large retorts 
 were filled with coal, and that coal submitted to the 
 distillatory process, every one must be aware that a 
 considerable time would elapse before the entire of 
 the coal contained in the retort could become heated 
 to redness ; and, as the outer surface would first 
 become so, it would, after being decomposed and 
 converted into coke, become so close and compact a 
 coating to the more central part of the coal in the 
 retort as to render the passage of the gas from that 
 
ON CARBONIZATION. 
 
 165 
 
 part extremely difficult ; and it would also follow, 
 that although the quantity of gas evolved during 
 the first two or three hours of the process might he 
 very considerable, it would hourly decrease in 
 volume, and so much so, that during a very consi- 
 derable portion of the latter part of the distillatory 
 process there would not be so much gas generated 
 as would repay the manufacturer for the coals neces- 
 sarily used for keeping his retort at a proper work- 
 ing heat. A system like this could not be expected 
 to continue in use for any length of time : its errors 
 were too palpable to remain unnoticed. At the 
 time it was practised, such as were engaged in the 
 manufacture of gas considered that, if the expense 
 of carbonising could be reduced to less than fifty 
 per cent, on the coals carbonised, further reduction 
 could hardly be expected. A few years’ practice, 
 however, proved how little was then known about 
 the matter ; for, instead of carbonization being car- 
 ried on at fifty per cent., it has, in some instances, 
 been reduced to as low as sixteen per cent., when 
 working retorts on an extensive scale. This reduc- 
 tion, however, was not made all at once, nor was it 
 altogether effected without increasing the wear and 
 tear of retorts, or otherwise, by a loss in the quantity 
 of gas procured from a given quantity of coals. 
 The retorts were first reduced from twenty inches 
 in diameter to twelve, which last named size were 
 for a considerable time generally used ; but now 
 
166 
 
 ON CARBONIZATION. 
 
 have, in their turn, given way in most cases to the 
 elliptical, small, or large D-shaped retorts. 
 
 At the time when cylindrical retorts were used, 
 it became a question with some whether the manu- 
 facturer could not increase his profits by working 
 his retorts at a lower temperature than was neces- 
 sary to obtain at the rate of about 7,400 cubic feet 
 of gas from a ton of the best Newcastle coals; to 
 effect which, the length of time necessary for ac- 
 complishing the process would be eight hours — 
 each retort being charged with 160 pounds of coals, 
 and the heat worked at a bright cherry-red visible 
 by day-light. To ascertain the fact, numerous ex- 
 periments were made at different gas establishments, 
 and with retorts of such shapes as were generally 
 in use, the results of all which tended to prove in 
 favour of eight hours’ charges, the retorts being 
 worked at a bright cherry-red heat visible by day- 
 light : in all places where, as in London, the price of 
 coal is high, and where from the form of the retort, 
 160 pounds of coal formed a proper charge, as well 
 as being particularly applicable to the twelve-inch 
 cylindrical, and twelve-inch square, or to the twelve- 
 inch D retorts. Where coals are very cheap, 
 working the retorts at a low temperature may not 
 be of any great consequence as it affects the manu- 
 facturer ; but generally speaking, it is a system 
 which ought carefully to be guarded against 
 When it is considered that by working the re- 
 
ON CARBONIZATION. 
 
 167 
 
 tort at a low temperature, not more than about 
 5,926 cubic feet of gas can be expected from a ton 
 of the same description of coals, which, if decom- 
 posed at a higher temperature, produces 7,400, there 
 evidently arises a loss, upon each ton of coal carbon- 
 ised, of 1,474 cubic feet of gas, which at the 
 London price, 9s. per 1,000 cubic feet, amounts to 
 13s. 3d. Under such circumstances, it will not be 
 difficult to understand, that even where coals are 
 cheap, it cannot be to the advantage of the manu- 
 facturer to work his retorts at a low temperature. 
 We are aware that some of our readers may object 
 to our speaking of 7,400 cubic feet being the pro- 
 duction of gas from a ton of Newcastle coals ; we 
 are also aware, that the House of Commons has 
 been informed within the last four years by a 
 gentleman, who is said “ to possess a sound know- 
 ledge of chemistry, joined to such mechanical talent 
 and indefatigable diligence, as qualify him to conduct 
 with success any great undertaking committed to 
 his care,” that the average quantity of gas procured 
 in London from a ton of coals is 8,500 cubic feet ; 
 that at Birmingham the proportion is 6,500 ; at 
 Macclesfield, 6,720 ; at Stockport ,7,800, (half Can- 
 nel coal used) ; at Manchester, 9,500 (Cannel coal 
 used) ; at the Liverpool Old Gas Works, 8,200 
 (Ormskirk and Wigan slack) ; at the Liverpool 
 New Gas Works, 9,500 (Wigan Cannel used) ; 
 at Bradford, 8,000, at Leeds, 6,500, at Sheffield, 
 
168 
 
 ON CARBONIZATION. 
 
 8.000, (partly Cannel,) at Leicester, 7,500, at Derby, 
 
 7.000, and at Nottingham, 7,000. We are further 
 aware, that the managers of some of the London 
 Gas Companies, at the present day, speak of obtain- 
 ing about 9,600 cubic feet of gas from a ton of 
 coals, but this is the maximum spoken of, others 
 quote. 9,000 as the result of their average working ; 
 but giving the manufacturer the benefit of the 
 highest amount mentioned, which, if procured at 
 all, must be at an immense cost of fuel for heat- 
 ing the retort, and at an enormous expense also for 
 wear and tear; our position is not weakened as 
 regards the working retorts at a low temperature ; 
 on the contrary, additional strength is thereby 
 given to it ; for at a low temperature, the quantity 
 of gas produced will not be increased beyond what 
 we have already quoted, that is to say, 5,926 cubic 
 feet to the ton (say in round numbers 6,000) ; 
 whilst taking 9,000 cubic feet to the ton, as the 
 present average produce on the other side, there 
 would arise a loss upon each ton of coal carbonised 
 of 3,000 cubic feet of gas, which, at the London 
 price, 96*. per 1,000 cubic feet, amounts to 
 1 /. 7s. Taking into consideration (from the re- 
 marks just made) the profits on one hand, and com- 
 paring them with the losses on the other, it would 
 appear to be more advantageous to charge such 
 retorts, as we have been speaking of, with 160 
 pounds of coals, and to work them at such a heat 
 
ON CARBONIZATION. 
 
 169 
 
 as would, from a ton of coals, produce from 7,400 to 
 9,000 cubic feet of gas. 
 
 Whilst some were pursuing experiments, for the 
 purpose of ascertaining whether it would be more 
 profitable to work the retorts at high or at low tem- 
 peratures, others supposed that it would be more 
 profitable to work the retort at six hours’ charges, 
 decreasing the quantity of coals submitted to car- 
 bonization, at one charge, from 160 to 120 pounds, 
 or even to 100 pounds. The parties who favoured 
 the short charges were led to expect immense ad- 
 vantages from their adoption, from considering 
 that, when the retorts were worked at eight hours’ 
 charges, four-fifths of the gas produced was evolved 
 during the first six hours of the process, and from 
 having probably noticed also that the gas produced 
 during the two last hours of the charge was of 
 very low illuminating power. That when retorts 
 are worked at eight hours’ charges of 160 pounds 
 of coal to each, and at a bright cherry-red heat 
 visible by daylight, four-fifths of the gas which 
 would be produced during the entire eight hours 
 would come over during the first six hours of the 
 charge, the following table being the results of 
 numerous experiments, made in the large way under 
 my own observation, will very clearly demonstrate # 
 It may not be improper to remark, that I was led 
 to make these experiments during the summer of 
 1816 (the reader conversant with matters con„ 
 
170 
 
 ON CARBONIZATION. 
 
 nected with gas-lighting will be aware there was 
 not, at that time, such a thing as a station-meter in 
 existence, nor any other gas-meter that could be 
 depended upon for registering the quantity of gas 
 which might pass through it), from having found 
 it difficult to ascertain the quantity of gas generated 
 by any kind of approximation during the short 
 days of the preceding winter, when the street-valve 
 frequently did not remain shut during one entire 
 charge. As one part of my duty, then, was to 
 report the quantity of gas daily generated at the 
 works of a London Gas Company with which I 
 was then connected, I considered that, by a series 
 of experiments made on different kinds of coal, I 
 might obtain such a knowledge of the proportions 
 in which the gas was evolved, as would furnish me 
 with proper materials for making my calculations 
 from, even should the communication between the 
 street-mains and the gas-holder not be shut off 
 more than half the time of one charge. 
 
 Table exhibilin g the Ratio at which the Gas is evolved 
 from Newcastle Coals , when the retorts are worked at 
 Eight Hours' Charges : — 
 
 During the 1st hour of the process 2,000 cubic feet are generated. 
 
 2nd 
 
 99 
 
 1,495 
 
 3rd 
 
 99 
 
 1,387 
 
 4th 
 
 99 
 
 1,279 
 
 5th 
 
 
 1,189 
 
 6th 
 
 
 991 
 
 7th 
 
 99 
 
 884 
 
 8th 
 
 
 775 
 
 the process. 
 
 Total 10,000 cubic feet obtained during 
 
ON CARBONIZATION. 
 
 171 
 
 Since the station-meter has been adopted, I have 
 had ample means of verifying the above, and find 
 the proportions as stated in the above table, so 
 nearly approaching to what the station-meter has 
 indicated, that I see no necessity for alteration 
 therein. I may here remark, that no gas establish- 
 ment, however small, ought to be without a station- 
 meter ; but as there are some, even at this day, not 
 provided with one, to persons having the manage- 
 ment of them , the above table will be found useful 
 for filling up their carbonising account-book, when 
 circumstances will not permit of the valve from 
 the gas-holder towards the street or supply-pipe 
 being kept closed during an entire charge; for 
 if the total be considered as one, then the cubic 
 feet of gas as therein stated, to be generated 
 during each hour of the charge, will be decimal 
 parts of one. It follows, therefore, that if the quan- 
 tity of gas actually generated during any part of 
 the process be known, the heat of the retort con- 
 tinuing equable throughout the entire charge, the 
 total quantity of gas made during that entire charge 
 may be known also, by dividing that which is 
 known by the sum of the decimals in the table 
 corresponding with the hours upon which the ob- 
 servations may have been made. Thus, for ex- 
 ample, supposing such a number of retorts charged 
 as produced, from the beginning of the second to 
 the end of the fifth hour of the process, 6,741 
 
172 
 
 ON CARBONIZATION. 
 
 cubic feet of gas, and we wished to know what 
 quantity would be produced during the entire 
 charge, by referring to the table, it will be found 
 that — 
 
 During the 2nd hour of the process, * 1495 cubic feet of gas are 
 
 generated. 
 
 99 
 
 3rd 
 
 99 
 
 1387 
 
 99 
 
 99 
 
 4th 
 
 99 
 
 1279 
 
 99 
 
 99 
 
 5th 
 
 99 
 
 1189 
 
 99 
 
 the divisor. 
 
 Their sum 5350 in this case will be 
 
 Then 6,741 4- 5,350 = 12,600 cubic feet, the quan- 
 tity of gas produced during the entire charge. 
 
 Having spoken at some length as to working the 
 retorts at eight hours’ charges, we may now notice, 
 that it has become a very prevalent practice to work 
 them in several establishments at six, and in some, 
 at four hours’ charges ; the four hours’ charges 
 are not, however, much practised, except where 
 Cannel-coal is used for the production of gas. In 
 the former editions of this work we gave it as our 
 opinion, that, in most cases, it would be to the 
 advantage of the manufacturer to work his retorts 
 at eight hours’ charges, and the subsequent practice 
 of many years has not had a tendency to produce 
 any considerable change in the opinions we then 
 expressed : for whenever retorts are worked at short 
 charges, a smaller quantity of coals must be used 
 for each charge ; and to work that diminished 
 charge well off, the retort must be kept at a very 
 
ON CARBONIZATION. 
 
 173 
 
 high temperature : for, when the short processes are 
 followed, the frequent charging and drawing so 
 cools the retorts, if attempted to be worked at such 
 a heat, as is best adapted for eight hours’ charges, 
 as to make it very difficult to keep that degree of 
 heat up, thus rendering it necessary to keep the 
 retorts at nearly a white heat, in order that the 
 coal may be properly carbonised within the period 
 required. The more rapid destruction of the retort 
 will be one of the consequences, and the lower 
 specific gravity of the gas another ; for any heat 
 above a bright cherry-red visible by day-light will 
 have a tendency to make the gas lighter, conse- 
 quently of less illuminating power ; and, though it 
 may be increased in bulk, it will not at all in the 
 same proportion be increased as to the quantity of 
 light it may afford, for reasons I shall elsewhere 
 state. 
 
 That the expense of heating the retorts will be 
 increased where short charges are worked, there 
 can hardly be a doubt, and that such is the case, 
 I may here mention that my own practice during 
 a great number of years, in the working of ellip- 
 tical and small D-shaped retorts set in ovens, and 
 heated by means of furnaces, has on the gross 
 fallen, for the article of fuel for heating the retorts, 
 under thirty per cent, upon the value of the coals 
 used for making gas. In an official document, laid 
 before a Committee of the House of Commons in 
 
174 
 
 ON CARBONIZATION. 
 
 1837, it was reported, that, in London, where it 
 states six hours’ charges prevail, thirteen bushels of 
 coke are used for heating the retorts for every ton 
 of coals carbonised. It states, also, that every ton 
 of coals used for making gas produces thirty-six 
 bushels of coke, and that the coke is sold for 12s. 
 per chaldron; further, that 17s. is the average price 
 paid per ton for coals by the London gas manufacturers. 
 Now, if we can suppose the above data to be correct, 
 carbonization is carried on in London at about 
 twenty-six per cent, upon the value of the coals 
 carbonised, which fact we come at thus : — One ton 
 of coals cost 17s. To carbonise it, requires thirteen 
 bushels of coke, which sells at 12s. per chaldron of 
 thirty-six bushels, consequently one bushel is worth 
 fourpence : therefore, 13 bushels x 4 = 52 pence 
 for coke for fuel, and 17s., the price of one ton of 
 coals X 12 ==■ 204 pence, is the cost of the coals 
 used for making gas = VW — AV or -ft of the 
 cost of the coals carbonised in the retorts. Were 
 the facts really so, it is evident a considerable ad- 
 vantage would be gained by the adoption of short 
 charges in the saving of coals or coke used for fuel ; 
 but, unfortunately for the party who made this 
 statement, no single gas establishment in London 
 is to be found where carbonization is carried on at 
 so low a per-centage : some of the managers of the 
 best arranged and best paying ones in the metro- 
 polis do not pretend that they heat their retorts at 
 
ON CARBONIZATION. 
 
 175 
 
 a less expense than thirty per cent, upon the cost 
 of the coals used for making gas, and it is generally 
 believed by persons acquainted with the operations 
 of the London gas companies, that the average 
 cost of carbonising in the different gas-works 
 situated in London, Westminster, and Southwark, 
 is nearer forty per cent, than thirty. Supposing, 
 therefore, that 9,000 cubic feet be the average 
 produce of gas from a ton of coals, and that only 
 7,400 would be obtained from a like quantity were 
 the retorts worked at eight hours’ charges, we are 
 of opinion, after all, that when we have set off 
 against the increased quantity of gas obtained, its 
 illuminating inferiority and the increased cost for 
 fuel and for replacing burnt-out retorts, and fire- 
 bars arising out of working the retorts at short 
 charges, as well as for increased expenses for repairs 
 of furnaces, we shall find at the year’s end little if 
 any saving arising out of the departure from work- 
 ing the retorts at eight hours’ charges with about 
 160 pounds of coal to one retort for each charge. 
 Indeed, we are quite certain, that where cylindrical 
 or the small D-shaped retorts are used, the eight 
 hours’ charges will always be the most advanta- 
 geous to the manufacturer. Where the elliptical, 
 the kidney-shaped, or the large D-shaped retorts 
 are used, we are of opinion that a charge of 120 
 pounds of coal may be worked off advantageously in 
 six hours ; and in cases of emergency, such shaped 
 
176 
 
 ON CARBONIZATION, 
 
 retorts might be worked at four hours charges 
 with one hundred pounds of coal to each for a 
 charge, in either case causing the temperature of 
 the retort to be kept a little higher than to afford 
 a bright cherry-red heat visible by day-light, being 
 very careful, however, to prevent the retort from 
 approximating towards incandescence, which must 
 be guarded against for reasons already given, and 
 which, when we speak of the chemical constitution 
 of coal-gas, will be more fully dwelt upon. 
 
 Were it requisite, we could, from numerous ex- 
 periments made in the large way at different times 
 and under different circumstances, most satisfactorily 
 prove the general superiority of the longer process 
 to the shorter ; but we deem it not necessary now 
 to do so, though we considered, when our former 
 labours were laid before the public, it was needful 
 to furnish our readers with the details of various 
 experiments made with cylindrical and other retorts 
 worked at six and eight hours’ charges respectively. 
 The first of the experiments alluded to was carried 
 on for one week with ninety-two cylindrical retorts 
 worked at six hours’ charges ; in which time 857,667 
 cubic feet of gas, about 110 chaldrons of coke and 
 breeze, 7f tons of coal tar, and 1,864 gallons of 
 ammoniacal liquor, were produced ; value altogether, 
 at the then selling prices of the products, 870/. 
 The expenditure for producing the above result was 
 the cost of 140 tons of coal for making gas, and of 
 
ON CARBONISATION. 
 
 177 
 
 58 tons of coals for heating the retorts, and an 
 increase of the stokers’ wages (two more being 
 necessary than would have been required had the 
 retorts been worked at eight hours), amounting 
 altogether to 360/. The average quantity of gas 
 procured from one ton of coals during the entire 
 experiment amounted only to 6,126 cubic feet. 
 
 Another experiment was continued also for a 
 week with cylindrical retorts worked at eight hours’ 
 charges, in which time the same quantity of gas, 
 viz. 857,667 cubic feet of gas, was obtained ; to 
 procure which, however, upon the average of the 
 whole week, only seventy-four retorts were kept in 
 action. In addition to the gas already named, there 
 was, in the carrying out of this experiment, obtained 
 103 chaldrons of coke and breeze, 6-§- tons of coal 
 tar, and 1,536 gallons of ammoniaeal liquor ; value 
 altogether, at the then selling prices of the pro- 
 ducts, 851/. The expenditure for producing the 
 above amount was, for 116 tons of coals for making 
 gas, and 29 tons of coals for heating the retorts, 
 266/. The average quantity of gas obtained from 
 one ton of coals, during the entire experiment, 
 amounted to 7,393 cubic feet. 
 
 By comparing the results of the two experiments 
 just noticed, the reader will observe, that the same 
 quantity of gas was generated under one as under 
 the other mode of operation, notwithstanding there 
 were fewer retorts used and less coal carbonised 
 
 N 
 
178 
 
 ON CARBONISATION. 
 
 when the retorts were worked at eight hours’ 
 charges than when they were worked at six hours’ 
 charges ; and that the expense of fuel for heating 
 the retorts in use when the distillatory process was 
 extended to eight hours was considerably less ; and 
 the proportion of gas obtained from a ton of coals 
 in that case greater than when the process was only 
 continued to six hours. 
 
 Now if from the products when working at 
 
 six hours’ charges £ 870 
 
 we take the products when working eight 
 
 hours’ charges 851 
 
 we have a difference of . . £ 19 
 
 which being subtracted from the difference between 
 the expenditures as already specified, viz. 
 
 Expenditure when working the retorts at 
 
 six hours’ charges £ 360 
 
 Ditto ditto at eight hours’ charges 266 
 
 Difference ... 94 
 
 Less . . 19 
 
 leaves .... £ 75 
 
 as a balance in favour of working eight hours’ 
 charges for one week over what was the result 
 when the retorts were worked at six hours’ charges, 
 857,667 cubic feet of gas being produced in each 
 
 case. 
 
ON CARBONISATION. 
 
 179 
 
 Plaving compared the quantity of coals actually 
 used when working six hours’ charges, with what 
 was used to produce the same quantity of gas from 
 eight hours’ charges, I shall next point out the 
 quantity of gas generated when working the same 
 number of retorts at' eight hours’ charges, which 
 had been worked at the process of six hours. The 
 experiment was carried on for one entire week during 
 each day, of which the average number of retorts 
 worked was ninety-two. There were produced from 
 this series of experiments 1,070,000 cubic feet of 
 gas, 128 chaldrons of coke and breeze, 8 tons of coal- 
 tar, and 1,945 gallons of ammoniacal liquor, value 
 altogether, at the then selling prices of the products, 
 1,060/. The expenditure for producing the above 
 amount was, for 144 tons of coal for making gas, 
 and 36 tons of coal for heating the retorts, 330/. , 
 the quantity of gas obtained from one ton of coals 
 during the entire experiment amounted to 7,430 
 cubic feet. 
 
 Products per experiment just named ... £ 1,060 
 Products per experiment, when 92 retorts 
 were worked at an average at six hours’ 
 charges, see page 176 870 
 
 Difference in favour of eight hours’ charges £190 
 
180 
 
 ON CARBONISATION. 
 
 Expenditure when working 92 retorts, at 
 
 six hours’ charges £360 
 
 Expenditure when working 92 retorts, at 
 
 eight hours’ charges 330 
 
 Leaves a difference of expenditure in favour 
 
 of eight hours’ charges, of ... 30 
 
 To which if we add the difference in favour 
 
 of eight hours’ charges for products . 190 
 
 we have . . . £220 
 
 From the above recapitulation, it appears, that, 
 by working ninety-two cylindrical retorts for one 
 week, at six and at eight hours’ charges respectively, 
 there would be a balance in favour of eight hours’ 
 charges amounting to 220/. ; and in this proportion, 
 let the number of retorts be what it may, an advan- 
 tage will always be gained by working cylindrical 
 retorts at eight hours’ charges, instead of adopting 
 the six hours’ process. 
 
 After the reader has carefully examined the results 
 of the three experiments as just given, it is expected 
 it will not be necessary to make any additional com- 
 ment on the imaginary advantage from decreasing 
 the time for working off one charge of the retort, 
 particularly as the care which was taken in making 
 them, enables the author to lay them before his 
 readers, as such as can be depended upon. If we, 
 however, refer to the two first, and pursue our cal- 
 
ON CARBONISATION. 
 
 181 
 
 culations a step further, we shall find still greater 
 advantages arising from working cylindrical or 
 small D-shaped retorts at eight hours’ charges ; 
 for we consider it has been proved, that when such 
 retorts are worked at six hours’ charges, they do 
 not remain serviceable more than about two-thirds 
 of the time they would do if worked at the eight 
 hours’ process. This more rapid destruction of the 
 retorts arises principally from the necessity of work- 
 ing them at a higher temperature than would be 
 required were they otherwise worked ; for unless 
 they he kept at almost a white heat when working 
 at six hours’ charges, the frequent charging and 
 drawing so cools the retorts, that, were they not 
 kept at that high temperature, they would soon be 
 unable to extract the gas from the coals with which 
 they were charged, owing to their decrease of tem- 
 perature, so that, instead of drawing good bright 
 coke from them at the end of each charge, the 
 retorts would contain a great quantity of tar, and 
 the coal would not be half carbonised. In working 
 at a very high temperature, the fire requires to be 
 increased, and consequently the grate-bars are more 
 rapidly burnt out, and the destruction of every part 
 of the fire-work is very materially accelerated. 
 
 The following statement is made for the purpose 
 of bringing before the reader the annual balance in 
 favour of working eight hours’ charges with cylin- 
 drical or small D-re torts, over those of six hours. 
 
182 
 
 ON CARBONISATION. 
 
 when it is required to produce the average weekly 
 quantity of 857,667 cubic feet of gas by either 
 process. 
 
 At page 178, the balance in favour of working 
 eight hours’ charges for ©ne week, over those of 
 six hours, the quantity of gas as above mentioned 
 being produced in either case, is stated at 75/., or 
 at the rate of 3,900/. per annum, and this balance 
 is for coals, products, and labour only. The first 
 cost of setting one retort on the flue-plan is about 
 23/. when four are heated by one fire ; this includes 
 pipes to the hydraulic main, coke, hearth, &c., con- 
 sequently a series of four retorts set in that method 
 would cost 92/. The cost of replacing a cylindrical 
 or small D-retort so set, including repairs of fire- 
 work, &c., is about 15/., or at the rate of 60/. for 
 a series of four retorts. 
 
 By the six hours’ process, it would require 
 ninety-two retorts to be kept constantly 
 at work to produce 857,667 cubic feet 
 of gas per week. Retorts so worked 
 would not at an average, remain service- 
 able (if set on the flue-plan) more than 
 four months, consequently 276 would 
 be burnt out in a year, and the cost 
 of replacing each being 15/., the cost 
 of replacing that number amounts to. £4,140 
 
 Wear and tear of grate-bars, &c. . 140 
 
 £4,280 
 
ON CARBONISATION. 
 
 183 
 
 By the eight hours’ process, it would require 
 seventy-four retorts to be kept con- 
 stantly at work to produce 857,667 
 cubic feet of gas per week. Retorts 
 so worked, if set on the flue-plan, 
 would remain serviceable six months, 
 consequently there would be but 148 
 burnt out in a year : the cost of re- 
 placing each being reckoned 15/., the 
 
 cost of replacing that number would 
 
 amount to £ 2,220 
 
 Wear and tear of grate-bars, &c 80 
 
 £2,300 
 
 Balance in favour of eight hours’ charges, 
 so far as relates to the wear and tear 
 
 of retorts, furnace-bars, &c £1,980 
 
 If to the above we add the balance for coals, 
 products, and labour, as already stated 
 at page 182 3,900 
 
 their sum . . . £5,880 
 
 shows the annual balance in favour of working 
 eight hours’ charges (with cylindrical or small 
 D-retorts set on the flue-plan), when it is required 
 to produce in that time, by either mode of working, 
 44,598,684 cubic feet of gas. 
 
 Considerable as is the advantage gained by the 
 manufacturer from working cylindrical or small 
 
184 
 
 ON CARBONISATION. 
 
 D-shaped retorts at eight hours’ charges instead of 
 six, both as regards the products, and also the wear 
 and tear of retorts, yet the practice of working 
 these descriptions of retorts at six hours’ charges 
 continues in many gas establishments to be per- 
 severed in. 
 
 The cause which perhaps first induced the ma- 
 nufacturer to work cylindrical retorts at less than 
 eight hours’ charges was a want of sufficient room 
 in the gas-holders for the gas necessary for the 
 light he had to supply, which led him to shorten 
 the process of carbonization, under an idea that he 
 would procure a greater quantity of gas in a shorter 
 time, he being well aware of the much more rapid 
 generation of the gas during the beginning than 
 towards the end of an eight hours’ charge. Instead, 
 however, of his obtaining a greater quantity of gas 
 in a given time from a given number of retorts 
 worked at six hours’ charges than he would have 
 obtained had he worked the same number of retorts 
 at eight hours’ charges, we think we have said 
 enough to show he could not by any possibility 
 obtain so much, and that the smaller quantity of 
 gas would be generated at more expense than the 
 greater. We therefore repeat, that on all occa- 
 sions where the cylindrical or small D-shaped 
 retorts are used, it is the most advantageous to 
 work them at eight hours’ charges. In order in 
 some measure further to elucidate this point, we 
 
ON CARBONISATION. 
 
 185 
 
 may observe, that, whenever pit-coal is to be sub- 
 mitted to the process of distillation, the time for 
 completing the process cannot be shortened to less 
 than eight hours, unless we have the means of 
 exposing the coal to the action of the heat in thin 
 strata, say four inches. When coal is so exposed 
 in cylindrical retorts, that retort which, when 
 worked at the eight hours’ process, is capable of 
 effectually carbonising 160 pounds of coal, would 
 only carbonise about forty-eight pounds, which is 
 the weight of a layer of four inches in thickness on 
 the bottom of the retort ; the section of a cylinder 
 whose altitude is four inches, base eleven inches, 
 and length about six feet, being in that ratio to the 
 capacity of the retort whose inside diameter is twelve 
 inches, and working length about six feet. We 
 have been told by persons having the management 
 of the carbonising department in different manu- 
 factories, that when the six hours’ process is fol- 
 lowed, the charge is from 100 pounds to 120 pounds. 
 In such cases, the masses of coal are by no means 
 so diminished as to cause the process to be performed 
 advantageously. When the retort is so charged and 
 worked, the heat proceeding in all directions towards 
 the centre of the coals therein, will meet with 
 nearly the same obstacles to prevent the extrication 
 of the gas as if the retort had been charged with 
 160 pounds of coal. 
 
 With respect to six hours’ charges, when 
 
186 
 
 ON CARBONISATION. 
 
 worked off by cylindrical or small D-shaped retorts 
 set on the oven-plan, the same arguments, which 
 we have already advanced when speaking of retorts 
 set on the flue-plan, will hold good in favour of 
 eight hours’ charges here also. We may, therefore, 
 from what has been said, conclude that, whenever 
 cylindrical or small D-shaped retorts are used, let 
 the mode of setting be what it may, the operator 
 ought never to work off his charge in less than 
 eight hours, taking care to keep his retorts at such 
 a heat as will ensure his procuring from 7,400 to 
 8,000 cubic feet of gas from one ton of coals. 
 
 When the semicircular (or large D-shaped), el- 
 liptical, or kidney-formed retorts are used, the 
 charge can be worked off in much less time than 
 it can be with the cylindrical or small D-shaped 
 retorts. In using any of these descriptions of 
 retorts, it would be advisable to introduce the 
 coal into them by means of sheet iron trays (say 
 three trays for each retort) extending, when placed 
 end to end, to nearly the entire length of the retort, 
 and being of such breadth and form as to fit to the 
 bottom of the retort (not over close), and turned up 
 at their sides and ends about four inches. By 
 having two sets of such trays for the retorts in 
 action, the time usually lost in charging and draw- 
 ing would be greatly decreased, as would also be the 
 stoker’s labour. By the mode most generally prac- 
 tised, the raking the red-hot coke out of the retort 
 
ON CARBONISATION. 
 
 187 
 
 is not only very laborious, but also attended with 
 much loss of time, both which might be avoided 
 by the mode suggested; for by using trays, the 
 spare ones might be charged with the proper quan- 
 tity of coal preparatory to the time for drawing, 
 by which means almost the only time occupied in 
 the operation of drawing and recharging would be 
 that required for breaking the joints of the mouth- 
 piece lids, reluting them, and restoring, and securing 
 them in their places. This part of the work, too, 
 might also be abbreviated by having a spare set of 
 lids ready luted to replace those taken off as soon 
 as the new charge was introduced into the retort. 
 To these advantages, the less loss of heat by the 
 retort cooling from its being internally exposed is 
 to be added. 
 
 Carbonization, when carried on by means of 
 semicircular, large D-shaped or kidney-formed re- 
 torts, when properly set, is always effected with 
 greater advantage than it can be by cylindrical or 
 small D retorts ; for as the great art of making gas to 
 advantage depends upon exposing coal to the action 
 of heat in thin strata, such kind of retorts as we 
 have been speaking of are particularly adapted to 
 the purpose. The large D retorts, if worked at a 
 heat rather higher than a bright cherry-red visible 
 by day-light, will work off a charge of 160 pounds 
 of Newcastle coals in four hours, and produce, at an 
 average, 9,600 cubic feet of gas from a ton of New- 
 
188 
 
 ON CARBONISATION. 
 
 castle coals, with an increase in bulk of coke (par- 
 ticularly adapted for use in the parlour-fire and 
 also for culinary purposes) of forty per cent, upon 
 the quantity of coal carbonised. Consequently, five 
 large D retorts will produce as much gas during 
 the space of twenty-four hours as can be produced 
 from twelve cylindrical retorts worked at eight 
 hours’ charges with 160 pounds of coal to each 
 retort, every charge, or sixteen cylindrical retorts, 
 worked the same length of time with 120 pounds 
 of coals to each retort for one charge. 
 
 As what has been said on the subject of carboni- 
 zation, when carried on by means of the semicircular 
 or large D-shaped retorts, applies in all essential 
 points to the working of large square retorts, it will 
 not be necessary to dwell further upon this case in 
 this place. 
 
 The next mode of carrying on the process of car- 
 bonization is by means of elliptical retorts. In the 
 elliptical retort is combined the durability of the 
 cylindrical one with the advantages obtained by 
 exposing the coal in a thin layer to the action 
 of the heat upon a large surface : therefore, when 
 it is used, the process will be accomplished in 
 about four hours. I have had for many years oppor- 
 tunities of making my observations upon the work- 
 ing of elliptical retorts, and the results of these 
 observations induce me to pronounce them most 
 admirably adapted for promoting the interest of the 
 
ON CARBONISATION. 
 
 189 
 
 gas manufacture. Five elliptical retorts are capable 
 of carbonising thirty-two hundred weight of coal 
 per diem, and of generating from that quantity of 
 coal about 17,000 cubic feet of gas, or at the rate of 
 12,590 cubic feet to the ton; but, on the average 
 mode of working, we may consider that five such 
 retorts will in twenty-four hours carbonise twenty- 
 seven hundred weight of coals, and produce from 
 12,000 to 14,000 cubic feet of gas, or from 8,890 to 
 10,370 cubic feet from one ton of coals. From 
 twenty-seven hundred weight of coals, when elliptical 
 retorts are used, will be produced a chaldron and a 
 half of saleable coke. W e may here remark, that 
 the stokers find it less laborious to work elliptical 
 retorts, even when worked at four hours’ charges, 
 than it is to work the same number of cylindrical 
 or small D-shaped retorts at eight hours’ charges, 
 their shape affording more room for raking out the 
 coke more rapidly than either of the other shaped 
 retorts affords ; and the coke, not being so compact 
 when produced in the elliptical retort, is drawn 
 therefrom with much less trouble than it can be 
 from retorts of a circular or D shape. 
 
 As experience has taught us that the most favour- 
 able results arise to the gas manufacturer by charging 
 elliptical retorts with 120 pounds of coals to each, 
 and working such charge off in four hours, I shall 
 from these data calculate what number of elliptical re- 
 
190 
 
 ON CARBONISATION. 
 
 torts would be necessary to be worked for producing 
 857,667 cubic feet of gas in one week (supposing 
 10,370 cubic feet to be produced from one ton of 
 coals), the coal it would require for producing it, and 
 the quantity of coal necessary for fuel for heating 
 the retorts if set five in one oven, with the products 
 obtained ; and after having stated the annual cost 
 for retorts and grate bars, strike a balance between 
 the most favourable mode of working cylindrical 
 retorts and that of working elliptical retorts. 
 
 I find that, in employing elliptical retorts, that 
 35 retorts would be required to be kept constantly 
 at work ; that these would carbonsie in one week 
 nearly 83 tons of coals ; and that 26 J tons of coals 
 would be required as fuel for heating them, making 
 the weekly expenditure for coals about £199. 
 
 The amount of products would be, for 95 
 chaldrons of coke and breeze, for 3i 
 tons of coal tar, for 1,200 gallons of 
 ammoniacal liquor, and for 857,667 
 
 cubic feet of gas £789 
 
 To work the number of retorts stated to be 
 in action when cylindrical retorts were 
 worked at eight hours’ charges, it 
 required ten stokers by day and ten by 
 night ; but to work the number of el- 
 liptical retorts as above, it would re- 
 quire only five day and five night stokers ; 
 
ON CARBONISATION. 
 
 191 
 
 consequently there would, in the latter 
 case, he ten less in pay, and their wages, 
 at 36s. each per week, would be . . . £18 
 
 The above sum of £18 being in reality a 
 saving arising to the manufacturer by 
 working elliptical retorts, therefore it 
 must be added to the products as above 
 
 stated, and we shall then have . . . 807 
 
 as the total for products obtained at a cost for coal 
 of £199, as has been already stated. 
 
 Now, if from the products when working 
 cylindrical retorts at eight hours’ 
 
 charges, see page 177 £85 1 
 
 we take the products arising when working 
 elliptical retorts, at four hours’ charges, 
 when producing the same quantity of 
 gas as the cylindrical ones as above . . 807 
 
 the difference is £44 
 
 which being subtracted from the difference between 
 
 the expenditure in each case, that is to say, 
 Expenditure when cylindrical retorts are 
 
 worked at eight hours’ charges . . . £266 
 
 Expenditure when elliptical retorts are 
 
 worked at four hours’ charges ... 199 
 
 67 
 
 less 44 
 
 leaves 
 
 £23 
 
192 
 
 ON CARBONISATION. 
 
 as a balance in favour of working elliptical retorts 
 at four hours’ chargesfor one week, when producing 
 a like quantity of gas as had been produced by work- 
 ing cylindrical retorts at eight hours’ charges, or at the 
 rate of £1 196 per annum on coals, products, and labour. 
 
 At page 183, the annual expense of cylindrical 
 retorts when worked at eight hours’ charges, together 
 with the wear and tear of grate bars, is stated to be, 
 when worked so as to produce 44,598,684 cubic 
 feet of gas in that period, £2,300. When elliptical 
 retorts are used as above specified, they will remain 
 in a sound working state about twelve months : if, 
 therefore, we calculate the expense of elliptical re- 
 torts with their appendages for one year, and compare 
 the various results one with another, we shall find 
 how far the elliptical retorts are advantageous. 
 
 By using elliptical retorts, worked at four 
 hours’ charges, about 35 retorts would 
 be required to be kept constantly at work 
 to produce 857,667 cubic feet of gas 
 per week : such retorts so worked would 
 remain serviceable twelve months, con- 
 sequently there would be only 35 burnt 
 out in one year. The cost of replacing 
 them, at £ 1 8 per retort, would amount to £630 
 
 Wear and tear of grate bars ..... 60 
 
 £690 
 
ON CARBONISATION. 
 
 193 
 
 The expense incurred by the annual de- 
 struction of cylindrical retorts, &c., 
 when worked at eight hours’ charges, 
 so as to obtain 44,598,684 cubic feet 
 of gas, has been stated at .... £2,300 
 The expense incurred by the annual de- 
 struction of elliptical retorts, &c., and 
 of like power, as above ..... 690 
 
 Annual balance in favour of elliptical retorts £1,610 
 To which we are to add the annual balance 
 in coals, products, and labour in favour 
 of the employment of elliptical re- 
 torts as above described, over that of 
 cylindrical ones, worked at eight hours’ 
 charges £1,196 
 
 The sum £2,806 
 
 is the total annual balance in favour of 
 elliptical retorts, when compared with 
 results produced during the same period, 
 and when the same quantity of gas is 
 procured by means of cylindrical or 
 small D-shaped retorts. 
 
 If we add to the last named balance, the an- 
 nual balance in favour of working cy- 
 lindrical retorts at eight hours’ charges, 
 over such retorts worked at six hours’ 
 charges, when it is required to gene- 
 
 o 
 
194 
 
 ON CARBONISATION. 
 
 rate by either 44,598,664 cubic feet 
 of gas in a year, as stated at page 183 
 preceding £5,880 
 
 We have £8,686 
 saved in one year, by using semicircular (or large D- 
 shaped), kidney-formed, or elliptical retorts, in prefer- 
 ence to carbonising with cylindrical, or small D- 
 shaped retorts, let the latter be set as they may, and 
 worked at six hours’ charges, with 120 pounds of 
 coals to each as an average charge. 
 
 In concluding this chapter, we deem it necessary 
 to apprize our readers, that we have considered it 
 expedient to abide by the prices paid for coals and 
 labour, and received for products given in the former 
 editions of this work, because, by doing so, we show 
 what were the results as to profits, when working at 
 such prices as were then the current ones, viz. 
 coals for making gas, about 38 shillings per ton ; 
 coals for heating the retorts, about 31 shillings per 
 ton; stoker’s wages 36 shillings per week; coke 
 produced from cylindrical retorts was sold at 27 
 shillings per chaldron ; and that produced from the 
 elliptical retorts, at 22 shillings per chaldron : the 
 breeze (or small coke) at 18 shillings per chaldron : 
 the coal tar at £8 per ton : the ammoniacal liquor 
 at 3d. per gallon; and the gas at 15 shillings for 
 one thousand cubic feet. 
 
 As in bringing out our results, we have in each 
 
ON CARBONISATION. 
 
 195 
 
 case stated the quantity of coals used for making 
 gas, and for heating the retorts, and the quantities 
 of coke and breeze, of coal tar, of ammoniacal liquor, 
 and of gas produced, the reader can put the prices 
 to each, which may suit his particular locality, and 
 following out the method we have pursued, he will 
 come to such results as will be applicable to the par- 
 ticular gas work in which he may be interested, but 
 which will vary with respect to those which we 
 have advanced, in such proportion as the lower prices 
 of coals and labour on the one hand, and the lower 
 prices of the products on the other, may bear upon 
 the question. As regards the expenses of replacing 
 burnt-out retorts, and repairing fire-work, we are 
 not aware that we need make any remark beyond 
 this — that they must mainly depend upon the price 
 at which retorts, fire-bricks, &c. can be delivered at 
 the place where the repairs are called for, and there- 
 fore may be more or less than we have stated, ac- 
 cording to such circumstances. 
 
 o 2 
 
196 
 
 CHAPTER VII. 
 
 On the Hydraulic Main, Connecting, H, and Dip Pipes. 
 
 By the term “ Hydraulic Main,” as it is used in gas- 
 light establishments, is understood a cast-iron cylinder 
 or pipe of from twelve to fourteen inches in diameter, 
 which is supported in a horizontal position, some- 
 what higher than the top of the bed of brick-work 
 by which the retorts are inclosed, with the front of 
 which it lies parallel. Its situation is shown at E, 
 figure 1, Plate IX., and at E, figure 1, Plate X. Its 
 use is to receive the “ dip pipes' (a section of one of 
 which is given at figure 1, Plate XXII.) through 
 which the gas, as it is evolved from the retort, after 
 pursuing its course through the “ connecting pipe” 
 (see figure 2, Plate XXII., and the “H pipe,” figure 
 3 of the same plate) passes, together with a portion of 
 tar and ammoniacal liquor (both in a state of vapour), 
 first into the hydraulic main, and from thence the 
 different gaseous products are conveyed to the washer 
 or to the condenser. The diameter of the hydraulic 
 main is different in different establishments; in small 
 works it is sometimes not more than ten inches in 
 diameter, in larger ones it is from twelve to four- 
 teen, according to the number of retorts which may 
 be worked into it. In works where from forty to 
 
HYDRAULIC MAIN, ETC. 
 
 197 
 
 sixty retorts of any of the descriptions hitherto 
 named work into one hydraulic main, it need not 
 be more than twelve inches in diameter. 
 
 The hydraulic main is generally constructed of 
 flanch pipes ; sometimes however it is made of a dif- 
 ferent shape (see transverse section, figure 4, Plate 
 XXII.), in lengths of nine feet each. One end of it 
 is closed by a blank flanch, so as to be perfectly gas 
 tight. The other end is also closed by means of a 
 cast iron flanch, with a hole cast in it (see figure 5, 
 Plate XXII.), in such a position, that when it is 
 jointed to the hydraulic main, and that is fixed in its 
 place, the lowermost part of the hole cast therein shall 
 be on a level with that at which the fluid in the hy- 
 draulic main is intended to be kept. It is desirable 
 that semi-flanches of boiler plate should be placed 
 between each of the different lengths of which the 
 hydraulic main is formed, for the purpose of keeping 
 the fluid it contains at its proper level in each length. 
 The bottom of the hole in the exit end flanch 
 and the tops of the semi-flanches just spoken of, 
 should each be about two inches and a half above 
 the line formed by the bottom of the dip pipes; 
 under such arrangement, the gas, as it is discharged 
 from the retort, will always have to force its way 
 through that depth of fluid before it can enter into 
 the hydraulic main. 
 
 For explaining what end the dip pipes answer, we 
 have given a section of the cylindrical hydraulic 
 
198 
 
 HYDRAULIC MAIN, ETC. 
 
 main, showing one of them in its place (figure 6, 
 Plate XXII.). The dip pipe is generally about two feet 
 in length, and three inches diameter inside ; at the 
 top is a socket for receiving the H pipe of the same 
 diameter. At about eight inches from the spigot 
 end of the dip pipe is a circular saddle of about nine 
 inches diameter, cast to the radius of the exterior 
 surface of the hydraulic main. The hydraulic main 
 is cast with holes at proper distances, for receiving 
 such a number of dip pipes as there are retorts to 
 work into it, which dip pipes are jointed upon it by 
 means of iron or rust cement in the usual way. 
 When the dip pipes are all jointed in their places, 
 the range of the spigot ends of these pipes will 
 equally descend into the hydraulic main, and of 
 course, supposing the hydraulic main be placed so 
 as to lie perfectly level, which it always ought to do, 
 should one of the dip pipes be immersed to the depth 
 of two inches and a half in any liquid that the hy- 
 draulic main may contain, each dip pipe of the range 
 will be equally immersed. 
 
 Now, when it is considered that if there were not 
 some contrivance for preventing the gas returning 
 from the main pipes towards the retorts when the 
 mouth pieces are removed during the operation of 
 drawing and charging the retorts, either by stop- 
 cocks, or valves upon each of the gas conducting 
 pipes, or other means, the process of making gas 
 would not only be attended with much waste of gas. 
 
HYDRAULIC MAIN, ETC. 
 
 199 
 
 but it would also be attended with extreme danger ; 
 for, as the gas would be passing over, by means of 
 the conducting pipes (there being no hydraulic main, 
 but merely a common receiving main for all these 
 pipes), in a range of sixty retorts, from fifty-two of 
 them, whilst eight were being drawn, it must follow 
 that, without some contrivance for shutting off the 
 gas then making from the open retorts, the gas then 
 making from the fifty-two retorts would escape at 
 the mouths of those retorts which had their lids re- 
 moved, and burst forth with such a body of flame as 
 could not be approached : indeed more serious con- 
 sequences might ensue from the admission into the 
 open retorts of atmospheric air. 
 
 The necessity for preventing such things happen- 
 ing is obvious, and a more simple, and at the same 
 time safe, method than that of the hydraulic main 
 and dip pipes could hardly have been devised : for 
 had stop-cocks or valves been used, they would either 
 have been attended with considerable trouble or 
 ever liable to get out of order ; so much so, that no 
 dependence could be placed upon them : for the tar 
 and ammoniacal salts would in a short time so clog 
 the plugs of the one and the spindles and sliding 
 parts of the others as to render it a matter of great 
 difficulty to move them. 
 
 It must be clear to every reader who may take 
 the trouble to refer to Plate X., figure 3, that unless 
 the pressure upon the hydraulic main from the 
 
200 
 
 HYDRAULIC MAIN, ETC. 
 
 purifying vessel be greater than a vertical column 
 of water equal to the distance between the bend 
 part of the H pipe and the water level of the dip 
 pipe in the hydraulic main, the gas, after having 
 once entered the hydraulic main, cannot be forced 
 back into the retort. In mentioning the pressure 
 from the purifier (we refer, in speaking of it, to 
 such as are constructed for purifying the gas by 
 means of the cream of lime), it is to be understood 
 that, whatever depth of lime in solution the gas, 
 after entering the purifier, has to rise through before 
 it can escape towards the gas-holder, is considered 
 to be the pressure at which the purifier is worked. 
 Thus, for instance, the most usual depth of the 
 purifying mixture, when lime and water are used, 
 through which the gas bubbles up in the process of 
 purification, being ten inches in the purifying vessel, 
 the purifier in such case is said to be worked at ten 
 inches pressure. The length of the dip pipe has been 
 stated at two feet : from the top of it to the bend 
 part of the H pipe may be stated at six or eight 
 inches, making together about two feet six inches ; 
 consequently, before the pressure in the purifier can 
 be sufficient to force back the gas from the hydraulic 
 main through the conducting pipes to the retorts 
 undergoing the operation of drawing, it would 
 require to be three times greater than what the 
 wet lime purifier is usually worked at. But, as 
 there is a possibility when the wet lime purifier is 
 
HYDRAULIC MAIN, ETC. 
 
 201 
 
 used, and more particularly so if it be not exceed- 
 ingly well constructed, of its being choked up, there 
 ought to be some contrivance to indicate to the 
 workmen when such happens to be the case, or 
 when the pressure there was so considerably on the 
 increase as to endanger the safety of the retorts. 
 This might be accomplished by having a pressure 
 gauge fixed in such a situation that it could always 
 be consulted, or by means of a small bell, which 
 might be made to ring from its detent being 
 liberated by a striking rod attached to a piston 
 working in a bored pipe, and which would be raised 
 high enough to do so by any increased pressure of 
 gas deemed dangerous acting under the piston, the 
 whole contrivance bearing a strong resemblance to 
 the alarum of a clock. 
 
 We have spoken of the wet lime purifier, because 
 in many gas-works, notwithstanding the superiority 
 of the dry lime purifier, it is still used. In the latter, 
 the pressure seldom exceeds two or three inches, so 
 that any inconvenient pressure upon the retorts or 
 the hydraulic main is not very likely to occur when 
 such mode of purification is followed. It is de- 
 sirable, however, in this case also to have any stop- 
 page between the retorts and the purifier indicated 
 as soon as possible, for which purpose either a pres- 
 sure gauge, or a bell, as already mentioned, is par- 
 ticularly applicable. 
 
 The hydraulic main, with the dip pipes, form a 
 
202 
 
 HYDRAULIC MAIN, ETC. 
 
 series of hydraulic valves (or joints), than which, 
 in the manufacture of an elastic fluid like coal 
 gas, nothing could be so safe or so well adapted. 
 Figure 7, Plate XXII., exhibits a longitudinal sec- 
 tion of the hydraulic main and dip pipes ; and figure 
 8 a front view of the same. It is of considerable 
 importance that the hydraulic main should be con- 
 structed of pipes or castings of the best quality, 
 that the joints should be sound, and the work alto- 
 gether well turned out of hand ; for an accidental 
 derangement of its parts generally puts a stop to 
 the production of gas, for obvious reasons. Previous 
 to the retorts being brought into action, the hy- 
 draulic main must be filled to the height of the 
 under side of the hole in the round flanch at the 
 end of it already described with water, so that all 
 the dip pipes may be sealed thereby. Before the 
 retorts have been long in action, however, the water 
 will be forced gradually through the hole in the 
 end flanch, and its place will become occupied by 
 the coal-tar and ammoniacal liquor which hav0 
 been produced during the distillatory process. As 
 the two latter are of greater specific gravity than 
 the former, they will, as they accumulate, subside 
 in the hydraulic main, and the water, being lighter 
 than either, will be the first displaced therefrom. 
 
 Accidents have been heard of, occasioned by the 
 gas in the hydraulic main forcing the glans from 
 the top of the H pipes ; but such accidents must 
 
HYDRAULIC MAIN, ETC. 
 
 203 
 
 have arisen from great carelessness on the part of 
 the operator, or from the clogging up of the puri- 
 fier ; for, by attending to the observations already 
 made, as to the situation of the hydraulic main and 
 the manner of putting it up, no accident of the 
 kind can possibly happen. 
 
 It is from a very erroneous notion that some 
 constructors of retort furnaces and their appendages, 
 of which the hydraulic main is one, place the hy- 
 draulic main nearer to the mouths of the retorts 
 than we have described : by its being so, the gas 
 conducting pipes, by being brought more contiguous 
 to the furnaces, so heat the tar on its way to the 
 hydraulic main as to cause it to be converted into 
 pitch before it can get there, which in a short time 
 so completely fills the gas conducting pipes as en- 
 tirely to stop the passage of the gas from the retorts. 
 The consequences resulting therefrom are these, — 
 the glans of the H pipes require to be removed, the 
 joint of the retort-lid broken, and a loss of all the 
 gas that may be generating from the retort till a 
 man has been able, by pushing an iron bar heated 
 at one end through the H pipe and down the gas 
 conducting pipe, to clear away the pitch and open a 
 passage for the gas, secure the joint between the 
 glans and H pipe, re-lute and secure the retort-lid. 
 Owing to the gas conducting pipes being of small 
 diameter in the early stages of the gas manufacture, 
 their choking up was of frequent occurrence ; and 
 
204 
 
 HYDRAULIC MAIN, ETC. 
 
 where there were forty retorts in action it was no 
 uncommon thing to have as many pipes to clear in 
 the course of twenty-four hours. The gas conduct- 
 ing pipes were then seldom more than two inches 
 in diameter inside : for many years back, however, 
 the diameter has been increased to three inches. 
 These being made very slight, and being placed 
 further from the fire-work, are not liable to be 
 choked up. The action of the air upon their ex- 
 terior keeps them cool enough to prevent the tar 
 from adhering to their sides, as was the case when 
 pipes of smaller diameter were used. When the 
 pipes of three inches in diameter are used, such part 
 of the tar as is therein condensed before it reaches 
 the hydraulic main returns to the retort, where it 
 is decomposed, and afterwards passes over with the 
 gaseous products by which the proportion of gas 
 obtained from a ton of coals is increased. In short, 
 by increasing the diameter of the gas conducting 
 pipes, which are but appendages to the hydraulic 
 main, H, and dip pipes, their choking up is avoided, 
 and, consequently, the gas, instead of being fre- 
 quently wasted (as was the case when smaller sized 
 gas conducting pipes were used), is increased, and 
 the labour consequent upon the use of the smaller 
 sized pipes avoided. 
 
205 
 
 CHAPTER VIII. 
 
 On the Washer, Condensing Main, and various other methods of 
 Condensation. 
 
 Gas, as it is evolved, is mixed with tar and an 
 ammoniacal fluid in a state of vapour, which pass 
 over with it from the retort to the hydraulic main ; 
 it therefore becomes necessary that, as much as 
 possible, these two products should be condensed 
 and lodged in their proper reservoir before the gas 
 reaches the purifier. In order that this condensa- 
 tion may be properly effected, the products generated 
 should be exposed to a large surface of some cold 
 body when on their passage to the purifier : by such 
 means the tar and ammoniacal vapours are in a 
 great measure precipitated, by the loss of their 
 caloric, in a fluid state, and are so separated from 
 the gas ; and being of much greater density than 
 the gas, subside and drain through the pipes to the 
 vessels appropriated to their reception. When the 
 gas is well cooled, it is much more fit for the lime 
 in the purifier to act upon than if it were brought 
 to the purifier directly from the hydraulic main in 
 a hot state ; for whenever it is so, it is impregnated 
 with tar and other matters, which very soon render 
 
206 
 
 ON THE WASHER, 
 
 the purifying medium (whether that be lime and 
 water or moistened lime) useless, by depositing 
 themselves thereon, and by that mixture preventing 
 the gas from acting thereupon. The consequence 
 of bringing the gas in a hot state to the purifier is, 
 that a much greater portion of lime will be required 
 for the purifying process, or otherwise the gas will 
 pass through the purifier to the gas-holder hardly 
 acted upon. The use of impure gas ought on all 
 occasions to be avoided, for whenever it is used it is 
 almost impossible to obtain a good light ; when it 
 is submitted to combustion, it smokes and emits a 
 disagreeable odour ; the plugs of the stop-cocks on 
 the fittings become choked up with tar, which, how- 
 ever surprising the case may seem, has been found 
 in situations distant a mile and a half from the 
 manufactory, after the gas had passed through 
 various pipes of different diameters and placed at 
 different levels. 
 
 The great preventive against impure gas finding 
 its way into the gas-holder is its being thoroughly 
 condensed, or cooled, before it reaches the purifying 
 vessel : on that almost as much depends as upon the 
 purifying process which is there accomplished ; for 
 whether gas be purified by lime and water, by 
 moistened lime, or by any other purifying medium, 
 it is of the utmost importance that it should be 
 deprived of the tar, ammonia, &c., which were 
 generated at the same time as it was before it enters 
 
CONDENSING MAIN, ETC. 
 
 207 
 
 the purifier ; and it may be considered as a general 
 rule which the manufacturer ought ever to observe, 
 let the mode of purification be what it may, never 
 to submit his gas to the purifying process till it has 
 been well condensed or cooled. 
 
 Experience having taught the manufacturer the 
 necessity of attending to the subject of condensing 
 or cooling the gas manufactured, he, of course, 
 adopted such means as he considered most advisable 
 for effecting that object. In some manufactories, it 
 was thought that the gas would have been suffi- 
 ciently condensed from its being conveyed from the 
 hydraulic main by a pipe laid in a direct line from 
 the retort-house to the purifier ; in others, the gas 
 was conveyed to the purifier through a worm-pipe 
 t placed in the tank of the gas-holder ; and again, in 
 others, by ranges of pipes laid parallel to each other 
 at a considerable depth and with a certain declivity 
 from one end of the works to the other ; whilst 
 some, in addition to these contrivances, proposed a 
 tank into which the ranges of pipes, as last specified, 
 should convey the gas at the bottom, and, by means 
 of a contrivance something similar to a shower-bath, 
 cause the gas to be washed there before it could 
 make its exit towards the purifier. Most, if not all, 
 of these methods have been tried by different opera- 
 tors, and have been found more or less effective. 
 The first could hardly be expected to answer, unless 
 the distance from the retort-house to the purifier 
 
208 
 
 ON THE WASHER, 
 
 had been much greater than is generally the case ; 
 the others, possessing similar properties, produced 
 results proportionably analogous to the length and 
 temperature of the main through which the gas 
 was conveyed. But all of these methods were ex- 
 pensive, and attended by inconveniences which it 
 was of the utmost importance to avoid. By each 
 of the methods spoken of, one very great evil some- 
 times occurred, that is to say, the condensing main 
 became choked up by a deposition of ammoniacal 
 salts. This was more frequent when the manufac- 
 tory was extensive and the diameter of the con- 
 densing main was too small, as was sometimes the 
 case formerly when the condensing pipes had been 
 laid down without a proper inquiry having been 
 first made as to the possible quantity of gas to be 
 supplied, and, consequently, to be manufactured. 
 Such an oversight as this, when the manufacture 
 was, as it were, in its infancy, is not to be wondered 
 at ; but now, when the mode of obtaining light by 
 means of coal-gas has become so general, the ma- 
 nagers of gas establishments generally know pretty 
 nearly what number of lights they will have to 
 furnish before they commence erecting their appa- 
 ratus, consequently will guard against their power 
 of condensation being too small, and will also take 
 means to prevent any stoppage of the gas in the 
 condensing main, or in the vessel appropriated to 
 the condensing (or cooling) of the gas, so as to 
 
CONDENSING MAIN, ETC. 
 
 209 
 
 preclude even a possibility of accident. Should the 
 condensing main (where it is still used) or the con- 
 denser, however, become choked, the most serious 
 consequences might ensue ; for, whenever such is 
 the case, the pressure upon the hydraulic main will 
 accumulate to an alarming degree, so much so as to 
 force the fluid it contains over the H pipes into the 
 retorts, which will endanger the whole of them, by 
 being rapidly converted into steam. Indeed their 
 safety can only be effected by removing the lids 
 from the mouth-pieces ; an operation which, under 
 such circumstances, it is no easy matter to perform. 
 There are several objections against using con- 
 densing mains ; first, the expense of laying them 
 down is enormous ; secondly, they fail to perform 
 the process of condensation equally well with other 
 methods of performing the same at one-third of the 
 expense, and which are perfectly safe in their opera- 
 tion ; and thirdly, they are much more likely to be 
 choked up than the condensing vessels now gene- 
 rally used, and much more difficult to cleanse. In- 
 deed there are so many objections against them that 
 they ought never to be used in any gas manufactory. 
 
 It was not till the year 1817 that any other 
 mode was used except that of passing the gas 
 through a condensing main, for the purpose of cool- 
 ing it, and partially depriving it of the tar and 
 ammoniacal fluid which had come over along with 
 it from the hydraulic main in a state of vapour. 
 
 p 
 
210 
 
 ON THE WASHER, 
 
 In August of that year a condensing vessel, as 
 described by figures 1, 2, 3, and 4, Plate XI., was 
 brought before the notice of the public by Mr. 
 John Perks, who in that month took out a patent 
 for bis invention. His condensing vessel consisted 
 of a tank made of cast-iron plates with a bottom 
 about twelve inches deep, divided into compart- 
 ments, as shown in figures 4 and 5. Over this part 
 of the vessel was placed a cast-iron cover, cast with 
 boles in it in such situations that, when fixed in its 
 place, two of such boles should fall or be directly 
 over one of the compartments of the bottom (figure 
 2, Plate XI.). Over these holes were fixed cast- 
 iron flanch pipes which were bolted down upon the 
 plate (figure 2), and which are represented in 
 figures 3 and 4. On consulting figure 4, it will be 
 seen that the gas enters into this condensing vessel 
 by the pipe marked 1, through which it descends 
 into the compartment marked i, from whence it has 
 no means of escaping (the bottom vessel being filled 
 with some fluid to the height of the dotted line 
 a, b) except by ascending through the pipe 2 ; it 
 then passes through the bend g , and descends 
 through the pipe 3 into the division marked j, 
 rising from that compartment by the pipe 4, de- 
 scending again by pipe 5 into the division 7c, and 
 thence rising by the pipe 6 ; and thus descending 
 and rising in the direction of the arrows shown 
 upon figures 1 and 3, till it reaches the pipe nearest 
 
CONDENSING MAIN, ETC. 211 
 
 to B in these figures, when it is carried away to- 
 wards the purifier. The figures 1, 2, 3, and 4, in 
 the plate, are drawn from a scale of one inch to 
 three feet, so that the dimensions of the bottom are 
 about six feet by four feet six inches, and the length 
 of the upright pipes (forty-eight in number) about 
 eight feet six inches each ; these with the bends 
 make a length of pipe for the gas to travel through 
 of about 432 feet or 144 yards, notwithstanding the 
 condenser stands upon so small a base. The tank 
 surrounding the upright pipes is about ten feet in 
 depth, and is, when the vessel is brought into action, 
 to be filled with water as high as the top of the 
 upright pipes, by which means the pipes are kept 
 constantly cool, and the condensible products fall 
 into the square recesses at the bottom, from whence, 
 by a contrivance of the inventor, they are conveyed 
 to their proper receivers. For making our explana- 
 tion of this condenser more intelligible, we add, 
 that figure 1 is a plan of the top, showing the 
 situation of the bend pipes, &c. Figure 2 is a plan 
 of the under side of the plate upon which the up- 
 right pipes are supported, showing the openings 
 into the lower chambers and the plan or position 
 of the upright partitions therein. Figure 3 is a 
 side view (in elevation) of the condensing vessel, the 
 side plates being supposed to be removed. The 
 pipes E and E and the bend beneath are for carry- 
 ing off the condensations. The dotted lines a , b , 
 
 p 2 
 
212 
 
 ON THE WASHER, 
 
 show the height at which the fluid in the bottom 
 will be constantly kept in that part of the vessel. 
 An opening is made or left at the bottom of each 
 partition which divides the lower vessel, allowing 
 the condensed matter to flow from one compartment 
 to another, and to be carried off by the pipe E. 
 Figure 4 is an end view of the condensing vessel 
 (in elevation), the end plates being supposed to he 
 removed. 
 
 About the same period as that we are now speak- 
 ng of, as was mentioned in the former editions of 
 this work, a condensing vessel, different in construc- 
 tion and principle from the above, was invented by 
 Mr. John Malam, which has recently been adopted by 
 several gas companies, and is reported to be very effec- 
 tive in its operation. The condenser just alluded to, 
 as proposed by Mr. Malam, is a vessel constructed of 
 cast iron plates about nine feet long, five feet wide, 
 and four feet deep. Into this vessel he introduces 
 cast iron plates, at distances of from six to eight 
 inches from each other, with raised edges of about 
 three inches in height ; these he bolts to the sides of 
 the vessel, perfectly parallel to each other; they are 
 in length about eight feet six inches, so that being 
 secured to the sides of the vessel and to one end of 
 it, the other end of the plate remains at the distance 
 of about six inches from the opposite end of the 
 vessel. The lowermost of these plates being con- 
 nected to one end of the vessel, the next plate above 
 
CONDENSING MAIN, ETC. 
 
 ,213 
 
 it is connected to the opposite end, the third plate 
 to the same end as the first, the fourth to the same 
 end as the second, and so on alternately till all the 
 plates are fixed. This being done, preparatory to 
 bringing the condenser into action, water is intro- 
 duced at the top (through the hole over which the 
 exit pipe is to be afterwards fixed), which fills the 
 uppermost shelf to the height which the projecting 
 part of it allows ; the water then runs over and fills 
 the second, from thence the third is filled, and so on 
 until the whole range are so. From considering 
 this matter, it is evident, if the entrance pipe he at 
 the bottom of the vessel to the right, should gas be 
 introduced therein by its means, it will pass over a 
 sheet of water equal to the area of the lower shelf, 
 and as the next shelf above approaches no nearer to 
 the end towards the left than six inches, it will, by 
 that opening, rise above it and pass towards the 
 right, where it will again find an opening at the end 
 of the third shelf, and so it will pass alternately to 
 right and left till it reaches the exit pipe above the 
 top shelf of the vessel. The condensible products 
 find their way from the top shelf to the bottom of 
 the condenser, whence they are carried off towards 
 the tar cistern, by means of the pipe F, of figure 8, 
 Plate XI., which figure represents a longitudinal ver- 
 tical section of a condenser, similar to the one which 
 we have been describing : A B top plate or cover, 
 CD bottom plate, E gas entrance pipe, G gas exit 
 
214 
 
 ON THE WASHER, 
 
 pipe. A condenser of this kind may be recommended 
 to the notice of the manufacturer, inasmuch as its 
 first cost will be moderate, its durability may be de- 
 pended upon, and its action is certain. 
 
 In considering the two modes of condensation last 
 mentioned, we cannot fail to observe the facility they 
 afford for removing any obstruction, and their effi- 
 ciency for answering the purpose of the gas manufac- 
 turer, so far as relates to the gas generated being 
 well condensed and cooled before it is allowed to 
 enter into the purifier. W e have already stated the 
 distance the gas would have to travel in passing 
 through such a condenser as is described in Plate XI., 
 figures 1, 2, 3, and 4 ; and if we suppose the upright 
 pipes to be always surrounded by cold water, the 
 effect must evidently be very superior to the old mode, 
 or condensing main. Various modifications of this 
 condenser are in use up to the present time ; but are 
 now generally without that part of the tank which 
 surrounds the upright pipes, it being considered by 
 many that on the outer surface of the pipes the air 
 alone will sufficiently cool the gas. Such condensers 
 generally resemble figures 3 and 4, Plate XI., without 
 the upper tank, the lower one remaining as there 
 shown, and divided into compartments as exhibited 
 in the plan, figure 2 of the same plate. Others again 
 construct the upper part of their condensers of boiler 
 plate, formed into square pipes by riveting (see plate 
 XII., figures 1 and 2), the tank in which the con- 
 
CONDENSING MAIN, ETC. 
 
 215 
 
 densing pipes stand being open at the top, and the 
 products of condensation deposited therein being 
 carried therefrom towards the tar cistern by means 
 of the pipe J. Circular pipes, however, are not the 
 best formed for cooling the gas, for when gas passes 
 through such, that which is near the centre will be 
 but little acted upon, if at all, by the cold body by 
 which they may be surrounded — it is therefore al- 
 ways better that the gas should present itself to the 
 cooling medium in very thin sheets, in order that 
 every part of it may equally be acted upon by the 
 adjoining cold surfaces ; by such means a thorough 
 condensation (or cooling) of the gas will be more 
 certainly effected. In the condenser, figures 1, 2, 3, 
 and 4, Plate XI., the bends at the top are easily re- 
 moved in the event of any obstruction presenting 
 itself, when, by forcing down each of the pipes a rod 
 kept ready for the purpose, the passages may be easily 
 cleared, the obstructing matter will fall down into 
 the lower vessel, and as there is a sufficient opening- 
 left there at the bottom of each of the partitions, 
 such obstructing matter can be withdrawn from 
 thence. In the ends of the condenser, figure 8, Plate 
 XI., there are circular openings opposite each of the 
 gas ways, each covered by a lid, and made gas tight 
 by means of screws and a pasteboard joint, when the 
 vessel is in action, but which lids can be removed, 
 should there be any stoppage, and the salts or other 
 obstructing matter can be drawn out through the 
 
216 
 
 ON THE WASHER, 
 
 said holes, and when that is done, the lids can be re- 
 secured in their places as before. 
 
 A B C D, figure 5, Plate XI. is a longitudinal 
 vertical section of another condenser, which is drawn 
 from a scale of five-eighths of an inch to a foot. It 
 is made of cast iron plates, and rests upon a bed of 
 brick- work, as shown in the figure. At about one foot 
 from the bottom is a range of plates, a aa a, together, 
 of the same size as the bottom, and which are jointed 
 to the vessel. Upon these stand rows of cast iron plates, 
 one of which is shown at E. Their lower edges oc- 
 cupy such situation as is shown in the plan ABCD, 
 figure 6. In that plan, the pipe which conveys the 
 gas into the condenser is shown at E ; it then passes 
 between the upright plates in the direction of the 
 arrows, till it reaches the exit pipe F, and that pipe 
 leads toward the purifying apparatus. It is to be 
 noticed, that these upright plates do not rise to the 
 top of the condenser, there is a space of about six 
 inches left between the top and the plates which fit 
 over them. The entrance and exit pipes E and F 
 are placed about one foot from the top of the vessel, 
 as shown in the transverse vertical section, figure 7. 
 The range of cast iron plates aa a a, already men- 
 tioned, do not lie perfectly horizontal, but with a 
 small declivity to the right, by which arrangement 
 the condensed matter drains towards the openings 
 a, b, c , figure 6, and thence by the pipe a, figure 5, 
 and a, b , c, figure 7, is discharged into the receptacle 
 
CONDENSING MAIN, ETC. 
 
 217 
 
 E, which is carried across the vessel, and is filled with 
 water for the pipes a b c to dip in, and form an hy- 
 draulic joint. It follows therefore, that as the con- 
 densable products accumulate, they flow over the 
 partition which forms the part E, and run into the 
 chamber G, from whence, when it is necessary, they 
 may he drawn off by the cock H, figures 5 and 6. 
 A, B, C, D is a plan of this condenser, the arrange- 
 ment of which is already described, and figure 7 is 
 a transverse vertical section of the same vessel. 
 
 Before we conclude this chapter, we propose to 
 describe two more condensers, one of which is appli- 
 cable to small works, the other, according to its size, 
 will answer well for gas-works of any magnitude ; 
 hut before we do so, we propose to make a few ob- 
 servations relative to a vessel used at some gas- 
 establishments by which the gas is made to pass 
 through a fluid before it enters the condenser, which 
 causes it to be deprived of an additional portion of 
 the tar and ammoniacal fluid which had come over 
 with it from the hydraulic main. The vessel we are 
 speaking of is called in gas-manufactories “ The 
 Washer T W e now proceed to describe it. ABC D, 
 figure 9, Plate XI., is a plan of the top of the 
 washer, and figure 10 of the same plate is a longi- 
 tudinal vertical section thereof. The figures 9 and 
 10 are drawn from a scale of a quarter of an inch to 
 a foot. The vessel is constructed of cast-iron plates, 
 and one of such size as is given in the figures is 
 
218 
 
 ON THE WASHER. 
 
 sufficiently large for an establishment where about 
 twelve elliptical retorts are worked at one time. 
 The washer is fixed underground and connected by 
 the pipe E to the pipe which brings the gas from 
 the hydraulic main. Before bringing it into use, 
 it is filled with water as high as the dotted lines 
 eeffy figure 10, consequently the whole of the 
 bottom marked # is filled with water also : it there- 
 fore follows, as a natural consequence, that the gas 
 which enters the washer by the pipe E finds its 
 way into the space marked G, from which it cannot 
 escape except by passing through the water below 
 e e and f f and through the space also filled with 
 water at * : this it effects ; and having entered the 
 chamber H, it is from thence conveyed by the pipe 
 F towards the condenser. On noticing figure 10, 
 it will be observed that one end of the washer is 
 placed two or three inches lower than the other. 
 At the lower end, at e, a pipe is fixed which leads 
 towards the tar cistern, where it dips into a pipe 
 filled with water so as to form an hydraulic joint 
 in the usual way (as described in figure 3, Plate 
 XII.) Whilst the washer contains water only, the 
 gas passing through it is cleansed to a considerable 
 extent ; but the place of the water, very soon after 
 the washer has been in use, becomes occupied by tar 
 and ammoniacal liquor, and when it is so, it answers 
 no very useful purpose, as the mixture the gas has to 
 pass through in the washer much resembles what 
 
CONDENSING MAIN, ETC. 
 
 219 
 
 has by that time been deposited in the hydraulic 
 main. The use of it is not at all recommended, 
 from its augmenting also the pressure on the water 
 in the hydraulic main, and it is spoken of here 
 only from its being occasionally used. 
 
 A condenser which will answer for a gas-work 
 where only two or three retorts are used is exhi- 
 bited in Plate XII . , figures 1 and 2, which figures 
 are drawn from a scale of a quarter of an inch to a 
 foot. Figure 1 is a longitudinal vertical section of 
 this condenser, in which G H I J represents a 
 trough made of boiler-plate riveted together, in 
 which the pipes BCDE stand, which are also 
 made of boiler-plate riveted together, open at the 
 bottom and closed at the top by means of a flanch. 
 The upright pipes BCDE are connected to- 
 gether by the flanch sockets a, b , c. The tank 
 G H I J being nearly filled with water, it is evident, 
 from examining figure 1, that if the gas be intro- 
 duced into the condenser by the pipe A, it will 
 descend down B, and through the double socket a, 
 into the pipe C, which it will ascend; from thence 
 it will proceed through the double socket b into the 
 pipe D, descending down that to the double socket 
 c, through which it will pass into the pipe E, and 
 thence through the exit pipe F towards the purifier. 
 The pipes BCDE are hollowed out at the 
 bottom, in order that whatever may be condensed 
 in them, as the gas passes, may be deposited in the 
 
220 
 
 ON THE WASHER, 
 
 trough G H I J, from which it may be drawn by a 
 cock placed at a proper level, as shown in figures 5 
 and 6, Plate XI., or carried off by a pipe to the 
 tar cistern, as may be most convenient. Figure 2 
 is a plan of the trough and of the condensing pipes 
 BCDE, showing also the entrance pipe A and 
 the exit pipe F. 
 
 Plate XII., figure 3, is a longitudinal vertical 
 section of a condenser, ABEF, with a tar cistern 
 below it, E F C D : this figure and figure 4 are 
 drawn from a scale of a quarter of an inch to a foot ; 
 we propose in this place to describe the condenser 
 only. It is made altogether of cast-iron plates : 
 EF is the bottom of the condenser. In it are 
 placed two tiers of plates, with an inclination, as 
 shown in the figure marked a and b. The lower 
 range of the lowermost tier is cast so as to form a 
 trough, c, which extends to the entire width of the 
 plates a and b when put together. When the plates 
 marked b are fixed in their places, the width of the 
 condenser is divided into a number of long, narrow 
 gas ways by the partitions marked d d, which are 
 shown in section by figure 5, and in plan by figure 
 6 ; both drawn from a scale of three inches to a 
 foot. These partitions are about six inches shorter 
 than the entire length of the condenser, conse- 
 quently when fixed they alternately fall so much 
 short of the ends of the condenser, as better seen at 
 figure 4, in which the direction the gas takes is 
 
CONDENSING MAIN, ETC. 
 
 221 
 
 pointed out by arrows. Those which are brought 
 close to the end A E are about four inches deeper 
 at that end than in the other part, in order that 
 they may dip into the trough c, which is constantly 
 filled with a fluid. This trough receives all the 
 products of condensation which are carried off by 
 the pipe g, shown therein, into the tar cistern H. 
 When the partition plates d d are all fixed in their 
 places, and the pipe g secured to its situation in the 
 trough (the pipe into which it dips, h It, being first 
 fixed in its place and filled with water, as must also 
 be the trough c), the upper range of plates a are 
 laid upon the partition plates and screwed down to 
 them by means of bolts passing through the plates 
 b and the partition plate d, through the hole shown 
 in figure 5, three such being cast in each partition 
 plate. When this is done, the top plates are jointed 
 together in the usual way, as are also the side plates 
 hli ( figure 4). This being done, the condenser 
 itself, ijkl (figure 4), will be completely closed, 
 and then the tank A B E F may be filled with 
 water. The orifice e in this figure represents the 
 pipe which brings the gas into the condenser. 
 Figure 4 is a plan of the condenser, showing the 
 condensing part, ijkl , which is not so wide as the 
 tank I J A B by about twelve inches, e is the 
 situation of the pipe which brings the gas into the 
 condenser ; it then passes in the direction of the 
 arrows between the partition plates ddd, till it 
 
222 
 
 ON THE WASHER, 
 
 comes to f, which is the situation of the exit pipe, 
 and from which the gas passes towards the purifier. 
 The condensable products fall into the trough cccc, 
 which, when full, runs over the pipe whose situation 
 is marked at g, by which they are conveyed into the 
 tar cistern H. Figure 5 is a plan of part of one 
 of the partition plates, and figure 6 is a section of 
 the same : these two figures are drawn from a scale 
 of three inches to a foot. Figure 7 exhibits a part 
 of one of the end plates of the condenser, drawn 
 from a scale of one inch to a foot. The holes 4, 5, 
 and 6, are opposite the gas ways numbered 4, 5, 6, 
 in figure 4, and are for the purpose of clearing away 
 any salts, & c., that may accumulate in the con- 
 denser. The three holes opposite the gas-ways 
 1, 2, 3, figure 4, are shown as covered by a lid 
 which can be easily removed, should it be needful, 
 at any time, to examine the internal state of the 
 condenser ; and they can be very quickly replaced. 
 The mode of securing these lids is shown at figure 
 8, which is drawn from a scale of three inches to a 
 foot. In this figure, a a a represents a bolt which 
 may be made with a quick square-thread screw ; this 
 bolt must be of sufficient length to pass through 
 the lid d d 9 the pasteboard flanch e e , the thickness 
 of the end plate of the condenser f f, and the cross 
 piece b b , which will enter inside the end plate, as 
 at b b, figure 7. cccc are the openings which 
 correspond with those marked 4, 5, 6, figure 7. It 
 
CONDENSING MAIN, ETC. 
 
 223 
 
 is evident that when the pasteboard flanch is placed 
 upon the inner face of the lid, and the cross bar 
 passed through the openings b b , by its being moved 
 a little to the right or left of these openings, it will 
 lay hold of the inside of the end plate of the con- 
 denser, and, consequently, may be screwed up by 
 means of the bolt a, so as to form a perfectly secure 
 joint. In the condenser described by figures 3 and 
 4, Plate XII., there are twelve holes at each end 
 corresponding with the gas-ways, and three of these 
 are covered with one lid, so that there are four lids 
 at each end. When removed, an iron rake can he 
 introduced through them, by which means all con- 
 densed matters can be extracted ; and, as the work- 
 men can see from one end of the gas-way to another, 
 they can be certain of all impediments being re- 
 moved before the lids are refixed. In a condenser 
 of the size shown in the plate, the whole operation 
 of taking off the lids, cleaning out the condenser, 
 and refixing the lids, can be perfonned by a couple 
 of workmen in three or four hours. This descrip- 
 tion of condenser I think well adapted for any gas 
 work, from having used such for several years, 
 during which period they never created any trouble 
 from stoppage or otherwise, and they were found 
 very effective in their operations. 
 
224 
 
 CHAPTER IX. 
 
 On the Situation and Construction of Vessels for receiving the Tar 
 and Ammoniacal Liquor. 
 
 As every ton of coal when submitted to distillation 
 in close vessels for the purpose of collecting the 
 gas evolved, and its other products, produces from 1 
 to 1^ cwt. of coal tar, and from eleven to thirteen 
 imperial gallons of ammoniacal liquor, it becomes 
 necessary that they should be received into some 
 vessel after they leave the hydraulic main, otherwise 
 they would soon fill the line of pipes between the 
 hydraulic main and the purifier, and consequently 
 stop the process. To prevent this, a cast iron pipe 
 is sometimes connected to one end of the hydraulic 
 main, distinct from that pipe which leads to the 
 washer or condenser, and which has a declivity 
 towards the vessel appropriated for receiving the con- 
 densable products. This vessel is called the “Tar 
 Cistern,” or “Tar Well.” The tar cistern ought 
 always to be placed between the condenser and the 
 purifier, in order that condensation may be properly 
 effected before the tar and ammoniacal liquor are 
 allowed to enter it. In most cases, the tar cistern is 
 so situated as not to receive the tar and ammoniacal 
 liquor till they have with the gas passed through the 
 
FOR TAR AND AMMONIACAL LIQUOR. 
 
 225 
 
 condenser. Under such arrangement there is but 
 one connexion to the hydraulic main, (instead of two,) 
 which conveys away from it all the products evolved, 
 and all pass together to be condensed ; after which 
 process the pipes are so arranged as to allow the tar 
 and ammoniacal liquor to be carried into the tar 
 cistern, and the gas to enter into the purifier. In 
 this case the top of the tar cistern must be situated 
 below the level of the bottom of the condenser and 
 purifier, otherwise the pipes between it and the con- 
 denser, and also between it and the purifier, would 
 soon be filled with tar. 
 
 The tar cistern may be made of any convenient 
 shape, and constructed of cast iron plates, or of brick 
 or stone well puddled under the bottom and round 
 the sides, so as to prevent any leakage. In all cases 
 it ought to be closed at the top, with the exception of 
 a very small aperture to prevent the ammoniacal 
 liquor losing its strength from exposure to the air. 
 
 To prevent the gas from entering into the tar cis- 
 tern, the pipe which brings the tar and ammoniacal 
 liquor into it descends through the top of it nearly 
 to the bottom inside. This pipe is received into 
 another of two or three inches greater diameter, cast 
 with a flanch at one end, upon which a blank flanch 
 is jointed. The larger pipe is put upright into the 
 tar cistern before the one which brings the tar and 
 ammoniacal liquor into it is fixed so as to stand upon 
 the closed end ; it is then filled with water, and the 
 
 Q 
 
226 
 
 CONSTRUCTION OF VESSELS 
 
 first named pipe is dropped into it so as to have a dip 
 of two or three feet. With such dip no gas can es- 
 cape ; for when the distillatory process commences, 
 the tar and ammoniacal liquor drain down the inner 
 pipe, and the outer one being already filled, they run 
 over the top of it and are deposited in the tar cistern, 
 whilst the escape of gas into it is prevented by the 
 dip already mentioned. 
 
 When the tar cistern is constructed of cast iron 
 plates, it can be made either circular, oblong, or 
 square, as may be most convenient. The one shown 
 in figure 3, Plate XII., (under the condenser,) is about 
 twelve feet long, seven feet six inches wide, and six 
 feet deep. Such size was found to be sufficiently 
 capacious where twenty small D retorts were con- 
 stantly worked during the winter months, and a 
 proportionate number during the months of summer. 
 It was furnished with a cock at one end for drawing 
 off the tar and ammoniacal liquor, which would draw 
 off* either one or the other as was desired. This was 
 effected by means of a pipe inside the tar cistern of 
 about six feet in length, which was attached to the 
 cock inside the vessel, and by means of a moveable 
 joint could be raised or depressed so that its upper end 
 could be raised by a pulley and chain so as to be sur- 
 rounded by the ammoniacal liquor, or depressed so 
 as to dip into the tar : in one case allowing tar, and 
 in the other ammoniacal liquor, to issue from the 
 cock when opened. C, D, E, F, figure 3, Plate XII. 
 
FOR TAR AND AMMONIACAL LIQUOR. 227 
 
 is a longitudinal vertical section of a cast iron tar 
 cistern, resting upon a base of stone or brick-work 
 about fifteen inches in height. At the end near C E 
 is placed a pipe # # closed at the bottom and filled 
 with water, into which dips the pipe o 3 which brings 
 the tar and ammoniacal liquor into it from the con- 
 denser ; and, by a similar arrangement, the tar and 
 ammoniacal liquor which are brought direct (by 
 means of a separate pipe) from the hydraulic main 
 enter into the tar cistern also. 
 
 When it is deemed expedient to make a tar cistern 
 under ground of n*asonry or brick-work, it ought 
 always to be circular in its plan, and with an inverted 
 dome for its bottom, as shown in figure 9, Plate XII., 
 which is the vertical section of a tar cistern, about 
 nine feet deep, and eight feet in diameter, at the 
 widest part. In a tar cistern of that size, the ground 
 having been excavated, and a thickness of about 
 eighteen inches of well tempered clay laid over the 
 bottom, let the stone f be fixed, against which let the 
 inverted arch be built of brick, laid in Roman cement, 
 puddling well at the back of the said brick-work 
 about one foot in thickness at one time. Afterwards 
 carry up the perpendicular part of the work, and 
 when that is done, finish the upper part or dome upon 
 proper centering, leaving a circular opening as a a at 
 the top for bringing the tar pipes into it, which open- 
 ing can be covered with a flag stone when the brick- 
 work, puddling, and filling in are completely finished 
 
 Q 2 
 
228 
 
 CONSTRUCTION OF VESSELS 
 
 and the tar pipes fixed in their places. Only one 
 tar pipe b y and one dip receiving pipe c c, are shown. 
 It is supposed to be brought directly from the hy- 
 draulic main, the other dip and receiving pipe would 
 bring the tar and ammoniacal liquor from the washer 
 and condenser, but being precisely similar to the one 
 shown in the figure, it need not be further dwelt 
 upon. The tar or ammoniacal liquor can be pumped 
 out of this tar cistern at pleasure, by a pump fitted 
 with a moveable suction pipe working at its joint in a 
 stuffing box. This suction pipe can be raised so that 
 its extreme end shall be in the/. ammoniacal liquor^ 
 which, being of less specific gravity than the coal tar, 
 always occupies the uppermost part in the tar cistern. 
 The suction pipe is raised by having a chain attached 
 to it which comes through the top of the tar cistern, 
 and is then secured to a barrel fixed in a frame (with 
 a pall at one end of it) which is turned by a winch, 
 so that when fixed at any particular height it will re- 
 main stationary, and the pump may be worked till 
 the ammoniacal liquor is lowered beneath the end 
 of the suction pipe, when the pall may be disengaged 
 and the pipe again lowered and the pumping con- 
 tinued. When it is desired to obtain tar, the best way 
 to proceed is by turning the winch upon the barrel 
 the reverse way to what had been done when ammo- 
 niacal liquor was wanted ; this will allow the end of 
 the suction pipe to fall nearly to the bottom of the 
 tar cistern, where the thickest portion of the tar is 
 
FOR TAR AND AMMONIACAL LIQUOR. 229 
 
 deposited. When it is in that situation, if the pump be 
 worked, the tar raised by it will be of the best quality 
 which the cistern contains, and more free from am- 
 moniacal liquor than if pumped from near the surface. 
 Figure 9, Plate XII. exhibits a brick tar cistern, 
 drawn from a scale of a quarter of an inch to a foot. 
 It will be quite large enough for a gas work where 
 from six to nine elliptical retorts are worked at an ave- 
 rage throughout the year. In it a a is the top open- 
 ing already noticed, b the tar pipe, c c the receiving 
 pipe for sealing the tar pipe b, dd fourteen inch brick- 
 work laid in Roman cement, e e puddle at the back 
 of the brick-work, which is to be put in about one 
 foot in thickness at one time, great* care being taken 
 that the clay of which the puddling is formed be well 
 tempered before it is laid in its place, and well wetted 
 and trampled upon after it is there : for on the good- 
 ness of the puddle the soundness of the tar cistern 
 depends, more than upon the execution of the brick- 
 work. It is of the utmost importance that the tar 
 cistern should be quite tight, not only on account of 
 preventing waste of the tar and ammoniacal liquor 
 it may receive, but also to prevent an escape of either 
 of these fluids, which would percolate through the 
 ground, particularly if of a gravelly nature, and, if 
 by such means it found its way into any adjacent 
 spring or well, would soon render the water unfit 
 for use. 
 
230 
 
 CHAPTER X. 
 
 On the Purifiers used in the Coal Gas Manufactory, and the best 
 mode of purifying Coal Gas. 
 
 During the process of decomposing coals in close 
 vessels, it is found that on their being heated to a 
 certain degree, a part of the carbon of which they are 
 formed unites with a part of the oxygen, and pro- 
 duces carbonic acid gas. Whilst this process is going 
 on, a part of the hydrogen of the coal is combined 
 with another portion of carbon and caloric, which 
 forms carburetted hydrogen gas. Olefiant gas, or 
 bi-carburetted hydrogen, carbonic oxide, hydrogen, 
 and sulphuretted hydrogen are also produced. Every 
 kind of coal gas is a mechanical mixture of all these 
 gases, and as the component parts of the coal sub- 
 mitted to distillation vary, so will the quantities of 
 the gaseous products above named (carburetted and 
 bi-carburetted hydrogen being the principal) vary 
 also. 
 
 When the gas produced from coal is burnt with- 
 out being purified, (that is, without being deprived 
 of the sulphuretted hydrogen, and carbonic acid gas 
 which it contains,) or if it be not properly purified, 
 it throws out sparks, and produces sulphurous acid, 
 owing to the oxygen of the air uniting with the sul- 
 
PURIFIERS. 
 
 231 
 
 phur burnt with the gas. Such gas sends forth a 
 suffocating odour that is highly offensive and inju- 
 rious to health. Where it is burnt, the levity of 
 the odour arising thence carries it to the uppermost 
 part of the room, and there it is easily perceived. It 
 tarnishes all metallic substances, and discolours paint- 
 ings in the execution of which metallic oxides may 
 have been used. 
 
 The general way of freeing coal gas from sulphur- 
 etted hydrogen and carbonic acid gas, and rendering 
 it fit for use, has been either by passing it through 
 lime and water mechanically mixed so as to be of 
 the consistence of cream, or by making it percolate 
 through layers of slaked lime, so wetted before it is 
 put into the purifier that, on handling it, it will not 
 soil the fingers, as will be more fully shown hereafter, 
 when describing what is generally denominated the 
 dry lime purifier in contradistinction to the wet lime 
 purifier ; by some modification of one or of the other 
 of which purifiers almost all the gas made at the 
 present day is purified. It may also be purified by 
 passing it through very dilute solutions of sub-acetate 
 of lead, green sulphate of iron, or chloride of lime. 
 
 For the purification of coal gas when it is manu- 
 factured in the large way, various methods have 
 been adopted ; but they have all given way to one 
 or the other of the two which we have named; that 
 is to say, either to that by lime and water mixed to 
 the consistence of cream, or to that by slaked lime 
 
232 
 
 PURIFIERS. 
 
 thoroughly damped. Besides these modes, purifiers 
 have been constructed by which the gas was acted 
 upon by lime in a semi-fluid state : others proposed 
 to effect the purification by passing the gas through 
 red hot cylinders filled with clippings of iron : others 
 used a compound of lime with pot or pearl-ashes and 
 charcoal or coke, which was formed by pouring a 
 strongly impregnated solution of pot or pearl-ashes 
 in water, upon recently burnt and unslaked lime; 
 the quantity of the solution required being so much 
 as would slake the lime, or cause it to fall to powder. 
 This being done, dry pot or pearl-ashes were added 
 to about one-fifth of the whole weight of the lime, 
 and also about one-fourth of the bulk of the lime, 
 of charcoal, or coke broken into small pieces ; the 
 whole was perfectly mixed together, and when so, 
 formed the absorbent or purifying stratum. The 
 apparatus which was used was enclosed within a 
 square box or case internally divided into compart- 
 ments by an endless web of wire-gauze, upon which 
 the purifying mixture was spread. The web was 
 extended upon cylindrical rollers, which were acted 
 upon by machinery, and by which the abstraction 
 and renewal of material were effected. The whole 
 of the contrivance was of a very complex description, 
 and not a whit the more efficient than the present 
 ones in general use. Some again proposed to purify 
 the gas in the retort where it was generated. We 
 advert to these as some of the methods which have 
 
PURIFIERS. 
 
 233 
 
 from time to time been proposed to the attention of 
 the public, but which we need not dwell upon fur- 
 ther in this place, our object being rather to describe 
 what has been generally proved and acknowledged 
 to be useful, than to take up the reader’s time in de- 
 scribing apparatus which have failed to be so. 
 
 We may here however remark, that when coal 
 gas was first employed for the purpose of procuring 
 light, it was allowed to proceed to the place where 
 it was intended to be burnt without undergoing any 
 purifying process other than passing it through water, 
 and it appears that some time elapsed before lime 
 and water were used as a purifying medium. For 
 several years after lime mixed with water was used 
 for the purpose of purifying coal gas, the operation 
 was performed by means of a cast-iron square or 
 cylindrical vessel, enclosing another vessel of the 
 same shape, but of smaller dimensions, which was 
 secured inside to the top of the outer one in such 
 a manner as to be perfectly gas tight. The inner 
 vessel had no bottom, and the sides of it were drilled 
 full of holes to the height of six inches from the 
 lower edge. 
 
 When such a purifier as we are speaking of was 
 circular in shape, an upright shaft rested upon a step 
 in the bottom, and was brought through a stuffing 
 box at the top. At the head of the shaft was fixed 
 a horizontal bevel wheel, to be driven by a pinion on 
 one end of a shaft, to which the winch to be turned 
 
234 
 
 PURIFIERS. 
 
 by hand was applied at the other. The speed at 
 which the upright shaft was driven was about ten 
 revolutions in a minute. At the lower end of the 
 shaft, and at a distance of four or five inches from 
 the bottom of the purifier, were fixed four or more 
 vanes, each of which was in length about three 
 inches less than the semi-diameter of the outer vessel, 
 and in breadth about four inches. Their use was 
 to stir up the lime and keep it from subsiding. This 
 was effected by a man turning the winch already 
 mentioned, which gave motion to the pinion, con- 
 sequently to the horizontal bevel wheel fixed upon 
 the shaft, with its shaft and the vanes (or, as the gas 
 light manufacturer terms them, “the agitators”) 
 thereunto attached. 
 
 In using this description of purifier it was neces- 
 sary that there should be a vessel of sufficient 
 capacity for mixing a sufficient quantity of lime and 
 water for one charge, situated at such a height as 
 would allow it to be turned, by means of a cock or 
 valve, into the purifier, whenever it was necessary 
 to introduce a new charge into it. This vessel was 
 required to be fitted with agitators similar to those 
 in the purifier, so that the mixture might be pro- 
 perly effected before it was allowed to enter into the 
 purifying vessel. The admission of the mixture 
 into the purifier was accomplished by means of a 
 small vessel attached to the outside of it, the top 
 thereof rising to the same height as that to which 
 
PURIFIERS. 
 
 235 
 
 it was desired the mixture should rise inside the 
 purifier. Between this vessel and the purifier was 
 a slide valve, opened for the purpose of charging 
 the purifier, hut kept closed when it was in action. 
 Previous tc introducing a new charge of clean lime 
 and water into the purifier, the impure mixture had 
 to be drawn off by means of a vessel and valve 
 nearly similar to that shown at Q, figure 1, Plate 
 XIII., the action of which will he fully described 
 when we come to speak of the triple wet lime puri- 
 fier. We will only here remark, that it must be 
 evident that so soon as the impure matter was drawn 
 off in a single purifier such as we have been speaking 
 of, below the perforated openings in the inner cylin- 
 der, as already mentioned, till those openings were 
 again completely covered by the new charge, all the 
 gas made would pass into the gas-holder in an 
 impure state, thus deteriorating the quality of the 
 whole stock of that article. 
 
 Having mentioned the manner of charging and 
 discharging the purifying vessel, we are next to 
 consider how the gas is brought into it, acted upon 
 therein, and allowed to pass thence into the gas- 
 holder. In a preceding chapter, when speaking of 
 the condenser, we described how the gas passes 
 from the retorts towards it, and from the condenser 
 to the purifier. In such a purifier as we are now 
 speaking of, it was introduced at the top into the 
 interior chamber which we have described. And 
 
236 
 
 PURIFIERS. 
 
 as the purifying mixture, when the purifier was 
 charged, ascended to a height of about eleven inches 
 above the lower edge of the interior vessel, it is 
 evident that the gas accumulated therein till the 
 capacity of the vessel became too small for its bulk, 
 which continually increased till the gas forced its 
 way beneath the inner vessel and through the holes 
 in its vertical sides, and bubbled up through the 
 purifying mixture into the space unoccupied by the 
 lime and water in the outer vessel ; from which, by 
 means of pipes properly arranged, it was conveyed 
 to the gas-holder. It is evident, then, that no gas 
 could pass from the retorts to the gas-holder with- 
 out first having passed through the purifier, and 
 (except during the time employed in removing an 
 old charge of lime and water and replacing it by a 
 new one) it must pass through the purifying mix- 
 ture also, which mixture being constantly kept 
 agitated, so acted upon the crude gas, by the laws 
 of chemical affinity, as to take up the sulphuretted 
 hydrogen gas, &c., and to allow the carburetted 
 hydrogen gas nearly free from such impurities to 
 pass to the gas-holder. 
 
 What has been stated relative to the cylindrical 
 purifier is applicable to the square one. In some 
 establishments the purifier was formerly of rect- 
 angular base ; and when so, it was furnished with 
 two upright shafts and with double sets of agitators. 
 But either of the latter shaped vessels are less ser- 
 
PURIFIERS. 
 
 237 
 
 viceable than the former ; for in them the angular 
 points cannot he affected by the agitators, and, con- 
 sequently, a considerable portion of the charge is 
 lost to the manufacturer : this cannot happen to him 
 when the cylindrical purifier is used ; for in it every 
 part of the mixture is kept constantly agitated and 
 is brought into use. 
 
 Purifiers of the description spoken of were all 
 •single vessels, and therefore, for reasons already 
 given, not thoroughly effective ; in addition to 
 which, the greater proportion of gas being generated 
 during the first period of distillation, it would be 
 more acted upon than that which was evolved 
 during the latter part of the process, when the 
 purifying mixture had become saturated with sul- 
 phureous particles. In consequence of this, it has 
 been thought expedient to employ a series of puri- 
 fiers : the one nearest to the condenser receives the 
 gas in its most impure state ; after passing through 
 it, it enters into a second, where it is again sub- 
 mitted to the purifying process, and so on, through 
 any number of vessels, but which, in practice, never 
 exceeds three. Under this arrangement, so soon as 
 the gas is found to give evidence of impurity by the 
 application of a proper test, the impure mixture 
 should be drawn from the first purifier, and the 
 purifying mixture contained in the second allowed, 
 by means of proper pipes and valves, to be conveyed 
 into it ; and the purifying mixture in the third, by 
 
238 
 
 PURIFIERS. 
 
 similar means, brought into the second ; after which 
 there should be introduced into the third a fresh 
 or new charge of clean purifying mixture. By 
 these means the gas could never find its way into 
 the gas-holder (as when single vessels were used) 
 without undergoing the purifying process to a con- 
 siderable extent. By it, also, the last vessel of the 
 series, provided proper care were taken, would never 
 become foul inside, as was the case when single* 
 purifiers were used. For the reasons we have given, 
 as well as from much experience, we are decidedly 
 of opinion, that when wet lime purifiers are used, 
 however small the establishment may be, more than 
 one should be employed, whenever the purity of the 
 gas is of the least importance. In large works, 
 more than one becomes a matter of absolute neces- 
 sity. We are, therefore, to inquire which is the 
 best arrangement for placing two, three, or more 
 wet lime purifiers so that they may be the most 
 effective in their operations, and at the same time 
 the most economical as regards the cost of con- 
 structing and that of working them. The best 
 arrangement for wet lime purifiers which has fallen 
 under my notice, as well as the best construction 
 of the purifier itself, were effected some years ago 
 by Mr. John Malam, of Hull, (at the time when he 
 was employed at the Westminster gas-works). It 
 is shown in section and plan, figures 1 and 2, Plate 
 XIII., which are drawn from a scale of a quarter 
 
PURIFIERS. 
 
 239 
 
 of an inch to a foot. ABCD, figure 1, is a ver- 
 tical section of a treble purifier, placed upon a 
 foundation of brick-work, and figure 2 is a plan 
 thereof. EE, F F, G G, figure 1, are sections of 
 the three interior chambers bolted to the tops of 
 their respective vessels by the flanches expressed in 
 the plate. It will be observed, that the bottoms of 
 these chambers branch out into a kind of broad 
 flanch, by which means the gas is acted upon by a 
 greater portion of the purifying mixture than if the 
 vertical sides had no such appendage. H is the 
 axis or shaft, upon which the agitators 1 1 are fixed. 
 KKK are three cylindrical vessels for the purpose 
 of charging the respective divisions of the purifier, 
 into which the purifying mixture is introduced by 
 the bend pipes LLL. MMM are the pipes which 
 convey the gas into the interior chambers. N is 
 the pipe which conveys the purified gas to the gas- 
 holder after it has passed through the three series 
 or compartments of the purifier. O is the feed 
 pipe for bringing the purifying mixture from the 
 vessel where it is prepared into the purifying appa- 
 ratus. P P P exhibit the openings near the bottoms 
 of the cylindrical vessels K K K, for emptying the 
 respective vessels or compartments of the purifier, 
 which is effected by the slide valves, or cocks, 
 Q Q Q. In this figure the height to which the 
 purifying mixture rises is shown in the two lower 
 vessels ; but the upper one is exhibited as not 
 
240 
 
 PURIFIERS. 
 
 charged. The agitators are driven by hand, or 
 other power, in the same way as has been already 
 described when we were speaking of the single 
 purifier. 
 
 When this purifier is first brought into action, 
 the purifying mixture is turned into the uppermost 
 of the vessels marked K, from whence it enters into 
 the uppermost purifier by the bend L, till it rises 
 to the height of the uppermost edge of the vessel 
 K. When such is the case, by opening the upper- 
 most of the slide cocks, Q, that charge is emptied 
 from the first into the second vessel, which being 
 done, the uppermost purifier is again charged. The 
 middle cock, Q, is then opened, which allows the 
 charge in the second purifier to enter into the lower- 
 most one ; and whilst this is performing, that in the 
 uppermost one is emptied into the second. The 
 mixture is at the same time entering into the upper- 
 most one, which is known to be properly charged 
 when the mixture rises to the top of its supplying 
 vessel K. This being performed, the gas in its 
 crude state is allowed to enter into the interior 
 chamber of the lowermost purifier by the pipe M, 
 which being filled, it flows under the flanch part 
 of it, and through the purifying mixture, into the 
 outer part of that vessel marked R R, which is un- 
 occupied by the purifying mixture : from thence, by 
 the next pipe M, it is conveyed into the interior 
 chamber of the middle purifier, where the action is 
 
PURIFIERS. 
 
 241 
 
 the same as in the lower one ; and thence, by the 
 uppermost pipe M, it is conveyed into the highest 
 vessel, where, after having again undergone the 
 purifying process, it is allowed to enter the gas- 
 holder by the pipe N. 
 
 On examining the figures 1 and 2, Plate XIII., 
 it must appear obvious, that the gas enters into the 
 lowermost purifier in its most impure state ; whence, 
 after having been acted upon therein, it rises into 
 the second in a purer state, and from thence into 
 the top one. Under such circumstances, it follows 
 that the charge in the lowermost vessel is rendered 
 useless first : on its being so, it is drawn off by open- 
 ing the bottom cock, Q ; whilst this is being done, 
 the gas generated has to pass through two purifying 
 vessels before it can enter the gas-holder ; but, in 
 the single purifier, as has before been noticed, during 
 the time of charging, the gas passes into the gas- 
 holder in an impure state ; thus, by mixture with 
 the pure gas, deteriorating its quality. The bottom 
 purifier being emptied, the mixture in the second is 
 turned into it, and that in the top one into the 
 second when the top one is to be recharged. The 
 lowermost vessel, consequently, always contains the 
 mixture which is most acted upon by the gas in its 
 impure state. 
 
 By placing the purifiers one over another, a con- 
 siderable saving in the expense of erecting them is 
 effected, inasmuch as the top of the lowermost vessel 
 
 R 
 
242 
 
 PURIFIERS. 
 
 answers as a bottom to the one immediately above 
 it, whilst the top of the middle vessel becomes the 
 bottom of the uppermost one. The savings are not 
 derived thence alone, for when they are placed 
 separately, there must be a considerable outlay in- 
 curred for extra foundations, for pipes, and for 
 machinery for driving the agitators, which would 
 all be saved by adopting the triple purifier. Not- 
 withstanding what has just been remarked, even 
 where the saving of room is of great importance, 
 the placing a series of single purifiers, apart from 
 each other and at different levels, has been, and still 
 is, a very prevailing system in those manufactories 
 where wet lime is used for purifying the gas. 
 
 To give further details relative to the means of 
 purifying coal-gas by passing it through a mixture 
 of lime and water held mechanically in solution is 
 quite unnecessary ; for, although different operators 
 may employ different shaped vessels for the purpose, 
 yet they all must allow the gas to pass through a 
 sufficient column of the purifying mixture to render 
 the purification as complete as the wet lime process 
 will make it ; and, provided that be effected, the 
 manufacturer’s object is attained. 
 
 Our next business will be to notice the system of 
 purification by what is called, though improperly, 
 yet in contradistinction to the preceding system, 
 “ The Dry Lime Purifier .” Mr. Reuben Phillips, 
 of Exeter, was the first person who obtained a patent 
 
JFz^- J. 
 
 riwu.13. 
 
 SFvgf. % 
 
 Scale i mck/foa.Foob Tfoo? S. JPecJfsSto/v. 
 
 .Zorulons: I\i£>lushj(ul Zry JZ.jfeJbe/'b 20 $ > 'J?eb?J&4l 
 
 I 
 
 -Day&Houglue, Lahog™ to Queens. 
 
PURIFIERS. 
 
 243 
 
 for an apparatus for purifying coal-gas by means 
 of slaked lime, which, under certain modifications 
 and with various improvements, is used in a great 
 number of gas-works throughout this and other 
 countries where gas is manufactured. As, since I 
 first witnessed the operation of the dry lime purifier, 
 I have put up, during the last twenty years, a great 
 number of them, I can speak of the results obtained 
 therefrom with that confidence which nothing save 
 extensive experience can warrant. Prior to my 
 being convinced, by experience, of the superiority 
 of the dry lime system over the wet one, I was a 
 decided advocate for the latter ; but, after fixing and 
 working dry lime purifiers at the Southampton, 
 Portsea, and Newport (Isle of Wight) gas-works, 
 I never have been in the habit of fixing or recom- 
 mending wet lime purifiers wherever I have been 
 employed. In speaking of the dry lime purifier, it 
 is not, however, to be supposed that the lime is 
 introduced into the purifier in a perfectly dry state*; 
 such is not the case. I now propose to give a 
 description of the dry lime purifiers, and to offer a 
 few remarks as to the mode of their operation, 
 which I trust will be intelligible to the reader. 
 
 The purifiers on Mr. Phillips’s plan are generally 
 square (constructed of cast-iron plates) ; and, where 
 there are about 500 lights to be supplied, they are 
 about five feet square and from two to three feet 
 deep. It requires two of them for every establish- 
 
 R 2 
 
244 
 
 PURIFIERS. 
 
 ment, in order that when the lime in one vessel 
 becomes so impure as to be no longer able to 
 deprive the refrigerated gas, as it passes through it, 
 of its impurities, such as sulphuretted hydrogen, 
 &c., the communication of the gas thereto may he 
 shut off, by means of valves attached to the appa- 
 ratus, and a communication opened to the one con- 
 taining clean lime. Thus there is continually only 
 one in action at one time, and whilst that is so, the 
 impure lime is removed from the other, and a fresh 
 charge of clean lime introduced, to be ready for use 
 when it becomes needful for another change of 
 purifier to take place. These vessels are secured at 
 the bottom by an hydraulic joint, and round the 
 top of each is a trough, of about six inches in 
 breadth and ten inches in depth, nearly filled with 
 water, into which the cover or lid dips, so as to 
 prevent an escape of gas from the top. Each vessel 
 is fitted with shelves of plate-iron, perforated with 
 holes of about three-eighths of an inch in diameter, 
 and distant from centre to centre three-quarters of 
 an inch. These shelves, when fixed in their places, 
 rest upon slight ribs cast inside upon the plates 
 which form the sides of the purifier, in such a way 
 as to divide the purifying vessel into three or four 
 longitudinal compartments. At the bottom of each 
 purifier (near the middle) is fixed the pipe which 
 brings the impure gas into it ; and a few inches 
 above the top of this pipe is placed the first shelf. 
 
PURIFIERS. 
 
 245 
 
 covering the entire of the inside of the vessel ; at 
 about eight or nine inches above it is placed the 
 second, and the succeeding ones at equal distances 
 one from another. In charging this purifier, the 
 first shelf is laid in its place and covered with fresh 
 slaked lime so far wetted as, on trial, not to adhere 
 to or discolour the hand. In that state it is spread 
 over the entire surface of the first shelf, to a depth 
 of from three to four inches ; it is then wetted by a 
 watering-can, which holds about a gallon for a 
 purifier of the size named, the contents of which 
 are emptied uniformly over the surface of the lime. 
 The second, third, &c., shelves are treated in pre- 
 cisely the same manner ; and when they are all 
 placed in their situations, the lid, which covers the 
 entire of the top, is lowered into its place, dipping 
 into the hydraulic trough already alluded to ; on 
 this being done, the purifier is ready for action. 
 On one side of each purifier, and above the top 
 shelf, is the exit pipe for conveying the purified gas 
 to the gas-holder. It has been already noticed, that 
 the impure gas enters into the purifiers alternately, 
 as they happen to be in action, below the bottom 
 shelf ; and as that shelf and those above it are 
 covered to a certain thickness with the damped 
 lime, the gas is compelled to percolate through the 
 lime upon each tier of shelves before it can pass 
 away from the purifier ; and thus, according to the 
 laws of chemical affinity, the sulphuretted hydrogen 
 
246 
 
 PURIFIERS. 
 
 and carbonic acid gases, &c., are arrested, and the 
 purified gas only is allowed to find its way to the 
 gas-holder. 
 
 In using purifiers of this description, it is found 
 that they perform the operation of purifying better 
 than wet lime purifiers, without being attended by 
 several weighty objections incidental to the latter. 
 When the lime in the dry lime purifier is saturated 
 with sulphuretted hydrogen and carbonic acid gas, 
 it is removed from the purifier into a proper recep- 
 tacle, through which there is a current of air, which, 
 passing over the saturated lime, carries off its volatile 
 impurities (which are very offensive) through the 
 main flue of the retorts into the chimney, where 
 they are entirely destroyed. The impure lime ex- 
 tracted after this operation, being strongly impreg- 
 nated with substances favourable to vegetation when 
 judiciously applied, becomes a very useful manure. 
 
 The dry lime purifiers which we have described 
 will answer very well in small works ; but in large 
 establishments, much space would be occupied by 
 such purifiers when of sufficient power to effect the 
 purification of the gas generated, for in works of 
 magnitude ranges of purifiers of considerable extent 
 would be required, in order that one range might 
 be employed whilst the other was undergoing cleans- 
 ing and recharging, in precisely the same manner as 
 was the case when but two purifiers were used. To 
 obviate this difficulty, a dry lime purifier was invented 
 
PURIFIERS. 
 
 247 
 
 by Mr. John Malam, of Hull, for which he obtained 
 a patent in 1823. 
 
 Plate XIV., figure 1, represents an elevation of 
 two of the purifiers and the valve in all the leading 
 parts similar to those for which the patent just 
 alluded to was obtained. Figure 2 is a plan of the 
 same. These tw’o figures are drawn from a scale of 
 a quarter of an inch to a foot. Figure 3 is a ver- 
 tical section of one of the purifiers showing the lid, 
 trough, and shelves upon which the lime is to be 
 placed. Figure 4 represents the bottom of the lift- 
 ing valve, supposing it to be turned upside down, 
 and figure 5 is a section of the said lifting part of 
 the valve. Figures 3, 4, and 5, are drawn from a 
 scale of half an inch to a foot. In figures 1 and 2 
 the corresponding parts are marked with similar 
 letters of reference. In figure 1, A and B represent 
 two of the purifying vessels (of which it w*ill be 
 seen by referring to figure 2 there are four, and 
 which on that figure are marked ABCD), each 
 with its lid or cover marked g and h in its place, 
 as if the purifying vessels were in action. These 
 are supported upon piers of brickwork as at ooo o. 
 E is the outer case of the centre valve, by the action 
 of which the purifiers A, B, C, or D can be thrown 
 out of action at pleasure. Through the bottom of 
 this valve the pipes marked 1, 2, 3, 4, 5, 6, 7, and 8, 
 the gas entrance pipe at the centre i and the exit 
 pipej rise to the height of about twelve inches, and 
 
248 
 
 PURIFIERS. 
 
 when the valve is prepared for action it is filled with 
 water to the depth of about ten inches, so that the 
 pipes just named are all surrounded to that depth 
 with water. The interior or lifting part made of cast- 
 iron, represented in figure 2 and in figures 4 and 5 
 on a larger scale, (which will be more fully described 
 hereafter,) is then placed over the pipes with its 
 open part downwards, which dips in the water to the 
 height at which the water stands in the valve, and 
 so that the part marked 1 in figure 4 shall be over 
 the pipe marked I figure 2 ; when it is so, it is 
 evident that the gas which enters the valve at its 
 centre by the pipe i cannot escape therefrom but by 
 passing down the pipe 1, no other pipe in the valve 
 being connected with that partition, the water 
 sealing the partition plates of the lifting valve: and 
 on examining figure 2, it must likewise be evident 
 that (in the situation the lifting part of the valve is 
 there shown without its top to expose the orifices of 
 the pipes) the gas passing down pipe 1 will proceed 
 by the pipe opposite thereto into the purifier marked 
 C, into which purifier it enters below the bottom tier 
 of shelves as shown in section in figure 3. After 
 having percolated through the lime spread over the 
 shelves in the way described at page 245, it finds 
 its way to the top of the purifier, from whence it 
 descends towards the bottom over the partition 
 plate e f, which goes quite across the purifier and 
 close to its bottom, and rises about six inches above 
 
PURIFIERS. 
 
 249 
 
 the top tier of plates upon which the lime is laid. 
 This plate is cast with a flanch at each side and at 
 the bottom, so that it may he jointed to the sides 
 and bottom and made gas-tight. On reaching the 
 bottom of this partition, the gas makes its exit from 
 the purifier C by the bend-pipe shown at the side 
 opposite to that at which it made its entrance ; and 
 through the pipe thereunto connected it proceeds 
 again to the valve rising through the pipe marked 
 2 into that partition of the lifting valve which 
 encloses the pipes marked 2 and 3. From that 
 partition it cannot escape except by passing down 
 the pipe 3 ; it does so, and by the pipe in a line 
 therewith it finds its way under the bottom shelf 
 of the purifier A, where, after having percolated 
 through the lime as already mentioned when speak- 
 ing of the purifier C, it passes over the partition ef, 
 and thence, by means of the pipe k, again into the 
 valye into which it rises by the pipe marked 4 ; here 
 again it can find no way of escape except by descend- 
 ing 'through the pipe marked 5, the pipes 4 and 5 
 being enclosed within one partition of the lifting 
 part of the valve. The pipe marked 5 conveys the 
 gas by the pipe m into the purifier marked B, in 
 which it percolates through the lime till it rises to 
 the top of that purifier ; it then descends over the 
 partition e J\ and thence by the bends and pipes 
 shown, as proceeding from the end opposite to that 
 at which it entered that purifier, it finds its way 
 
250 
 
 PURIFIERS. 
 
 into the centre valve through the pipe marked 6. 
 On referring to the plan of the centre valve, it will 
 be seen that the lifting part of that valve shuts off 
 all communication with pipe 6 from all the pipes 
 the valve contains except the one marked j, and that 
 that pipe is connected with the one which leads 
 toward the gas-holder — the gas having, ere it 
 reaches the pipe j, been thoroughly deprived of all 
 its impurities from having passed through three 
 purifying vessels, each containing seven tiers of lime 
 of from three to four inches in thickness, through 
 which number of purifiers it is always obliged to 
 pass on its way from the condenser to the gas-holder. 
 In figure 2, the purifier marked D is represented as 
 entirely shut off from the centre valve, the partition 
 of the lifting part of that valve which falls over the 
 entrance pipe thereto and exit pipe therefrom, pipes 
 7 and 8 shutting off all gas communication of any 
 other part of the centre valve with the purifier D. 
 Such will be the case with respect to the purifiers 
 C, A, or B, according to the position in which the 
 lifting valve may be placed ; for if the valve be lifted 
 and turned one quarter round, that part which now 
 covers pipes 7 and 8 will, when again lowered, shut 
 off the entrance and exit pipes of the purifier C, and 
 throw it out of and bring the purifier D into action 
 when the part of the lifting valve which is repre- 
 sented over the pipe marked 1 would fall over the 
 pipe marked 3, which would convey the impure gas 
 
PURIFIERS. 
 
 251 
 
 into the purifier A, thence by a similar route to the 
 purifier B, and. subsequently to C, from whence, after 
 it had returned to the valve, it would find its way 
 to the gas-holder by the pip ej. It is evident, there- 
 fore, that by raising the lifting part of the valve so 
 that its lowermost edge may be above the top of the 
 pipes in the valve, (till it is in such a position it 
 cannot he turned round,) turning it one quarter 
 round and then lowering it into the water, the gas 
 can he shut off in succession from the purifier D, 
 (as shown in figure 2,) C, A, or B, as may be ne- 
 cessary. The interior or lifting part of the valve 
 has an upright rod or shaft passing through its top 
 at the centre, secured by a collar above, and a nut 
 and washer below, as shown in figure 5 ; which nut 
 ought to be screwed up very tight, and the end of 
 the rod should be well burred up to prevent the 
 nut slipping or the shaft turning without the lifting 
 part turning with it. This shaft passes through a 
 stuffing-box as shown at the top of E, figure 1, and 
 is continued (having a square thread screw about 
 eighteen inches long at its upper end) through the 
 dome-shaped casting marked j\ which is supported 
 by four cast-iron pillars equidistant secured to the 
 lid of the valve E. The tongue d , figure 1, slips 
 over the shaft c , and is secured thereto by a key in 
 the situation as shown in the figure which represents 
 the lifting part of the valve as let down in its place : 
 the opposite end of the tongue has a notch in it. 
 
252 
 
 PURIFIERS. 
 
 which works upon a narrow slip cast upon each of the 
 four pillars already mentioned (of which two only 
 are shown, a and b). These slips do not rise to the 
 entire height of the pillar, but sufficiently high to 
 indicate when the lower edge of the lifting part of 
 the valve is clear of the top of the upright pipes 
 therein. We will suppose now that the pillars are 
 so placed that they are respectively opposite to the 
 purifiers D, C, A, and B, and that if the tongue he 
 lowered upon the slip attached to the pillar opposite 
 D, the purifier D will be thrown out of action if 
 opposite C ; the purifier C, opposite A ; the purifier 
 A, and opposite B, the purifier B will be thrown 
 out of use. When therefore it is necessary to throw 
 any one of the purifiers out of action, the lifting 
 valve is raised by means of the handle e , which works 
 upon the screwed part of the shaft c, till the tongue 
 rises above the slip attached to the pillar towards 
 which it then points, the tongue is then laid hold of 
 and turned to the left till the notch at the end of 
 it is directly over the slip attached to the next pillar, 
 when by the handle and screw it is lowered till the 
 tongue rests upon the top of the stuffing-box already 
 described, when the operation of shifting the valve 
 is finished. The whole operation does not occupy 
 more than a few minutes. 
 
 Figure 2 is a plan of the purifiers A, B, C, and 
 1); their centre valve shown without its top, and 
 the lifting part of the valve also without its top, 1, 
 
PURIFIERS. 
 
 253 
 
 2, 3, 4, 5, 6, 7, and 8, situation of pipes for convey- 
 ing the gas from one part of the valve, and from one 
 purifier to another, and subsequently by means of 
 the pipe j, continued in plan at j, outside the valve, 
 towards the gas-holder. The impure gas enters this 
 valve through the pipe marked i, outside the valve 
 at its centre, a, b, c, d, plans of outside of troughs ; 
 and e /, the partition plates over which the gas passes 
 when leaving each purifier, as has been already de- 
 scribed. 
 
 Figure 3 is a vertical section of the purifier C, in 
 a direction parallel to b d, figure 2, which is given 
 for showing how the gratings or perforated shelves 
 are fixed. It will be seen that there are slips k k 
 cast on the side plates upon which one end of the 
 shelves rest, and also that there are steps cast inside 
 the end plates, as at h, for receiving the T-shaped 
 cross-bars, upon which the other ends of the shelves 
 or gratings are supported. In this figure the grat- 
 ings are represented as in two lengths for each tier, 
 and are marked e and f. They ought not, however, for 
 convenience of handling, to be more than two feet 
 in length by one foot six inches in width. I have 
 found in practice, cast-iron gratings (about three- 
 eighths of an inch in thickness, with a rim round 
 each about one inch or one inch and a quarter broad, 
 cast solid, the other part being cast with open slits 
 about a quarter of an inch in breadth, and distant 
 from each other a quarter of an inch, so as to 
 
254 
 
 PURIFIERS. 
 
 give them the appearance of a grating) very prefer- 
 able to shelves made of boiler-plate, and perforated 
 as has been already described, being much more du- 
 rable, and more easily, and at less expense, replaced 
 when worn out. a, b , c, d } section of the trough 
 which goes round the purifier, to be kept filled with 
 water to a depth of five or six inches, into which 
 trough the lid marked g or h drops, so that, when 
 in its place, as shown in this figure, the escape of gas 
 is prevented by an hydraulic joint. In the centre 
 of the lid must be fixed an eye-bolt, through which 
 a hook can be fixed attached to a swinging crane with 
 a screw or pulleys (not shown in the figure) thereto 
 for raising the lid when it is required to cleanse and 
 recharge the purifier, during which operation the lid 
 can be swung on one side so as to be out of the way, 
 and swung back, and again lowered into its place when 
 the operation is completed. The pipe marked with 
 an arrow shows in what a situation the gas is brought 
 into the purifier, namely, below the bottom lime 
 shelf. 
 
 Figure 4 represents the bottom of the lifting part 
 of the valve, supposing it to be laid upon its top, 
 consequently the reverse way to that shown in 
 figure 2. 
 
 Figure 5 is a section of the lifting part of the 
 valve, with a part of the upright shaft, the collar and 
 nut for securing it. 
 
 Having sufficiently explained the construction of 
 
PURIFIERS. 
 
 255 
 
 this purifier, and the manner in which, by the action 
 of the centre valve, the purifier A, B, C, or D, can 
 be thrown out of action at pleasure, we come now to 
 speak of the mode of working it ; and in doing so, we 
 will suppose that the machine is perfectly new, and 
 is about to be used for the first time. We will also 
 suppose that the lifting part of the centre is placed 
 in the position shown in figure 2, so that there is no 
 communication between the centre valve and the pu- 
 rifier D, but between the centre valve and the inlet 
 and outlet pipes, and the purifiers C, A, and B. The 
 lids being removed from each of these purifiers, the 
 first row or tier of gratings are placed on the lower- 
 most ledges and the cross-bar, as shown in figure 3, 
 and covered with lime, in precisely the same way as 
 has been already described when speaking of this 
 same purifier in its more primitive form, taking care 
 that each tier of lime be well wetted before the next 
 set of gratings above it are fixed in their places, and 
 thus proceeding with each row of gratings and layers 
 of lime upon them till the proper number are fixed 
 in the purifier C. Proceed in exactly the same manner 
 with the gratings and layers of lime in the purifiers 
 marked A and B, till the entire of the gratings they 
 are intended respectively to contain are in their places, 
 and the layers of lime well wetted are upon them. 
 This being done, let the lids be lowered over the re- 
 spective purifiers. To prevent the lids forcing the 
 water out of the troughs of their respective purifiers. 
 
256 
 
 PURIFIERS. 
 
 a hole three quarters of an inch in diameter is tapped 
 and drilled in each, and these are each fitted with a 
 screwed plug, which should be removed prior to low- 
 ering the lid, to allow the compressed air caused by 
 its immersion in the water to escape. These plugs 
 should also be removed when the lids are to be lifted, 
 to prevent the water being drawn out of the trough. 
 It is well to have also a smaller hole tapped in each 
 lid, say of half an inch diameter, fitted with a short 
 piece of iron tube, a cock, and a jet burner for testing 
 the gas, as will be hereafter described. These cocks 
 should be kept always shut, except when it may be 
 necessary to test the purity of the gas. We will 
 now suppose the lids are all lowered into their places, 
 and that the gas then being made has found its way 
 through the washer and condenser to the pipe i, by 
 which it enters at the centre of the lifting part of 
 the valve, as has been already described, and thence 
 into the purifier C, which purifier it enters in its 
 most crude state, and passes through the seven layers 
 of lime which are placed therein, and by which it is 
 deprived of a large portion of the impurities which 
 it contained when it first entered into that vessel. 
 The gas so far purified, returns to the centre valve, 
 and thence under the lowermost layer of lime in the 
 purifier A : in that it passes through the seven layers 
 of lime as before in the vessel C, which take up an 
 additional quantity of the impure matter ; it then re- 
 turns again to the centre valve doubly purified, and 
 
PURIFIERS. 
 
 257 
 
 thence again under the lowermost layer of lime in 
 the purifier B, passes through an equal number of 
 layers of lime in that purifier, as it had done in pass- 
 ing through the purifiers C and A respectively, 
 whence it proceeds, trebly and practically thoroughly 
 purified, to the centre valve, which it enters by the 
 pipe marked 6, and thence by the pipe j it flows to 
 the gas-holder. From what has been said, it will 
 he understood that the gas enters (when the position 
 of the lifting valve is as shown in figure 2) first into 
 the purifier C, next into A, and lastly into the puri- 
 fier B, when on its way from the condenser to the 
 gas-holder. It follows then in consequence, that as 
 the purifier C receives the gas in its most impure 
 state, the lime therein will he first saturated with 
 impure matter : when such is the result in the purifier 
 C, the lime in the purifier A will be but slightly 
 discoloured, and that in the purifier B hardly changed 
 from the state in which it was when the operation 
 was commenced. Whilst the purifiers C, A, and 
 B are in action, the purifier D should be charged 
 with lime in the same way as the others were, and 
 its lid lowered preparatory to its being brought into 
 use. To know when it is necessary to throw the 
 purifier C out of action, the gas must he tested at 
 the jet burner attached to the lid of the purifier B 
 (the last of the acting series as the lifting part of 
 the centre valve is placed), where the gas is in its 
 most pure state. If the test applied indicate the 
 
258 
 
 PURIFIERS. 
 
 slightest trace of impure matter, it is time to throw 
 the purifier C out of action, which is effected in the 
 way already described ; then A becomes the first of 
 the series, B the second, and D the third or last. 
 When such is the case, let the lid of the purifier C 
 be removed, and the impure lime withdrawn thence, 
 then let it be well washed and cleansed inside ; let 
 the gratings also be well washed preparatory to the 
 said purifier being again charged, in order that no 
 impure matter may remain upon them, or within that 
 vessel when the fresh charge is introduced. By 
 being careful as to these matters, the purity of the 
 gas will be greatly ensured ; for it is very essential 
 towards ensuring the purity of the gas, always to 
 keep quite clean the last purifier of the series in 
 action, which the gas has to pass through. Let 
 the purifier C be again charged with lime, and when 
 the gas tested at purifier 1) (then the last of the 
 acting series) indicates impurity, throw the purifier 
 A out of action, by doing which the purifier C will 
 be brought into use ; then proceed with the purifier 
 A as has been done with the purifier C, and so on in 
 succession continually as the case may require ; for, 
 having begun with C as the first of the series, A be- 
 came next so, and now B, by throwing A out of 
 action, has become so, and C is the last. The next 
 change will make D the first of the series, and A 
 the last, and the charge which throws D out of ac- 
 tion will leave the lifting part of the centre valve in 
 
PURIFIERS. 
 
 259 
 
 the same situation as when the purifier was first 
 brought into action : for either the purifiers (C, A, 
 B), (A, B, D), (B, D, C), or (D, C, A), in the order 
 in which the letters stand, must, from the construc- 
 tion of the centre valve, be in action at one time, as 
 has been very fully explained, and as a reference to 
 the plate will show. 
 
 In order that the public may, on all occasions, be 
 supplied with pure gas, we have been very particular 
 in describing such a purifier as cannot fail to furnish 
 it, if the directions for its proper management be 
 attended to. This description of purifier possesses 
 many advantages over the wet lime apparatus : first, 
 from its construction it admits of each purifier of 
 the series, as it is thrown out of use, being tho- 
 roughly cleansed ; so that when the purifier is again 
 brought into action, its interior is free from all 
 impurities : such can never be the case with the 
 wet lime purifiers, for, when they are once brought 
 into action, there is no means of cleansing the inside 
 of them without entirely stopping the operation of 
 making gas, and much labour and expense in re- 
 moving their lids or man-holes, left for the purpose 
 of getting into them ; whence it follows that they 
 generally are worked for a very long period without 
 any attention being paid to the extraction there- 
 from of the impure matter which gradually accu- 
 mulates therein. The consequence of these several 
 facts is, that even when three wet lime purifiers are 
 
 s 2 
 
260 
 
 PURIFIERS. 
 
 used, one after another, the interior of the last of 
 the series becomes so foul, as to deprive the fresh 
 lime introduced of much of its purifying power ; 
 that is, the impure matter saturates it to a certain 
 extent, and thus so far is injurious : but, where a 
 single wet lime purifier only is used, the evil is 
 much greater ; so that to expect pure gas from 
 works where only one wet lime purifier is used, is 
 to expect what may be set down as impossible, let 
 the purifier be charged with fresh lime ever so often. 
 In the second place, the dry lime purifier does not 
 produce so great a bulk of offensive matter as the 
 wet one. In the first, the lime, when it is removed, 
 does not exceed its hulk when first slaked. In 
 the latter, being mixed with water till it is of the 
 consistence of cream, the quantity of matter drawn 
 off from the purifier is amazingly increased, and 
 requires, in extensive works, very large tanks or 
 cess-pools for its reception, in which the saturated 
 lime subsides, and becomes of the consistence of 
 mud ; whilst the water, impregnated also with 
 much impure and offensive matter, is pumped off, 
 and evaporated in pans under the fire-places for 
 heating the retorts, engendering by its noisome 
 smell a most abominable nuisance, which extends to 
 a considerable distance from the manufactory in all 
 directions. And if by any chance the cess-pools 
 should overflow (which has often happened), and 
 the impure water find its way into a drain or sewer. 
 
PURIFIERS. 
 
 261 
 
 it would soon contaminate such sewer through all 
 its ramifications, and show its deleterious effects in 
 every house it passed by, from the vapours arising 
 from it finding their way into the house through 
 sinks, crevices, or otherwise, discolouring all the 
 white painting, tarnishing all silver and plated 
 goods, &c., as well as annoying the inmates by its 
 very disagreeable odour. The removal of the sub- 
 sided lime is also another cause of nuisance ; for, in 
 carrying it away from time to time from the works, 
 in every thoroughfare through which it may pass, 
 the noxious properties which it contains give out 
 their offensive odour abundantly from the jolting 
 of the vehicle employed. As the dry lime purifier, 
 on the contrary, produces no liquid to be disposed 
 of, and when the impure lime requires to he re- 
 moved, it is in a perfectly dry state ; consequently 
 the removal can be effected without any nuisance 
 being created. With respect to the efficiency, as a 
 means of purifying coal-gas, of the wet lime purifier, 
 compared with that of the dry lime purifier, the 
 latter far exceeds the former, as must be quite 
 evident when what has been said upon the matter 
 is duly considered. 
 
 We consider what we have said quite enough for 
 all practical purposes, on the subject of purifying 
 coal-gas ; but before we conclude this chapter, we 
 may remark that M. Blondeau de Carolles has re- 
 cently objected to the use of lime as a sufficient 
 
262 
 
 PURIFIERS. 
 
 medium of purification ; stating that the lime used 
 in the ordinary purification decomposes the hydro- 
 sulphate of ammonia, seizes the sulphuretted hydro- 
 gen, and, liberating the ammonia which mixes with 
 the lighting gas, communicates thereto a disagree- 
 able odour, and diminishes its illuminating power : 
 he therefore recommends that the gas, after passing 
 the ordinary purifier, should be made to pass through 
 layers of coke covered with layers of chloride of 
 calcium, both of which substances have the property 
 of absorbing ammonia. (See “ The Chemist ” for 
 February, 1841, page 50.) 
 
 For depriving gas of its ammonia, a patent was 
 obtained in January, 1841, by Mr. Alexander Angus 
 Croll, superintendent of the Gas Light and Coke 
 Company’s Works, Brick-lane, Middlesex. He 
 proposes to pass the gas as it comes from the retorts 
 through a vessel similar to the single wet lime 
 purifier filled with a solution of chloride of manga- 
 nese in water, in the proportion of one hundred- 
 weight of the former to forty gallons of the latter. 
 The gas is made to pass through this solution by 
 pressure from the retorts, in the usual way, and the 
 ammonia and a portion of its sulphuretted hydrogen 
 are abstracted ; the remaining portion of the sulphu- 
 retted hydrogen is extracted by the usual methods. 
 When the solution is saturated with ammonia* 
 which can he known by the application of proper 
 tests, it is to lie drawn off and the vessel recharged 
 
PURIFIERS. 
 
 263 
 
 with a fresh solution. He also states that sulphuric 
 or muriatic acid may be used in a washer for the 
 same purpose, the former in the proportion of 2J 
 pounds of sulphuric acid (specific gravity 1*845) to 
 100 gallons, through which the gas is to pass, till 
 the mixture indicates a specific gravity of 1*170; 
 and, on being tested, is found to be saturated with 
 ammonia. When muriatic acid is used, it should 
 he of specific gravity 1*165, and in the same propor- 
 tion as mentioned for sulphuric acid, which is to be 
 drawn off when it attains a specific gravity of 1*170. 
 The patentee prefers using sulphuric acid, but states 
 that sulphate of manganese and muriate of iron may 
 also be used for these purposes. In his “ Specifi- 
 cation,” Mr. Croll claims the method of reproducing 
 the ammoniacal salts, &c., which he there describes, 
 but which it is not necessary to dwell upon here, 
 for the invention being patented, the patentee will 
 of course answer any inquiry that may be made 
 relative to the mode of operation. 
 
 We shall not say more on the subject of purifi- 
 cation here, than that in practice, when the wet 
 lime purifier is used, about an imperial bushel of 
 unslaked lime is considered sufficient for purifying 
 from 10,000 to 12,000 cubic feet of gas, when ob- 
 tained from almost any of the Newcastle coals, in 
 which proportion the purifier ought to be charged 
 for larger or for smaller quantities ; however, as the 
 qualities of coal vary considerably, perhaps no spe- 
 
264 
 
 PURIFIERS. 
 
 cific quantity can be put down as a general rule. 
 The operator must frequently test the gas imme- 
 diately after it has passed through the purifier ; and 
 when he finds his test discoloured, he will of course 
 change his lime. Indeed the testing the gas at 
 stated intervals, and acting with the purifiers ac- 
 cordingly, is the only way of ensuring pure gas. In 
 the dry lime purifier, the same quantity of lime in 
 proportion to the quantity of gas to be purified, as 
 has been mentioned for the wet lime purifier, will 
 be sufficient. Most kinds of quick lime double their 
 bulk on being slaked. 
 
CHAPTER XI. 
 
 On the Gas-holder (Gasometer) and its Construction, with Descrip- 
 tions of such as are generally used. 
 
 The gas-holder (or, as it was formerly, and is still 
 sometimes, though improperly, called the gasometer) 
 is that vessel in which the purified gas is stored up 
 for use. It has been made of various sizes and 
 shapes. It is now generally cylindrical, though 
 some years ago many were constructed either square 
 or oblong, at the caprice of the manufacturer. 
 When speaking of the gas-holder, we are to he un- 
 derstood as referring to two distinct parts ; that is 
 to say, a capacious inner vessel in large works, 
 almost universally made of sheet-iron, which is 
 closed at the top and open at the bottom, and a tank 
 of cast-iron, brick-work, or masonry (formerly large 
 wooden vats were occasionally used), of about a foot 
 or eighteen inches greater diameter than the gas- 
 holder itself, for containing water into which the 
 gas-holder sinks as the gas is drawn away from it 
 by supplying the company’s customers, and which 
 rises therein as it receives the purified gas from the 
 manufactory : it is however so contrived, that it 
 cannot rise high enough to raise its bottom edge 
 nearer than two inches to the surface of the water 
 
266 
 
 THE GAS-HOLDER, 
 
 which the tank contains — a precaution necessary 
 to be taken, in order to prevent the gas from blowing 
 under the lower edge of the gas-holder. 
 
 Before entering upon various topics connected 
 with the construction of gas-holders, and tanks for 
 them to work in, it may be desirable to describe one 
 of the most simple construction. Plate XV., figure 
 1, is a vertical section of a gas-holder (working in 
 a cast-iron tank), of its bridge, chain, and counter- 
 poise, or balance- weights ; A B C D is a section of 
 the gas-holder ; E F G H a section of the tank ; 1 1, 
 cast-iron flanch pipes jointed together in the usual way, 
 so as to form columns for supporting the frame K K. 
 Upon this frame are placed carriages for bearing the 
 grooved wheels L L, over which runs the chain 
 suspending the gas-holder, and sustaining the 
 balance-weight M. N is the pipe which conveys 
 the gas into the gas-holder after it has been purified ; 
 O another pipe similar to the former, by which the 
 gas is conveyed into the main pipe connected with 
 the streets, where the gas is to be used. It need 
 hardly be remarked, the upper end of these pipes, N 
 and O (the inlet and outlet pipes), must rise two or 
 three inches above the surface of the water in the 
 tank, to prevent a possibility of water getting into 
 them. Upon the horizontal part of the pipes N 
 and O are placed valves for shutting off the re- 
 spective communications when the vessel is full, or 
 when it may be desired not to work it. The figure 
 
AND ITS CONSTRUCTION. 
 
 267 
 
 represents the gas-holder as if it were about half 
 full of gas. Plate XV., figure 2, represents the 
 plan of the gas-holder just described. It will be 
 seen, by referring to the figure just described, that 
 the gas-holder is suspended by a chain over two 
 grooved wheels, fixed upon a cast-iron frame placed 
 over it ; one end of which chain is made fast to an 
 eye-bolt at the centre of the top of the gas-holder, 
 and to the other is attached a rod or frame for 
 supporting certain weights which counterpoise a 
 certain part of the gas-holder. It is to be observed 
 that, by putting more weights upon the counter- 
 poise support, or frame, the gas-holder works at less 
 pressure, and consequently does not force the gas 
 into the street mains with such velocity as it does 
 when the weight is there diminished : for, if the 
 balance-weight and weight of the gas-holder be very 
 nearly equal, then there will be but little or any 
 impetus arising from the weight of the gas-holder 
 to discharge the gas ; it would, in consequence, 
 escape with such languor at the orifices of the 
 burners as to afford but a very feeble light. To 
 obtain a good light, the gas-holder should never be 
 worked at less than from fourteen-tenths of an 
 inch to two inches pressure ; or, in other words, the 
 surface of the water inside the gas-holder should be 
 from fourteen-tenths of an inch to two inches below 
 the surface of the water contained between the 
 
268 
 
 THE GAS-HOLDER, 
 
 outside of the gas-holder, and the tank or vat in 
 which it may he suspended. 
 
 If we suppose the tank to be filled with water, 
 and the gas-holder partly filled with gas, we can so 
 adjust the counterpoise or balance-weight as to pro- 
 duce an equilibrium between it and the gas-holder. 
 When the counterpoise is so adjusted, the water 
 will stand at the same level inside the gas-holder, 
 as what it stands at between the outer surface thereof 
 and the inside of the tank. But, by diminishing 
 the counterpoise, the gas-holder will, by its gravity, 
 have a tendency to descend ; and the greater that 
 tendency may be, so much more will the water 
 descend within it. Under these circumstances, the 
 included gas will he compressed beyond the pressure 
 of the atmosphere, in exact proportion to the weight 
 of a column of water whose height is equal to the 
 difference between the surface of the water inside 
 the gas-holder, and the surrounding surface of the 
 water between the outside of the gas-holder and the 
 tank in which it works. 
 
 For ascertaining the pressure at which the gas- 
 holder works, a small pressure gauge may be 
 attached to the top of it, or connected to the outlet 
 pipe therefrom, which may be secured from acci- 
 dental injury by a wrought-iron case. When, from 
 the gas having been allowed to enter into the gas- 
 holder, it has risen but a few feet out of the water, 
 
AND ITS CONSTRUCTION, 
 
 269 
 
 if the graduated scale on the pressure gauge be 
 inspected, it can he seen at what pressure the gas- 
 holder is then working ; and by increasing or dimi- 
 nishing the counterpoise or balance-weight, the 
 gas-holder can be regulated or adjusted to the de- 
 sired pressure. One of the uses of the gas-holder 
 is to regulate the emission of the gas towards the 
 burners where it is to be used, which could not be 
 effected without some such contrivance as the gas- 
 holder ; the gas being evolved from the retorts in 
 very unequal proportions during the different periods 
 of the distillatory process, as has been already no- 
 ticed in the chapter relative to carbonization. 
 
 On considering the matter a little closely, we 
 cannot fail to perceive that, as the gas-holder fills 
 with gas, the weight thereof will be continually 
 increasing ; for we know that “ a body immersed, in 
 a fluid will sink to the bottom if it be heavier than 
 a bulk of fluid equal to it ; and if it be suspended 
 in it, it will lose as much of what it weighed in air 
 as its bulk of the fluid weighs.” The case is pre- 
 cisely the same with the gas-holder : for when the 
 gas first begins to enter into it, its top is level with 
 the water, it will therefore be counterpoised in such 
 a situation by a weight that wants as much of the 
 absolute weight of the gas-holder as the quantity of 
 water weighs which is thereby displaced. As the 
 gas is allowed to enter the gas-holder, the latter 
 rises out of the water, and of course, as it does so, 
 
270 
 
 THE GAS-IIOLDER, 
 
 its weight increases ; therefore, if the balance-weight 
 be barely sufficient to support the gas-holder, so 
 that it may work at a certain pressure when it first 
 begins to rise out of the water, it follows that, as it 
 rises, the pressure increases by the increasing weight 
 of the gas-holder. If then the gas-holder be worked 
 without any contrivance for regulating the pressure, 
 the quantity of gas it may contain (from the varia- 
 bility of the pressure) cannot be accurately ascer- 
 tained ; nor can the gas therefrom, when permitted 
 to flow to the burners where it is to be used, be 
 uniformly supplied, so that the flame from the 
 burner shall continue of a constant height during 
 the time it may remain burning ; for when the gas- 
 holder is nearly full of gas, it will work at a much 
 greater pressure than when it is nearly empty. 
 The flame, therefore, will be much longer in the 
 first case than in the last, without any possibility, 
 for want of an equalizer of pressure, of its being at 
 a uniform height. It is evident, from what has 
 been just said, that unless there be some contrivance 
 in works of magnitude for keeping the gas-holders 
 at a uniform pressure at all heights, very serious 
 inconveniences must inevitably ensue. 
 
 When the manufacture of coal-gas was in its 
 infancy, a spiral pulley (on the principle of the fusee 
 of a watch) was used for the chain to work over, 
 for the purpose of counteracting the evils attendant 
 upon the want of uniformity in the pressure of the 
 
AND ITS CONSTRUCTION. 
 
 271 
 
 gas-holder. It answered the intended purpose ; 
 but it was clumsy, inconvenient, and expensive. A 
 deviation therefrom was made for gas-holders work- 
 ing on the ordinary principle, built upon the theo- 
 rem we have already mentioned ; that is to say, “ a 
 body immersed in a fluid loses as much weight as 
 an equal bulk of the fluid weighs.” It will doubt- 
 less appear evident to our readers, that the only 
 mode for effecting the purpose (when gas-holders 
 are fitted up with a constant equilibrium apparatus) 
 will be by increasing the weight which is suspended 
 as a balance over the friction-wheels, in proportion 
 to the weight of water displaced by the descent of 
 the gas-holder : and therefore, as the balance-weight 
 itself remains the same, it must be done by a com- 
 pensation of weight in the chain supporting it. To 
 ascertain the weight per foot of this chain, we are 
 first to consider what quantity of water will be 
 displaced by the sides of the gas-holder being im- 
 mersed therein to the depth of one foot, and thence 
 the weight of that water, which can be done by 
 multiplying the circumference of the gas-holder in 
 inches, by 12 inches, the depth spoken of, and that 
 again by the thickness of the metal of which the 
 gas-holder is composed, making an allowance for 
 overlap of plates, rivets, and internal stays of 20 
 per cent., which will give the bulk of water dis- 
 placed in most cases. Thus the circumference 
 of a gas-holder, 60 feet diameter, being 188*4 
 
272 
 
 THE GAS-HOLDER, 
 
 feet or 2260 inches x = 27,120 X °f an 
 inch (the thickness of the iron of which the sides 
 are composed) — 1695 cubic inches ; to which 
 add 20 per cent, for overlap of plates, &c., (339) we 
 have 2034 cubic inches of water displaced by the 
 immersing a gas-holder 60 feet in diameter one 
 foot deep in water. The water displaced weighs 
 1 177 oz., or 73 lbs. 9 oz. ; 2034 cubic inches of 
 plate-iron, specific gravity 7*788, weigh about 573 
 lbs., of which it loses 73 lbs. 9 oz. by immersion ; 
 consequently the chain of equilibration must have 
 each foot of it of such weight as to make up for the 
 difference on a foot rise, or the whole length to 
 make up the difference of the whole rise. For 
 example: we will suppose the weight M, figure 1, 
 Plate XV., is resting upon the ground near the foot 
 of the column marked I, in which situation the 
 gas-holder, ABCD, would be acting with the 
 greatest pressure (supposing there were no weight 
 or chain) ; we will further suppose that the entire 
 height the gas-holder rises is 18 feet: it follows 
 therefore that the weight of each foot of chain 
 from M towards L should be one-half of the weight 
 of the water displaced by the immersion of the 
 gas-holder ; because, as the gas-holder descends one 
 foot, the chain from the centre of its top descends 
 also with it, consequently adding to the weight of 
 the gas-holder the weight of one foot of chain ; but 
 as that descent raises the counterbalance M, and 
 
AND ITS CONSTRUCTION. 
 
 273 
 
 shortens the chain from M towards L one foot, it 
 takes away the weight of one foot of that part of 
 the chain ; consequently what is lost in weight 
 there, being added to what is gained in weight by 
 the chain which passes over the pulley, which is 
 placed over the centre of the gas-holder, gives the 
 entire weight of the water displaced by immersion 
 of the gas-holder ; and thus the pressure is kept 
 uniformly the same at every height of the gas- 
 holder. Therefore, if there be given the weight of 
 the sides of the gas-holder, which is immersed into 
 the water one foot, and the specific gravity of the 
 material of which it is composed, the specific gra- 
 vity of water being 1-000, we can easily ascertain 
 what weight one foot in length of the equilibration 
 chain ought to be by the following — 
 
 Rule. As the specific gravity of the material of 
 which the gas-holder is composed 
 Is to the specific gravity of water, 
 
 So is the weight of that part of the gas-holder 
 which becomes immersed in water 
 
 To the weight of a bulk of water equal to that 
 which is displaced by the immersion of the gas- 
 holder : consequently, from what has been already 
 premised, to double the weight of that part of the 
 chain supporting the counterpoise which is equal in 
 length to such immersion, whether it lie one foot or 
 any greater number of feet. 
 
 Example 1st. Given the specific gravity of sheet- 
 
 T 
 
274 
 
 THE GAS-HOLDER, 
 
 iron 7*788, and the weight of one foot in height of 
 the sides of a gas-holder constructed of such mate- 
 rial 573 pounds, to find the weight of water dis- 
 placed by the gas-holder, and consequently to find 
 the weight of one foot in length of the equilibration 
 chain, — 
 
 Specific 
 Gravity of 
 Sheet-Iron. 
 
 Specific 
 Gravity of 
 Water. 
 
 Weight in lbs. Weight of Water 
 
 of one foot in in lbs. displaced 
 
 height of sides by one foot descent 
 of Gas-holder. of Gas-holder. 
 
 Say, as 7*788 : 1*000 : : 573 : 73*57 
 
 nearly one-half of which is the weight per foot of 
 the equilibration chain, namely, 36*785 pounds, or 
 36 pounds 12 ounces. 
 
 Example 2nd . Given the specific gravity of sheet- 
 copper 8*878, and the weight of one foot in height 
 of the sides of a gas-holder constructed of such ma- 
 terial 653 pounds, to find the weight of water dis- 
 placed by the gas-holder, and consequently to find 
 the weight of one foot in length of the chain of 
 equilibration, — 
 
 Specific Specific 
 
 Gravity of Gravity of 
 Copper. Water. 
 
 Weight in lbs. Weight of Water 
 
 of one foot in in lbs. displaced by 
 
 height of the sides one foot descent 
 
 of Gas-holder. of the Gas-holder. 
 
 Say, as 8*878 : 1*000 : : 653 : 73*55 nearly, 
 
 one-half of which is the weight per foot of the 
 chain of equilibration, namely, 36*775 pounds, or 
 36 pounds 12 ounces, as in the first example : hence 
 it is evident that whatever may be the specific 
 gravity of the material of which the gas-holder is 
 constructed, the weight per foot of the equilibration 
 chain will always be equal to the weight of one- 
 
AND ITS CONSTRUCTION. 
 
 275 
 
 half of the bulk of water displaced by the gas-holder 
 being immersed one foot. 
 
 This matter, it is hoped, has been made sufficiently 
 clear to the reader, so that he can with ease adjust 
 the weight of the equilibration chain. We shall next 
 introduce something relative to the pressure of 
 fluids, which is a subject of importance to those who 
 may have occasion to construct tanks for the gas- 
 holders to work in, or other vessels of magnitude 
 sometimes required in a gas-manufactory. We do 
 so from being aware how very frequently weight 
 and pressure are confounded by those who have 
 not made themselves thoroughly acquainted with 
 the laws of Hydrostatics. 
 
 Proposition I. If any part of a fluid be raised 
 higher than the rest by any force , and then left to 
 itself the higher parts will descend to the lower 
 places , and the fluid will not rest till its surface be 
 quite even and level ; 
 
 For, the parts of a fluid being easily movable 
 every way, the higher parts will descend by their 
 superior gravity, and raise the lower parts till 
 the whole come to rest in a level or horizontal 
 plane. 
 
 Corol. 1. Hence water, which communicates with 
 other water by means of a close canal or pipe, will 
 stand at the same height in both places. In the 
 same way, should a glass syphon be held with the 
 bend part downwards and water be poured into one 
 
 t 2 
 
276 
 
 THE GAS-HOLDER, 
 
 of the legs, it will pass through the bend and stand 
 at the same height in each of its legs. 
 
 Corol. 2. For the same reason, if a fluid gravitate 
 towards a centre ; or, in other words, if it be received 
 into an inverted cone, it will despose itself into a 
 spherical figure, the centre of which is the centre of 
 force. Like as the sea in respect of the earth. 
 
 Proposition II. When a fluid is at rest in a 
 vessel , the base of which is parallel to the horizon , 
 equal parts of the base are equally pressed by the 
 fluid ; 
 
 For upon every part of the base there is an equal 
 column of the fluid supported by it. And as all the 
 columns are of equal height, by the last proposition, 
 they are of equal weight, and therefore they press 
 the base equally; that is, equal parts of the base 
 sustain an equal pressure. 
 
 Corol. 1. All parts of the fluid press equally at 
 the same depth ; for if a plane, parallel to the ho- 
 rizon, be conceived to be drawn at that depth, then 
 the pressure being the same in any part of that 
 plane, by the proposition, therefore the parts of the 
 fluid, instead of the plane, sustain the same pressure 
 at the same depth. 
 
 Corol. 2. The pressure of the fluid at any depth 
 is as the depth of the fluid ; 
 
 For the pressure is as the weight, and the weight 
 is as the height of the fluid. 
 
 Proposition III. When a fluid is pressed by 
 
AND ITS CONSTRUCTION. 
 
 277 
 
 its own weight , or by any other force ; at any 
 point it presses equally, in all directions whatever. 
 
 This arises from the nature of fluidity, by which 
 it yields to any force in any direction. If it cannot 
 recede from any force applied, it will press against 
 other parts of the fluid in the direction of that force. 
 And the pressure in all directions will he the same. 
 For, if it were less in any part, the fluid would 
 move that way, till the pressure be equal every way. 
 
 Corol. 1. In a vessel containing a fluid the pres- 
 sure is the same against the bottom as against the 
 sides ; or even upwards at the same depth. 
 
 Corol. 2. Hence, and from the last proposition, 
 if ABCD (Plate I., fig. 5) be a vessel of water, 
 and there be taken, in the base produced, DE to 
 represent the pressure at the bottom ; joining A E, 
 and drawing any parallels to the base, as F G, H I ; 
 then shall F G represent the pressure at the depth 
 A G, and H I the pressure at the depth A I, and so 
 on ; because the parallels F G, HI, ED, by similar 
 triangles, are as the depths A G, A I, A D ; which 
 are as the pressures by the proposition. 
 
 And hence the sum of all the F G, HI, &c., or 
 area of the triangle A D E, is as the pressure against 
 all the points G, I, &c., that is, against the line A D. 
 But, as every point in the line C D is pressed with 
 a force as D E, and that thence the pressure on the 
 whole line C D is as the rectangle ED, DC, whilst 
 that against the side is as the triangle A D E, or 
 
278 
 
 THE GAS-HOLDER, 
 
 \ A D, D E ; therefore the pressure on the hori- 
 zontal line DC is to the pressure against the ver- 
 tical line DA, as DC to JDA. And hence, if 
 the vessel be an upright rectangular one, the pres- 
 sure on the bottom, or whole weight of the fluid, 
 is to the pressure against one side as the base is to 
 half that side : and, therefore, the weight of the 
 fluid is to the pressure against all the four upright 
 sides as the base is to half the upright surface. 
 And the same holds true also in any upright vessel. 
 Or, in the cylinder, the weight of the fluid is to the 
 pressure against the upright surface as the radius 
 of the base is to double the altitude. 
 
 Moreover, when the rectangular prism becomes 
 a cube, it appears that the weight of the fluid on 
 the base is double the pressure against one of the 
 upright sides, or half the pressure against the whole 
 upright surface. 
 
 Corol. 3. The pressure of a fluid against any 
 upright surface, as the gate of a sluice or canal, is 
 equal to half the weight of a column of the fluid 
 whose base is the surface pressed, and its altitude 
 the same as the altitude of that surface. 
 
 For, the pressure on a horizontal base, equal to 
 the upright surface, is equal to that column ; and 
 the pressure on the upright surface is but half that 
 on the base, of the same area. 
 
 So that, if b be the breadth, and d the depth of 
 such a gate or upright surface, then the pressure 
 
AND ITS CONSTRUCTION. 
 
 279 
 
 against it is equal to the weight of the fluid, whose 
 magnitude is ^-£«P = ^AB, A D 2 . 
 
 If the fluid be water, a cubic foot of which weighs 
 1,000 ounces, or 62J pounds ; and, if the depth A D 
 be 12 feet, the breadth AB 20 feet; then the con- 
 tent, or \ AB, AD 2 , is 1440 feet, and the pressure 
 is 1,440,000 ounces, or 90,000 pounds, or 40 -l tons 
 weight nearly. 
 
 Proposition IV. The pressure of a fluid , on the 
 base of the vessel in which it is contained , is as the 
 base and 'perpendicular altitude , whatever be the 
 figure of the vessel that contains it. 
 
 If the sides of the base be upright (Plate I., fig. 
 6), so that it be a prism of an uniform width 
 throughout, then the case is evident ; for then the 
 base supports the whole fluid, and the pressure is 
 just equal to the weight of the fluid. 
 
 But if the vessel be wider at the top than bottom, 
 then the bottom sustains, or is pressed by, only the 
 part contained within the upright lines a C, b D 
 (Plate I., fig. 7) ; because the parts ACo, BD^, 
 are supported by the sides AC, B D ; and these 
 parts have no other effect on the part ab DC than 
 keeping it in its position by the lateral pressure 
 against a C and b D, which does not alter its per- 
 pendicular pressure downwards ; and thus the pres- 
 sure on the bottom is less than the weight of the 
 contained fluid. 
 
 And, if the vessel be widest at the bottom, then 
 
280 
 
 THE GAS-HOLDER, 
 
 the bottom is still pressed with a weight which is 
 equal to that of the whole upright column A B D C 
 (Plate I., fig. 8) : for, as the parts of the fluid are 
 in equilibrio, all the parts have the same pressure 
 at the same depth ; so that the parts within C c and 
 dT> press equally as those in cd , and therefore 
 equally the same as if the sides of the vessel had 
 gone upright to A and B, the defect of fluid in the 
 parts AC a and BDi being exactly compensated 
 by the downward pressure or resistance of the sides 
 a C and b D against the contiguous fluid. And 
 thus the pressure on the base may be made to exceed 
 the weight of the contained fluid, in any proportion 
 whatever. 
 
 So that, in general, be the vessels of any figure 
 whatever, regular or irregular, upright or sloping, 
 or variously wide and narrow, in different parts, if 
 the bases and perpendicular altitudes be but equal, 
 the bases always sustain the same pressure ; and as 
 that pressure, in the regular upright vessel, is the 
 whole column of the fluid, which is as the base and 
 altitude, therefore the pressure in all figures is in 
 the same ratio. 
 
 Coral. 1. Hence, when the heights are equal, the 
 pressures are as the bases ; and when the bases are 
 equal, the pressure is as the heights ; but when 
 both the heights and bases are equal, the pressures 
 are equal in all, though their contents be ever so 
 different. 
 
AND ITS CONSTRUCTION. 
 
 281 
 
 Corol. 2. The pressure on the base of any vessel 
 is the same as on that of a cylinder of an equal base 
 and height. 
 
 Corol. 3. If there be an inverted syphon, or bent 
 glass tube, the legs of which are of different lengths, 
 containing two different fluids that balance each 
 other, or rest in equilibrio, then their heights in 
 the two legs above the point of meeting will be 
 reciprocally as their densities : or. 
 
 As the height of one fluid is to the height of the 
 other. 
 
 So is the density of the latter to the density of 
 the former : 
 
 So, if the longer leg of the syphon contain water 
 to the height of fourteen inches, it will be kept in 
 equilibrio by introducing quicksilver to the height 
 of one inch in the shorter leg ; quicksilver being 
 nearly fourteen times heavier than water. If the 
 quicksilver be raised to two inches, it would balance 
 a column of water twenty-eight inches high ; and 
 so on. 
 
 Since, then, the pressure of fluids of equal densi- 
 ties is directly as their perpendicular heights, with- 
 out any regard to their quantities, it appears that 
 whatever the figure or size of vessels be, if they are 
 of equal heights and if the areas of their bottoms 
 are equal, the pressure of equal heights of water are 
 equal upon the bottoms of these vessels ; even though 
 the one should hold a thousand, or ten thousand. 
 
282 
 
 THE GAS-HOLDER, 
 
 times as much water as would fill the other. To 
 confirm this by an experiment, let two vessels be 
 prepared of equal heights, but very unequal con- 
 tents, such as A B (Plate I., fig. 9), and A B (Plate 
 I., fig. 10). Let each vessel be open at both ends, 
 and their bottoms D d } D d, be of equal surface. 
 Let brass bottoms C C, equal in weight, be exactly 
 fitted to both vessels respectively, not to go into 
 them, but for them to stand upon ; and let a piece 
 of wet leather be put between each vessel and its 
 brass bottom, for the sake of closeness. Join each 
 bottom to its vessel by a water-tight hinge I, so 
 that it may open like the lid of a box ; and let each 
 bottom be kept up to its vessel by equal weights E 
 and E, hung to lines which go over the pulleys F 
 and F (whose blocks are fixed to the sides of the 
 vessel at &), and the lines tied to hooks at h and h, 
 fixed in the brass bottoms opposite to the hinges I 
 and I. Things being thus prepared and fitted, hold 
 the vessel AB (figure 10) upright in your hands 
 over a basin on a table, and cause water to be poured 
 into the vessel slowly, till the pressure of the water 
 bears down its bottom at the side d, and raises the 
 weight E ; and then part of the water will run out 
 at d. Mark the height at which the surface H of 
 the water stood in the vessel, when the bottom 
 began to give way at d ; and then holding up the 
 other vessel A B (figure 9) in the same manner, 
 cause water to be poured into it at H ; and you will 
 
AND ITS CONSTRUCTION. 
 
 283 
 
 see that when the water rises to A in this vessel, 
 just as high as it did in the former, its bottom will 
 also give way at d, and it will lose part of the 
 water. 
 
 The natural reason of this paradoxical pheno- 
 menon is, that since all parts of a fluid at equal 
 depths below the surface are equally pressed in all 
 manner of directions, the water immediately below 
 the fixed part B c (figure 9) will he pressed as much 
 upwards against its lower surface within the vessel, 
 by the action of the column A i , as it would be by 
 a column of the same height, and of any diameter 
 whatever ; and, therefore, since action and re-action 
 are equal and contrary to each other, the water im- 
 mediately below the surface B c will be pressed as 
 much downward by it as if it was immediately 
 touched and pressed by a column of the height i A, 
 and of the diameter B c ; and, therefore, the water 
 in the cavity BD^ will be pressed as much down- 
 wards upon its bottom C C as the bottom of the 
 other vessel (figure 10) is pressed by all the water 
 above it. 
 
 To illustrate this a little further, let a hole be 
 made at f in the fixed top B c (figure 9), and let a 
 tube G be put into it ; then, if water be poured into 
 the tube A, it will (after filling the cavity B^) rise 
 up into the tube G, until it comes to a level with 
 that in the tube A, which is manifestly owing to 
 the pressure of the water in the tube A, upon that 
 
284 
 
 THE GAS-HOLDER, 
 
 in the cavity of the vessel below it. Consequently, 
 that part of the top, B c, in which the hole is now 
 made, would, if corked up, be pressed upward with 
 a force equal to the weight of all the water which 
 is supported in the tube G ; and the same thing 
 would hold good at g, if a hole were made there. 
 And so, if the whole cover, or top, B c, were full of 
 holes, and had tubes as high as the middle one, A i, 
 put into them, the water in each tube would rise to 
 the same height as it is kept into the tube A, by 
 pouring more into it, to make up the deficiency that 
 it sustains by supplying the others, until they are 
 all full ; and then the water in the tube A would 
 support equal heights of water in all the rest of the 
 tubes. Or, if all the tubes except A, or any other 
 one, were taken away, and a large tube, equal in 
 diameter to the whole top, B c, were placed upon it, 
 and cemented to it ; and then, if water were poured 
 into the tube that was left in either of the holes, it 
 would ascend through all the rest of the holes until 
 it filled the large tube to the same height that it 
 stands in the small one, after a sufficient quantity 
 had been poured into it : which shows that the top 
 B c was pressed upward by the water under it, and 
 before any hole was made in it, with a force equal 
 to that wherewith it is now pressed downward by 
 the weight of all the water above it in the great 
 tube ; and, therefore, the re-action of the fixed top 
 B c must be as great in pressing the water down- 
 
AND ITS CONSTRUCTION. 
 
 285 
 
 ward upon the bottom C C, as the whole pressure 
 of water in the great tube would have been if the 
 top had been taken away, and the water in that 
 tube left to press directly upon the water in the 
 cavity BDrfc. 
 
 After what has been said relative to the pressure 
 of fluids, it is hardly necessary to say more, for the 
 things, on mature consideration, must appear so 
 plain, that to offer further elucidations would 
 merely take up time without answering any bene- 
 ficial purpose. We here remark, that the four 
 foregoing propositions are fundamentally the same 
 with what are given by Dr. Hutton in the second 
 volume of his Course of Mathematics ; and, that for 
 the experiment to explain the equality of pressure 
 in vessels of unequal capacity, but of equal heights, 
 and having bases of equal area, we are indebted to 
 the published lectures of the ingenious Mr. Fergu- 
 son. Under the sanction of two names so eminent 
 in their respective writings for correctness and 
 perspicuity, addition would be useless, explanation 
 unnecessary. 
 
 When cast-iron tanks are required to be con- 
 structed for gas-holders to work in, it would be 
 causing the manufacturer needless expense, should 
 each tier of the upright curved plates, which form 
 the sides of the tank, be of the same uniform thick- 
 ness from the top to the bottom of the tank. For 
 it has been shown in Proposition III., Corol. 2, 
 
286 
 
 THE GAS-HOLDER, 
 
 that the horizontal pressures of a fluid vary directly 
 as the depths at which they are exerted ; and, con- 
 sequently, that the re-acting force (as the strength 
 of the side of the vessel containing the fluid), which 
 neutralizes the horizontal pressure, varies likewise 
 in the same ratio. Tanks being at the present day 
 very seldom made more than eighteen feet deep, and 
 often less ; shallowness, for many reasons, being 
 desirable, the iron-founder finds it expedient to 
 cast, for their construction, rectangular curved iron 
 plates ; and as there is a difficulty, amounting almost 
 to an impossibility, in casting such plates when of 
 large dimensions less than five-eighths of an inch 
 thick, it is never done. The proportionate thick- 
 ness of each tier of plates at different depths, as 
 exemplified in the next sentence in practice, ap- 
 proaches near enough the theoretical truth (though 
 double in result) for practice, as several contin- 
 gencies are to be provided for, besides the necessity 
 of strength sufficient for resisting the lateral pres- 
 sure of the contained fluid, such as the action of 
 chemical solvents, and accidental injury, &c. When 
 a cast-iron tank is to be constructed, thirty-four feet 
 in diameter and eighteen feet deep, the plates which 
 form the bottom, being segments made by circles 
 concentric with the great circle cutting sectors of 
 the same, are about three-quarters of an inch in 
 thickness. The plates forming the side, being por- 
 tions of the great cylinder, are each about eight feet 
 
AND ITS CONSTRUCTION. 
 
 287 
 
 in length and six feet in depth. The lower tier are 
 seven-eighths of an inch, the middle three-quarters, 
 and the upper five-eighths of an inch, in thickness. 
 The breadth of the flanches round each plate is 
 three inches and a half from the inside, and the 
 thickness of the flanch is equal to the thickness of 
 the plate. In putting a cast-iron tank together, 
 the joints are made with iron cement and screw- 
 bolts, in the way hereinafter mentioned for jointing 
 flanch pipes. The screw-bolts are five-eighths of 
 an inch in diameter : in the bottom and in the 
 lowermost tier of the side-plates, they are placed 
 about five inches asunder, in the middle tier of 
 plates six inches, and in the upper one seven. The 
 lowermost tier of plates is generally surrounded by 
 three wrought-iron belts, the middle one by two, 
 and the upper tier by one : these belts are made of 
 the best iron, four inches broad and five-eighths of 
 an inch thick, and keyed together, and then drawn 
 tight by means of wooden wedges rising to the 
 same height as the flanches upon the plates, by 
 which an equal pressure upon each hoop is obtained 
 in every part of its bearing. 
 
 It will be obvious to the reader, that the tank of 
 which I have been speaking is a single vessel ; and, 
 therefore, in the construction of single vessels of 
 larger or smaller dimensions, he will be able, from 
 what has been said, to calculate upon the thickness 
 of metal which he ought to use ; but there has occa- 
 
288 
 
 THE GAS-HOLDER, 
 
 sionally been used a tank so formed as to exhibit its 
 boundary lines in the plan by two concentric circles : 
 the radius of the outer one being about nine inches 
 more than the semi-diameter of the gas-holder, of 
 the inner one about nine inches less. It is only 
 between these that the water is introduced for the 
 gas-holder to work in. This species of tank pos- 
 sesses some advantages over the former one, espe- 
 cially where water is not very plentiful. In it the 
 interior range of plates will not require to be of so 
 much strength as the exterior ; it is, however, a 
 mistaken notion, which leads some persons to sup- 
 pose that the exterior plates might with safety be 
 made more slight in this than in a vessel con- 
 structed on the ordinary principle, to be entirely 
 filled with water. 
 
 Circular-shaped tanks are to be preferred to 
 any other, for various reasons, amongst the most 
 prominent of which are the uniformity of resistance 
 to pressure at equal depths by every part of their 
 upright surfaces, and the least surface with the 
 greatest content ; for, in square tanks the angular 
 points will be liable to give way, and the making of 
 such to contain the necessary fluid will be attended 
 with difficulties which never present themselves in 
 the construction of cylindrical vessels. 
 
 Formerly wooden vats were occasionally used in 
 lieu of tanks for the gas-holder to work in, but of 
 late years the practice has been discontinued, and it 
 
AND ITS CONSTRUCTION. 
 
 289 
 
 is not likely to be again adopted. When they were 
 used, the back-maker generally guaranteed tbe dura- 
 bility of tbe vat for some specific period ; be was 
 therefore careful to construct it of such materials 
 and workmanship as to prevent, on bis part, any 
 failure in tbe terms of bis contract. 
 
 Of late years the practice of making tanks for tbe 
 gas-holder to work in, of brick-work or of rubble 
 masonry sunk into tbe ground, has been very much 
 followed ; by which, where tbe ground is at all 
 favourable, an immense saving of outlay is effected. 
 The usual mode of constructing such tanks is to 
 excavate tbe ground to a depth of about two feet 
 deeper than it is proposed shall be the working 
 height of the gas-holder ; and for gas-holders of 
 about forty feet in diameter, the excavation should 
 be full fifty-two feet diameter at the top, sloping 
 down so that it may be about forty-eight feet dia- 
 meter at the bottom. When the ground is all got 
 out, the entire of the bottom ought to be puddled 
 over with well-tempered clay, to one foot in thick- 
 ness, trodden and beaten with rammers when in its 
 place. The inlet and outlet pipe, with the upright 
 or rising parts jointed together, should be then 
 fixed in their places, and have piers of brick-work 
 or masonry laid in Roman-cement, built round 
 them to the height of about three feet to keep them 
 upright. When that is done, a circle of forty-one 
 feet diameter should be struck, which will show the 
 
 u 
 
290 
 
 THE GAS-HOLDER, 
 
 situation of the inner face of the tank ; and to it let 
 a course of brick-work, twenty-two inches thick, he 
 laid all round, except where an opening may he left, 
 where the inlet and outlet pipes are brought in : 
 carry up another course of hrick-work of the same 
 thickness, and upon that lay two courses more with 
 an offset outside of about two inches. Then cover 
 the openings which had been left for the inlet and 
 outlet pipes, either by slabs or by turning arches 
 over them. When this is done, let the entire of 
 the bottom and the back of the walls be covered 
 with puddle to the depth of another foot, so that 
 the entire thickness thereof, with what had been 
 already laid, shall be two feet. Next carry up the 
 side walls to the height of six feet in eighteen-inch 
 work, letting the workmen go on at the same time 
 with the puddling at the hack of the wall, in courses 
 of not more than one foot at one time. This 
 puddle should he put in very soft, so that a man in 
 trampling it will sink nearly to his knees. The 
 puddle should, to the height of six feet, not be less 
 than eighteen inches in width, or so as to fill in 
 between the back of the wall and the excavation 
 entirely. The remaining twelve feet of the side 
 walls should he of fourteen-inch work up to the 
 level of the ground, and finished at the top with 
 three courses of nine-inch hrick-work, and a coping 
 of three-inch Yorkshire flagging. In building this 
 description of tank (which is supposed to be of 
 
AND ITS CONSTRUCTION. 
 
 291 
 
 brick laid in lime and sand-mortar), the bricklayers 
 will find it most convenient to work by movable 
 trammels slipped over an upright centre pole or 
 rod. The puddle is put in one foot in depth at one 
 time, till the whole of the back of the wall, to the 
 level of the ground, is completely filled in ; and, 
 from its being put in very wet, by the trampling of 
 the workmen it is forced into the joints of the 
 brick-work, and into the pores of the bricks, so as 
 entirely to prevent any escape of water from the 
 tank. The upper twelve feet of the puddle may 
 decrease in width from eighteen to twelve inches, 
 with a regular batter ; but as it is put in, it must 
 be filled in with ground well rammed in at the 
 back of it, so as compactly to replace the ground 
 which had in the first instance been removed. A 
 tank of this kind is quite as trustworthy for holding 
 water as a tank of cast-iron ; and may, where the 
 circumstances as to ground are favourable, be con- 
 structed at one-half of the expense, or even less. 
 
 When tanks are constructed of rubble masonry, 
 the walls must be made of about one-third greater 
 thickness than where brick is used ; in all other 
 respects the mode of procedure, as regards puddling, 
 &c., what has been already spoken of relative to 
 brick tanks, must be attended to, except that the 
 excavation will have to be made of so much more 
 diameter as the walls are of greater thickness. 
 Sometimes a considerable saving may be effected 
 
 u 2 
 
292 
 
 THE GAS-HOLDER, 
 
 by leaving a core in the bottom of the tank, as 
 shown in figure 5, Plate XV. For as the centre- 
 casting, for securing the internal stays of the gas- 
 holder, need never be of a length greater than two- 
 thirds of the height of the gas-holder, it must be 
 evident that, where a gas-holder eighteen feet in 
 height is used, if ground or other matter be left 
 remaining to the height of six feet at the middle of 
 the tank, provided there be no obstruction to the 
 distance of eighteen inches from the side walls all 
 round the tank, to prevent the gas-holder from 
 going down, it will work quite as well as if the 
 bottom had been made so as to form a horizontal 
 plane. The figure alluded to shows what the form 
 of the bottom would be in such case, in which A A 
 is that part of the ground which is not removed at 
 all, and B B the puddle laid over it to staunch the 
 bottom. In this case, as before, the walls must be 
 built upon a bed of well-tempered clay one foot in 
 thickness, not put in very soft ; and the puddling 
 at the back of the wall must be executed as has 
 been already directed. 
 
 The next subject presenting itself to our notice, 
 is the construction of gas-holders of such dimen- 
 sions as are required in large manufactories. Those 
 similar to figure 1, Plate XV., containing 15,000 
 cubic feet, are generally made of plate-iron, (number 
 16 wire-gauge, and weighing about 2 lbs. 11 oz. 
 to the square foot,) riveted together with quarter- 
 
AND ITS CONSTRUCTION. 
 
 293 
 
 inch rivets seven-eighths of an inch asunder. When 
 gas-holders of magnitude first began to be con- 
 structed, they were encumbered either with a heavy 
 wooden frame-work inside, which answered no useful 
 purpose, or otherwise the interior was so loaded 
 with iron stays, that it became necessary to use an 
 immense balance-weight, thus removing one evil as 
 it affected the pressure by introducing another. 
 Experience has now taught the manufacturer that 
 he cannot construct his gas-holder too light. In- 
 stead of the cumbrous wooden frame or weighty 
 iron stays formerly used, that vessel consists now, 
 in many instances, of nothing save the plate-iron 
 riveted together, and angle-iron round the bottom 
 and the top inside, for keeping it in form. Where 
 gas-holders are used without being suspended by a 
 chain or chains, and without any counterpoise, and 
 simply being kept in an upright position by guide- 
 rods, friction-rollers, &c., the above is the general 
 mode ; but when the gas-holder is suspended, and 
 a counterpoise is used, whether the suspension be 
 from the centre or from three or more points in 
 the circumference, then light internal or external 
 stays will be required for keeping it in shape. For 
 this purpose, rods of three-quarters of an inch in 
 diameter, of the best iron, will generally be of suf- 
 ficient strength ; but the arrangement of them, so 
 as best to meet the strain upon the gas-holder, must 
 be left to the gas-holder maker, who, from practice, 
 
294 
 
 THE GAS-HOLDER, 
 
 is the best qualified to dispose them in a judi- 
 cious manner, according to the mode of suspension 
 adopted. 
 
 As in most gas establishments, the gas passes 
 through a machine, sometimes called " a governor ,” 
 and sometimes “ a regulator ,” after it has left the 
 gas-holder and is on its way to the street mains (as 
 will be hereafter described), and which so adjusts 
 itself to circumstances as to keep the pressure upon 
 the street mains uniformly the same, though there 
 may be an inequality in the pressure of the gas- 
 holder, the use of compensating chains, balance- 
 weights, &c., are in this case not needed ; but in 
 works where there is no governor or regulator, the 
 equable emission of the gas must depend upon the 
 gas-holder exerting an equal pressure upon the gas 
 therein, at all heights of its rise or fall. We there- 
 fore think it desirable, first, to show how to calcu- 
 late the pressure of any gas-holder where compen- 
 sating chains and balance-weights are not used ; 
 and, secondly, to ascertain what weight should be 
 attached to the compensating chain to cause the 
 gas-holder to work at some specific pressure. To 
 find the pressure at which a gas-holder would work, 
 supposing it unencumbered with weights and chains, 
 but supposing it to be constructed as if to be used 
 with such appendages : if the diameter and depth 
 of the gas-holder in feet, the weight in pounds, of a 
 superficial foot of the plate-iron of which it is con- 
 
AND ITS CONSTRUCTION. 
 
 295 
 
 structed, and the extra weight for overlap, angle- 
 iron, stay-rods and rivets, he given to find the pres- 
 sure at which it will work ; we first find the area 
 of the top in square feet, by multiplying the square 
 of the diameter by -7854. Then, to find the super- 
 ficies of the sides, say, as 7 is to 22, so is the 
 diameter of the gas-holder to its circumference ; 
 and the circumference thus found being multiplied 
 by the height of the vessel, gives the area of the 
 cylindrical surface, which, being added to the area 
 of the top of the gas-holder in superficial feet, the 
 sum will express the number of square feet of plate- 
 iron required for constructing it, less and an allow- 
 ance for the lapping over of the plates. Multiply the 
 number of square feet of plate-iron, as above, re- 
 quired for constructing the gas-holder by the weight 
 of one square foot of the material of which it is 
 constructed, and to the product add the weight of 
 rods, rivets, angle-iron, and an allowance for the 
 lapping over of the joints ; the sum will be the 
 absolute weight of the gas-holder. Reduce the 
 absolute weight into ounces, and the area of the top 
 of the gas-holder into square inches, by multiplying 
 its area in superficial feet by 144. Next, divide the 
 weight in ounces by the area of the top of the gas- 
 holder in square inches, the quotient will express 
 the pressure upon every square inch in ounces. 
 But, as we speak in other language, by saying the 
 gas-holder works at so many tenths of an inch 
 
296 
 
 THE GAS-HOLDER, 
 
 pressure, if we divide the pressure upon each square 
 inch in ounces by the weight of a cubic inch of 
 water, -5787, the quotient will express the pressure 
 in inches and decimal parts of an inch. 
 
 Hence, by proceeding as above, it will be found 
 that a gas-holder of 15,000 cubic feet capacity, if 
 made 33 feet in diameter and 17 feet deep, would 
 weigh about 3| tons, and would, if unencumbered 
 with the compensating chain and balance-weights, 
 work at l T Vth inch pressure, nearly throughout 
 its rise and fall, whilst a gas-holder of 15,000 cubic 
 feet capacity, if made so as to be 42 feet in diameter 
 and 1 1 feet deep, though it would weigh about four 
 tons, would, under similar circumstances with the 
 former, work at about lj inch pressure nearly uni- 
 formly. On considering this matter, it will be seen 
 that, as the diameter of the gas-holder is increased, 
 supposing the plate-iron of which it is composed to 
 be of the same thickness, the pressure decreases. 
 
 To ascertain what weight should be attached to 
 the compensating chain to cause the gas-holder to 
 work at some specific pressure, find the area of the 
 top of the gas-holder in square inches, as in the 
 former case, and multiply that area in square inches 
 by the weight of one cubic inch of water, *5787 
 oz., should it be desired to work the gas-holder at 
 one inch pressure ; by the weight of two cubic 
 inches of water, or 11*574 oz., if it be desired to 
 work at two inches pressure ; or by Hrths, -}~§-ths. 
 
AND ITS CONSTRUCTION. 
 
 297 
 
 -ffths, 44ths, &c., of *5787 ; if it be desired to work 
 the gas-holder at -fj-ths, births, -fgths, -ffths, &c., 
 pressure; this in each case will give a weight in 
 ounces which, reduced into pounds, will show how 
 much less the counterpoise should weigh than the 
 gas-holder to which it is attached : for example, we 
 will take a gas-holder 33 feet in diameter, as above, 
 whose absolute weight has been stated as 3f tons, 
 or 8400 lbs. 
 
 The area of a circle 33 feet diameter is 855*3 
 superficial feet x 144 = 123,163, the area of said 
 circle in square inches : — we will suppose it is de- 
 sired to work this gas-holder at -firths pressure ; 
 -ffths of *5787 = *8102 nearly x 123,163, the area 
 of the top = 99,786 oz., nearly = 6237 lbs. ; which 
 weight being supposed to be uniformly spread over 
 the entire of the top of the gas-holder, must be 
 deducted from the absolute weight of the gas- 
 holder, the difference will be the weight of the 
 balance- weight to be applied as a counterbalance. 
 In this case the absolute weight of the gas-holder 
 was stated to be 3f tons or 8400 lbs., deducting 
 therefrom 6237 lbs. as just found, leaves 2163 lbs., 
 or 19 cwt. 1 qr. 71bs., as the counterbalance when 
 intended to work at -hfth pressure. 
 
 After what has been already said relative to the 
 gas-holder, we shall first notice such as have been 
 used, and then describe such as are generally adopted 
 now. Square or parallelopipedal-shaped gas-holders 
 
298 
 
 THE GAS-HOLDER, 
 
 appear to have been much used in the early stages of 
 gas-lighting. The objections against them having 
 been already noticed, we will not add more here than 
 that such are now very rarely constructed. These were 
 followed by cylindrical ones ; but with encumbrances 
 of internal wooden frames, or heavy iron stays, which 
 so loaded them as to render their action very heavy. 
 Soon after the cylindrical gas-holders had begun to 
 be generally adopted, Mr. Clegg invented and put up 
 a gas-holder at the Westminster gas-works, with a 
 rotary or revolving motion, which remained in ac- 
 tion for several years ; but it has long since been 
 taken to pieces, so that there is no gas-holder 
 on that plan now in use, nor is it at all probable 
 such a one will be again put up, as the telescopic 
 gas-holders answer all the ends it was intended to 
 answer, at much less expense, and in a more simple 
 manner. We have had several plans laid before us 
 for constructing gas-holders to work with air-vessels, 
 instead of regulating the pressure by means of a com- 
 pensating chain or weight ; but very few of them 
 were ever tried, and when they were so, their action 
 and cost being taken into consideration, it was found 
 they offered no advantages such as could warrant 
 their general adoption ; it is, therefore, at this time 
 unnecessary to give any description of them. Another 
 kind of gas-holder, called the “ Collapsing gas-holder,” 
 was several years ago invented by Mr. Clegg, it 
 worked in a very shallow tank, into which the lower 
 
AND ITS CONSTRUCTION. 299 
 
 edges of its sides and ends were immersed. It oc- 
 cupied a much greater area of base than any of those 
 we have mentioned. When it was full of gas, the end 
 view was represented by an equilateral triangle, the 
 bearings being from the angle opposite to the base. 
 This gas-holder was so constructed that the sides 
 had a tendency to close with each other, and there- 
 fore when the valve of supply was open, such ten- 
 dency expelled the gas. In such a* gas-holder it is 
 evident that certain parts of each end required to be 
 constructed of a flexible material, to get that to with- 
 stand the action of the gas, and to remain perfectly 
 without cracks or other fissures, were insuperable 
 objections to its use. Many years before the tele- 
 scopic gas-holder, now so much used, was thought 
 of Mr. William Stratton, of Gutter-lane, Cheapside, 
 obtained a patent for a kind of double gas-holder. 
 One of the objects he had in view was doubling the 
 capacity of the gas-holder (or nearly so) without in- 
 creasing the dimensions of the original tank, in works 
 where it might be requisite for want of ground to 
 turn it to the best account (particularly where the 
 demand for light had increased beyond the expecta- 
 tions of the manufacturer) ; in such cases he supposed 
 it would be worthy of attention. The invention 
 did not, however, come much into use. The tank he 
 prepared was formed of two upright ranges of cast- 
 iron plates, at about two feet asunder, connected to- 
 gether by plates at the bottom. When this tank 
 
300 
 
 THE GAS-HOLDER, 
 
 was filled with water, it formed a ring of water, into 
 which the gas-holders dipped. This arrangement 
 required two gas-holders, of which more will be 
 said hereafter. The tank was supported upon piers 
 of brick. Within the interior circle of it was a space 
 equal to the diameter of the internal ring, and equal 
 also in height to the height of that ring which might 
 he used for the reception of castings or other heavy 
 stores. The entrance and exit pipes of gas-holders 
 constructed on this principle were situated between 
 the interior and exterior upright plates of which the 
 tank was formed, and rose between the two gas- 
 holders which were bulged out for the purpose. At 
 equal distances round the tank were placed four 
 columns for supporting a semi-circular shaped frame. 
 Upon this frame were placed two carriages for sup- 
 porting grooved wheels, over which the gas-holders 
 were suspended. 
 
 For a tank of eighteen feet in depth, the outer 
 gas-holder was about thirty-five feet in depth, and 
 the inner one about seventeen feet six inches. At 
 the centre of the top of the outer gas-holder was a 
 stuffing-box, through which was introduced a cast- 
 iron pipe of three or four inches in diameter, with a 
 broad flanch at the bottom, through which it was 
 bolted to the centre of the top of the inner gas-holder. 
 To the upper end of the same pipe was fastened the 
 chain which passed over the grooved wheels just 
 mentioned, the opposite ends of which chain were 
 
AND ITS CONSTRUCTION. 
 
 301 
 
 attached to the top of the outer gas-holder, so that 
 the interior gas-holder acted as a balance weight to 
 the exterior and vice versa. 
 
 If we suppose this double gas-holder to have been 
 empty, it must appear evident that the outer one 
 would have risen about seventeen feet six inches above 
 the tank, and the inner one to very nearly the same 
 height. If then the gas has been allowed to enter, 
 the outer gas-holder would have risen, and as it did 
 so, the inner one must of necessity have descended, 
 because they were connected together by the suspend- 
 ing chains, and therefore the inner one would sink 
 as much as the outer one rose : so that when the 
 outer one had risen seventeen feet six inches, the 
 inner one would have descended through a like 
 space, and then there would be a distance of thirty- 
 five feet between the upper surface of the top of the 
 inner gas-holder, and the inside of the top of the 
 outer gas-holder. Such space would have been oc- 
 cupied by gas, thus nearly doubling the capacity 
 of the vessel acting in a tank of the same diameter 
 and depth as when a single gas-holder was used. 
 The centre supporting pipe which has been men- 
 tioned was open both at its top and bottom, so that 
 when the double tank was used, there could not be 
 any apprehension of a lodgment of gas beneath the 
 lower gas-holder, as from its levity it would be sure 
 to escape through that pipe should any leak take 
 place in the top of the interior gas-holder. The 
 
302 
 
 THE GAS-HOLDER, 
 
 gas-holder of which we have been speaking was 
 well adapted for producing a regular pressure at all 
 heights of its rise, without the compensating chain 
 and balance weights usual in the other constructions ; 
 for by considering the nature of the arrangement, 
 it will be evident, that as one vessel rose out of the 
 water the other one descended into it ; so that if it 
 had been constructed to work at a given pressure at 
 one height, it would uniformly have maintained such 
 pressure at all other heights of its rise or fall. 
 
 Were all the different kinds of gas-holders but 
 briefly described which have from time to time been 
 submitted to the notice of the gas-light manufacturer, 
 much space would be taken up and no useful end at- 
 tained, we therefore propose to bring this chapter to 
 a close by describing those three or four only gene- 
 rally used now, concluding with the telescopic, any 
 one of which will very well answer the purpose of 
 the gas-light manufacturer. 
 
 Plate XV., fig. 3, is a vertical section of a gas- 
 holder, working upon a centre column in a brick 
 tank. We will suppose the gas-holder in this case 
 to be eighteen feet deep, — when of that depth the 
 centre column marked A A should be about forty 
 feet in height, and three feet six inches in diameter 
 inside, (clear of the inside flanches not shown in the 
 figure, the scale being too small, by which it is bolted 
 and joined together,) and may be cast in lengths of 
 ten feet each. The lowermost flanch of the bottom 
 
AND ITS CONSTRUCTION. 
 
 303 
 
 piece being cast very broad and strong for the pur- 
 pose of being bolted to a casting laid beneath a base 
 of brick-work laid in Roman-cement, and through 
 which casting and brick-work the bolts pass, as well 
 as through the flanch just mentioned, so that all are 
 screwed up together so as to form a compact and 
 very heavy mass, and thus afford security to the 
 column. The flanch at the upper end of the bottom 
 piece of the column, as well as the flanches of the 
 pieces above it, and at the lower end of the upper- 
 most piece, are cast inside, so that the exterior sur- 
 face of the column may present a vertical surface 
 without any projections from top to bottom. The 
 top of the uppermost piece of the column may be 
 cast with a bold broad moulding outside, and with a 
 face at the top for the carriages to stand upon, which 
 support the three pulley- wheels C, D, E, by the chains 
 passing over which the gas-holder E E and the 
 balance weight G are suspended. The column is 
 jointed together by means of bolts and nuts, and rust- 
 cement ; it must be constructed so as to be perfectly 
 water tight to the height at which the water stands 
 in the tank, which is represented in this figure by 
 the dotted line B B ; the upper part may be cast in 
 open work, which will save weight in the castings, 
 and give the column a lighter appearance. There 
 will be seen, on referring to the figure at the centre 
 of the gas-holder, and forming a part of it, a cylinder 
 of plate-iron of sufficient diameter inside to slide up 
 
304 
 
 THE GAS-HOLDER, 
 
 and down with the least friction against the internal 
 column; at the top of which cylinder, and connected 
 also with the top of the gas-holder F F, is fixed a 
 very strong cast-iron ring, through which, and 
 through the top of the gas-holder, as well as through 
 the angle iron of the cylinder we are speaking of, 
 pass three eye bolts, to which is attached one end of 
 each of the chains which pass over the pulley-wheels 
 and meet inside the column, where they are secured 
 to the balance weight G which rises and falls 
 therein as the gas-holder is depressed or elevated. 
 
 A gas-holder for working with an upright centre 
 column may be constructed of No. 16 wire-gauge 
 plate-iron ; but the small cylinder which works upon 
 the column ought to be at least of No. 12 wire gauge, 
 for if lighter, it is apt, by friction against the column 
 when pressed close thereto by action of the wind, 
 particularly when very high, to be very soon injured, 
 and hence to become leaky ; to prevent which every 
 precaution should be taken, as from the situation of 
 that part of the gas-holder it would be difficult to 
 repair without discontinuing to use it, and emptying 
 the tank. This is a great objection to the use of the 
 centre column mode of suspending gas-holders, so 
 much so, that now they are very seldom constructed 
 on that plan. This kind of gas-holder being sus- 
 pended from near its centre, requires the internal 
 stays and braces to be of nearly similar arrangement 
 to that adopted in gas-holders suspended from their 
 
AND ITS CONSTRUCTION. 
 
 305 
 
 centre. H represents the inlet, and I the outlet 
 pipe ; J J J J J brick-work of which the tank is 
 composed ; KKKKKK puddle under the bottom 
 and round the walls of the tank. This mode of sus- 
 pending gas-holders was invented by Mr. John 
 Malam of Hull, who put up several thereafter ; and 
 on the same plan several were put up some years ago 
 by different gas companies. 
 
 Plate XF., Figured, is a vertical section of a 
 gas-holder suspended from four or more points of 
 its upper circumference, and represented as working 
 in a brick-tank. For a gas-holder of forty feet 
 diameter four points of suspension are sufficient, but 
 in larger gas-holders it is well to have six or even 
 more points of suspension. In figure 4, it is sup- 
 posed that the gas-holder is forty feet diameter, and 
 that it is suspended from four equidistant points, 
 (plans of two such gas-holders marked N and O 
 is represented in Plate VI.) ; A B represent two 
 cast-iron columns each about fourteen feet high, 
 secured to the top of the tank by means of screw- 
 bolts, each three or four feet in length, which are 
 built in the brick-work forming the walls of the 
 tank, and pass through a stone at their lower end, 
 so that when the nuts above the bottom flanch of 
 the column are properly screwed up, the columns 
 stand quite firm and in a perfectly vertical position. 
 There are two other such columns so secured (see 
 plan already referred to) which are not shown in 
 
 x 
 
306 
 
 THE GAS-HOLDER, 
 
 this section. On the top of each column is fixed a 
 carriage for supporting the pulley- wheels, (as C and 
 D on columns A and B), over which run the 
 chains which suspend the gas-holder and support 
 the balance-weights E and F. For causing the 
 gas-holder to work vertically and for preventing 
 it from being skaken by the action of the wind, 
 there is attached to each column a rack about six 
 inches greater in length than the gas-holder is in 
 height, in each of which works a pinion connected 
 to a shaft, as G G, which passes through the box H, 
 secured to the centre of the top of the gas-holder. 
 As the pinions are fixed and keyed to the ends of 
 the shaft G G, (which is in one piece or connected 
 by couplings,) it is evident that in whatever direction 
 one pinion moves, the other must necessarily move 
 in the same, in the racks attached to the pillars 
 A and B ; therefore if two other pillars were fixed 
 with racks attached to them, so that another shaft 
 similar to G G should pass through the box H so as 
 to be at right angles with G G, the pinions at the 
 end of this second shaft would act in their respective 
 racks similarly and simultaneously with the pinions 
 at the ends of the shafts G G ; consequently, as the 
 gas-holder rises or falls, the pinions turn equably 
 in one direction or in the reverse, and so keep the top 
 of the gas-holder perfectly level and its sides always 
 vertical, thus rendering guide-rods or friction-rollers 
 unnecessary. Though not absolutely necessary to 
 
AND ITS CONSTRUCTION. 
 
 307 
 
 furnish each of the four pillars with pulley-wheels, 
 suspension-chains, and balance-weights, it is found 
 in practice better to do so, for gas-holders of forty 
 feet diameter, when suspended from two points only, 
 are liable to sag and get out of form, from the force 
 of gravity acting unopposed upon the gas-holder 
 in the great interval between the two points of 
 suspension, which is not the case when they are 
 suspended from four points. When gas-holders of 
 sixty feet diameter (or of a larger size) are worked 
 on this plan, instead of the shaft G G passing quite 
 across the top of the gas-holder from the rack on 
 the column A to the rack on the column B, it is 
 found more convenient that the box H should be 
 made about three feet six inches diameter inside, so 
 that a bevel-toothed wheel of about three feet 
 diameter can work therein horizontally. In this 
 case, the shaft proceeds from the rack attached to 
 the column A, &c., to the box H, and from the 
 rack attached to the column B, &c., to the box H 
 at the end at A B, &c., are fixed and keyed pinions 
 as already described ; hut at the end of both of the 
 shafts which enter into the box H, are fixed and 
 keyed bevel pinions which simultaneously work into 
 the bevel-wheel therein contained, and consequently 
 the bevel pinions and the common ones all move at 
 the same speed upon the bevel-wheel and into the 
 teeth of the respective racks, producing precisely the 
 same effects as if there were a shaft G G all of one 
 
 x 2 
 
308 
 
 THE GAS-HOLDER, 
 
 piece. The shafts G G or G H will in all cases 
 have to be supported upon carriages bolted upon the 
 top of the gas-holder at about ten feet from each 
 other, to prevent the shaft from sagging and to 
 cause the pinions to work freely in their respective 
 racks, &c. The carriages should each have a 
 coupling over the shaft to keep it in its place as 
 the gas-holder goes down. The nearer to the cir- 
 cumference of the gas-holder one set of carriages 
 can be fixed the better, so that there may be as 
 short a distance between them and their respective 
 racks as possible, in order that the intermediate part 
 of the shaft should not be bent or twisted, for 
 should such happen from any heavy gust of wind 
 or from any other cause, the pinion would not work 
 freely in the rack, and hence an unsteady motion 
 would be produced. The gas-holder , bed, forty 
 feet diameter and twelve feet deep, is usually made 
 of No. 16 wii'e-guage plate-iron. The internal 
 stays radiate from the lower end of a flanch pipe 
 about eight feet in length (the top end of which is 
 secured to the crown of the gas-holder below the 
 box H) to the angle iron which connects the top 
 with the sides of the gas-holder as at a c, and also 
 to the angle iron at the bottom as at b d. In a forty 
 feet gas-holder there are about twelve such stays, each 
 of three-quarters-inch round iron, radiating from the 
 bottom of the centre flanch pipe to the uppermost 
 angle iron, and the same number placed alternately ra- 
 
AND ITS CONSTRUCTION. 
 
 309 
 
 diating from the same centre to the angle iron fixed 
 at the bottom of the gas-holder. The dotted line 
 e e shows the height at which the water stands in 
 the tank ; 1 1 the tank ; J the inlet, and K the 
 outlet pipe ; L L the side wall of the tank, which 
 in this figure is shown as if executed in brick. 
 The bottom of the tank M M is also represented as 
 of brick, it may, however, be formed simply of clay, 
 well tempered and worked with rammers, so as to 
 present a horizontal surface ; or it may be made of 
 the form shown in figure 5 of this plate, as may be 
 thought most expedient. N N represents the puddle 
 round the vertical walls of the tank, and O O well- 
 tempered clay laid for the bottom to rest upon. For 
 gas-holders of this description, a great number of 
 which have been fixed, Mr. John Malam, of Hull, 
 took out a patent in the year 1823. 
 
 Plate XV., figure 5, is a vertical section of a 
 gas-holder suspended from three equidistant points 
 of the circumference by chains passing over pulley- 
 wheels fixed upon carriages on a triangular bridge, 
 and also of a brick-tank for the gas-holder to work 
 in. Figure 6 of Plate XV. is a plan of the same, 
 in which corresponding parts are marked with cor- 
 responding letters of reference. In figure 5, G G 
 represents a section of the tank. F F are the side 
 walls supposed to be built of brick laid in lime and 
 sand mortar. A A represents a part of the ground 
 which had not been disturbed when the excavation 
 
310 
 
 THE GAS-HOLDER, 
 
 was made and which is represented as covered with 
 well-tempered clay to a thickness of two feet as at 
 BBBB, upon which the side walls F F are built. 
 BB at the back of the side walls is to be well 
 grouted in with thin puddle well trodden down, as 
 has been already directed, till it reach the level of 
 the ground. The inlet and outlet pipes for the gas 
 are not shown in this figure ; but they must be 
 fixed in precisely the same way as that shown in the 
 description of figures 3 and 4 of Plate XV. In carry- 
 ing up the side walls, it will be necessary, when they 
 come to within about three feet six inches of their 
 height, to build in four stones in the situations in 
 which the four columns a , b, c , d stand, with holes 
 made through them, to correspond with the bolt- 
 holes cast in the bases of the columns marked a , b , 
 c, d, or four cast-iron plates of the same size as the 
 said bases, and with holes cast in them to correspond 
 with the holes cast in the bases of the columns. 
 Through each of these stones or plates are to be 
 passed four three-quarter-inch screw-bolts, with their 
 heads underneath the plate or stone round which the 
 brick-work is to be built, each set of bolts being 
 kept in its exact position by a trammel made for the 
 purpose, so that when the pillars a, b , c, d are fixed 
 in their places, the holes in the flanch of the base 
 of each respectively shall receive the bolts over 
 which each is to be placed and secured thereto by 
 nuts working upon the upper part of its bottom 
 
AND ITS CONSTRUCTION. 
 
 311 
 
 flanch or base, so that when the nuts are screwed 
 up, the plate built into the brick-work, together with 
 the brick-work between that plate or stone and the 
 column, shall be inseparably connected together 
 and form as it were one compact and solid mass. 
 The columns a , b, c , d are to stand in a proper 
 position for supporting the frame CDEH, (shown 
 in plan at figure 6,) and which frame must admit 
 of the small pulleys f 9 g , and A, (figure 6,) allow- 
 ing their respective chains to fall just within the 
 circumference of the top of the gas-holder, and so as 
 to divide that circumference into three equal parts 
 in order that the points of suspension may be equi- 
 distant one from the other. If they be so, it is 
 evident that if the chain of suspension which passes 
 over the pulley-wheel g (figure 6) be brought over 
 the pulley-wheel at d, and be sufficiently long to be 
 connected with a shackle to the horizontal part of 
 the balance-rod, (which in this case is T-shaped,) if 
 the chain which passes over the pulley-wheel h (figure 
 6) in like manner be brought over the pulley-wheel 
 e and connected to the horizontal part of the ba- 
 lance-rod, and the chain which passes over the 
 pulley- wheel f (figure 6) be also passed over the 
 pulley-wheel nearest to E, and connected to the 
 middle part of the T balance-rod, the upper part of 
 that lying perfectly horizontal when the chains are 
 all tight and the top of the gas-holder is level, in 
 whatever degree the gas-holder may rise or fall, the 
 
312 
 
 THE GAS-HOLDER, 
 
 top will always maintain a horizontal and the sides 
 a vertical position ; for, the three chains from the 
 three points of suspension being all connected to one 
 weight, as that weight rises or falls so must also the 
 points connecting it by means of the chains with 
 the three points of suspension, below which is the 
 centre of gravity of the gas-holder, hence there need 
 be no apprehension of the gas-holder itself having a 
 tendency to alter its motion from that of a direct 
 rising or falling one. Where gas-holders suspended 
 in this way, however, are erected in the open air, it 
 will be desirable to place friction-rollers in carriages 
 built into the side walls of the tank about four 
 inches below the level, at which the water is pro- 
 posed to stand to prevent any oscillatory movement 
 from the influence of high winds. These friction- 
 rollers may be about six inches in diameter and four 
 inches wide on the face working against the side of 
 the gas-holder. They should be placed at not less 
 than ten feet nor more than fifteen feet asunder. 
 The columns a , b , c, d may be of cast-iron or built of 
 brick (as square piers) as may be most advisable, 
 though iron is the better of the two materials, giving 
 a more workmanlike finish and costing very little 
 more than brick. The columns should be about 
 two feet higher than the utmost rise of the gas- 
 holder, in order that the top of the gas-holder, 
 which is always made of a convex form outside, may 
 not, when the gas-holder is at its height, touch the 
 
AND ITS CONSTRUCTION. 
 
 313 
 
 triangular frame C D H (figure 6). C D E repre- 
 sents the depth of the triangular frame, which will 
 of course vary according to the length of the pieces 
 C, D, and H, figure 6. For a gas-holder of from 
 twenty to thirty feet diameter, if made of good 
 Baltic timber, the pieces of which it is composed 
 need not be more than twelve inches deep by four 
 inches in thickness, ij k l is a section of the gas- 
 holder which must he furnished with internal stays 
 similar to those mentioned in the description of 
 figure 4, of Plate XV. The pulleys, wheels, chains, 
 and balance-weights are not shown in this figure, 
 but the situation of the former are shown upon 
 figure 6. The three chains meet at E, (figure 6,) 
 which is the situation of the balance-weight. 
 
 Figure 6, Plate XV. is a plan of figure 5 of the 
 same plate upon which the corresponding parts are 
 marked with similar letters of reference, conse- 
 quently very little remains to be explained here, 
 beyond noticing that the sides of the triangular 
 frame are kept from warping by the blocks placed 
 between them in the situations marked * *, which 
 blocks are kept in their places by -§- screw-bolts and 
 nuts, two of which pass through each block and 
 through the adjacent parts of the bridge, where they 
 are screwed by their nuts upon square washers of 
 iron. For security, it will be well to strengthen 
 the angles at a and c of the frame by wrought-iron 
 braces or clips to lap over at each side about nine 
 
314 
 
 THE GAS-HOLDER, 
 
 inches, each brace or clip should be about four 
 inches broad and of an inch in thickness. These 
 should be secured to the frame by two-inch wood- 
 screws through holes countersunk in the plate for 
 receiving their heads. This mode of suspending 
 gas-holders answers exceedingly well for small 
 works, for which it is generally to be preferred 
 from its small cost and the steadiness with which it 
 works. It may here be remarked, that, as there are 
 three compensating chains used in gas-holders of 
 this kind when finding the weight per foot of each 
 chain, the three must be considered but as the weight 
 of one, which being found as directed at page 271, 
 one-third of that will be the weight of each of 
 these ; so where four chains are used, divide the 
 weight so found by four, where six by six, and so 
 on. We have been very full in our explanation of 
 the mode in which this gas-holder is suspended and 
 acts, because the large telescope gas-holders now so 
 generally used in London and in several other 
 large gas establishments are suspended from three 
 points at their circumference in a similar manner 
 as this is : the chief case of difference between the 
 two modes being merely that the triangular frame 
 in which the pulley-wheels work is for adequately 
 supporting the weight of the uppermost of these 
 large gas-holders, constructed of bridges of iron, 
 cast in pieces and with open work ; and, when 
 bolted together, each bridge, in its upper and lower 
 
AND ITS CONSTRUCTION. 
 
 315 
 
 outline, is of the shape of a common parabola, the 
 form of curve most suitable for the beam to have, in 
 cases like this, where the weight is applied to any 
 one given point thereof. 
 
 W e have already had occasion to mention that 
 the idea of doubling in one tank the capacity for 
 gas of the gas-holder working into it had been 
 acted upon, many years ago, by Mr. Stratton, and 
 although his plan was never extensively brought 
 into use, yet we consider that a modification of it 
 might he advantageously carried into effect, being of 
 opinion that his gas-holder might be so constructed 
 as to answer quite as well, if not better, than the 
 telescope gas-holders we are now about to describe, 
 and with a much less expense of erection. In speak- 
 ing of telescope gas-holders, we must remark, that 
 some of those which we have noticed and seen 
 described, and pointed out as vast improvements, we 
 think highly objectionable, particularly those in 
 which three or more gas-holders are suspended from 
 pulley-wheels placed on the tops of columns with 
 but one set of balance-weights to meet all contin- 
 gencies. With respect to those in which three gas- 
 holders slide one within another, we have no hesita- 
 tion in affirming that, supposing the uppermost (or 
 outside) gas-holder to be forty-five feet diameter and 
 the chains and balance-weight adjusted, so that till 
 the groove formed by the turning in of the iron at 
 its lower edge, for the purpose of forming an hy- 
 
316 
 
 THE GAS-HOLDER, 
 
 draulic joint rises to the top of the water, it should 
 work at 44- pressure, it will no sooner have that 
 groove with the water, which will be lifted up with 
 it clear of the water in the tank, than the pressure 
 will be increased to between and 4-o, owing to 
 the quantity of water that groove will contain and 
 the extra iron used for forming the bottom and 
 sides of the said groove ; again, when the bottom of 
 the second gas-holder rises above the water in the 
 tank, a like increase of pressure will, for the same 
 reasons, take place, so that then the pressure will 
 have been increased from what it was originally, 
 44 to between 44 an d 44- That such will be the 
 case may easily be ascertained, by finding the weight 
 of water contained in each groove, and the extra 
 quantity of iron for forming that groove, making an 
 allowance for rivets, &c. The gross sum in ounces 
 being thus ascertained, the pressure in tenths of an 
 inch can be found by the method already described. 
 The pressure is also found variable in the way de- 
 scribed in practice, and hence, where but one gas- 
 holder is used in a manufactory, the telescope one is 
 to be objected to, unless a governor or regulator be 
 used between that gas-holder and the main pipe of 
 supply. Where several telescope gas-holders are used, 
 the evil of inequality of pressure, may, to a cer- 
 tain extent, be remedied by working from two or 
 three at the same time, having always one gas- 
 holder at work at the greatest and one at the 
 
AND ITS CONSTRUCTION. 
 
 317 
 
 lightest pressure ; this contrivance, however, will not 
 entirely counteract the evil we are speaking of. 
 More effectually to obviate this variability of pres- 
 sure, it is now the practice to have two sets of 
 balance-weights and chains where there are two 
 gas-holders working in one tank on the telescope 
 plan, one set to each, three where there are three, 
 and so on, as described by figures 1, 2, and 3, Plate 
 XVI. 
 
 Plate XVI., figure 1, represents a vertical section 
 of two gas-holders working into one tank on the 
 telescope plan, with a section of a cast-iron tank 
 and an elevation of the pillars for supporting the 
 triangular frame, from which the upper gas-holder 
 and its balance-weight are suspended by chains 
 passing over the pulley-wheels fixed upon the said 
 frame. In figure 1, A AAA represents in section 
 the tank, B B the side plates, C C bottom, made of 
 cast-iron plates, as has been already described, DDD 
 pillars of brick-work laid in Roman-cement, each 
 built upon a cast-iron plate, with holes cast in it 
 for receiving bolts intended to secure the bases of 
 the columns E F, G H, I J. The holts passing 
 through the bottom plate and through the brick- 
 work, pass also through holes cast in the base of 
 each column, when the nuts are screwed up so as 
 to connect the bottom plate, the brick-work above 
 it and the base of the column firmly together, and 
 thus to afford to each column the required stability. 
 
318 
 
 THE GAS-HOLDER, 
 
 At the top of each pair of columns is a cast-iron 
 box, as K K K in the figure, to which boxes the 
 upper ends of the lower columns are secured and 
 kept in their position ; these boxes serve also as 
 bases upon which to secure the second range of 
 columns LM, NO, P Q, which again are sur- 
 mounted by the cast-iron boxes RRR; these, in 
 addition to the purpose answered by the boxes 
 KKK, serve also for securing the carriages S S, 
 upon which are supported the pulley- wheels TTT. 
 These pulley-wheels have each their compensation 
 chain, which is attached to the top edge of the 
 lower or outer gas-holder, and to a balance-weight 
 which comes into action when the trough at the 
 bottom of the upper gas-holder rises out of the 
 water in the tank, thus preventing the extra pres- 
 sure arising at that point whenever the gas-holders 
 are not provided with a second set of balance- 
 weights. The upper tiers of columns have boxes 
 above them similar to those already described, upon 
 which rests and is secured the triangular frame 
 C C, D D, E E, whereon are fixed the pulley- wheels 
 0, e, d , c, b, over which pass the chains (shown by 
 dotted lines) for suspending the upper or interior 
 gas-holder. These chains all meet and are con- 
 nected to the T balance rod, below the outer groove 
 of the pulleys e , d, c (not shown in the figure). As 
 the mode of suspension of this description of gas- 
 holder is similar to that of the gas-holder shown at 
 
AND ITS CONSTRUCTION. 
 
 319 
 
 Plate XV., figures 5 and 6, it will not be necessary 
 to dwell further upon it in this place, e f g h is a 
 section of the upper or interior gas-holder, i i its 
 top ; its bottom is represented by the dotted line jj. 
 abed is a section of the lower or exterior gas- 
 holder, it is without a top, but the upper edge of its 
 sides or ring is represented by the dotted line k k , 
 and its bottom by the dotted line ll. * * show the 
 situation of the trough formed round the outside of 
 the top gas-holder (as shown more at large at figure 
 3, where the same parts are marked by similar 
 letters). To ensure the inner and outer gas-holder 
 working freely together, it will be well to fix small 
 friction-rollers (about ten feet apart) on the upper 
 edge of the outer one, at the part where it is turned 
 over, to work against flat vertical bars fixed on the 
 outside of the inner gas-holder, by which means the 
 sides are kept equidistant and parallel to each other 
 at all heights of their rise and fall. We shall now 
 suppose that the gas-holder we are speaking of is 
 quite empty — in such case both the parts of which 
 it is formed will be immersed in the tank, so that 
 the top of the inner one i i, will be about an inch 
 and a half above the water in the tank, and the 
 bottoms of both the inner and outer one will rest 
 upon the bottom of the tank. On the gas being 
 allowed to enter by the inlet pipe (not shown in 
 the figure), the gas-holder efgh rises or is lifted 
 first till its lower edge jj , and the trough at e and 
 
320 
 
 THE GAS-HOLDER, 
 
 h rise just out of the water in the tank. So soon 
 as that is the case, the weight passing over the 
 pulley-wheels T T T come into action, and sustain 
 the additional weight caused by the water in the 
 trough, and the iron of which that trough is formed, 
 consequently no additional pressure is thrown upon 
 the gas-holder. The gas-holder continues to rise 
 till it is in the position shown in the figure, and 
 ultimately till the lower edge of the outer gas- 
 holder all d has a dip of about two inches only in 
 the water of the tank ; in that position the inner 
 and outer gas-holders are both full. In emptying 
 the telescope gas-holder, the outer or bottom one 
 will sink into the water contained in the tank first, 
 and consequently will be the first emptied by the 
 exit pipe (not shown in the figure). It is evident 
 that telescope gas-holders ought to be made very 
 true, so that the trough shown at * * should always 
 be perfectly horizontal ; for, supposing the trough 
 to be six inches deep and three inches wide, if the 
 gas-holder be of forty-five feet diameter, a very 
 slight deviation from the horizontal plane upon the 
 entire base would cause the trough to be nearly 
 empty at one side (and thus allow the gas to escape 
 where there was no hydraulic joint formed), whilst 
 it might be quite full of water at the other. Great 
 care is also needful in order to suspend telescope 
 gas-holders, so that the top shall be always perfectly 
 level and the side vertical. 
 
AND ITS CONSTRUCTION. 
 
 321 
 
 Figure 2, Plate XVI., is a plan of figure 1 of 
 the same plate, showing the plan of the gas-holder 
 and tank, and of the triangular bridge and pulley- 
 wheels, also of the brick pillars (which are built 
 outside of the cast-iron tank, and with their upper 
 surface level with the bottom of that tank) for the 
 pillars EF, GH, IJ to stand upon. To give 
 greater stability to the triangular frame, it may be 
 strengthened by the cross braces marked in 
 addition to the blocks shown between C C and D I), 
 as was fully described in referring to figure 6, 
 Plate XV. 
 
 Plate XVI., figure 3, shows in section a portion 
 of the top and side of the gas-holder ef gh, and also 
 a portion of the side of the gas-holder abed. This 
 figure is given in order to show more clearly the 
 lap-over of the interior upper one for forming the 
 trough holding the water, into which the lap-over 
 of the outer or bottom one dips, and so forms an 
 hydraulic joint as at li # c. 
 
 We conclude this chapter by remarking that the 
 water in the tank in which the gas-holder works 
 does never require to be changed or renewed, though 
 this has been often unreasonably thought necessary : 
 only what is lost by evaporation has to be replaced, 
 which is very trifling at all times: and even in 
 summer, when the gas-holders are fixed in the open 
 air, the deficiency thereby occasioned is generally 
 replenished by occasional showers, the tank receiving 
 
322 
 
 THE GAS-HOLDER, 
 
 all the rain which falls upon the top of the gas- 
 holder. It will always be desirable to fit a waste 
 pipe in each tank to prevent the water rising too 
 high from heavy rains, which might cause it to flow 
 down the inlet and outlet pipes, and thus stop the 
 gas-way to and from the gas-holder, till such water 
 was pumped out of the syphons or receiver attached 
 to each gas-holder elsewhere explained. Should a 
 brick or stone tank happen to be leaky, but which, 
 if proper precautions be taken in their formation 
 they rarely will be, the loss by leakage must of 
 course be made good, or the gas-holder cannot be 
 worked to its full extent ; for how muchsoever the 
 top of the gas-holder rises (when quite down) above 
 the level of the water in the tank, so much gas 
 room is lost in working it, as in that portion of it 
 the gas cannot be expelled. We have very recently 
 seen it very gravely asserted in print, that the sur- 
 face of the water in the tank for the gas-holder 
 gets covered with a stratum of coal-oil a few inches 
 deep, which prevents the evaporation of the water, 
 and allows the gas in the gas-holder to be saturated 
 with this volatile substance so as to increase its 
 illuminating powers. That such should be the case 
 is entirely beyond our comprehension, and altogether 
 at variance with full twenty-five years extensive 
 practice, during which period we never observed 
 any such deposit ; a thin pellicle of coal-tar formed 
 from the redundant tar from off the tarred coating 
 
AND ITS CONSTRUCTION. 
 
 323 
 
 of the gas-holder being nearly all that ever rests 
 upon the surface of the water in a tank, the gas- 
 holder in which never contains gas ineffectually 
 refrigerated and purified : as to the gas being ren- 
 dered of more illuminating power by being impreg- 
 nated with the volatile particles of a stratum of 
 naphtha supposed to be floating on the water within 
 the gas-holder, we can only say that, so far from 
 that seeming to be the case practically, the illumi- 
 nating power of the gas is as greatly deteriorated 
 by being kept for a time over this supposed volatile 
 inflammable oil, as by being confined in any other 
 close vessel. 
 
 y 2 
 
324 
 
 CHAPTER XII. 
 
 On various kinds of Valves, Syphons, and Tar-Wells. 
 
 The necessity of adopting effectual means for shut- 
 ting off all communication between the gas-holder 
 and the street mains, as well as from one main pipe 
 to another, under their various ramifications, pointed 
 out the necessity of using valves of one description 
 or another. Various descriptions of valves have 
 been, and still are, used by the gas-light manufac- 
 turer ; but, for most purposes, the ordinary slide 
 valve answers as well as any other. It is easily 
 managed, and is particularly applicable to the main 
 pipe of supply, as thereby the pipe can be opened to 
 the full extent of its bore, or only partially, as may 
 be requisite, according to the quantity of gas which 
 may be necessary to pass through it in a given time 
 — a thing which cannot be accomplished, either by 
 the hydraulic or by the pneumatic valve. 
 
 Plate XVII., figure 1, is a vertical section of 
 an hydraulic valve, particularly useful in the con- 
 nexions upon the works. It is cylindrical, with a 
 flanch at its top and bottom, and cast with a flanch 
 quarter-bend projecting upwards from one side of 
 it. At the bottom is bolted and jointed a double 
 
ON VALVES, SYPHONS, AND TAR-WELLS. 325 
 
 cup, which rises to the lower part of the quarter- 
 bend just mentioned. Through the centre of this 
 cup is an opening of the same diameter as the bend. 
 This centre part projects a few inches below the 
 bottom of the valve, and is furnished with a flanch 
 for jointing it to the pipe which brings the gas into 
 the valve. Through the bottom of the valve is 
 brought a wrought-iron bend, as shown in the 
 figure, which is connected to an upright pipe of the 
 same material, which rises as high as the top of the 
 valve, and is for the purpose of introducing water 
 into the inner ring of the double cup, the outer 
 cylinder of which, being bored near its bottom, 
 allows the water to pass into the outer ring. The 
 top of this supplying pipe is covered by a cap, which 
 is kept screwed on, save when it may be necessary 
 to furnish a supply of water. The top of the valve 
 is covered with a blank flanch, which is jointed and 
 secured thereto by screw bolts in the usual way. 
 At the centre of the top is fixed a stuffing-box, the 
 bottom of which is tapped for receiving the square- 
 thread lifting screw. The lifting screw is sur- 
 rounded by a wrought-iron case, with a thread 
 inside for the thread of the lifting screw to work 
 in. This case, or female screw, is movable in the 
 stuffing-box, and of sufficient height to work the 
 lifting screw to the greatest height that may be 
 required. It is made with two projecting handles 
 outside, which serve as a wrench for raising or 
 
326 
 
 ON VALVES, SYPHONS, 
 
 lowering the screw. The bottom of this screw is 
 secured to a double inverted cup, as shown in the 
 figure, and therefore that is lifted or lowered with 
 it. The inverted cup is so constructed, that when 
 let down it falls between the two cylinders forming 
 the lower one ; and thus, if we suppose the bottom 
 double cups to be nearly filled with water, and the 
 upper one immersed in it, it follows, that a valve so 
 constructed is capable of sustaining double the 
 pressure of one made with but a single cup. At 
 the same time we may remark, that the double cup 
 valve, equally effective with the single cup valve, 
 will not occupy much more than half the room. 
 Figure 2 is a plan of this valve, which, from what 
 has been said, does not require further description. 
 
 Plate XVII., figure 3, is a vertical section of a 
 pneumatic valve, which, from the stuffing-box at 
 the top to the step for the spindle at the bottom, 
 is rather more than twice the diameter of the main 
 on which it is intended to be used. The body of 
 the valve is square, as shown in the plan, figure 4, 
 A few inches from the top, at one side, is cast a 
 socket, and in a direct line therewith, at the other 
 side, is cast a spigot, in order that it may be intro- 
 duced into the range of main pipes wherever re- 
 quired. The inner faces of the socket, as well as 
 - of the spigot, project about an inch inward, and 
 require to be chipped and filed, so as to present 
 perfectly plane and smooth vertical surfaces. 
 
AND TAR-WELLS. 
 
 327 
 
 Through the top of the valve, which is htted with 
 a stuffing-box, is introduced the spindle, so that the 
 lower end of it rests in the step at the bottom of 
 the valve, and the collar beneath brass couplings in 
 the bottom of the stuffing-box, so that when the 
 stuffing-box is fitted and the glan bolted down, 
 should the wrench, or key, be applied to the square 
 top of the spindle, the spindle will turn freely 
 round, but without being raised. If, then, we 
 suppose the valve to be open, as shown in the 
 figure, there will rest upon its bottom two wedge- 
 shaped pieces of iron, with their points downwards, 
 and between them a third piece, also wedge-shaped, 
 with the apex cut off. The spindle passes through 
 the latter, which is fitted with a screw for receiving 
 it, and it is thereby raised or lowered, as the valve 
 may require to be shut or opened. Upon the centre 
 piece, at a convenient distance from the top, is 
 bolted a spring, which is also connected to the side 
 pieces, so as to act between the top of them and the 
 bolt which secures it to the middle piece. In its 
 natural position, this spring has a tendency towards 
 drawing the side pieces together, and of pushing the 
 middle one downwards. This contrivance allows 
 the three pieces to be lifted together, without the 
 outer ones rubbing against the inside of the valve 
 till they touch the top. The further ascent of the 
 outer pieces being then arrested, the middle one 
 continues to be raised by the screw till they are 
 
328 ON VALVES, SYPHONS, 
 
 completely wedged up against the interior of the 
 socket and spigot, and as these wedge-shaped pieces 
 are faced with cork or leather, the pressure can be 
 carried to such pitch as ensures a gas-tight joint 
 upon each. When the valve is in such position, 
 the spring will he elongated horizontally, and so 
 remain till the spindle is turned for lowering the 
 interior pieces, when it again resumes its former 
 shape, and thus draws the side pieces towards each 
 other, and pushes the middle piece downwards. 
 Figure 4 is a plan of figure 3. It exhibits the 
 flaneh to which the top is to be secured, the socket 
 and spigot shown in figure 3, and the top of the 
 inner pieces, with the facings of cork. This is an 
 effective and simple valve, of small size, and can 
 be got up at a very trifling expense when compared 
 with others more commonly adopted. 
 
 “ Syphons” and “ Tar-wells ” (but why either 
 should he so called we could never learn) we are 
 next to mention : the former are of two kinds ; the 
 larger size are distinguished by their diameters, two, 
 three, or four inch, &c., syphons ; the smaller, 
 which are used on the service pipes, are generally 
 termed “ gun-barrel syphons ,” or “ bottle syphons.” 
 The shape of the vessel itself is similar in each case, 
 but the furniture and use are different. The larger 
 sized syphon is a cast-iron cylindrical vessel, of about 
 a foot in depth, and of the diameter inside which 
 corresponds with its distinguishing name. It has a 
 
AND TAR-WELLS. 
 
 329 
 
 fianch round the top, to which is bolted a blank 
 fianch, which forms its lid, generally with a paste- 
 board fianch well soaked in linseed-oil, and with a 
 coat of white-lead laid on each side of it, between 
 the lid and fianch of the syphon through which 
 the holts for securing the lid pass, so that when the 
 nuts are screwed up, a gas-tight joint is formed : 
 or the joint may be made with iron-cement in the 
 usual way. Through the centre of the lid (which 
 is generally cast with a boss upon it) a hole is 
 drilled and tapped for receiving a piece of three- 
 quarter-inch wrought-iron tubing, which descends 
 to within about two inches of the bottom of the 
 syphon, and rises about three inches above the lid. 
 Another piece of iron tubing, of an inch or an inch 
 and a half in diameter, of the form of a bend, is 
 screwed into a hole drilled and tapped into the side 
 of the syphon (as shown in figure 5, Plate XVII., 
 which represents a vertical section of this syphon), 
 so that one end of it rises nearly perpendicularly 
 somewhat higher than the top of the syphon, for 
 connecting it by means of a hole drilled and tapped 
 into the under side of the main pipe (before it is 
 laid down), through which any condensed matter 
 descends into the syphon, whence it is occasionally 
 removed by means of a portable pump, which screws 
 upon the upright pipe passing through the lid. 
 The top of that pipe is secured by a cap of wrought- 
 iron, which screws upon it, and is only taken off 
 
330 
 
 ON VALVES, SYPHONS, 
 
 when it is necessary to ascertain whether the syphon 
 contains water, and, if so, during its removal. 
 
 The gun-barrel syphon is generally about eight 
 inches deep and four inches diameter (see vertical 
 section, Plate XVII., figure 6). Through the 
 blank flanch at the top is introduced a piece of 
 three-quarter-inch wrought-iron tube, which de- 
 scends nearly to the bottom, generally called “ the 
 suck pipe,” On each side of this syphon is a piece 
 of wrought-iron tube, bent as shown in the figure. 
 This syphon is used upon the service pipe to answer 
 the same purpose there as that answered by the 
 larger one upon the street mains. 
 
 Figure 7, Plate XVII., is a section of the im- 
 properly-so-called tar-well. It is a cylindrical vessel 
 of about ten inches diameter inside, and twelve inches 
 deep when used upon any main of less than ten inches 
 diameter ; but when it is used upon larger mains, 
 the diameter of the body of the tar-well must be two 
 or three inches more than the diameter of such mains. 
 This vessel is cast with a socket at one side and a 
 spigot at the other, similar to those of the pipes with 
 which it is connected ; therefore, a tar-well with a 
 socket and spigot similar to those of a two-inch pipe 
 is called a two-inch tar- well, one for a three-inch 
 pipe, a three-inch tar-well, and so on. 
 
 From the condensation which takes place in the 
 main pipes, it is found necessary to lay the large 
 pipes, and also the small or service pipes with a small 
 
JPlale, _ 27 . 
 
 J;07uicr/i/ FioblcJJuu^ by Z.Ifeberb, 20 1<SA1. 
 
 C . Mbtftcryis, ct2lt> 
 
f] 
 
 
 
AND TAR-WELLS. 
 
 331 
 
 declination, in order that the condensations may, 
 from this inclined position of the pipes, descend to 
 the lower parts of said pipes, where the syphons 
 or tar-wells must be fixed for receiving any condensed 
 matter. Over the syphon, as well as over the tar- 
 well, is generally placed a wooden block bored out at 
 the centre, and fitted with a cast-iron bush, and lid 
 at the top, lying level with the pavement, for the 
 purpose of being able to get at and unscrew the cap 
 of the suck-pipe, and to connect the portable pump 
 thereto. 
 
 On referring to the plans of the gas-holders and 
 tanks N and O, Plate VI., it will be observed that 
 the inlet pipes ee enter each of these gas-holders 
 from a cylindrical vessel something similar in shape 
 to figure 5, Plate XVII., and the exit pipes from 
 the said gas-holders enter into the same vessels by 
 the pipes f and g. These vessels will vary in size 
 according to the size of the inlet and outlet pipes. 
 For four- inch pipes, a vessel eighteen inches dia- 
 meter inside, and about two feet six inches deep, will 
 be amply sufficient. It must be cast with a parti- 
 tion that shall approach to within about two inches 
 of the bottom, and rise about three inches and a half 
 above the top of the flanch, in order that two semi- 
 circular lids may be thereto secured in the usual way, 
 so as to be gas tight. On the outside of this vessel 
 must be cast two sockets, for receiving the spigot 
 ends of the cast-iron pipes which pass through the 
 
332 
 
 ON VALVES, SYPHONS, 
 
 wall where brick or stone tanks are used, and into 
 the gas-holder tank, one on each side of the par- 
 tition already alluded to, and with such an angle 
 between the two as will bring the upright parts to 
 the positions in which it is desired they should stand. 
 One of the semicircular cast-iron lids is to have a 
 socket cast upon it for receiving an upright pipe of 
 the same diameter as the inlet pipe, and the other, 
 in addition to such a socket, is to have a second 
 socket cast upon it for receiving a two-inch cast-iron 
 pipe, which pipe is to be carried up to the surface of 
 the ground, where it will terminate with a flanch 
 about two inches broad. A cast-iron blank-flanch, 
 with a boss on the centre, must be secured to the 
 upper flanch by three half- inch screw holts, and 
 made gas tight by means of a pasteboard joint. 
 Through the centre of this blank flanch or lid must 
 be drilled and tapped a hole, through which must be 
 screwed a sufficient length of three-quarters-inch 
 wrought-iron pipe, to descend to within about five 
 inches of the bottom of the cylindrical vessel (with the 
 partition therein as already mentioned), and to come 
 through the top of the blank flanch, with its screwed 
 part about three inches, in order that a cap may be 
 screwed thereon. The object of this pipe is to draw off 
 any condensed water by means of a portable pump, from 
 the cylindrical vessel to which the inlet and outlet pipes 
 are jointed, whichpipes must be laid with a fall of about 
 three-quarters of an inch to the yard towards that 
 
AND TAR-WELLS. 
 
 333 
 
 vessel, to prevent any lodgment of water in them. 
 The use of the partition-plate in the cylinder is to 
 prevent the gas entering into the gas-holder except 
 by the inlet pipe, for it is evident that the suction pipe 
 will always allow full five inches in depth of water at 
 the bottom of the cylinder or receiver (to which depth 
 it must be filled, by pouring water down the three- 
 quarter-inch pipe before the gas-holder is brought 
 into action), consequently the partition-plate will 
 always have a dip of three inches, which will effectu- 
 ally prevent any communication between the inlet 
 and outlet pipes in that vessel. Pieces of the same 
 sized pipe as the inlet and outlet pipes are placed up- 
 right in the larger sockets on the lid of the receiver, 
 into which they are secured by well made lead joints. 
 At the upper end of these pipes are jointed the quarter- 
 bends which connect with the pipes leading towards 
 the purifier, and towards the governor or regulator 
 P, Plate VI. It will be best to connect an hydraulic 
 valve with each of the bends just spoken of, before 
 the pipes c, g and f are connected ; when a regulator 
 is used, should that not be the case, and the street 
 main be supplied immediately from the gas-holder N 
 or O, then hydraulic valves should be used only upon 
 the inlet pipes, that is, upon those between the gas- 
 holder and the purifier and slide valves (to work 
 with a screw), on each of the bends connected with 
 the outlet pipes, so that the orifice of supply to the 
 streets may be enlarged to the full bore of the pipe, 
 
334 ON VALVES, SYPHONS, AND TAR-WELLS. 
 
 or lessened to such size as may be sufficient for the 
 supply. By "adopting this plan, the pipes e e, g g, 
 which run nearly parallel to the coke-store Q Q, 
 will lie about eighteen inches below the surface of 
 the ground. A brick wall will require to be built 
 round the valves, so as to leave an opening round 
 them about two feet square, which opening can be 
 covered by a cast-iron plate, or Yorkshire flag, with 
 a hole over the spindle of the valve, so that the valve 
 can be raised or lowered by means of a T-shaped key. 
 Under this arrangement there is no necessity for any 
 syphon well to the gas-holder tank, and the earth 
 round the upright pipes can be replaced to the regular 
 level of the ground, and thus a considerable saving 
 will be effected, particularly where brick or stone 
 tanks are used for the gas-holder to work in, as the 
 syphon well would require to be built, in such cases, 
 very water tight, and well puddled. 
 
335 
 
 CHAPTER XIII. 
 
 On the laying down of Main Pipes in the Streets, &o., the Ar- 
 rangement of their diameters, and remarks thereon : also on the 
 Service Pipes, Gas-fittings, and Burners. 
 
 The results of a great many years’ experience in the 
 casting of pipes for the conveyance of gas now ob- 
 tained at all the large iron-works throughout the 
 country, renders it almost needless to enter into any 
 long details upon the subject of the weight or form 
 of pipes used by the gas-light manufacturer. Ge- 
 nerally speaking, all he has to do is to give his order 
 for the number and kind of pipes, bends, branches, 
 &c., he may require, for all of which the respectable 
 iron-founder is prepared with patterns of such thick- 
 ness of metal as experience has proved most proper. 
 We shall especially here have occasion to speak about 
 that arrangement of the street mains in which those 
 of the largest diameter are nearest to the manufac- 
 tory, and the branches from them are proportioned 
 to the demand they will have to supply ; but before 
 we do so, we will give a description of the various 
 kinds of cast-iron pipes used, and the mode of con- 
 necting them together. 
 
 Plate XVIII., figure 1, is a longitudinal section of 
 
336 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 the socket pipe. These pipes are connected together in 
 the following manner : — the workman having intro- 
 duced the spigot end of one pipe into the socket of 
 the pipe adjoining, passes gasket or spun-yarn round 
 it till the socket is filled therewith (when well set 
 up by means of a proper caulking-tool and mallet) 
 to within from an inch and a half to three inches of 
 its entire depth, the smaller depth left vacant being 
 sufficient for the lead which forms the joints in all 
 pipes up to four inches diameter, and the larger 
 depth being sufficient for pipes of from fourteen to 
 eighteen inches diameter, the depth for the lead 
 gradually increasing from one inch and a half to three 
 inches, as the diameters of the pipes increase from 
 four to fourteen inches. This being done, he makes 
 a roll of clay, of a sufficient length to go quite round 
 the pipe, and passing it underneath the pipe, he 
 forces the clay close up to the edge of the socket, 
 quite round, and joins it at the top, where he forms 
 an opening or lip for receiving the melted lead which 
 he has ready for use. Things being thus arranged, 
 he takes a sufficient quantity of lead in his ladle, and 
 pours it into the socket through the opening just 
 mentioned, till the socket is entirely full, which is 
 known by the lead rising to the top of the clay. 
 So soon as the lead is set, the clay is removed, and 
 he proceeds to make the next joint in a similar 
 manner. After making two or three joints, and al- 
 lowing the lead to become quite cold, the lead is 
 
AND BURNERS. 
 
 337 
 
 driven up (or, as it is generally termed, set up) by 
 means of a caulking-tool and mallet, and thus joints 
 perfectly gas-tight are formed. The centres of the 
 adjoining pipes must be brought into a line by means 
 of the gasket used before the melted lead is intro- 
 duced ; for unless this precaution is taken, the out- 
 side of the spigot end of the pipe will not be equi- 
 distant from the internal surface of the socket, in 
 which case the body of lead introduced for making 
 the joint will not be of equal thickness throughout, 
 consequently a joint so made will be more likely to 
 become leaky than those made in a workmanlike 
 manner, as we have just described. 
 
 Roman-cement has, in some cases, been used for 
 making good the joints of socket pipes, and, as far 
 as tried, has been found to answer that purpose. 
 In making the joints according to this method, it 
 is only required to bring the centres of the adjoin- 
 ing pipes into a line, and then to introduce the 
 cement, just mixed, between the socket and spigot by 
 means of a blunt instrument, forcing it up so as 
 entirely to fill the cavity. Roman-cement increases 
 in bulk by drying ; consequently it forces itself so 
 compactly between the outside of the spigot and the 
 inside of the socket of the respective pipes, as effec- 
 tually to form a joint. It has been ascertained by 
 experiment, that cast-iron pipes thus connected 
 together are less liable to fracture at the joint than 
 in any other part. 
 
338 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 To prevent the necessity of using any material 
 (beyond white or red-lead* which may be applied by 
 means of a brush) for filling the cavity between the 
 outer surface of the spigot and the inner surface of 
 the adjoining socket, when socket pipes are used, 
 a description of pipe has of late years been manu- 
 factured, and which has been very generally used, 
 differing somewhat from the socket pipes we have 
 been speaking of. They are cast with a collar 
 round the socket of from three to four inches broad, 
 and to that depth the pipe is about twice as thick 
 as it is in any other part ; their sockets are also cast 
 stronger than those for pipes where lead joints are 
 used. Being thus prepared, the outer surface of the 
 spigot end is turned so as to be very slightly conical, 
 and the interior of the socket is bored by means of 
 an instrument so gauged as that when the spigot 
 end of a second pipe of the same bore is introduced 
 into it, the two pipes fit closely, similar to the 
 ground stopper of a decanter. In laying such pipes 
 down in the streets, the workmen give the spigot 
 end a thin coat of red or white-lead, introduce it 
 into the adjoining socket, and drive it home by 
 means of a tolerably heavy wooden mallet. Where 
 there is a considerable distance of pipe to be laid in 
 a straight line, turned and bored pipes are well 
 adapted for the purpose ; and although they are 
 generally charged by the iron-founder at a some- 
 what higher price than the ordinary socket pipes. 
 
AND BURNERS. 
 
 339 
 
 they are much cheaper in the end from the saving 
 of gasket, lead, labour, and time in laying ; for an 
 expert pipe-layer would lay ten turned and bored 
 pipes (supposing the ground to be got out ready) in 
 less time than it would take him to make a couple 
 of lead joints. 
 
 Figure 2, Plate XV II /., is a view of socket pipes 
 when joined together. 
 
 Figure 3, Plate XVIII., is a longitudinal section 
 of flanch pipes, in which the manner of connecting 
 them together is shown. The joint is made by first 
 introducing a small ring of the diameter of the pipe 
 made of iron, covered with yarn or any pliable 
 material which is between the two flanches, which 
 flanches are kept together by means of screw-bolts 
 and nuts, and gas tight by means of iron-cement 
 well caulked up. 
 
 To make iron-cement for this purpose, or for 
 making any other flanch joints as in tanks, in con- 
 necting the mouth-pieces to the retorts, the dip 
 pipes to the hydraulic main, &c., take iron turnings 
 or borings and pound them in a mortar till they are 
 fine enough to pass through a fine sieve ; then, with 
 one pound of these borings so prepared, mix two 
 ounces of sal-ammoniac in powder, and one ounce of 
 flowers of sulphur, by rubbing them well together 
 in a mortar, and afterwards keep the mixture dry 
 till it may be wanted for use. When it is so, for 
 every part thereof by measure, take twenty parts of 
 
340 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 iron-borings, prepared as above-mentioned, and mix 
 them well together in a mortar or other iron vessel. 
 The compound is to be brought to a proper con- 
 sistence by pouring water gently over it as it is 
 mixing ; and when used, it must be applied between 
 the flanehes by means of a blunted caulking-iron, 
 where it is to be well set up ; when so, the nuts of 
 the connecting bolts must be screwed up very tight 
 and the loose cement scraped off, after which the 
 face of the joint must be smoothed by a small trowel 
 so as to give the joint a workmanlike appearance. 
 The affinities between the ingredients of which the 
 above cement is composed, are such as cause a degree 
 of action and re-action amongst them, and also 
 between them and the surfaces of the iron flanehes ; 
 ultimately causing the cement and the surface of 
 the flanehes to become a species of pyrites, cohering 
 together with considerable strength and compact- 
 ness. 
 
 Figure 4, Plate XV III., is a view of flanch pipes 
 joined together. 
 
 Figure 5, Plate XVIII., represents what is 
 called “ a branch pipe.” It has a socket at one end 
 and a spigot at the other, between which a pipe 
 branches off with a curve; and according to the 
 diameter of the curved part, it is called a two, three, 
 or four-inch, &c. branch pipe. Its use is to lead off 
 from the larger mains into streets at right angles 
 to them. The pipe itself being of like diameter 
 
AND BURNERS. 
 
 341 
 
 with the larger main, and the branch answering to 
 the socket of the pipe which may be continued from 
 it. It is more convenient to have the branch cast 
 with a socket upon it for connecting the pipe which 
 joins it, as in that case the workman has more 
 room for making his joint, and his pipes follow in 
 regular succession for his work. When a pipe of 
 this description has a branch from each side, it is 
 called “ a double branch pipe.” 
 
 Figure 6, Plate XVIII., is a cast-iron pipe used 
 for the same purpose as the former ; but instead of 
 branching out with a curve, the pipe leads off at 
 right angles. Pipes of this description are termed 
 “ outlet pipes.” It is better that the outlet should 
 be cast with a socket upon it than with a spigot, for 
 the same reason as that given when speaking of 
 branch pipes. 
 
 Figure 7, Plate XV III., represents what is 
 called “ a diminishing pipe.” It is used when it is 
 required to decrease the diameter of the range of 
 main pipes, the socket at one end answering to the 
 spigot of the larger main, and that at the other 
 receiving the spigot end of the smaller main. 
 
 Figure 8, Plate XVIII. When a pipe is cast so 
 as to form a double bend, or somewhat to resemble 
 the Roman letter S, it is called “ an ess pipe.” 
 
 Figure 9, Plate XVIII., is “ a bend pipe.” It 
 is called a quarter-bend, eighth, or sixteenth-bend, 
 as it forms such part of the periphery of a circle, 
 
342 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 and according to the radius with which it may be 
 struck : the diameter of the pipe in inches is always 
 prefixed for the sake of distinction to the foregoing 
 denominations, as one, two, three-inch quarter-bend, 
 &c. The uses of the ess pipe and bend are too 
 obvious to require any explanation. 
 
 It is sometimes necessary to make a junction 
 between the spigot ends of two socket pipes. This 
 may be effected by means of “ the thimble-joint,” as 
 exhibited in figures 10, 11, and 12, Plate XVIII.; 
 or by “a double socket,” which is a casting of from 
 six to eight or ten inches long, and in diameter 
 about one inch more than the outer diameter of the 
 pipes to be connected : it is brought over the pipes, 
 the pipes to be joined in a way similar to what is 
 shown in the thimble-joint (figure 12, Plate XVIII.), 
 and jointed with gasket and lead in the ordinary 
 way, or by an iron-cement joint. The double socket 
 should be cast with a bead round each end outside 
 for the purpose of affording strength, and to prevent 
 its being split by caulking up the joint. 
 
 When it is requisite to carry a smaller main pipe 
 from a larger one already laid down, a part of the 
 main pipe is sometimes cut out and a branch pipe 
 introduced into the vacant interval. This object is 
 more easily effected by cutting a hole of the diameter 
 required through the side of the main, and by means 
 of two castings somewhat like the thimble-joint, 
 one of which must be cast with a socket upon it to 
 
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 -Larutans Tu-b & ird?erZ> y 20 **<Feb y i#4J 
 
 JDay&mtgM., utk'totte&t&ov 
 
AND BURNERS. 
 
 343 
 
 receive the spigot end of the pipe which is wanted 
 to be laid down, so that the pipe may be jointed 
 thereto in the usual way. 
 
 It will appear reasonable to most persons that the 
 main pipes for conveying gas may, with safety, be 
 cast much lighter than pipes of the like diameter 
 for conveying water ; for the internal pressure in 
 gas-pipes rarely exceeds an inch and a half head of 
 water. From the depth at which gas pipes are 
 generally laid, there can be no apprehension of 
 accident from external pressure ; and their situation, 
 when laid down, precludes almost all possibility of 
 their being much injured by oxydation outside. 
 
 In the arrangement of street mains, where new 
 works are to be built, the first thing to be con- 
 sidered for determining their size is to endeavour to 
 ascertain the quantity of gas which may be called 
 for in an hour for lighting public and private 
 lamps, fully equivalent to the conveyance of which 
 must be the diameter of the principal main pipe 
 from the manufactory to the point where the first 
 branch pipe is placed ; and, as the branches are 
 inserted, we must diminish the capacity of the lead- 
 ing main to nearly the amount of their respective 
 areas, so that, after the insertion of each of the 
 branches, the leading main may have its diameter 
 (consequently its capacity) lessened to nearly the 
 extent of the branch pipes proceeding from it : con- 
 sequently, though the first portion of the leading 
 
344 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 main may be fourteen or sixteen inches in diameter 
 or more, it may terminate in a pipe of two inches or 
 even one and a half inch diameter. 
 
 To ascertain the diameter of pipes capable of sup- 
 plying a certain quantity of gas in a certain time, it 
 is stated by persons conversant with the subject, that, 
 as precisely the same laws exist with respect to the 
 rate of discharge through orifices or tubes in or 
 connected with a reservoir, of elastic as of non-elastic 
 fluids at any pressure, so the initial velocity (or pri- 
 mary pressure) of the gas in the main pipe varies 
 directly as the square root of the column of water 
 pressing on the gas-holder, and inversely as the 
 square root of the gravity of the gas, and also the 
 volume of gas discharged from the end of the pipe 
 varies directly as the square of its diameter, and in- 
 versely as the square root of its length. All these 
 theoretical deductions are sufficiently justified by 
 practice, with the one exception, however, of the in- 
 verse ratio of the square root of length, which re- 
 gards pipes of nearly equal length only , with heavy 
 fluids, as water, according to Bossut, who states that 
 this rule, even in this case, is merely an approxima- 
 tion, not deduced from principle, but from experi- 
 ment (See Dr. Gregory’s Mathematics for Practical 
 Men, 2nd Ed.) ; consequently with respect to the 
 influence which the length of the pipe exerts upon 
 the volume of gas discharged at its end in compari- 
 son with that discharged at the end of a like pipe 
 
AND BURNERS. 
 
 345 
 
 of very different length, our safest plan is to found 
 and build up our knowledge thereof on the results 
 of experiment solely, for thereby alone can the amount 
 of friction, and consequent retardation, of the gas in 
 straight pipes be nearly found. In the practice of 
 gas-lighting, by far the greatest attention is paid to 
 the diameters of the mains being adequate to the 
 supply thence required, as in this point an error of 
 calculation is highly injurious ; the retardation of 
 the gas by friction along the sides of the pipes is very 
 seldom taken into consideration, it being found that 
 the pressure of the gas at any one point in the same 
 level is the same when no lights are burning, and no 
 leaks exist, and consequently the difference of pres- 
 sure felt at these scattered spots, when the burners 
 are lighted in the district, arises merely from the 
 decrease of volume produced at every burner by the 
 portion of gas drawn off from the length of main 
 between the burner and the gas-holder, or by a loss 
 of velocity, and consequently of volume discharged 
 caused by the gas having had to pass through bent 
 and angular branch and service pipes. That the re- 
 tardation, and consequent decrease of volume in the 
 gas discharged, arising from its friction, along the 
 straight side of a tube is inconsiderable, the foregoing 
 sentence in a wise explains ; of this we have also 
 ample testimony in filling the street mains with gas 
 on the first night of lighting up a town, when the 
 gas traverses the said mains, expelling the air with 
 
346 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 wonderful rapidity. The great levity of gas, how- 
 ever, counteracts many of the effects we might sup- 
 pose would be produced, and renders calculation very 
 uncertain on this subject, which is still well worthy 
 the investigation of the experimental analyst. 
 
 Dr. Ure, in his Dictionary of Manufactures and 
 Mines, has given a formula founded on the deduction 
 by experiment, that through a pipe 250 feet long, 
 one inch in diameter, 200 cubic feet of gas are trans- 
 mitted in one hour. He, calling the diameter D, 
 the volume of gas transmitted in one hour K, and 
 
 the length of pipe L, makes D = s/K^/jr, andsub- 
 
 455,000 
 
 joins a table of proportions hence said to be deduced. 
 A learned friend has favoured me with a formula 
 founded on Dr. Ure’s hypothesis, widely different 
 
 from the former, D = v ^^ - - , — — Y : this gives 
 
 ’ \12\ 10 2 . 2y/250.) 6 
 
 nearly the same results as those in the Dr.'s table. 
 
 The results of that table are altogether erroneous, 
 
 and more especially so in the case of pipes of large 
 
 diameter, the number of feet discharged being in 
 
 every instance strikingly too small for practice ; 
 
 which error principally arises from the wrongly 
 
 surmised influence of the length of the pipes upon 
 
 the velocity of the gas pervading them. For instance, 
 
 a pipe of 16.65 inches in diameter is there found 
 
 requisite, being 2,000 feet in length, for the hourly 
 
AND BURNERS. 
 
 347 
 
 ransmission at, I suppose, the ordinary one-inch 
 pressure of 8000 cubic feet of gas, whereas a pipe 
 of the foregoing diameter is found in practice ca- 
 pable of transmitting at one-inch pressure the very 
 much greater number of 1 10,000 cubic feet. Whence 
 we may reasonably conclude the practical inutility of 
 this rule, involving as it does results from friction 
 in the motion of gas actually impossible. 
 
 From experiments carefully made many years ago, 
 and confirmed by many subsequent ones, we are 
 aware that when the gas-holder is worked with a 
 pressure of one inch, a tube one quarter of an inch 
 in diameter will deliver 20 cubic feet of gas in one 
 hour, a tube half an inch diameter will deliver 90, 
 and a tube one inch in diameter will deliver 500 
 cubic feet of gas in one hour. Supposing, therefore, 
 that the inverse ratios of the length of the pipes have 
 very little if anything to do with the diameters of 
 the supply pipes, and that in practice we may take 
 the squares of the diameters for finding the sizes of 
 main pipes without any reference to their lengths, 
 having from actual experiment ascertained what 
 quantity of gas a pipe of one-inch bore will discharge 
 in one hour, when the gas-holder is worked at a 
 certain pressure, we may find the diameter of any 
 other pipe capable of delivering some other specific 
 volume of gas in a like time, under a similar or any 
 other pressure. 
 
 If we should be desirous of knowing what the di- 
 
348 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 ameter of the pipe ought to he which would supply 
 18,000 cubic feet of gas in an hour, when the gas- 
 holder is worked at one-inch pressure, we should 
 proceed thus 
 
 As the quantity of gas passing through a pipe 
 of one-inch diameter, the gas-holder working 
 at one-inch pressure. 
 
 Is to the quantity of gas required to be conveyed 
 through another pipe, the gas-holder working 
 at a like pressure, 
 
 So is the square of the diameter of the pipe whose 
 volume of discharge is known. 
 
 To the square of the diameter of the pipe for con- 
 veying the quantity of gas required, 
 
 C. feet. Cubic feet. In. 
 
 thus, as 500 : 18,000 : : l 2 : V36 = 6 inches. 
 
 In practice, however, in order to make ample al- 
 lowance for friction in the pipes, and other contin- 
 gencies, we may name 400 cubic feet as the quantity 
 which an inch pipe will deliver in an hour, when 
 the gas-holder is worked at one-inch pressure : pro- 
 ceeding under this datum to rind the bore of a pipe 
 sufficiently large for supplying 18,000 cubic feet of 
 gas in an hour, 
 
 C. feet. Cubic feet. In. 
 
 we must say as 400 : 18,000 : : l 2 : ^45 = 6, 7 
 inches the diameter of the required pipe. This rule 
 is quite enough to attend to practically ; but, in cases 
 where a greater nicety is required, and where it is 
 thought desirable to take into account the column 
 
AND BURNERS. 
 
 349 
 
 by which the gas is pressed, or the specific gravity 
 of the gas, what we said at page 344 will enable the 
 reader to follow up the matter so as to produce the 
 nicest theoretical results. 
 
 After what has been already advanced, the reader 
 will easily be able to calculate the size of main pipes 
 required for a gas manufactory where the quantity 
 of gas to be daily used is known. We shall there- 
 fore proceed to make a few observations relative to 
 the laying down of main pipes, to which the strictest 
 attention is indispensable. In a former chapter it 
 was observed that considerable condensation takes 
 place within the main pipes ; if, therefore, they be 
 laid perfectly horizontal, they will with difficulty 
 be kept unclogged by the condensed fluid. To fa- 
 cilitate the getting rid of condensed matter, the pipes 
 should be laid with a fall of about an inch in twelve 
 yards run, or a fall of about one foot in 150 yards : 
 if then the first 150 yards of main pipe be laid with 
 this fall, the next 150 yards are to have the same 
 rise. Under this arrangement, the water of con- 
 densation will fall to the lowest part, and a receiver 
 (a “ syphon” or “ tar- well”) being there fixed, will 
 receive it ; and thus the pipes can always be kept 
 clear of such a quantity of water as might impede 
 the passage of the gas, by examining the receiver 
 occasionally, and, when needful, drawing off the water 
 therein accumulated, the quantity of which may be 
 ascertained by unscrewing the cap on the suck-pipe 
 
350 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 of the receiver, and dropping a rod through that 
 pipe so as to touch the bottom, which on being with- 
 drawn will show the height at which the water stands 
 therein. Were this rule at all times attended to, 
 the introduction of many syphons and tar-wells 
 (receivers) on the range of main pipes might often 
 be dispensed with. In some cases the very uneven 
 surface of the street, &c., under which the pipes are 
 laid will not admit of this rule being carried fully 
 into effect ; but it may be observed, that a want of 
 care in this matter, on the part of the pipe-layer, is 
 often strikingly evident. 
 
 When the levity of the gas is considered, it is by 
 no means surprising we should notice with what 
 celerity it finds its way to the higher part of the 
 mains. So striking is the effect, that it must have 
 attracted the notice of almost every observer; for 
 when there has been an abundant supply of gas in 
 some situations in the metropolis, which are very 
 remote from the manufactory, persons residing in 
 other situations much nearer to the works have been 
 able to obtain but a very feeble light. If we were 
 asked from whence does this variability arise, we 
 should answer that we had no doubt but the more 
 distant points were situated on much higher ground 
 than the nearer, and that for that reason the gas 
 would have a natural tendency to press towards such 
 points. This levity of the gas has been particularly 
 observed in some of the theatres ; for it has often 
 
AND BURNERS. 
 
 351 
 
 been remarked there, when the lights to the lower 
 tier of boxes have burnt very feebly, that those near 
 the top of the house burnt with much vigour. Con- 
 sidering then the tendency which gas has to ascend, 
 it is evident that when towns are to be lighted with 
 gas which vary considerably in their level, it will 
 always be desirable to lay the pipes of the largest di- 
 ameter in the lowest parts, gradually decreasing their 
 size as they proceed towards those more elevated, if 
 it be intended that the gas should issue from burners 
 in both situations with a like impetus. 
 
 We need not add more relative to the main pipes, 
 and therefore turn next to the service pipes for 
 conveying the gas from the street mains into the 
 houses or other places where the gas is required. 
 These are made of welded-iron tubing, generally 
 made in lengths of nine feet with a female-screw 
 socket screwed upon one end, and having at the 
 other end a male screw with a similar thread in 
 order that they may be easily connected together* 
 Bends, T-pieces, &c., are made of the same material, 
 the former for insertion into a hole tapped and 
 drilled into the main pipe, or for making any bend 
 in the service pipe, and the latter for carrying off 
 branches from the service pipe to the right or left, 
 as may be needful. There are also used upon the 
 service pipe when circumstances render it necessary, 
 short lengths of tubing furnished with a double 
 socket called connecting pieces ; that is to say, pieces 
 
352 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 of tubing of from six to eighteen inches in length with 
 a male screw at one end and a female screw at the 
 other, wrought-iron crosses for branching off from 
 the principal service pipe in two directions and gun- 
 barrel syphons. The service pipes, bends connect- 
 ing, and T-pieccs are of different diameters, from half 
 an inch to an inch and half diameter. Pipes, bends, 
 &c., of larger bore are generally made of cast-iron. 
 The service pipe requires to be laid sloping, so as to 
 allow the condensations to drain off either into the 
 main pipe or the gun-barrel syphon. The service 
 pipe is generally carried by the gas company’s work- 
 men from the street main into the interior of the 
 house where the supply of gas is wanted, and the 
 end secured by means of an iron cap screwed thereon 
 to prevent any escape of gas till the gas-fitter has 
 prepared the inside work. 
 
 The best kind of tubing for internal work is what 
 is now well known to all gas companies and gas-fitters 
 as “drawn tin tube,” which can be connected together 
 by means of union joints or by soldering with the 
 blow-pipe. It is very stiff and yet can be bent where 
 necessary, so as to preclude the use of elbows, which 
 frequently could not be dispensed with when iron or 
 brazed copper tube were used for the internal work. 
 It is much more durable than either iron or copper 
 pipe not being acted upon by the gas which passes 
 through it; and where seen, it is not at all un- 
 seemly. 
 
AND BURNERS. 
 
 353 
 
 Various descriptions of burners have from time 
 to time been used, but all of them which are now in 
 use are in appearance nearly similar to those shown 
 in Plate XIX., which we shall now refer to. Fi- 
 gure 1 in that plate exhibits a vertical section of 
 the argand shank, or, as it is sometimes called, the 
 spout-burner. This burner is used when the fittings 
 are brought towards it in a horizontal direction. 
 It will be observed that it is constructed of two 
 concentric circles of metal joined to a small tube at 
 one side near the bottom, for screwing it to the 
 bracket or other fitting. These two circles are 
 connected together at the top by the circular steel 
 plate, as shown at figure 2, which is drilled with 
 the number of holes wanted. Figure 3 is a vertical 
 section of the argand crutch-burner. The body 
 of this burner is similar in all respects to that of the 
 shank-burner ; but as it is intended to be used at 
 the top of a pillar, the tubing is joined to the bottom 
 in a crutch-formed shape, from whence it derives its 
 name. The reader cannot fail, from a mere in- 
 spection of the figure, to observe the proportion of 
 parts maintained in its construction; but to give 
 him further explanation relative to the subject, we 
 subjoin the dimensions of the particular parts of 
 the body of the argand burners as shown in Plate 
 XIX. 
 
 Dimensions of the 12-hole argand burner : — 
 Outer diameter of the top -f-f- of an inch. 
 
 2 A 
 
354 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 Inner diameter of the top -i-f- of an inch. 
 Diameter of the circle of holes -f- „ 
 
 Diameter of each hole T V „ 
 
 The holes drilled in the top of this burner are 
 tV °f an inch from centre to centre. The diameter 
 of the bottom of this burner is -J- of an inch. The 
 bottom is bell-mouthed inside as shown in the figure. 
 This burner is 1 inch and in height, and the 
 distance from the top to the shoulder for supporting 
 the glass-holder is 1 inch. 
 
 Dimensions of the 15-hole argand burner: — 
 Outer diameter of the top 1 T V of an inch. 
 Inner diameter of the top 4Hr » 
 
 Diameter of the circle of holes -f- „ 
 
 Diameter of each hole, „ 
 
 The holes drilled in the top of this burner are of 
 an inch from centre to centre. The bottom of this 
 burner is 1-^ inch in diameter. The bottom is bell- 
 mouthed inside as shown in the figure. Height of 
 this burner 2 inches. Distance from the top to the 
 shoulder for supporting the gas-holder 1 J inch. 
 
 Before speaking of other burners, we must not 
 omit to mention that in order to secure a more 
 perfect combustion of the gas,- the supply of air 
 through the centre and between the exterior of the 
 argand burner and the glass chimney, Messrs. E. 
 and W. Dixon, Walsall, attached a conical piece to 
 the outside of the burners they manufactured which 
 rose just to the top of the burner, leaving a very 
 
AND BURNERS. 
 
 355 
 
 narrow passage for the air ; and, more recently, 
 Messrs. Platow, Morritz, and Co., of 40, Hatton 
 Garden, have manufactured an improved patent 
 argand gas-lamp, which is designated “ the double 
 cone burner.” The air-passage communicating with 
 the interior of the flame is contracted by inserting 
 therein a thin inverted metal frustum of a cone, 
 and the exterior of the flame is protected from an 
 excessive supply of air by a metal cone attached to 
 the glass-holder. This arrangement causes the light 
 produced to burn steadily and renders it very soft 
 and agreeable. A saving of gas is effected by its 
 use amounting to about ten per cent. ; whilst the 
 heat generated thereby is proportionably less than 
 when the common argand burners are used. 
 
 Plate XIX., figure 4, is a plan of the top of a 
 burner sometimes used as a street-light, and figure 5 
 is a vertical section thereof ; the dimensions of which 
 are as under : — 
 
 Diameter of the top, -§- of an inch ; it is drilled 
 with three holes each -g-V of an inch in diameter 
 and 4 of an inch asunder. It is 1-f- inch in length. 
 
 Figure 6, Plate XIX., is a vertical section of the 
 bat’s-wing burner. This burner is made of steel. 
 In it is drilled a hole of about -jV of an inch in 
 diameter, to within a small fraction of an inch of 
 the top, from whence is a slit across the burner, 
 falling about half-way of its length. When the 
 
 gas is turned to the burner and ignited, it exhibits 
 
 2 a 2 
 
356 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 itself in a flame somewhat similar to the shape 
 shown in the profile, figure 7. From this shape of 
 the flame it has derived its distinguishing appella- 
 tion. There is another burner sometimes called a 
 “ swallow’s-tail” and sometimes “a fish-tail” burner, 
 very similar in appearance, as to the flame it gives 
 out, with the bat’s- wing burner. The exterior 
 appearance of the burner is similar to that of the 
 bat’s-wing : — instead of the slit, as in that burner, 
 the fish-tail has two holes drilled obliquely to make 
 the flame cross. It is a very useful burner, and 
 consumes not much more than half the quantity of 
 gas that is consumed by the small sized bat’s-wing 
 burner. The combustion thereby is generally very 
 complete. 
 
 Figure 8 , Plate XIX., is the profile of a burner 
 from whence issues a single jet of flame. Figure 9, 
 profile of a burner yielding three jets of flame. 
 Figure 10 is the section of a fancy burner pro- 
 ducing eight jets. Figure 11, section of the union- 
 joint and the tube for connecting it. Figures 12, 
 13, and 14 are profiles thereof. Figure 12 shows a 
 part of the drawn tin tube, at the end of which, in- 
 tended to be introduced into the socket, is sometimes 
 soldered or screwed a brass collar. Figure 13 is 
 the socket, tapped for receiving the adjoining length 
 of tubing, upon which is soldered a screw fitting into 
 it. This part is shown by figure 14. When the 
 joint is to be made, the workman introduces the 
 
AND BURNERS. 
 
 357 
 
 tubing figure 12 through the socket figure 13, so 
 that the collar may rest against the bottom of the 
 socket. Upon this is placed a leather collar similar 
 to figure 15; and upon this again is screwed the 
 tubing shown at figure 14. It is evident that when 
 this is screwed up, the joint will be perfectly gas- 
 tight. 
 
 By examining the bat’s-wing burners, shown at 
 Plate XIX., figures 6 and 7, it will be seen that 
 they are screwed round the bottom outside, for the 
 purpose of being connected to a socket having a 
 corresponding female screw. When the tubing to 
 which they are to be attached rises vertically, the 
 upright socket, or cone, figure 16, is screwed upon 
 the top of that tube. This socket is tapped at each 
 end, the larger screw being that which is joined to 
 the tubing when connected ; the smaller one receives 
 the burner tip, whether “ bat’s-wing” or “ fish-tail.” 
 But when the tube of supply lies in an horizontal 
 position, the elbow socket, figure 17, is substituted 
 for the former. This socket is also fitted with two 
 screws, similar to those in figure 16. 
 
 Figure 18 exhibits a brass cross, used in forming 
 connexions. It is introduced when the fittings 
 branch off in three directions. To form the junc- 
 tions therewith four union joints would be required. 
 Each point of this cross is furnished with a screw 
 similar to that shown at figure 14 of this plate, and 
 intended to answer a like purpose. 
 
358 
 
 MAIN PIPES, GAS-FITTINGS, 
 
 Figure 19 shows a brass T-piece. It is used 
 when the fittings branch off in two directions. 
 There are provisions made in this for joining with 
 the tubing, similar to those described when speaking 
 of the cross, and the joint is made good in the like 
 manner. 
 
 Figure 20. A brass bend, sometimes used upon 
 the fittings ; each end of it is finished, so as to con- 
 nect with a union joint : it is not, however, used 
 where the fittings are of “ drawn tin tubing,” which 
 admits of being bent where needful. 
 
 Many devices might be introduced here of pillars, 
 brackets, pendants, chandeliers, candelabras, &c., 
 but they would only increase the bulk of the work 
 without adding to its utility. Persons desirous of 
 obtaining pillars, pendants, chandeliers, &c., will 
 find a great variety of patterns to choose from at the 
 establishments of all the gas-fitting manufacturers 
 in London and in the country, as pattern-books and 
 patterns in great variety are generally to be seen on 
 application to them. 
 
 It is of the utmost importance that the gas-fittings 
 in a shop, house, &c., should be judiciously arranged, 
 so that all the burners brought from one service 
 pipe may burn with an equal intensity of flame ; and 
 it is of no less importance, that the pipes and other 
 fittings should be done in the most workmanlike 
 manner, so that there shall not be the smallest leak 
 in any part of the work. The doing of all this 
 
AND BURNERS. 
 
 359 
 
 properly will be best effected by employing a respect- 
 able and experienced gas-fitter, wliicli can always be 
 done in towns where gas-works have been for some 
 years established ; but in such towns as may here- 
 after be lighted, we recommend, that the tradesmen 
 who undertake to do the fittings should each employ 
 one experienced gas-fitter, as the most certain means 
 of ensuring the work being properly done. For 
 want of such precaution, mistakes have arisen inju- 
 rious to the consumer and detrimental to the in- 
 terests of the gas manufacturer ; the former being 
 annoyed by escapes of gas, or by some of his lights 
 burning indifferently, speaks of the circumstance to 
 his neighbours, and thus prevents them from using 
 gas, so that thereby the manufacturer of that article 
 loses the profits upon a portion of gas which would 
 otherwise be supplied. 
 
360 
 
 CHAPTER XIV. 
 
 On the Gas-Meter. 
 
 Amongst the improvements which have been made 
 in the apparatus connected with the manufacture 
 and distribution of gas, the gas-meter holds an im- 
 portant place. When used between the purifier 
 and gas-holders, it measures and registers the quan- 
 tity of gas ready for use, which may be generated 
 when between the gas-holder and street mains ; the 
 quantity of gas supplied from the manufactory, for 
 lighting the public lamps and to meet the demand 
 by the private consumers ; and, when constructed 
 on a smaller scale and fixed in the houses of the 
 private consumers respectively, it points out the 
 number of cubic feet of gas that each may have 
 burnt in any specific time. 
 
 Before going into detail relative to the use of 
 this simple piece of mechanism, it may not be unin- 
 teresting to the reader should the history of its 
 origin be given, and the various changes it has 
 undergone, till brought to its present form. For- 
 merly, the general mode of charging persons for 
 gas, by the different gas companies, was a certain 
 sum per annum for burners of given dimensions. 
 
ON THE GAS-METER. 
 
 361 
 
 burning from sun-set till nine, ten, or eleven o’clock, 
 &c. But this mode neither answered the end of 
 the supplier nor that of the consumer of gas. The 
 improvident consumer was seldom careful to adhere 
 to the time of burning, or to the height of flame, 
 stipulated ; whilst he who was more scrupulous in 
 those points had no pecuniary advantage arising 
 from his carefulness ; consequently, an instrument 
 that would measure correctly the quantity of gas 
 used by each individual consumer became a thing 
 of importance ; for, by such a one, the improvident 
 would have to pay for his improvidence, whilst he 
 who burnt his gas carefully would be benefited 
 thereby in a pecuniary point of view, and the ma- 
 nufacturer would be certain of being paid in each 
 case the full value of the gas supplied. 
 
 The idea of selling gas by measure, instead of the 
 very unsatisfactory method of disposing of it by the 
 time of burning and size of burner, seems to have 
 originated with the Chartered (or Westminster) 
 Gas-light Company, in the year 1815; for, in the 
 latter end of that year, or very early in the ensuing 
 one, Mr. Samuel Clegg, who was at that time the 
 Company’s engineer, constructed a gas-meter of the 
 following description : — To a wooden frame were 
 attached two small cylindrical vessels, into each of 
 which worked a gas-holder, containing, we will say, 
 for the sake of speaking of a specific quantity, one 
 cubic foot. The pipes supplying these gas-holders 
 
362 
 
 ON THE GAS-METER. 
 
 were intended to be connected to the service pipe 
 leading into the house where the meter was to be 
 used. By means of a beam (supported at its middle, 
 and from the ends of which the gas-holders were 
 suspended over and into their respective vessels) 
 and a mercurial valve, the action of this recipro- 
 cating gas-meter was as follows : — the gas being 
 turned on from the street, filled one of these gas- 
 holders ; and when it became so, the beam we have 
 spoken of, acting upon a smaller beam attached to 
 the valve, shut off further supply to the one that 
 was full, and opened a communication to the empty 
 gas-holder, as well as from the full gas-holder to 
 the pipe for supplying the burners. By the time 
 the second gas-holder was full, the gas in the first 
 was consumed, and therefore it was down in its 
 tank, and the full one performed the action of 
 change, as the former had done when it was full of 
 gas. Thus they alternately were filled and emptied, 
 and the number of times they did so was pointed 
 out by an index, which consequently showed the 
 number of cubic feet of gas which had passed 
 through the meter. Had this answered the end in 
 view, it would doubtless have been adopted : the 
 process appeared in theory likely to have done so ; 
 but, on considering the nature of the valves and the 
 nicety of workmanship necessary, it is not surprising 
 that it failed in practice. Very considerable ex- 
 penses were incurred in endeavouring to bring it to 
 
ON THE GAS-METER. 
 
 363 
 
 perfection, and much time was spent upon it ; but, 
 ultimately, it was altogether abandoned. 
 
 Mr. Clegg next attempted to construct a gas- 
 meter having a rotary motion, instead of a vertical 
 one. It consisted of a cylinder divided into several 
 chambers, revolving upon a hollow axis enclosed in 
 another cylinder, which served as a case. For this 
 meter he obtained a patent, the specification with 
 elucidatory engravings of which was given in the 
 thirtieth volume of “ The Repertory of Arts” (Nos. 
 176 and 177, for January and February, 1817), to 
 which the reader who may feel curious as to the 
 matter is referred for its full description. It is 
 probable he will find some difficulty in understand- 
 ing its action ; for, perhaps, for an object which 
 was very soon afterwards accomplished by a method 
 exceedingly simple and beautifully mechanical, no- 
 thing of a more complicated nature could have been 
 devised than the rotary gas-meter, as described in 
 Mr. Clegg’s specification. The various ramifications 
 of scrolls and the friction arising from the axis of 
 his meter, that working in stuffing-boxes, were both 
 highly objectionable ; and, when we consider the 
 light pressure with which it was to work, we ought 
 to be surprised to find, under such circumstances, it 
 ever made one revolution. These were not the only 
 objections against it ; it was too large to be intro- 
 duced into the shops of tradesmen in general, who 
 seldom have much room to spare ; and, although it 
 
364 
 
 ON THE GAS-METER. 
 
 was put up in some places where many lights were 
 used, its performance was not such as could be 
 depended upon, and it was consequently removed. 
 
 When Mr. Clegg retired from the situation of 
 engineer to the Chartered Gas-light and Coke Com- 
 pany (on the 1st of April, 1817), the most improved 
 of his meters were from necessity used with stuffing- 
 boxes ; and, although he had done away with several 
 of the scrolls, shown in the drawing attached to his 
 specification, he had still two scrolls left in each cham- 
 ber, or division. And so far was he from appearing 
 to contemplate any other mode of introducing the 
 gas into the meter than that by a hollow revolving 
 shaft, that he had all his meters so made up to the 
 very time of his leaving the Chartered Gas Com- 
 pany. On the 4th of April, 1817, Mr. John 
 Malam, civil engineer, then in the employment of 
 the Chartered Gas Company, submitted a drawing 
 of a meter he had invented (similar to that as shown 
 at figures 3 and 4, Plate XX.) to the committee of 
 management of the gas-works situated in Great 
 Peter-street, Westminster ; and, on the 7th of that 
 month, he exhibited to that committee a meter such 
 as the drawings just mentioned describe, and put it 
 into action. Previous to the 13th of the same 
 month, it would appear Mr. Clegg had heard that 
 Mr. Malam was making gas-meters, for on that day 
 he wrote to Mr. Malam to guard him against in- 
 fringing upon his patent ; but, from the tenor of 
 
ON THE GAS-METER. 
 
 365 
 
 Mr. Clegg’s letter, it appears he had then no dis- 
 tinct idea as to what was Mr. Malam’s plan ; for, 
 he observes, the shutting off the gas may be effected 
 in various ways, that is to say, “ by valves, or sealing 
 the pipes with water.” If the reader examines the 
 figures representing Mr. Malam’s gas-meters, he will 
 find there is not a valve in either, and also that 
 there is not any pipe to be sealed with water. 
 
 Under such circumstances it cannot but be asto- 
 nishing to learn that, when Mr. Malain presented 
 his gas-meter to the Society of Arts, in 1819, Mr. 
 Clegg came forward to try to make it appear, in the 
 first place, that Mr. Malam’s improved gas-meter 
 was an infringement upon his patent, consequently 
 that the society could not award him anything for 
 his invention or improvement; and secondly, to 
 dispute about the priority of the invention, notwith- 
 standing the gas-meter for which Mr. Clegg took 
 out his patent, and the improved gas-meter which 
 Mr. Malam brought before the Society of Arts, 
 had nothing in common beyond the outer case in 
 which each was enclosed, and that each had a rotary 
 motion. It would not become us to enter into 
 detail relative to the proceedings which took place 
 before the Society of Arts on this occasion ; we may 
 however mention that, after a committee there com- 
 posed of some of the then most eminent chemists 
 and engineers in this or in any other country, had 
 for eight hours patiently investigated the business. 
 
366 
 
 ON THE GAS-METER. 
 
 they formed a resolution stating Mr. Mai am s gas- 
 meter new , ingenious, superior to other gas-meters, 
 and likely to he of great benefit to the public, 
 awarding him the society’s gold medal for his in- 
 vention. But, in consequence of some opposition 
 made to the resolution when it was brought before 
 the society, the matter was re-committed and under- 
 went another eight hours’ ordeal, from whence it 
 was sent again with the same resolution and the 
 same reward ; and on the 28th April, 1819, the 
 society, as a body, voted Mr. Malam their gold Isis 
 medal for his invention. 
 
 What we have now stated relative to the render- 
 ing the gas-meter really useful, we stated in the 
 former editions of this work, and probably should 
 not have thought of repeating it here, had we not 
 in several works in which the gas-meter has been 
 spoken of, seen the merit of the invention invariably 
 attributed to Mr. Clegg, and the improvements 
 solely to Mr. Crosley : and in no one case have we 
 noticed Mr. Malam as in any way connected with 
 those improvements, though they were the first step 
 towards causing the meter to be what it is. We 
 have been constantly connected with gas-works ever 
 since the period that Mr. Clegg conceived it prac- 
 ticable to produce a reciprocating gas-meter up to 
 the present day, and have been constantly and care- 
 fully on the watch to notice improvements as they 
 rose, and are quite prepared not only to say, but to 
 
ON THE GAS-METER. 
 
 367 
 
 prove also, by drawings in our possession made in 
 1816 (before Mr. Malam was connected with any 
 gas company), that be bad formed an idea relative 
 to employing tbe Archimedes screw as a gas-mea- 
 surer (precisely similar to wbat is used now) ; in tbe 
 beginning of which year be showed us a small one 
 he had made on that plan, having the L-shaped 
 pipe of supply, as shown at D, and receiving chamber 
 C C (figure 4, Plate XX.). As to our holding up 
 Mr. Malam as the inventor of the gas-meter in pre- 
 ference to Mr. Clegg, we do so under the most per- 
 fect conviction that we are correct : we have no 
 hesitation in admitting that Mr. Clegg was the first 
 person who patented a machine with a rotary 
 motion intended to measure gas ; but, at the same 
 time, we as strenuously assert that no useful instru- 
 ment for that purpose was made known till April, 
 1817, when Mr. Malam exhibited one in action at 
 the Westminster Gas Works. We have dwelt 
 rather longer upon this matter than we had in- 
 tended, in justice to Mr. Malam, and in defence of 
 what we had heretofore stated, thinking that, as the 
 gold Isis medal of the Society of Arts was all he 
 received for his invention, it would have been but 
 fair that, in connexion with the gas-meter, he should 
 have been allowed credit for what he did, instead of 
 every effort having been made to put his name aside, 
 to make room for that of another person. Some 
 one may say Mr. Malam only invented the L pipe 
 
368 
 
 ON THE GAS-METER. 
 
 and receiving chamber ; be it so : if that be admitted, 
 the rest follows, for the former completely changed 
 the mode of entrance of the gas into the meter, and 
 removed the great obstacle to the action of such an 
 instrument. 
 
 We shall not take up more of the reader’s time 
 on this point, but proceed to describe the meter first 
 submitted by Mr. Malam to the Committee of 
 Management of the Gas Works at Peter-street> 
 Westminster. 
 
 Plate XX., figure 4, is a section through the 
 axes, and figure 3 a section across the axis. 
 A A A A, figure 4, is the outer case of this meter, 
 within which the interior cylinder BBBB, with 
 the chamber C C attached thereto, revolves upon 
 the pivots a b, the former pivot ( a ) being attached 
 to the L-shaped pipe D, which brings the gas into 
 the chamber C C, from whence it is conveyed by the 
 openings a, b, c, d, figure 3, into the inner cylinder 
 A B C D, in rotation, as each of the said openings 
 rises above the level of the water expressed by the 
 dotted line in figure 3, and that marked c , figure 4. 
 
 On one side of the outer case is attached a vessel 
 of the breadth of the meter, which rises nearly from 
 the bottom to the height of the water-line in the 
 interior. This vessel is for the purpose of intro- 
 ducing the necessary quantity of water into the 
 meter, there being an opening through the outer 
 case within it, the proper height of the water will 
 
ON THE GAS-METER. 
 
 369 
 
 thus be known ; for so soon as the water rises above 
 the height with which the meter is intended to 
 work, it will run over the top of this vessel. The 
 opening at the top of this vessel is secured by a 
 small brass plug, which screws into it. The vessel 
 is kept closed when the meter is in action. When- 
 ever it may be desirable to empty the water out of 
 the meter, the introduction of a small syphon 
 through the opening to the bottom of the vessel 
 will accomplish it. The situation of this vessel is 
 shown upon figure 1, Plate XX., where the plug 
 we have been speaking of is marked g. 
 
 In front of this meter is a small vessel of semicir- 
 cular shape, rising rather more above the centre of 
 the meter than the water in the interior. It is 
 filled with water to form a joint, and through it is 
 brought the pivot b (figure 4), on which, as an axis, 
 is fixed a small pinion or crank acting upon the 
 necessary wheel-work, to point out the number of 
 revolutions made by the meter, or to express by 
 pointers, on a plate for the purpose, the number of 
 cubic feet of gas that has passed through it. This 
 meter being unincumbered by stuffing-boxes, and 
 revolving upon small pivots, is very little impeded 
 by friction, and the water rising above the centre 
 effectually precludes the possibility of a loss of gas. 
 
 The L-shaped pipe D conveys the gas into the 
 chamber C C, figure 4, and thence by the openings 
 abed , figure 3, into the chambers A B C D, the 
 
 2 R 
 
370 
 
 ON THE GAS-METER. 
 
 pressure of which gas between the surface of the 
 water and the divisional partitions, causes a rotary 
 motion to be given to the internal cylinder ; and 
 therefore it follows that, in one revolution of the 
 internal cylinder, every part of it must be filled 
 with gas. The capacity of that cylinder being 
 known, the quantity in cubic feet or in any other 
 measure is known also. 
 
 E is the exit pipe, which conveys the gas to the 
 burners when the meter is used for ascertaining the 
 quantity of gas consumed in a house or other build- 
 ing, &c., or for conveying it to the gas-holder when 
 it is constructed on a large scale for ascertaining 
 the quantity of gas generated. 
 
 On referring to figure 3, which shows the divi- 
 sional arrangement of the meter, the entrances to 
 and exits from the inner cylinder, we shall see its 
 action more clearly. Supposing the gas to be turned 
 on, and the stop-cock opened which conveys it from 
 the outer case when the opening a is just above the 
 water ; the opening cl being at the same time above 
 the water, that part of the chamber D which is 
 above the water will be the first filled with gas, and 
 the meter will be put in motion towards the left 
 hand till such time as the opening of exit from that 
 chamber 4 rises above the water, when the gas 
 
 o 
 
 which it contains will be allowed to escape into the 
 outer case. But before the opening of exit 4 rises 
 above the water, the opening of entrance d into the 
 
ON THE GAS-METER. 37 i 
 
 chamber D, will have sunk beneath the water, and 
 consequently, as the gas escapes from that chamber 
 into the outer case, its place will be occupied by the 
 water entering into it at d , as well as at the centre, 
 which allows a communication of water between all 
 the chambers to the level at which the water stands 
 in the meter. 
 
 The opening of exit 4 having risen above the 
 level of the water, the chamber D, as we have 
 already observed, is gradually filled therewith ; but 
 before it is so, the chamber A will have been filled 
 with gas, and the chamber B also nearly ready to 
 discharge itself ; for, almost as soon as the opening 
 of exit from the chamber D has risen above the 
 water, the chamber A will, by the opening «, be 
 nearly half filled with gas, and the opening b to the 
 chamber B, will be ready to rise above the water 
 also. The motion of the interior cylinder being 
 uniform, the exit 1 will next allow the chamber A 
 to commence emptying, which will not be entirely 
 accomplished till that chamber has sunk beneath 
 the water at the left hand side of the meter, the gas 
 at the time entering at b into the chamber B till 
 that is filled, and the exit 2 opened by its rising 
 above the water : before that takes place, the cham- 
 ber C commences filling, and fills gradually by the 
 opening c till the exit 3 is opened, and, when that 
 is the case, the chamber D will be in the same 
 situation as when the opening of entrance a was 
 
 2b 2 
 
372 
 
 ON THE GAS-METER. 
 
 just rising above the water, as has already been 
 described. Having described the action of this 
 meter through one entire revolution, it would be 
 but a repetition of the same thing to go further into 
 detail ; indeed it would be entirely useless to do so, 
 for if the reader draw a circle upon a card with the 
 radius of that circle which forms a section of the 
 outer case of the meter figure 3, and copy the 
 section of the interior cylinder A B C D of the same 
 figure, and connects the centres of the two by a 
 small pin to represent the pivot upon which the 
 interior cylinder works, he will have a simple 
 model of the gas-meter. Let him then fasten a 
 thread of silk across this model, at the height shown 
 by the dotted line, which will represent the height 
 of the water therein ; if he then moves the card 
 (which must be cut to the size of the interior cylinder 
 A B C E) as in the figure) representing the interior 
 cylinder from right to left, he cannot fail to under- 
 stand the meter’s action. 
 
 It may not be improper to remark, that such part 
 of the space between the concentric circles formed 
 by the interior cylinder and the external case will, 
 of course, when the meter is in action, be occupied 
 by gas above the level of the water; and therefore 
 the inner cylinder will have a velocity in proportion 
 to the diameter of the exit pipe, or the orifice sup- 
 plying the burners. Thus, for instance, if a meter 
 of sufficient capacity to supply ten lights be used to 
 
ON THE GAS-METER. 
 
 373 
 
 supply five lights, it will in this case make but one 
 revolution in the same time as it would have made 
 two had ten lights been supplied from it. 
 
 The meter as above described was found to answer 
 every purpose that was required ; but notwithstand- 
 ing its superiority over the patent gas-meter, the in- 
 ventor felt desirous of making a meter which would 
 occupy even less room than it did, but as he could 
 not decrease the diameter of the interior cylinder, 
 he adopted the following method, which completely 
 answered the purpose intended ; and, with certain 
 deviations from his plan, all rotary gas-meters slight 
 (having the axis upon which they work placed hori- 
 zontally) have been and still continue to be con- 
 structed. We now proceed to describe this im- 
 proved gas-meter. 
 
 Instead of there being a chamber C C, as described 
 in figure 4 attached to the interior cylinder, for the 
 purpose of receiving the inverted pipe D, the cham- 
 ber of this improved meter is at the centre, see 
 figure 1, Plate XX. By this contrivance the 
 meter, of which figure 2 of same plate is a section, 
 will be one-third less from A to A than one of the 
 same capacity made on the first plan, figure 4. 
 These two sections are of meters which, in one 
 revolution, allow equal quantities of gas to pass 
 through them, and they are laid down from the 
 same scale. 
 
 The outer case A A A A, the inner cylinder 
 
374 
 
 ON THE GAS-METER. 
 
 BBBB, the entrance pipe D, the exit pipe E, 
 the water-line c, &c., figure 2, being the same as 
 already described at pages 368, 369, and 370, pre- 
 ceding, a repetition of their uses, &c., in this place is 
 not necessary. We shall therefore turn to figure 1. 
 E F is a section of the chamber into which the L- 
 shaped D conveys the gas. A, B, C, D are the 
 chambers into which this meter is divided, and are 
 a range of gas-holders acting with a rotary motion 
 instead of a vertical one. These gas-holders receive 
 the gas by the openings a, b , c, d, and discharge 
 themselves into the outer case by the openings in 
 the rim of the interior cylinder 1, 2, 3, and 4. 
 
 Now, supposing the opening a to be just at the 
 top of the water, and the stop-cocks which allow 
 the gas to enter into and to discharge itself from 
 the meter to he opened, the opening d being above 
 the water, will allow that part of the chamber D 
 which is unoccupied by water, to be filled with gas, 
 the pressure of which between the surface of the 
 water and the divisional partition R, will cause the 
 internal cylinder to revolve on its axis towards the 
 left hand, which motion will bring the opening a 
 above the water ; and as that rises, the chamber A 
 will be emptied of water, and the space which the 
 water had occupied will he filled with gas. Whilst 
 this is doing, and prior to the opening b rising above 
 the water, the opening of exit 4 will have allowed 
 the gas to escape from the chamber D into the outer 
 
20 . 
 
 Jig i- ? 
 
 A A 
 
 T/uj s S TeUfc'Storis. 
 
 Zoruteru Tub * fry JE. Mefrerb, 20*'Tebrtta7y / lfr/Zl . 
 
 C.xiartcrro.deZfr 
 
 Day &Jfaghe., XxTijCog. to tfbtQiw&i' 
 
ON THE GAS-METER. 
 
 375 
 
 case. The gas will at this time he exerting itself 
 through the opening a , between the surface of the 
 water and the divisional partition S till the opening 
 1 is above the water. The chambers B and C 
 undergo the like operations, till the opening a is in 
 the position first described, and, when it is so, the 
 interior cylinder will have made one entire revo- 
 lution. 
 
 We would here, as on a former occasion, recom- 
 mend the reader to make a model on card-paper of 
 this meter to correspond with figure 1, marking 
 similar parts with similar letters and figures which, 
 having before him, will make the description given 
 more intelligible. 
 
 The utility of the gas-meter is now so well under- 
 stood that there is little occasion for saying much 
 about its mode of operation, as we expect we have 
 said quite enough to make those unacquainted with 
 its internal construction understand upon what 
 principle it acts, and that, if constructed properly, it 
 cannot fail to be a correct measurer. Most large 
 gas establishments have one or more fixed upon 
 their works for the purpose of registering correctly 
 the quantity of gas generated. No gas- work should 
 he without a station-meter, first, because without 
 one it is impossible to know what quantity of gas 
 may he produced, and secondly, because it would act 
 as a constant check upon the stoker, (particularly if 
 so constructed as to mark down the quantity of gas 
 
376 
 
 ON THE GAS-METER. 
 
 generated every hour as is frequently done), and we 
 must be aware that were that the only advantage 
 gained it would he an important one ; for from 
 idleness or inattention, he might during the night 
 neglect his fires or not charge his retorts properly. 
 In the former case, the heat of the retorts would be 
 so much decreased as to fail in extracting the gas 
 from the coal in a proper time, hence if he drew his 
 charge at the usual hour it would not be half carbo- 
 nized and the quantity of gas registered by the meter 
 would show that there had been some neglect, for 
 from the manager comparing what gas had been 
 made during the night with what had been made 
 during the same number of hours during the day, he 
 would at once notice the discrepancy, and then 
 ascertain whether the deficiency had arisen from 
 neglecting the fires or using smaller than the usual 
 charges in the retorts. As a matter of course 
 the station-meter would not be accessible to any 
 one save the manager of the works ; but the work- 
 men, knowing it would keep a correct account against 
 them of the gas made; would be very careful not to 
 neglect their duty. 
 
 We come now to speak of the gas-meter when 
 applied to the purpose of measuring and registering 
 the quantity of gas consumed in houses, &c., where 
 gas-lights are used. In doing so, we hope to make 
 it appear, that burning gas by meter is the most 
 advantageous method for the manufacturer as well 
 
ON THE GAS-METER. 
 
 377 
 
 as for the consumer. We shall assume, in the first 
 place, that the gas-meter is a correct measurer, and 
 we consider, when we reflect upon the vast number 
 of gas-meters which have been made (and for many 
 years used), of almost all sizes, with various contri- 
 vances of floats, &c., for keeping the water at a 
 certain height, and for shutting off* the supply 
 should the surface of the water from any cause fall 
 below its proper level, that in considering the gas- 
 meter a correct measurer, we are not assuming too 
 much. Assuming, then, that the meter measures 
 and registers correctly, it must be evident that the 
 gas manufacturer (with the exception of losses from 
 bad debts) will be paid for all the gas he supplies 
 to private consumers, those who burn extravagantly 
 paying more, and those who burn economically, less 
 than they had been in the habit of paying when 
 they were indiscriminately charged similar prices 
 for similar sized burners, supposed to burn with 
 equal heights of flame, and during a like number of 
 hours : and hence the economical consumer will he 
 benefited. Indeed, when shop-keepers and others 
 burn gas by meter, they have it in their own power 
 to use as little or as much as they please. In pri- 
 vate houses, hotels, &c., the gas-meter is indispen- 
 sable for the time of burning, and the number of 
 burners used at an average can hardly be so fixed as 
 to do ample justice between the Gas Company and 
 the consumer were no meter used ; whereas with the 
 
378 
 
 ON THE GAS-METER. 
 
 meter the consumer can light many or few lights 
 as required, the meter correctly registering the 
 quantity of gas consumed in both cases, from one 
 quarter of a year to another, so that it will always 
 show the quantity of gas consumed within some 
 specific period, thus preventing disputes and ques- 
 tions which, without it, must oftentimes arise. 
 By the consumer burning by meter, attending to 
 the height of the flame of his burners, and not 
 keeping them lighted longer than he may find ne- 
 cessary, he will soon find that a considerable saving 
 of expense will he the consequence, on comparing 
 what he may have to pay by meter, with what he 
 might have been in the habit of paying for his gas 
 when he burnt it by contract. We speak of a fair 
 and legitimate way of effecting a saving, without in 
 any way injuring the supplier ; we suppose he burns 
 his gas the same number of hours as he burnt it 
 when he paid for it by contract, and that he uses 
 the same number of burners, and we are prepared to 
 say if he does so, he will effect a very considerable 
 saving. In short, we are so persuaded of the utility 
 of the gas-meter, that we cannot fail most strongly 
 to recommend its use in all cases, to the parties who 
 manufacture as well as to those who consume the 
 gas, as being most equitable and satisfactory to 
 both parties, and most decidedly in favour of the 
 person who will cause attention to be paid to the 
 lights he may have in his establishment. 
 
ON THE GAS-METER. 
 
 379 
 
 We have already noticed that all the gas-meters 
 used at the present day are precisely the same in 
 principle, and nearly similar in construction, to the 
 one described by figures 1 and 2, Plate XX. Be- 
 fore we conclude this chapter, we may however add 
 that several attempts have been made (and in two 
 instances very large sums were expended) to pro- 
 duce a “ dry meter,” or one that would measure and 
 register the gas by an instrument not containing 
 water or any other fluid ; but as none of the dry 
 meters are used, or likely to be used, owing, first, to 
 a flexible material not being found which will with- 
 stand the action of coal-gas ; and secondly, to the 
 difficulties presenting themselves to prevent the 
 formation of such inlet and outlet valves as will 
 work with the requisite degree of certainty, it will 
 not be necessary to dwell further upon them in this 
 place. 
 
 Prior to those we have alluded to (which are of 
 recent date), a dry meter was patented by Mr. Malam 
 in 1822 or 1823, but it was never brought into use : 
 he however took out a patent in June, 1835, for a 
 wet meter, which, instead of revolving vertically 
 upon an horizontal axis, revolves on a nearly ver- 
 tical axis round a pivot upon which the interior 
 revolving drum rests. This meter has, up to the 
 present time, not been tried, except to a small extent, 
 upon gas-works with which the patentee is con- 
 nected. The specification of his patent may be seen 
 
380 
 
 ON THE GAS-METER. 
 
 in “ Newton’s London Journal,” vol. viii., at pages 
 139 to 144 inclusive, where various figures are given 
 explanatory of his invention. We may here remark 
 of this meter, that we have seen it in action, and 
 carefully examined its construction, and think well 
 of both ; consequently, regret it is not more gene- 
 rally known, and that the limits of this work will 
 not permit us fully to describe it : however, as we 
 have pointed out where a full description of this 
 meter may be seen, and as the work is easily ob- 
 tained (No. 50 thereof, conjoined series, price 2s. 6d., 
 contains the specification of Mr. Malam’s patent, 
 with figures of reference), the reader will find no 
 difficulty to prevent his making himself acquainted 
 with the principle upon which it acts and its mode 
 of operation. In perusing Mr. Malam’s specifica- 
 tion, and noticing the figures of reference, the reader 
 will not fail to observe that he had provided the 
 means, in the event of the water in his meter be- 
 coming, by evaporation or otherwise deficient, of 
 supplying such deficiency by means of a reservoir 
 of water placed on its top acting on the principle of 
 a bird fountain. We notice this because, in a patent 
 recently granted for a meter which has been named 
 (after the patentee) “ Hemming’ s Patent Protector 
 Gas-Meter,” one of the leading features is a fountain 
 of supply to keep the fluid in which the internal 
 drum works (which internal drum is precisely simi- 
 lar to that of the meters made by all gas-meter 
 
ON THE GAS-METER. 
 
 381 
 
 makers), at a uniform or fixed and certain level. 
 When we look at all the advantages the protector 
 gas-meter holds out, we cannot help observing that 
 a reservoir of supply to a meter which works in a 
 fluid (so the patentee states) found to be so little 
 subject to evaporation as to remove almost entirely 
 the defect of a variable level, we are inclined to con- 
 sider a fountain of supply a needless appendage, 
 however useful it may be, where water is used for 
 the interior cylinder or drum of the meter to work in. 
 
 Having made these remarks, we shall observe that 
 the Patent Protector Gas-Meter is, in principle and 
 in construction, precisely the same in all respects as 
 those in general use, with the following exceptions : 
 that is to say, first, a reservoir of supply connected 
 with a self-acting fountain for keeping the fluid in 
 which the interior drum works at a uniform level ; 
 secondly, small pieces of zinc attached to the brass- 
 spindle upon which the drum revolves, as well as 
 upon the train of wheel-work connected with the 
 counts for the purpose of neutralizing, by voltaic 
 influence, all chemical action upon the materials of 
 which the spindle and wheels spoken of are com- 
 posed ; and thirdly, adding to the water a sufficient 
 quantity of salt to form a strong brine, which it is 
 well known will not freeze even at much lower 
 temperatures than are ever experienced in this lati- 
 tude. This is the most recent improvement brought 
 before the public ; and, notwithstanding the remarks 
 
382 
 
 ON THE GAS-METER. 
 
 which we have deemed it our duty to make, we 
 consider that the means the patentee has adopted 
 for preventing the corrosion of the metal of which 
 the train of wheel-work is composed, will answer 
 the object he has in view ; and that his adopting 
 a saturated solution of sea-salt, instead of mere water, 
 for the drum of the meter to work in, will prevent 
 the inconvenience attendant upon the meters now 
 generally used from congelation during the severe 
 frosts which the climate of Great Britain is some- 
 times subject to. As regards the gas-meter, we 
 have no doubt but the time is near at hand when 
 further improvements will be made in its construc- 
 tion, in which its action will be simplified and its 
 bulk diminished, and consequently its cost lessened. 
 Meanwhile we are perfectly satisfied that all the 
 gas-meters manufactured by respectable tradesmen 
 may be relied upon as affording correct statements 
 of the gas which passes through them ; for should 
 the water in any rise above a certain level, it will 
 overflow the L-shaped pipe, and thus prevent the 
 gas from entering into, and consequently passing 
 through, the meter ; or should the water, by evapo- 
 ration or otherwise, sink too low, a float-valve will 
 fall upon the entrance pipe, and, in like manner, 
 nearly instantly shut off all communication from 
 the meter, so that in neither case can any gass pass 
 through it till the evil be removed. 
 
383 
 
 CHAPTER XV. 
 
 On the Governor, the Regulator, and Gas-Moderator. 
 
 The unfair manner in which many of the customers 
 of gas-light companies burnt their gas (previous to 
 the gas-meters being so very generally adopted) led 
 the persons who had the management of gas-works 
 to adopt measures for preventing the possibility of 
 its occurrence. The instrument for effecting this 
 object was originally called “ the governor ,” and, 
 more lately, also named “ the regulator ” The first 
 instrument of this kind which appears to have been 
 offered to the notice of the public was invented by 
 Mr. Samuel Clegg, and for it he obtained a patent, 
 under date the 9th of December, 1816. His inven- 
 tion is described in No. 176 for January, and No. 
 177 for February, 1817, of the second series of the 
 “ Repertory of Arts.” If the reader refers to the 
 description therein contained, he will understand 
 the properties of the governor, and perceive that its 
 action tends to keep the pressure constantly adequate 
 to the demand. It will effect the regulation in an 
 equal degree when the inequalities of pressure are 
 occasioned either by an increased or a diminished 
 consumption of gas, and also either by an increased 
 
384 
 
 ON THE GOVERNOR, REGULATOR, 
 
 or a diminished supply ; for the operation of it is to 
 adapt the orifice through which the gas passes to 
 the quantity required to pass, so as to keep the 
 volume discharged, and consequently the pressure 
 under which the gas may issue through each re- 
 spective burner, under all circumstances, nearly the 
 same. For the purpose of making the reader who 
 cannot easily refer to the numbers of the “ Repertory 
 of Arts,” understand the construction and principle 
 upon which the governor acts, we have given a 
 vertical section of one at Plate XXII. of this work, 
 figure 9. A B C D represents the outer case, which 
 may be made of sheet-iron, copper, or strong tin- 
 plates, with the top and bottom closed, all which 
 ought to be japanned inside and outside. JKLM 
 shows the form of the small gas-holder, which is 
 rendered more buoyant than it otherwise would be 
 by the air-vessel marked # * which goes round its 
 bottom. E, the inlet pipe, or that which brings 
 the gas into the governor ; F, the exit pipe. The 
 conical valve c, attached to the bottom of the up- 
 right spindle G, rises and falls with the gas-holder, 
 so as to contract or enlarge the orifice in the disc 
 I H (fixed in the pipe marked a a , above the entrance 
 of the pipe E into it), as the gas-holder ascends or 
 descends by the passing in or out of the gas. g h is 
 a shallow cup into which the outer case is fixed at 
 the centre of its bottom, or base, dde e are guide- 
 rods, for ensuring the vertical rise of the gas-holder. 
 
AND GAS-MODERATOR. 
 
 385 
 
 upon which slide the brackets ffff, attached to 
 the outside of the gas-holder. 
 
 If we suppose the governor to be connected to 
 the service pipe by means of the pipe E, and with 
 the pipe leading towards the burners, by means of 
 the pipe F, preparatory to bringing it into action, 
 it will he necessary to remove the lid at the top, and 
 to pour water into the case, or tank, till it rises to 
 within an inch of the top of the upright pipe a a. 
 This being done, the top must be put on, and made 
 gas-tight by a luting of bees’- wax and tallow ; the 
 nuts on the top of the guide-rods must also he 
 screwed up tight, and when this is effected, the 
 governor is ready for being used. The first thing 
 to be done, then, is to open the cock between the 
 pipe E and the main, which is placed on the service 
 pipe, and usually called the “ main cock.” When 
 that is done, if the gas-cocks between the governor 
 and the burners be gradually opened, they will allow 
 the gas to pass through the governor and escape 
 through the orifices of the burners where it is to 
 be consumed. It is evident that, under such an 
 arrangement, if the pressure from the street-mains 
 be, from any circumstance, increased, the gas will 
 flow with more rapidity into the gas-holder of the 
 governor. This increased impetus raises the gas- 
 holder in the tank, and, consequently, the cone c 
 along with it ; by this means lessening the orifice 
 of supply at I H, so that the supply of gas to the 
 
386 ON THE GOVERNOR, REGULATOR, 
 
 burners remains nearly unchanged, and the flame at 
 nearly its former height. The governor, if con- 
 structed to work at such a pressure as would ade- 
 quately supply a certain number of burners, would 
 prevent any consumer to that amount from burning 
 his gas too high, if he felt inclined so to do, for he 
 would always be obliged to open his cocks to their 
 full bore to enable him to obtain a light about three 
 inches in height ; — higher than which they would 
 not burn, let the pressure at the manufactory be 
 increased to what it might, as is evident from what 
 has been already stated. When the governor is 
 used for supplying ten lights, the cone should be 
 about three inches in length, and its base about 
 five-eighths of an inch in diameter : for four or five 
 lights, the cone need not be more than two inches 
 and a half long, and half an inch in diameter at its 
 base. The pipe of supply, E, and the exit pipe, F, 
 should, in either case, be three-quarters of an inch 
 in diameter. 
 
 Another description of governor, or regulator, 
 was constructed by Mr. Malam, soon after he had 
 invented the improved gas-meter. It was parallelo- 
 pipedal in shape, and served as a base, or pedestal, 
 for the meters of his invention to stand upon. 
 GHIK, Plate XX., figure 1, is a longitudinal 
 vertical section of this regulator, of the same length 
 as the diameter of the gas-meter with which it is 
 used. LMNO is a similar section of the gas- 
 
AND GAS-MODERATOR. 
 
 387 
 
 holder (constructed so as to act at a certain pres- 
 sure), which acts upon the pivot shown at M. P is 
 an upright pipe, which rises nearly as high as the 
 top of the gas-holder, when that is in a horizontal 
 position. Immediately over the centre of this pipe, 
 in the top of the gas-holder, is fixed a small hook, 
 to which is hung the wire attached to the cone, so 
 as to act freely in all directions. The wire for 
 supporting the cone is formed into two links, the 
 lowermost of which is connected to a hook rising 
 from the apex of the cone. Thus, as the top of the 
 pipe is entirely open, there cannot be any apprehen- 
 sion of the wire being bound or obstructed, so as to 
 prevent the cone from acting freely. The vertical 
 pipe Q is that by which the gas escapes towards 
 the burners. The manner in which the gas is 
 brought into this regulator will be better under- 
 stood by consulting the vertical transverse section 
 at figure 2. A A F G of that figure is a section of 
 the outer case, of a breadth equal to that of the 
 meter with which it is used. LMNO is a section 
 of the gas-holder, acting upon the pivots shown at 
 L and M. The upright pipe P, with the wire and 
 cone, have already been described in the explanation 
 of figure 1. S, figure 2, represents the pipe which 
 conveys the gas from the gas-meter to the regulator 
 by means of the pipe R, or from the service pipe 
 when the regulator is used without a gas-meter. 
 A pipe similar to that shown at S is also attached 
 
 2 c 2 
 
388 ON THE GOVERNOR, REGULATOR, 
 
 to the upright pipe Q (figure 1), for conveying the 
 gas from the regulator towards the burners. At 
 the bottom of the regulator, immediately beneath 
 the pipes P and Q, are soldered two screwed brass 
 rings, of about two inches in diameter, upon which, 
 when the regulator is in action, are screwed two 
 brass caps, having a short piece of pipe brazed into 
 the centre of each (which is cut out for the pur- 
 pose), with a cock for drawing off any condensation 
 which may descend into the pipes. The pipe 
 marked T, figure 1, is soldered upon the top of the 
 outer case of the regulator over a hole made therein. 
 This pipe is open at the top. It is for the purpose 
 of allowing the regulator to sustain a greater pres- 
 sure than it possibly could were the top entirely 
 closed. 
 
 On examining the sections of this regulator and 
 comparing them with the section of the governor 
 (figure 9, Plate XXII.), the reader will perceive 
 how far they differ in arrangement. If we begin 
 with the gas-holder, we shall observe that the base 
 of the regulator is much greater than that of the 
 governor, the latter being, for four or five lights, 
 not more than six inches in diameter, or an area of 
 about twenty-eight square inches ; whilst, , in the 
 regulator, it would be a rectangle, dimensions ten 
 inches in length by five inches in breadth, or an 
 area of fifty square inches. And as the length of 
 the gas-holder in the regulator is considerable, and 
 
AND GAS-MODERATOR. 
 
 389 
 
 that acting as a lever upon the fulcrum at M, any 
 change of pressure is immediately felt and checked ; 
 for there cannot possibly be that friction in its action 
 which occasionally impedes the operation of the 
 governor. The cone of the regulator is not made 
 so long and taper as the cone of the governor, con- 
 sequently a very small rise or fall of the gas-holder 
 is sufficient to bring it sensibly into action. As the 
 action of the cone in the regulator, as well as of that 
 in the governor, though somewhat different in each 
 case, is the means of keeping the lights at a proper 
 height, after what we have said about the governor, 
 we need not add any more here relative to the re- 
 gulator, as a mere inspection of the figures 1 and 2, 
 Plate XX., and figure 9, Plate XXII., renders our 
 doing so needless. 
 
 Figure 10, Plate XXII., is a vertical section of 
 a governor, or regulator, adapted for being placed 
 upon the leading main from the gas-works towards 
 the town or district to he supplied with light there- 
 from. The figure is supposed to represent the inlet 
 pipe A and the outlet pipe B as each being four 
 inches in diameter, and the centre pipe, in which 
 the cone and descending arrow are shown, of the 
 dimensions as given when describing figures 11, 12, 
 and 13, which show said pipe drawn to a larger 
 scale. The tank in which the gas-holder of this 
 governor works is represented as built of brick laid 
 in Roman-cement ; and, if so, it will be best that 
 
390 ON THE GOVERNOR, REGULATOR, 
 
 the side of the tank should not rise more than about 
 six inches above the floor of the building in which 
 the governor is placed. When the inlet and outlet 
 pipes are of four inches diameter, a tank three feet 
 diameter and two feet three inches deep will be 
 sufficiently large for the. gas-holder to work in. 
 The bottom of the tank is of solid brick-work 
 (about seven courses in thickness), the square up- 
 right centre pipe (figure 11) resting with its bottom 
 upon or in the second course. Every course of this 
 work should be well filled in with Roman-cement, 
 made of the consistence of grout. The side walls 
 C C are also laid in Roman-cement ; and, for greater 
 security under the bottom, as well as round the 
 tank outside, puddle should be used, as directed 
 when speaking of brick or stone tanks for the larger 
 gas-holders. The bottom and upright part of the 
 tank inside should also have a coat of Roman-cement 
 applied of about one inch in thickness. The gas- 
 holder may be made of No. 20 Birmingham wire- 
 gauge iron, or of strong tin plates ; its diameter, in 
 this case, would be two feet six inches, and its 
 height two feet three inches. The top of it had 
 better be of a convex shape. Upon the crown and 
 over the centre of the gas-holder is placed the 
 cylindrical vessel D D, intended to be filled with 
 water, and from three points of the upper edge of 
 which (in which S-hooks are inserted) the gas- 
 holder is suspended by means of the cords which 
 
AND GAS-MODERATOR. 
 
 391 
 
 pass over the pulleys shown, and then are connected 
 to a case E, containing shot, which works upon a 
 rod attached to the top of the gas-holder, directly 
 over its centre outside, which acts as a guide-rod, 
 causing the gas-holder to rise or fall vertically. 
 To the centre of the crown of the gas-holder inside 
 is secured the rod which supports the cone, which 
 rises and falls with the gas-holder, so as to close 
 partially or entirely the conical opening (shown at 
 figures 11 and 12), according as more or less gas 
 may be called for. The use of the vessel D D at 
 the top is to decrease the pressure gradually as the 
 shop and private lights are turned off, so that when 
 all are put out, the gas-holder may work at a proper 
 pressure for supplying public lights, and lights that 
 burn all night only, which object is effected by the 
 following means : — When the governor is first 
 brought into use, the vessel D D is filled with 
 water, and a sufficient quantity of lead-shot is put 
 into the counter-balance box E to cause the governor 
 to work with a sufficient pressure for affording a 
 proper supply of gas to the greatest number of 
 burners that may be lighted at one time during the 
 night. To the bottom of the vessel D D is con- 
 nected a piece of half-inch drawn tin tube, which 
 extends over the angle at the top of the gas-holder, 
 and to the end of it is attached a half-inch brass 
 cock, which is kept shut till the shops begin to 
 close. The workman then opens the cock, so as to 
 
392 
 
 ON THE GOVERNOR, REGULATOR, 
 
 allow the water to escape very slowly from the 
 vessel D D into the tank, till the vessel is entirely 
 empty, or till the pressure-gauge, placed in the 
 governor-house, indicates the pressure which is 
 needful for the night when the cock is closed, and 
 then no further adjustment of pressure is required. 
 This mode decreases the pressure much more equably 
 than it can be effected by hand, when the supply is 
 checked by decreasing the orifice of the main slide- 
 valve. The action of this governor being similar 
 to that for private houses, &c., already described at 
 page 385, when speaking of figure 9, no further 
 remark on that head is here required. 
 
 Figure 11 is a vertical section of the upright 
 square pipe for conveying the gas to and from the 
 gas-holder drawn on a larger scale than in figure 10, 
 upon which the dimensions are marked. The gas 
 enters by the pipe A, and rises up the partition 
 marked C, passing through the conical aperture 
 in the flanch (figure 13), which is jointed to the 
 top of the pipe. From the gas-holder the gas 
 descends down the partition E, (which is separated 
 from the partition C by a partition-plate D, cast 
 therewith to within about two inches of the bot- 
 tom,) and thence by the pipe B towards its de- 
 stination. To the bottom is jointed and secured, by 
 screw bolts, the blank flanch b c ; and previously to 
 the governor being used, water is poured down this 
 pipe till it rises as high as the dotted line a a , 
 
AND GAS-MODERATOR. 
 
 393 
 
 consequently the partition-plate D is sealed, and 
 the gas entering by the pipe A, cannot find its way 
 to the pipe B without passing through the conical 
 opening e into the gas-holder, and thence down the 
 partition C. i represents the rod by which the 
 cone j is suspended from the centre of the crown 
 of the gas-holder. 
 
 Figure 12, Plate XXII. In this figure the out- 
 line marked d, f \ h , b , g , c represents the plan of 
 the flanch at the bottom of the pipe (figure 11), and 
 of the blank flanch bolted thereto. **** repre- 
 sents the top of the pipe, showing the plan of the 
 partitions C and E and the position of the partition- 
 plate D ; also a plan of conical opening marked e, as 
 shown in section in figures 11 and 13. 
 
 Figure 13, Plate XXII. Vertical section of a 
 flanch with a conical opening for the cone j figure 
 11 to work in. It is to be jointed over the par- 
 tition C, figure 11, the cone being first dropped 
 down that partition before the gas-holder is sus- 
 pended. The rod i must have near its upper end a 
 collar, and a thread above it to pass through the 
 top of the gas-holder at the bottom of the vessel 
 D D, where it is secured in its place by a nut and 
 washer, &c., a little tow, well soaked in tallow, 
 being first twisted round the spindle beneath the 
 washer, so that when the nut is screwed up, the 
 gas-holder may, where the spindle passes through 
 it, be perfectly gas-tight. 
 
394 ON THE GOVERNOR, REGULATOR, 
 
 Figure 14, Plate XXII., is a vertical section of 
 the gas-moderator, as manufactured by Messrs. 
 Plato wand Co., 40, Hatton Garden, and 145, High 
 Holborn, London. The object of the manufac- 
 turers of the gas-moderator is, by that machine, 
 to render the flames of gas-burners steady and 
 uniform throughout the evening, and to prevent 
 those fluctuations of light occasioned by any sudden 
 increase or decrease of pressure. In short, it is 
 intended to produce precisely the same effects as 
 the governor already described by figure 9, Plate 
 XX., at pages 384, 385, and 386. The gas-mode- 
 rator is much more portable than the governor, and 
 can be attached to a single burner, in which case 
 it is not more than two inches in diameter, and 
 about as much in height. It is made ornamental in 
 its appearance. One for regulating from eight to 
 ten lights is not more than about three inches in 
 diameter, and about three inches in height. In 
 figure 14, Plate XXII., A is the gas inlet pipe ; 
 G the valve regulating the supply of gas to be 
 admitted ; C the rod which works the valve (some- 
 thing similar to the key of a wind instrument) ; 
 D D a flexible membrane (or diaphragm) coated 
 with gold-leaf and fitted gas-tight to the rod C 
 above and to a metal disc below ; E a spiral spring ; 
 F an adjusting thumb-screw by means of which the 
 situation of the valve G must be so adjusted as to 
 afford just a sufficient supply of gas to the burner 
 
AND GAS-MODERATOR. 
 
 395 
 
 or burners when there is the least pressure upon 
 the mains. Should an increase of pressure be put 
 upon the mains, or should an increase of pressure 
 occur from the putting out suddenly of many lights, 
 it will be immediately felt in the gas-moderator, 
 and acting upon the upper surface of the diaphragm, 
 D D, will press it downwards. The rod C, being 
 connected with the diaphragm, will be carried down- 
 wards with it ; and as it is also attached to the 
 crank that works the valve, the valve G will be 
 pushed towards the aperture through which the 
 gas enters, so that the opening will be less and the 
 quantity of gas admitted into the moderator under 
 this increased pressure will not be more than when 
 the pressure was less and the aperture greater. On 
 the pressure being again diminished, the spiral spring 
 pushes up the diaphragm, consequently the rod, 
 which acts upon the crank of the valve G, draws 
 the valve back, and thus enlarges the aperture 
 through which the gas enters. In this figure, B 
 represents the outlet which is furnished with a 
 union joint for connecting to the pipe which leads 
 towards the burners. The inlet pipe A is also 
 furnished with a similar union joint. 
 
 Either the governor or the gas-moderator may be 
 usefully employed in churches or other places of 
 worship, and in places of public resort to prevent 
 the adjustment of the lights by means of the regu- 
 lating or main cock, by which operation sometimes 
 
396 ON THE GOVERNOR, REGULATOR, &C. 
 
 a needless alarm is created which has occasionally 
 been attended by very serious consequences. In 
 shops, and more particularly for the lights in shop- 
 windows, where a sudden flaring up of the gas 
 might be injurious to goods there exhibited; in 
 private houses, hotels, warehouses, manufactories, 
 and workshops, where an equal supply to the bur- 
 ners on each floor is of importance, the governor or 
 gas-moderator ought to be used. Either will bene- 
 fit the consumer by keeping all his burners at a 
 proper height so as to prevent smoke from the gas, 
 too much heat being generated, and any risk arising 
 from fire. Indeed, it must be evident that an in- 
 strument constructed on such principles that the 
 consumer may adjust it so as to cause all the gas- 
 lights he may have in his establishment to burn 
 with a certain height of flame and no more, whether 
 he has fifty or five or one lighted, must be very 
 valuable, as it will save him from much personal 
 attendance, and be a complete check against care- 
 lessness or the wasteful expenditure of gas by any 
 persons in his employment. 
 
397 
 
 CHAPTER XVI. 
 
 On Tests. 
 
 In the chapter on the purification of gas, it was 
 stated to be necessary that tests be occasionally em- 
 ployed for ascertaining whether, by the purifying 
 process, the gas is effectually deprived of the sulphur- 
 etted-hydrogen gas, carbonic-acid gas, &c., which are 
 evolved with the proto and bi-carburetted-hydrogen 
 gases in the retorts. That this should be done fre- 
 quently appears requisite ; for it is absolutely neces- 
 sary that the manufacturer should supply his cus- 
 tomers with pure gas only ; and unless he causes 
 tests to be frequently taken, it is next to impossible 
 for him to know whether the gas he may supply be 
 pure or impure. 
 
 In some manufactories, a contrivance has been 
 adopted intending to indicate and register the im- 
 purities of the gas, and at the same time to denote 
 the periods when they occur. It consists of a cir- 
 cular card fixed upon an axis, communicating with 
 a time-piece. Upon this card are described three 
 circles, each divided into twenty-four equal parts, by 
 lines radiating from the centre. The outer circle 
 
398 
 
 ON TESTS. 
 
 is coated with acetate of lead, in solution, or some 
 other of the usual tests for detecting sulphuretted- 
 hydrogen gas, and the middle one with tincture of 
 litmus, or with a decoction of red cabbage for detect- 
 ing carbonic-acid gas. Upon each of these circles 
 a very small jet, of gas is made to play constantly. 
 The inner circle is divided into twenty-four equal 
 parts, marked from one to twelve day, and from one 
 to twelve night, and the card performs its revolu- 
 tion in twenty-four hours, consequently the im- 
 purities and the time when they happen are said to 
 become exactly registered, and that, by changing 
 these cards daily, a perpetual register is obtained. 
 F rom our own experience in the manufacture of gas, 
 we should be much inclined to doubt that the method 
 we have alluded to would indicate the time when the 
 most impure portions of gas would be passing through 
 the orifices spoken of, and playing on the card, 
 for the action of such gases, from their great diffu- 
 sibility in the atmosphere, could not be confined to 
 a point, consequently, unless the card were of large 
 diameter when the gas was very impure, its action 
 upon the card would extend itself over a considerable 
 portion thereof, and in consequence leave the time 
 of its greatest impurity but very faintly indicated. 
 A much more certain method for securing a con- 
 stant supply of pure gas is to have a small pipe con- 
 nected to the top of each of the purifiers, fitted with 
 a stop cock, (which we shall designate the “ test 
 
ON TESTS. 
 
 399 
 
 stop cock”) and a very small single jet burner, or 
 so that a piece of drawn tin or brass tube, bent at 
 right angles, can be attached to the cock by means 
 of a union joint. At this place, from time to time, 
 the gas ought to be tested by one or other of the 
 modes about to be mentioned, till the test solution 
 or test paper indicates a very trifling departure from 
 purity, and so soon as that is the case the purifier 
 must be shifted. If the first trial be carefully noted 
 down, and the manufacturer continues to use the 
 same number of retorts, the same description of coal, 
 and works with similar charges as to time and quan- 
 tity of coals, he will not find it necessary to take 
 tests except once or twice between the times of his 
 changing the moistened lime or lime and water in 
 his purifiers, that is to say, about an hour before the 
 time he thinks (from a week’s very careful observa- 
 tion) the purifying medium has become so saturated 
 with impure matter as to be no longer able to per- 
 form the purifying process perfectly. 
 
 We now proceed to describe the tests we have 
 been in the habit of using for detecting sulphuretted- 
 hydrogen gas, carbonic-acid gas, and ammoniacal 
 gas. 
 
 Tests for detecting sulphuretted-hydrogen gas. 
 
 1. Nearly fill a two-ounce phial with distilled 
 water, and add thereto as much acetate of lead as it 
 will take up : shake up the mixture, and then, with a 
 
400 
 
 ON TESTS. 
 
 camel’s-hair pencil, wet therewith a piece of writing- 
 paper. When this is done, open the “ test stop- 
 cock ” already mentioned, and hold the side of the 
 paper wetted with the mixture for a few seconds 
 close to the aperture of the single jet burner, so that 
 the gas may play upon it. If the gas thus tested 
 contain one cubic foot of sulphuretted hydrogen in a 
 volume of 20,000 cubic feet of carburetted-hydro- 
 gen gas, it will produce a sensible discoloration. 
 
 2. Add to two ounces of distilled water four 
 grains of nitrate of silver, and so soon as that is 
 dissolved, it is to be applied in the same way as 
 the first test. It is a more delicate test for sul- 
 phuretted-hydrogen gas than the solution of acetate 
 of lead. The phial in which this test is kept should 
 be coated with tinfoil, to protect the test from the 
 blackening action of the rays of light. 
 
 The above tests are what we have been in the 
 habit of using for detecting the presence of sulphur- 
 etted hydrogen, and in our practice we have generally 
 used pieces of writing-paper about three inches 
 square, noting at the back of them the time when 
 the test was taken. So soon as the test was taken, 
 the test paper was laid between the leaves of a small 
 blotting-book kept for the purpose, and thus became 
 a register of the purity of the gas at the times the 
 tests were taken. In this way we may ascertain the 
 presence in coal-gas of extremely small quantities of 
 sulphuretted hydrogen, and form a tolerably near 
 
ON TESTS. 
 
 401 
 
 estimate of its proportion, when too minute to be 
 otherwise measured, by comparing the shades of 
 colour given with a series that has been prepared 
 for the purpose, by exposing slips of card or writing- 
 paper prepared as we have described, to mixtures of 
 sulphuretted-hydrogen gas and common air in known 
 proportions. It will be necessary to keep the ni- 
 trate of silver tests, when discoloured by the action 
 of the sulphuretted hydrogen, in a book, excluded 
 from the light, as they are liable to change of 
 colour from exposure thereto. 
 
 3. Mix three grains of acetate of lead with two 
 ounces of distilled water in a wide-mouthed bottle, 
 by shaking the mixture well together, and it will 
 have a milky appearance. If it be then taken to the 
 “ test stop-cock,' and the bent-pipe we have already 
 mentioned be inserted into the bottle for about half 
 a minute, during which time the gas to be tested 
 will bubble up through the mixture — if the gas is 
 freed from sulphuretted hydrogen, the test will re- 
 main white and milky ; but if it contains sulphur- 
 etted hydrogen, it will appear dark and cloudy. This 
 is a delicate test for discovering minute portions of 
 sulphuretted-hydrogen gas, with which it forms a 
 black precipitate. 
 
 4. Into a wide-necked bottle put an ounce of dis- 
 tilled water, and then impregnate it with the gas 
 which is desired should be tried, by blowing it 
 through the water, as described in the third or pre- 
 
 2 D 
 
402 
 
 ON TESTS. 
 
 ceding test. If it contains sulphuretted hydrogen, 
 it will produce a foetid odour, resembling the smell 
 of putrefying eggs. Should a single drop of the 
 solution of nitrate of silver, mentioned as the second 
 test, of acetate of lead, mentioned as the first test, 
 or of chloride of bismuth, be dropped into water 
 impregnated with sulphuretted-hydrogen gas, in the 
 manner already described, it will instantly be ren- 
 dered black. 
 
 5. Impregnate distilled water with the gas to 
 be tried in a wide-mouthed bottle, and then let 
 it be poured upon a plate, or into a small evapo- 
 rating basin. Hold close to the surface a slip of 
 paper wetted with a solution of nitrate of silver. 
 If sulphuretted-hydrogen gas be present, it will es- 
 cape from the fluid and cause the paper to be black- 
 ened. 
 
 Test for detecting either sulphuretted-hydrogen 
 gas or carbonic-acid gas. 
 
 Tincture of litmus (the natural colour of which 
 is a dark blue, inclining to purple) may be employed 
 for detecting either of the above gases, the action 
 of either of which, upon the tincture of litmus, pro- 
 duces a redness. If a solution of pure barytes be 
 mixed with the tincture thus coloured by sulphu- 
 retted-hydrogen gas, no precipitate will be formed ; 
 but if the change of colour had been effected by 
 carbonic-acid gas, it will immediately become turbid, 
 and a soluble precipitate will fall down with effer- 
 
ON TESTS. 
 
 403 
 
 vescence in pure dilute muriatic or nitric acid. By 
 this criterion the action of carbonic-acid gas upon 
 litmus from that of sulphuretted-hydrogen gas may 
 be distinguished. 
 
 Tests for detecting carbonic-acid gas. 
 
 1. If an ounce of distilled water he tinged 
 slightly blue by tincture of litmus, and then im- 
 pregnated with the gas desired to he tried, if car- 
 bonic-acid gas he present it will speedily produce 
 the reddening effect. 
 
 2. Into an ounce of distilled water, impreg- 
 nated with gas, let fall twenty or thirty drops of 
 sulphuric acid. If carbonic-acid gas be present, 
 many minute air-bubbles will be rapidly disengaged. 
 
 Test for detecting ammoniacal gas. 
 
 To determine whether the gas has acid or alka- 
 line properties (the latter are characteristic of the 
 presence of ammonia), a small slip of litmus-paper 
 may be first introduced into it. If it be reddened, 
 the gas must he acid ; if not changed, a slip either 
 of litmus -paper reddened by vinegar, or of turmeric- 
 paper, may he introduced into it, when the alkaline 
 nature of the gas will be indicated by the usual 
 change of colour to blue or brown. Acid and alka- 
 line gases cannot both exist together in the same 
 mixture, as they immediately condense each other 
 into a solid form. 
 
 Were it necessary, many more tests might be 
 
 2 d 2 
 
404 
 
 ON TESTS. 
 
 added ; but these already mentioned are amply suf- 
 ficient for all practical purposes. Should the reader, 
 however, be desirous of pursuing his inquiries still 
 further into this subject, we refer him to the 2nd 
 volume of Dr. Henry’s “ Chemistry,” or to Dr. 
 Reid’s “ Chemistry,” in either of which works he 
 will find abundant information relative to chemical 
 re-agents, or tests. 
 
405 
 
 CHAPTER XVII. 
 
 On the Chemical constitution of Coal-Gas. Observations upon its 
 applicability to Illumination and other uses. 
 
 If we consider the qualities of coal-gas and the 
 various other products, gaseous, liquid, and solid 
 obtained from pit-coal by distillation in close ves- 
 sels, we are led to conclude that it is composed of 
 carbon, hydrogen, azote (or nitrogen), oxygen, sul- 
 phur, some earthy matter, and about one per cent, 
 of hygrometric water. That such are the compo- 
 nent parts of coal, found by its decomposition by 
 heat, was an opinion long ago entertained by several 
 eminent chemists ; but the most exact proportion of 
 each ingredient in the composition of specimens of 
 divers coals from the great coal basins, has been but 
 very lately ascertained by chemical analysis. We 
 are indebted for the most perfect elucidation of this 
 very important subject to the gas manufacturer, to 
 the researches of Mr. Thomas Richardson, aided by 
 Professor Liebig. As the bounds prescribed in this 
 work do not allow us to enter into such details as 
 those chemists give, we refer the scientific reader to 
 the 13th volume of the “ London and Edinburgh 
 Philosophical Magazine,” page 121, for August, 
 1838 ; or the “ Transactions of the Natural History 
 
406 
 
 ON THE CHEMICAL 
 
 Society of Newcastle-upon-Tyne,” vol. ii., page 401, 
 in which works the comparative quantities of the 
 constituents of coals of different localities are stated 
 at great length. 
 
 In the process of the distillation of pit-coal, in 
 order to obtain the greatest quantity of the carbu- 
 retted hydrogens, we find that when it is acted upon 
 by the heat most appropriate for its decomposition, 
 a red heat visible in full daylight, the zero point of 
 Wedge wood’s pyrometer, or 1077° Fahrenheit, the 
 following gaseous and vaporous products, partly in 
 mechanical, partly in chemical, mixture, are evolved, 
 viz., pure hydrogen, sub-carburetted hydrogen (1 
 atom carbon 4 - 2 ats. hydrogen), bi-carburetted hy- 
 drogen (1 at. carb. + 1 at. hydr.), aqueous vapour 
 (1 at. hydr. + 1 oxygen), ammonia (3 ats. hydr. 
 + 1 at. nitrogen), carbonic-acid gas (1 at. carb. + 2 
 oxyg.), (these two last-named products speedily 
 coalesce and form carbonate of ammonia), carbonic 
 oxide (1 at. oxy. 4- 1 carb.), sulphuretted hydrogen 
 (1 at. sulphur. 4- 1 at. hydr.). The proportion of 
 these products varies considerably according to the 
 different decomposing heats the coal is subjected to, 
 as also according to the respective descriptions of 
 coal used. All the above-named products, however, 
 and a residuum of about 60 parts of solid carbon 
 and other matter, or coke, in 100 parts of coal, con- 
 stantly attend the distillation of pit-coal in close 
 vessels; but from the inadequacy of the simple re- 
 
CONSTITUTION OF COAL-GAS. 
 
 407 
 
 torts, arising from the extent of their heated surface 
 being insufficient to diffuse upon the vaporous pro- 
 ducts nascent from the coal, the quantity of caloric 
 requisite to disengage the greatest possible quantity 
 of the carburetted hydrogens therefrom, much of 
 those valuable matters, into the composition of which 
 carbon and hydrogen enter, are merely volatilized 
 not decomposed, and leave the retort in a state of 
 vapour, as tar, ammonia, and water. The obviation 
 of this improvidence is the object of a patent, which 
 bids fair to cause a sensible revolution, from its utility 
 and simplicity combined, in the expense consequent 
 on the present mode of generating light-gas, the 
 merits and a description of which patent will be 
 discussed and given in the next chapter. 
 
 We are not to suppose that pit-coal is the only 
 substance which affords carburetted-hydrogen gas. 
 It is found ready formed on the surface of stagnant 
 waters and in marshes. In hot weather we may 
 observe large bubbles thereof rise through the for- 
 mer. This gas may be collected. For distinction’s 
 sake it is called the carburetted-hydrogen of marshes. 
 
 It contains, in the purest state in which we can 
 collect it, about twenty per cent, of azote. When 
 any kind of vegetable matter is submitted to such a 
 heat as is necessary to decompose it, it gives out 
 carburetted-hydrogen gas, and the proportion thereof 
 is greater when the process is carried on in close 
 vessels. Charcoal, wetted with water and submitted 
 
408 
 
 ON THE CHEMICAL 
 
 to the action of heat in a crucible or earthen retort, 
 will produce a gas which consists partly of carbonic 
 acid and partly of carburetted hydrogen. This gas 
 is also procured by making spirit of wine to trickle 
 through red-hot tubes, or by distilling camphor 
 therein. In short, carburetted-hydrogen gas is 
 obtained by distilling, in close vessels, either coal, 
 oil, wood, wax, or tallow, or all animal and vegetable 
 substances, into the composition of which carbon 
 and hydrogen enter. There is a curious variety of 
 carburetted-hydrogen gas obtainable from ether or 
 alcohol, which, when brought into contact with 
 chlorine gas, generates an oil that is heavier than 
 water, whitish and semi-transparent ; and which, if 
 kept, becomes yellow and limpid. It has a fragrant 
 smell, a sweetish taste, and is partly soluble in water, 
 to which its peculiar smell is imparted. This gas 
 has, by some, been termed oily carburetted hydrogen ; 
 by others bi-carburetted hydrogen (or olefiant) gas. 
 It is composed of carburetted hydrogen, super-satu- 
 rated with carbon. In the distillation of most kinds 
 of coal, a portion of this species of gas always comes 
 over with the common carburetted hydrogen : it 
 must be evident that the coals which yield the 
 greatest quantity thereof will always best answer 
 the gas-light manufacturer’s purpose, for the illumi- 
 nation afforded by coal-gas is chiefly produced by the 
 incandescence of particles of carbon precipitated, 
 in the flame, and consequently that gas which has 
 
CONSTITUTION OF COAL-GAS. 
 
 409 
 
 the most carbon in its composition possesses the 
 greatest illuminating power. 
 
 The gas produced during the first stage of the 
 distillation of pit-coal is heavier than that evolved 
 during the latter part of the process, but even then 
 it is very much lighter than atmospheric air. We 
 may state the average specific gravity of carburetted- 
 hydrogen gas obtained from coals (the heaviest about 
 *650, and the lightest about *406), at *528. When 
 procured from oil, it varies from *939 to *700, show- 
 ing an average of *8195. 
 
 We know, from the results of many experiments 
 made for the purpose of ascertaining what quantity 
 of gas could be obtained from a given quantity of 
 coal-tar, that one pound thereof yields about ten 
 cubic feet of carburetted hydrogen, mixed with 
 much olefiant gas. The number of cubic feet of gas 
 obtainable from one pound of coal-tar, as above-men- 
 tioned, is the average quantity which was produced 
 by the distillation of coal-tar in vessels of a syphon 
 shape, lying nearly horizontally. The tar was 
 allowed to enter the distillatory vessel, near the 
 mouth-piece of the upper leg, and to trickle over a 
 continuous red-hot surface till its decomposition 
 was properly effected. 
 
 Many individuals have attempted to generate gas 
 on a scale adequate to illuminating purposes from 
 coal tar ; amongst others the Marquis Montauban 
 recommends that the coal-tar be placed in a vessel 
 
410 
 
 ON THE CHEMICAL 
 
 with the requisite quantity of water, which mixture 
 is to be kept constantly agitated or stirred. This 
 vessel is to be placed above the distillatory vessel, 
 so that the mixture of tar and water may enter into 
 it in very minute quantities, through a bent-pipe 
 (syphon shaped), so fixed as to be kept always sealed 
 with the mixed fluid to prevent the escape of gas 
 from the retort. This contrivance formed a part 
 of the Marquis’s patent taken out in February, 1838, 
 for improvements in gas apparatus ; the specification 
 and drawings of which may be seen in “ Newton’s 
 London Journal,” conjoined series. No. 82, for 
 January, 1839. The Comte de Val Marino has 
 recently endeavoured to combine the vapour of coal- 
 tar with aqueous vapour for the purpose of procuring 
 from the mechanical mixture of the two, carburetted- 
 hydrogen gas. He uses three retorts, one of which 
 is supplied with water from a syphon ; another 
 contains coal-tar, the steam from one and the 
 vapour from the other are to pass simultaneously 
 into the third, where the steam and vapour combine ; 
 and that combination is resolved by heat into car- 
 buretted-hydrogen gas. This operation, though 
 feasible in theory, cannot be carried out in practice 
 on account of very many weighty objections. 
 
 Having alluded to the production of carburetted- 
 hydrogen gas from coal-tar, we return to what is 
 our more immediate object, the procuring of it from 
 coal, and this leads us to remark, that if we are de- 
 
CONSTITUTION OF COAL-GAS. 
 
 411 
 
 sirous of working the retorts to advantage, they 
 should always he kept at a bright cherry-red heat, 
 visible by day-light. Gas of the best quality in the 
 greatest quantity is thus produced. Here we must 
 stop, and not by any mistaken notion increase the 
 temperature to a higher degree ; for, if we bring it 
 to a white heat, the retort is in danger of being 
 melted, and the gas given out by this over-dose of 
 caloric ; from the operation of many chemical 
 affinities called thereby into action, is chiefly a mix- 
 ture of carbonic oxide and hydrogen gas, yielding a 
 bluish flame of but small illuminating power. Some 
 of the species of Newcastle coals abound with py- 
 rites, or sulphuret of iron ; these coals when distilled 
 produce a considerable portion of sulphuretted hy- 
 drogen, and such coal-gas consequently requires 
 great attention to be paid to its purification. 
 
 In the “ Repository of Arts,” vol. ii., No. 36, page 
 341, is an account of the quantity of carburetted- 
 hydrogen gas obtained from wood, by Messrs. So- 
 holowsky and Horrer of St. Petersburgh, and in 
 the first number of the “ Quarterly Journal of Sci- 
 ence and the Arts” is a paper by Mr. Brande, on the 
 application of coal-gas to illuminating purposes ; he 
 mentions the quantities of gas obtained from coal, 
 from the common willow, from the mountain-ash, 
 from white-birch, and from hazel-wood, all well 
 dried, and also from writing-paper. The results are 
 ol little value to the practical man, and are alluded 
 
412 
 
 ON THE CHEMICAL 
 
 to only for the purpose of calling the attention of 
 the curious towards them. 
 
 With respect to the superiority of light afforded 
 from carburetted-hydrogen gas, it may be observed, 
 that it has a decided advantage over other lights ; for 
 it has been ascertained that there is considerably 
 less carbonic acid produced by its flame than by the 
 flame of oil, tallow, or wax, and consequently on the 
 score of health, it is more adapted to small or ill- 
 ventilated apartments. Dr. Henry states that 100 
 cubic inches of carburetted-hydrogen gas require 220 
 cubic inches of oxygen for their combustion, and 
 produce 100 cubic inches of carbonic acid : 100 cubic 
 inches of the same gas obtained from wax, require 
 280 cubic inches of oxygen, and produce 137 cubic 
 inches of carbonic acid ; and 100 cubic inches of the 
 same gas, procured from lamp-oil, require 190 cubic 
 inches of oxygen for burning, and produce 124 cubic 
 inches of carbonic acid. Can any proof be desired 
 more decisive than the above (setting aside its eco- 
 nomy) in favour of using gas-lights ? But to pro- 
 duce good light, it is necessary that the gas should 
 be well purified ; for if it is not deprived of the sul- 
 phuretted hydrogen, it emits sparks, and produces, 
 when burnt, a portion of sulphurous acid by the 
 union of the oxygen of the air with the sulphur 
 precipitated during the process of combustion. 
 
 Although coal-gas, if allowed to escape unburnt, 
 emits a disagreeable odour, yet this circumstance 
 
CONSTITUTION OF COAL-GAS. 
 
 413 
 
 argues nothing against the use of it ; for, we are 
 well aware, if a candle or lamp be blown out, during 
 the time the wick of either may remain ignited, a 
 smell equally disagreeable is produced. It is not in- 
 tended that gas should be allowed to escape unburnt, 
 and it is most satisfactorily established, that during 
 its combustion (if properly purified) it is void of all 
 smell whatever. It may be considered that the 
 smell of unburnt gas is a fortunate circumstance 
 rather than otherwise ; for whenever there may 
 happen to be a leak in the pipes or gas-fittings, 
 thereby it is easily found ; whereas, if the gas were 
 void of smell, leaks might exist, and in some cases, 
 the most serious accidents occur from the explosive 
 nature of the gas when mixed with atmospheric air, 
 in the proportion of one part by volume of the former, 
 to nine of the latter, and in a close place, should a 
 light happen to be brought into contact with the 
 mixture. We therefore consider, that any attempt 
 to deprive coal-gas of its smell altogether, would 
 render the use of it likely to be dangerous. 
 
 As to the possibility of an explosion taking place 
 under ordinary circumstances, when we consider the 
 quantity of gas requisite to form an explosive mix- 
 ture with common air, we need hardly apprehend 
 it except in very small and confined places. A room 
 fifteen feet square, and nine feet high, if entirely 
 closed, would require an hourly escape of five cubic 
 
414 
 
 ON THE CHEMICAL 
 
 feet of gas into it for nearly forty-eight successive 
 hours, in order to be filled with an explosive mixture. 
 But in rooms having a fire-place, doors and windows 
 not fitting very closely, were there an escape of gas, 
 the stop-cock to a burner having been left open, or 
 from leaks, a very considerable time must elapse be- 
 fore a sufficient quantity of gas can escape and mix 
 with the air in the room so as to make an explosion 
 inevitable on a person with a light entering therein. 
 We opine that, under these circumstances, an explo- 
 sion would hardly take place, and indeed the expe- 
 rience of many years fully justifies us in this opinion. 
 
 Coal-gas possesses one great advantage over all 
 other artificial lights, inasmuch as it may be made 
 to burn in any direction, and thus to throw the 
 strongest rays of light upon the spots where they 
 are most wanted, a thing very difficult to effect 
 wherever lamps or candles are used. By turning the 
 cock which supplies the gas-burner, a brilliant flame 
 can be instantaneously produced ; and that again, in 
 as short a time lowered to such a degree as scarcely 
 to be perceived. In either case the light will remain 
 for any length of time without any variation of 
 height or intensity of flame, provided the pressure 
 or supply of gas remain the same. The application 
 of gas-lights for the purposes of lighting streets, 
 church'es, chapels, houses, &c. &c., is now too well 
 known to require any details thereof; we may, how- 
 
CONSTITUTION OF COAL-GAS. 
 
 415 
 
 ever, notice that we still are of the opinion expressed 
 in the former editions of this work laid before the 
 public, in which we stated, that it might be advan- 
 tageously used in light-houses, and suggested means 
 for distinguishing one light-house from another 
 merely by the varied arrangement of the lights. 
 
 Coal-gas has of late years been applied to the 
 heating of churches, chapels, shops, counting-houses, 
 &c., instead of stoves, hot-air flues, steam, or hot- 
 water pipes, and has been found to answer the pur- 
 pose intended. It is burnt in stoves constructed for 
 the purpose, of such different sizes as the size of the 
 place to be warmed may render necessary. For an 
 ordinary-sized room, a gas-heating stove, twelve 
 inches diameter and about two feet in height, will 
 be sufficiently large : it may be constructed of cast 
 or plate-iron, with a register at the top, and open 
 at the bottom. In the interior near the bottom is 
 a brass pipe formed into a ring, and perforated 
 with small holes about an inch apart, this ring being 
 connected to a pipe leading from the service pipe. 
 When the stove is required to be used, the gas is 
 turned into the circular pipe and lighted, and the 
 heat generated ascends between the outer case and 
 an internal cone through the register at the top, 
 whence it diffuses itself equably over the apartment, 
 the temperature of which can be regulated to pre- 
 cisely what may be desired, by increasing or decreas- 
 
416 
 
 ON THE CHEMICAL 
 
 ing the gas flame by means of the stop-cock. This is a 
 very cleanly mode of warming rooms ; and if the gas- 
 heating stove be properly attended to, by no means 
 an expensive one. It is particularly applicable to 
 churches and chapels, to counting-houses, shops, and 
 all those places where the dust from a coal fire is 
 objectionable. 
 
 Coal-gas has also been used to some extent for the 
 purpose of cooking by means of the gas-cooking 
 apparatus, which is in arrangement nearly similar 
 to the gas-heating stove, except that it is not fur- 
 nished with the internal cone. The gas-cooking 
 apparatus, as well as the gas-heating stove, are manu- 
 factured by Mr. Charles Rickets, of 5, Agar-street, 
 Strand, London, and also by several other gas-appa- 
 ratus manufacturers in town as well as in the 
 country. 
 
 Coal-gas cannot be manufactured, by means of the 
 apparatus at present known, with economy, on a 
 small scale, as, for instance, where but three or four 
 lights are wanted ; it is in the large way only that 
 the manufacture thereof can be profitable. For the 
 lighting of towns and large manufactories, it is most 
 advantageously employed, but in the former case, 
 were the street-lamps only lighted, it would yield 
 but little profit to the manufacturer, to answer 
 whose views many shops and interiors of public and 
 private buildings ought to be supplied therewith 
 
CONSTITUTION OF COAL-GAS. 
 
 417 
 
 from the same range of main pipe as feeds the 
 street-lamps. The price of coals can exert but 
 little influence upon the price of the gas produced 
 from them, for where coals are plentiful, it follows 
 that they will be cheap, and hence also will be the 
 coke produced therefrom ; but where coals are dear, 
 the coke will also sell for a higher price and find 
 a more ready market. 
 
418 
 
 CHAPTER XVIII. 
 
 On the Gas-Regenerators, and other Apparatus devised for most 
 effectually converting into carburetted-hydrogen gas the Tar 
 and Ammonia produced from the coal in the retort, as they, in a 
 state of vapour, are on their passage to the Hydraulic Main. 
 
 It has for many years been well known to the gas- 
 manufacturer that carburetted-hydrogen gas can be 
 obtained by the decomposition of liquid coal-tar by 
 heat; but no apparatus has as yet been constructed 
 sufficiently simple and effective profitably to effect 
 that object. Many years ago, I was induced to 
 adopt a modification of the present gas-generating 
 apparatus, designed to cause light gas to be evolved 
 from the vapour of tar and ammonia remaining sus- 
 pended in the gas after it had passed through the 
 hydraulic main, which project was at that time 
 thought likely to succeed in practice, but never- 
 theless on trial was found useless, and consequently 
 abandoned. The old beaten routine of gas ma- 
 nufacture in the generating department to all ap- 
 pearances continued everywhere to be persevered 
 in up to the year 1830, when Mr. James Down, 
 of Leicester, took out a patent for improvements 
 in making gas for illumination, the specification 
 and drawings of which may be seen in “ Newton’s 
 
ON THE GAS-REGENERATOR, ETC. 
 
 419 
 
 London Journal” (second series) for June, 1831, 
 No. 39, page 131. The method he proposed 
 was, that the gas obtained from two common re- 
 torts should be made to pass through a vessel con- 
 taining ignited carbonaceous matter placed above 
 them, and heated by the same furnace, prior to its 
 reaching the hydraulic main. This vessel was 
 divided into a number of vertical compartments, 
 which were filled with charcoal or coke by means of 
 movable lids on their tops, which charcoal or coke 
 became red hot, and whilst so the gas had to force 
 its way through it. The patentee says, “ I claim as 
 my invention, first, making or generating gas for the 
 purposes of illumination by passing crude or nascent 
 gas through a long stratum of ignited charcoal or 
 coke, whereby I evolve an additional quantity of 
 gas from certain portions of the residuum, which, in 
 the modes hitherto adopted, are useless for those 
 purposes ; and whereby I do away with the necessity 
 of a separate purifying apparatus : and, secondly, 
 the improved box or vessel contrived to obtain that 
 object by means of the extended stratum of charcoal 
 or coke hereinbefore described.” We never saw Mr. 
 Downs apparatus in operation, nor are we aware 
 of its having been used elsewhere than at Leicester ; 
 and from our own experience in the manufacture of 
 gas, we are led to give it as our opinion, that the 
 gas thence evolved must have been very deficient in 
 purity and illuminating power, and the vessel into 
 
 2 e 2 
 
420 
 
 ON THE GAS-REGENERATOR, ETC. 
 
 which the charcoal or coke was introduced must 
 have been found exceedingly troublesome, particularly 
 if as described in the specification and drawings 
 thereunto attached, setting aside difficulties which 
 must inevitably arise by working more than one 
 retort into it, particularly at the times when the 
 retorts had to be drawn or charged. 
 
 For the next improvement which has fallen under 
 our notice, a patent was taken out by Mr. John 
 Malam, of Hull, in June, 1835, the specification 
 and descriptive figures of which are given in “ New- 
 ton’s London Journal,” (conjoined series,) No. 50, 
 for May, 1836, at page 137. In the specification, 
 Mr. Malam states, that “ the improvements in the 
 apparatus for generating gas for illumination con- 
 sist in an addition to the retort commonly in use 
 for the purpose of effecting a more perfect decom- 
 position of the vapour arising from the coal in the 
 process of distillation, and rendering that part which 
 would otherwise be condensable into tar and am- 
 monia into a permanent elastic gas, thereby greatly 
 increasing its quantity and rendering the gas more 
 pure and of a better quality. Retorts,” he adds, 
 “ of the ordinary construction, with my improve- 
 ments, may be worked at a much lower temperature 
 than usual, as that portion of the vapour which 
 passes off from the first process of distillation is 
 perfected by the second, and thus the durability of 
 the retort is considerably increased : which advan- 
 
ON THE GAS-REGENERATOR, ETC. 421 
 
 tages are obtained from the ordinary quantity of 
 coal and at no additional labour or expense in the 
 mode of heating or working.” As our attention 
 has been particularly called to this invention, and 
 as we have now had the results of the gas-regene- 
 rator (such is the designation Mr. Malam gives to 
 his invention) constantly before us for a period of 
 upwards of eighteen months, verifying to the fullest 
 extent the remark made by us when alluding to this 
 patent in the preceding chapter at page 407, we 
 furnish a plate of the gas-regenerators, which we 
 shall in the first place describe, and after having 
 done so, transcribe, for our reader’s consideration, 
 the results obtained by their use, carefully noted by 
 us and others at those places where we have had 
 them in operation. 
 
 Plate XXI., figure 1, represents a front elevation 
 of three elliptical retorts, (the retorts may be of any 
 shape but the elliptical, large D or kidney-shaped 
 answer best,) with their “ regenerators ” and con- 
 ducting pipes. Figure 2 is a sectional elevation of 
 the furnace, retorts, and regenerators with their 
 flues ; and figure 3 is a longitudinal section of the 
 same ; a, a, a being the mouth of the retorts through 
 which they are charged with coal; b, b, h, the con- 
 necting pipes through which the gas and vapour 
 produced by the distillation in the retorts ascend to 
 the regenerators ; c, c, c are the mouth-pieces of 
 the regenerators ; and d, d, d are the ascending 
 
42*2 ON THE GAS-REGENERATOR, ETC. 
 
 pipes from which the gas passes to the hydraulic 
 main e, and from thence it is conveyed to the con- 
 denser, purifiers, and gas-holder in the ordinary 
 manner. It will be seen that the regenerators are 
 fixed above the retorts, supported by an arch, with 
 openings f, f , /, f, /, f, f left for the purpose of trans- 
 mitting the heat to them more readily, but not in- 
 tended for the passage or draught of flame. The heat 
 passes from the furnace g g, circulating under the 
 two lower retorts and through the openings h , h, Ji, 
 Ji, h , h to the upper retort, above which it operates 
 upon the regenerators through the openings marked 
 f above described ; after which the current of flame 
 passes through the flues at the extremity of the 
 furnace as seen at i, i, i, better shown in the hori- 
 zontal section figure 4, and vertical section figure 5, 
 and from thence over the regenerators to the main 
 flue or chimney k, as will be seen by the direction of 
 the arrows. It will be perceived, by reference to the 
 longitudinal section figure 3, that the coal under 
 distillation in the retort is discharging its gas and 
 vapour through the connecting pipe b, to the rege- 
 nerator, which is furnished with an internal cy- 
 linder l /, (through which the gas and vapour per- 
 colate,) left somewhat shorter than the external 
 cylinder, that the gas and vapour may pass out at 
 its extremity into the body of the regenerator, and 
 be also adequately submitted to the action of the 
 heat therein. It will be seen that the internal 
 
ON THE GAS-REGENERATOR, ETC. 423 
 
 cylinder has a mouth-piece m , separated from that 
 of the regenerator for the purposes of adjusting it 
 over the opening of the connecting pipe b, and 
 cleaning it from any deposit ; and the cylinder may 
 be removed altogether at pleasure, and a fresh one 
 substituted without disturbing the regenerators, 
 that it may be more readily and effectually cleansed. 
 After the gas, with the vapours suspended therein, 
 has been submitted to the action of the heated in- 
 ternal surfaces of the regenerators, it passes off in- 
 creased in volume and in a more pure and perfect 
 state, through the ascending pipes d, d, d , to the 
 hydraulic main e, as will be clearly seen in the 
 figures. For the better illustration of the regene- 
 rator with its internal cylinder and connecting 
 pipes, we have shown, at figures 6 and 7, the front 
 or mouth end upon a larger scale ; and the same 
 letters of reference point out the parts corresponding 
 to those shown in the above-named figures. Figure 
 5 is a section of three regenerators of a D shape. 
 Figure 8, front view of the lid for the internal 
 cylinder of the regenerator, of which a section is 
 shown at m, figure 7. It is to be noticed, that the 
 retorts and regenerators may be of different forms 
 from those we have described, and they may be set 
 differently, and with a different internal arrange- 
 ment in the regenerator ; but in this improved 
 process, each retort is provided with a separate 
 regenerator, which is heated by the same furnace as 
 
424 
 
 ON THE GAS- REGENERATOR, ETC. 
 
 the retort, and this may be effected in various ways, 
 the one shown in the plate being merely for the 
 purpose of illustration. 
 
 In consequence of our having been for several 
 years almost constantly absent from England, our 
 attention was not called to the regenerators till the 
 autumn of 1839, since which time they have had 
 our almost undivided attention ; and the more we 
 have seen of their operation, so much the more we 
 are prepared to pronounce our decided opinion in 
 their favour. In order that the reader may know 
 upon what such an opinion is founded, we observe, 
 that having learnt the regenerators had been used 
 at the Wisbeach gas-works from the time that the 
 patent had been taken out, we were invited to go 
 down thither in November, 1839, where we found 
 twelve elliptical retorts, each furnished with its 
 regenerator, in precisely the same way as shown in 
 Plate XXI. The manager of the Wisbeach gas- 
 works was then using Whitton Park coal for making 
 gas ; and, with his assistance, we pursued a course 
 of experiments for a week, measuring the gas pro- 
 duced during the day-charges, which were weighed 
 to the retorts by noticing the rise of the gas-holder, 
 and making the necessary allowances for the change 
 of temperature ; there not being then any station- 
 meter at the Wisbeach gas-works. The results of 
 these experiments showed that during the time they 
 were carried on by the aid of the regenerators (the 
 
ON THE GAS-REGENERATOR, ETC. 
 
 425 
 
 retorts were each charged with 160 pounds of coals, 
 and worked off at eight hours’ charges), one ton of 
 Whitton Park coal produced from between 11,500 
 to 12,000 cubic feet of gas. Only one-third of the 
 quantity of tar and ammonia usually produced by 
 the distillation of coal in simple retort, was found 
 in the tar-well in these experiments. After having 
 ascertained so much, we proceeded to the Peter- 
 borough gas-works, where the same description of 
 coals were used (part of the same cargo as had been 
 delivered at Wisbeach, and upon which the trial 
 had been made there), precisely the same description 
 of retorts, and similarly set, but without the regene- 
 rators. We pursued our experiments there, and 
 found that from the same description of coals, and 
 retorts worked at similar heats, the average quantity 
 of gas procured from one ton of Whitton Park coal 
 was between 8,500 and 9,000 cubic feet. Up to 
 February, 1840, we had frequent reports of the 
 operations at Wisbeach ; all of which corroborated 
 our own experiments. In that month we went to 
 Wisbeach again, had a station-meter fixed, and 
 made some trifling alterations in the internal ar- 
 rangement of the regenerator ; having done which, 
 we continued our experiments up to the end of 
 March, and found that we obtained as much as 
 12,338 cubic feet from a ton of Butterknowl coals. 
 From that time up to the present, the reports made 
 to us, from time to time, by the manager of the 
 
426 
 
 ON THE GAS-REGENERATOR, ETC. 
 
 Wisbeach gas-works, show similar results. In the 
 summer of 1840 we erected a small gas apparatus 
 at a manufactory near London, where we put up 
 two elliptical retorts and two regenerators. This 
 apparatus was brought into action in November, 
 1840, and for some time was worked under our own 
 immediate control and inspection. From notes 
 made by us at the time, we make the following 
 extracts, beginning with the first day’s experiment, 
 and repeating such regularly for seven successive 
 days : the coal used was Townley Main ; and the 
 retorts were charged with 160 pounds thereof at 
 one time : — 
 
 1st day, 12,815 cubic feet of gas to the ton. 
 
 2nd „ 12,903 ditto ditto. 
 
 3rd „ „ quantity of gas not ascertained. 
 
 4th „ „ retort not worked. 
 
 5th ,, 12,935 cubic feet of gas to the ton. 
 
 6 th „ 12,193 ditto ditto. 
 
 7 th „ 12,715 ditto ditto. 
 
 Showing an average produce of something more 
 than 12,500 cubic feet of coal-gas, of the very best 
 quality, from one ton of coals. The specific gravity 
 of the gas so obtained, taken with great care, and 
 bringing into account the temperature, as well as 
 the barometric pressure, averaged -569. The retorts 
 were set singly (each with its regenerator) over a 
 coke-oven, which, when heated to a proper tempera- 
 
ON THE GAS-REGENERATOR, ETC. 
 
 427 
 
 ture, produced an exceedingly good coke. Taking, 
 however, all things into consideration, we are not 
 of opinion that coke-ovens are so eligible for heating 
 retorts as furnaces, where the gas-regenerators are 
 used. 
 
 From the results at Wisbeach, and at the Hull 
 gas-works, and from the attention we have paid to 
 the gas-regenerators, we are of opinion that their 
 adoption holds out to the gas manufacturer the 
 following advantages : — They will diminish the ex- 
 penditure of coals for making gas full twenty-five 
 per eent., and that of fuel for heating the retorts 
 to the same amount. The expenses of labour, ex- 
 cept in very small gas-works, will he reduced to 
 the same extent, as will also the wear and tear of 
 retorts, grate-bars, and furnaces. The quantity of 
 gas generated from a given quantity of coal will be 
 augmented at the minimum full twenty-five per 
 cent., but in many cases the increase of volume 
 thereof will amount from thirty-three to forty-one 
 per cent. The specific gravity of the gas will also 
 be increased fully twenty per cent., so that, sum- 
 ming up the above advantages, it may be fairly esti- 
 mated that such gas companies as may adopt the 
 use of Mr. Malam’s patent regenerators will save 
 thereby upon their operations full thirty per cent., 
 after making ample allowance, in the way of interest, 
 for the capital sunk in the first erection of regene- 
 rators, for their wear and tear, and purchasing or 
 
428 
 
 ON THE GAS-REGENERATOR, ETC. 
 
 renting the patent right. We apprehend we need 
 not say any more as to the advantages which the 
 regenerators hold out in a pecuniary point of view, 
 as every one interested in a gas manufactory can 
 very easily calculate for himself what savings would 
 by their use be annually effected, by comparing the 
 cost of coals (less what may be received for coke) 
 on a system by which 9,000 cubic feet of gas from 
 a ton of coals is the maximum obtained, with the 
 cost when 12,000 cubic feet of gas are obtained 
 from a ton, the fewer retorts he would have to 
 work in the latter case, and the consequent saving 
 in fuel, wear and tear of retorts and grate-bars, 
 lime, and labour. 
 
 That the subject of causing the gas in its crude 
 state to undergo a second distillation prior to its 
 being permitted to enter into the hydraulic main, 
 for the purpose of converting the many vaporous 
 particles of tar and ammonia with which it was 
 charged when it left the retort, into gas, has been 
 considered worthy the notice of scientific and prac- 
 tical men, appears evident from the attention lately 
 paid thereto by many eminent chemists, English 
 and foreign, and from more than one patent having 
 been taken out since Mr. Malam took out his patent 
 for the regenerators, for producing results somewhat 
 resembling those which he obtains, and in which, 
 though the apparatus be dissimilar in appearance, 
 still several of the more recent inventions are but 
 
ON THE GAS-REGENERATOR, ETC. 
 
 429 
 
 imperfect modifications of his perfect method. The 
 first that we shall notice was patented in February, 
 1838, by the Marquis Montauban (see “ Newton’s 
 London Journal,” conjoined series. No. 82, for Ja- 
 nuary, 1839, page 185). He proposed to use an 
 additional distillatory vessel which he called a de- 
 composer, to a nest of four or a greater number of 
 retorts, which vessel he proposed to fill with iron 
 tubes or plates, so as to afford a large heated surface 
 for the gas to pass over before it reached the hydrau- 
 lic main. When four retorts were set in one nest, 
 the gas from each of them was received into an iron 
 cylinder, and from that the gas generated by the 
 whole number was conveyed to the decomposer, 
 entering at one end thereof, and making its exit at 
 the other towards the hydraulic main. For the 
 reasons we named when speaking of the use of the 
 hydraulic main, a difficulty arose in consequence of 
 so many retorts working into one common cylinder, 
 which could not be got over without placing cocks 
 or valves upon each of the ascending pipes, so that 
 when one of the retorts had to be drawn and re- 
 charged, its communication with the said common 
 cylinder might be shut off. Such cocks or valves 
 were therefore provided ; but looking at the situa- 
 tion in which they were placed, most persons practi- 
 cally acquainted with the operations of a gas-light 
 manufactory would at once see that their being 
 kept in such a state as always to work quite freely 
 
430 ON THE GAS-REGENERATOR, ETC. 
 
 (a thing of very great importance, both as regards 
 the isolating a retort, as well as again connecting it 
 to the common cylinder) and to remain perfectly 
 gas tight, were things by no such means to be easily 
 effected. 
 
 The second originated with Mr. George Lowe, 
 engineer, who used double retorts set end to end in 
 the same brick-work, so that together they were of 
 about twice the length of those generally used. 
 Each had its separate mouth-piece, and hydraulic 
 main, and from the hydraulic main each could be 
 shut off at pleasure. The ends of these retorts were 
 connected together by means of a cast-iron pipe, so 
 that there was a communication between the two. 
 The mode of operation was as follows : the retorts 
 having attained a proper heat, one of them was 
 charged, and the connexion between it and the pipe 
 attached to its mouth-piece which led towards the 
 hydraulic main was shut off by means of a valve ; in 
 consequence, the gas as it was generated passed 
 through the uncharged retort, and by the pipe at- 
 tached to its mouth-piece entered the hydraulic 
 main when the first charge was thought to he about 
 half burnt off, the lid of the uncharged retort was 
 removed, and that retort was charged when the 
 valve between the hydraulic main and the first- 
 charged retort was opened, and the similar valve to 
 the second-charged retort closed ; in consequence, the 
 gas making therein had to pass over the red-hot coke 
 
ON THE GAS-REGENERATOR, ETC. 431 
 
 in the first-charged retort, on its way to the hydraulic 
 main ; and thus the two retorts were continued 
 to be charged alternately. We need not make any 
 remarks here about the valves, but it is evident that 
 from the time the lid of one retort was removed till 
 the charge was drawn, the retort recharged, and the 
 lid reluted and secured, the gas making in the other 
 must escape through it. To remedy this evil, as the 
 specification states, a patent was taken out in De- 
 cember, 1839, by Mr. Lowe, and Mr. John Kirkham, 
 engineers, jointly, for a mode of combining and 
 working retorts in the manufacture of gas from coal, 
 and in such a manner that the products alternately 
 of one of two retorts shall be caused to pass into and 
 mix with the products of the other retort, by which 
 means, whichever of the two retorts has been last 
 charged, the products thereof, during the early hours 
 of working, shall pass into the retort which, with its 
 charge, is in a highly heated state, from its having 
 been much longer at work; and the retorts are 
 so connected by means of a valve and apparatus ex- 
 ternal of the brick-work of the setting of the retorts, 
 that during the time of discharging and charging 
 either of the retorts, the gas from the other retort 
 shall not pass into the retort with which it is con- 
 nected, and which is long discharged of its contents 
 or recharged with coal. The times and modes of 
 drawing the retorts are nearly similar to what we 
 have already mentioned when speaking of Mr. Lowe’s 
 
432 ON THE GAS-REGENERATOR, ETC. 
 
 double retort ; the principal difference that we per- 
 ceive between one mode and the other is, that the 
 two retorts are connected together at the back and 
 outside the brick- work by a pipe, whereon is placed 
 a slide valve for the purpose of shutting off the con- 
 nexion between the two during the process of draw- 
 ing and charging either. The reader who may feel 
 desirous of obtaining further information relative to 
 this patent, which embraces several other matters, 
 such as upright retorts, intended to produce similar 
 results to those we have spoken of, the using of clay 
 retorts, the employing of coal-tar as fuel, &c. &c.> 
 will find the specification, with figures of reference 
 in Number 82 (new series) of the “ Repertory of 
 Patent Inventions” for October, 1840, page 193. 
 
 Having now noticed the inventions which appear 
 most likely to produce somewhat similar results to 
 what are effected by Mr. Malam’s patent gas-rege- 
 nerators, we shall very briefly notice the points in 
 which we think one has, both in theory and practice, 
 a most decided superiority over the other : meanwhile 
 again observing, that several of the patents taken 
 out subsequently to his are but mere modifications 
 of his method, and those by no means for the better, 
 as the scientific and practical reader will readily per- 
 ceive on comparing the several apparatus. The gas- 
 regenerators require no valves, the others cannot be 
 worked without them ; and we are of opinion that 
 it will always be found in practice, that the more 
 
ON THE GAS-REGENERATOR, ETC. 433 
 
 simple the construction of a machine is, so much 
 the more valuable it is. Valves fit for the purpose 
 intended are expensive in the first instance, and 
 very liable to become deranged. In very large 
 establishments, however, where there are plenty of 
 workmen, the use of valves for such purposes as are 
 intended in the patents we have alluded to is not 
 so objectionable as in small works (supposing they 
 do not get clogged with tar, and can be kept gas 
 tight) ; but we cannot fail to give it as our opinion, 
 that they are to a certain extent objectionable in all ; 
 therefore, supposing the same volume of gas to be 
 produced by one method as by another, we think the 
 patent gas-regenerators are to be preferred, being 
 simple, self-acting, and not liable to get out of order. 
 But even if we could admit the volume of gas pro- 
 cured to be similar in all cases, we are not at all 
 prepared to allow that the increase in volume, ob- 
 tained by passing the crude gas over so highly heated 
 a material as must be the interior of a retort when 
 to a certain extent filled with red-hot coke, is by 
 any means allied to so great a specific gravity as that 
 which is obtained by passing such gas through a 
 vessel heated to such an extent only as is sufficient 
 for arresting the vapours of tar and ammonia, and 
 converting them into such a valuable gas, with an 
 increase of illuminating power as well as of volume, 
 as can be produced by the regenerators. It being 
 well known that the illuminating power of well-pu- 
 
 2 F 
 
434 ON THE GAS-REGENERATOR, ETC. 
 
 rified coal-gas is increased as its specific gravity or 
 the proportion of carbon therein increases, it follows 
 that such gas will go further, and be of more value. 
 The regenerators once fixed, and their lids secured, 
 require no attention or attendance for weeks together ; 
 and when it may he necessary to examine their in- 
 terior, it can he done when the retort to which each 
 is attached is drawn, and will not occupy more time 
 than would be necessary for drawing and recharging 
 a retort. Practice has however most satisfactorily 
 shown, that the internal pipes in the regenerators 
 do not begin to get foul until a very long period 
 has passed, so that in most cases months may elapse 
 without its being necessary to examine their interior. 
 The regenerators, once properly fixed in their places, 
 will also last in the most effective state as long as 
 three or four sets at least of the retorts set under 
 them, a fact which experience has fully demonstrated, 
 as they can also be replaced with very little trouble 
 and expense. 
 
 Note. — All persons desirous of further information concerning 
 the gas-regenerators, may obtain all particulars relating to them, 
 by an application (post-paid) at the author’s address in London, 
 10, Arundel-street, Strand. 
 
435 
 
 CHAPTER XIX. 
 
 On the Method of ascertaining the Specific Gravity of Coal-Gas. 
 
 It being universally admitted that the illuminating 
 power of well-purified coal-gas increases very much 
 with the increase of its specific gravity, and that 
 that entirely depends upon the increased proportion 
 of carbon present in its constitution, we propose to 
 dedicate a page or two to the description of the 
 method we have adopted for experimentally ascertain- 
 ing the specific gravity of coal-gas, or any other gas. 
 In the first place, we have provided ourselves with a 
 very nicely adjusted scale-beam, upright standard, 
 one scale, and a copper flask, containing 61 ^ cubic 
 inches, with weights to exactly counterpoise the 
 flask when filled with common air, and its appur- 
 tenances, when they are attached by a hook to one 
 end of the scale-beam. We have also an exhausting 
 syringe, and a set of grain and smaller weights ; 
 and, in making our experiments, we make use both 
 of a barometer and a thermometer. We first note 
 the temperature and barometric pressure of the 
 atmosphere, and having so done, the pieces (see 
 
 2 f 2 
 
436 
 
 ON THE SPECIFIC GRAVITY 
 
 figures 3, 4, and 4*) are connected together and 
 screwed to the flask in the order in which they are 
 placed in Plate I., by uniting the cock (figure 3) to 
 the flask by means of the screw c ; to the screw b at 
 the other end of the cock we attach the piece, figure 
 4, which is fitted with a valve made of goldbeater’s 
 skin at a , over which we screw the piece, figure 4*, 
 fitted with a hook d, as shown. Things being so 
 far prepared, before we proceed further we calculate 
 what 61^ cubic inches of atmospheric air, at the 
 temperature and barometric pressure then noted, 
 weigh ; preparatory to doing which, we find what 
 61^ cubic inches (or any other content in cubic 
 inches of which a flask may be constructed) weigh ; 
 and as it is known that when the barometric pressure 
 is 30 inches, and the temperature 60 degrees, 100 
 cubic inches of air weigh 30^- grains, we proceed, 
 first, to find what 61 J cubic inches of air would 
 weigh under like circumstances, and say 
 
 Cubic inches. Cubic inches. Grains. Grains. 
 
 as 100 : 61-5 :: 30*5 : 18*7575; 
 
 this found, we put D for density, and pressure 
 = /rDl + at 0 — /cT) ( 1 + j f° r > the expansion 
 
 of the air between the freezing and boiling points 
 = *375, consequently, that for one degree Fahren- 
 *375 *025 
 
 heit 
 
 180 
 
 12 ’ 
 
 To find k being constant, we have 
 
OF COAL-GAS. 
 
 437 
 
 / -025 
 
 30 = * 18*7575 ( 1 + -r^t 
 
 
 12 
 
 ') 
 
 = k 18-7575 f 1 + ^28 
 
 12 
 
 )- 
 
 1-0583 
 
 = k 18-7575 (=55) = k 6-2525 . 3-175 
 1 -k -2084.3-175 = k -66167 
 
 ^(l + ^r=») 
 
 P = : 
 
 D _ £-66167 
 
 025 — 
 
 1 + ~12 * l ° ~ 32 
 
 The above is a formula by which D, or density, 
 is found, if p pressure, and t° temperature in degrees 
 Fahrenheit be given. Supposing the flask to con- 
 tain 61^ cubic inches, the barometric pressure to he 
 28 inches, and the temperature 45 degrees, we will 
 have 18*03 grains as the result; which we show 
 thus 
 
 Example. D = 28 . 
 
 •66167 
 
 -025 — — 
 
 1 + . 45° - 32° 
 
 = 18-03 
 
 r i -025 10 . -325 n „ 
 
 for 1 + - B -.13 = 1 + - l5 -=l.( B7 
 
 then, m \ e ll 28 - 18 0396884. 
 
 1 ’ y)/d 1 
 
 The same calculation will give just results m all 
 other cases, be the barometric pressure and tempera- 
 
438 
 
 ON THE SPECIFIC GRAVITY 
 
 ure what they may, if we substitute for p the actual 
 barometric pressure, and for t° the temperature in 
 degrees of Fahrenheit. 
 
 We attach the flask and its appendages to one 
 end of the scale-beam by the hook d, figure 4*, and 
 by weights put into the scale at the other end of 
 the beam, we very exactly balance it. We then 
 remove the flask from the scale-beam, unscrew the 
 piece, figure 4*, and screw on the exhausting syringe 
 upon the piece, figure 4, at a , and proceed to ex- 
 haust the flask, which, when we have accomplished, 
 we shut the stop-cock. To know when the most 
 perfect vacuum possible has been formed, after re- 
 moving the exhausting syringe, we screw on the 
 piece, figure 4*, and again attach the flask to the 
 scale-beam ; then, if the most complete rarefaction 
 has taken place, very nearly as many grain weights 
 will be required to be laid upon the thumb-piece of 
 the cock of the exhausted flask, as we found by our 
 calculation its contents of atmospheric air, at the 
 then temperature and barometric pressure, weigh, 
 to bring the scale and flask ends of the beam into 
 equilibrium. We again detach the flask from the 
 scale-beam, keeping the stop-cock shut, and remove 
 the pieces y figures 4 and 4 # , and then attach the 
 flask, by means of the screw b, to a union joint upon 
 the pipe, containing the gas of which we want to 
 know the specific gravity ; between which union 
 joint and the gas pipe there is fixed a stop-cock. 
 
OF COAL-GAS. 
 
 439 
 
 We then open the last-named cock, and afterwards 
 the cock attached to the exhausted flask ; upon 
 which the gas rushes into, and in a few seconds Alls 
 it from the pipe. We then shut both cocks, and 
 unconnect the flask and its cock from the union 
 joint, attach thereto the pieces, figures 4 and 4*, 
 and again hook it on to the scale-beam, as before ; 
 we then place grain (or smaller) weights upon the 
 thumb-piece of the cock attached to the flask, till 
 the weight in the scale at the opposite end of the 
 beam is exactly counterpoised ; we then subtract 
 this last-ascertained weight from the weight of air 
 which was necessary to fill the flask when the ex- 
 periment was made ; the difference, it is evident, 
 must be the weight of the gas then contained in 
 the flask : we therefore say, 
 
 As the weight of the atmospheric air necessary 
 to fill the flask in grains, &c. 
 
 Is to the weight of the gas contained therein also 
 in grains, &c., 
 
 So is 1000, the specific gravity of air. 
 
 To the specific gravity of the gas under trial. 
 
 For example, we found that the barometric pres- 
 sure was 30*52 inches, that the thermometer stood 
 at 46°, and that, after proceeding as above, we also 
 found it required 84 grains to counterpoise the 
 weight in the scale when the flask was filled with 
 gas : we first find, by the method already men- 
 tioned, that 61*5 cubic inches of air, the barometer 
 
440 ON THE SPECIFIC GRAVITY OF COAL-GAS. 
 
 standing at 30’ 52, and the thermometer at 46°, 
 
 weigh 19’66 grains ; 
 
 from which we take the counterbalance 8’50 „ 
 
 the remainder . 11*16 grains, 
 
 is the weight of 61*5 cubic inches of the gas under 
 trial : — we then say. 
 
 Specific Specific 
 Grains. Grains. Gravity. * Gravity. 
 
 As 19*66 : 11*16 : : 1000 : *567, the specific 
 gravity sought, being that of the coal-gas produced 
 by the addition of gas-regenerators to elliptical 
 retorts working at a cherry-red heat. 
 
441 
 
 CHAPTER XX. 
 
 Description of the Gas-Works at Bury St. Edmunds, given for the 
 purpose of showing the general arrangement of a Gas-Light 
 Manufactory. 
 
 As we have heard it frequently remarked, that 
 there is not a published plan of any existing gas- 
 work, and that it is very desirable such a plan should 
 be laid before the public, we take this opportunity 
 of furnishing a ground-plan, front, back, and side 
 elevation, and a vertical section of one recently 
 built at Bury St. Edmunds, all drawn from a 
 scale of one-sixteenth of an inch to a foot, which 
 we propose to describe. We remark, that similar 
 letters of reference are placed against corresponding 
 parts of the manufactory in the Plates II., III., IV., 
 V., and VI. 
 
 Plate II. represents a front elevation of the gas- 
 works, in which A A is the dwelling-house of the 
 superintendent or foreman, consisting of a parlour, 
 20 ft. x 15 ft. 9 in., with two bed-rooms over it, 
 and a kitchen, 16 ft. X H ft- 6 in. B is the 
 office, 16 ft. X 11 ft* 6 in. The fire-places in the 
 office and in the foreman’s house have descending 
 flues which lead into the chimney G (Plate VI.). 
 
442 
 
 DESCRIPTION OF THE GAS-WORKS 
 
 C is the retort-house and coal-store, one-half of 
 which is employed as a coal-store, the other for the 
 retorts, being roomy enough for the labour therein 
 required. This building is 50 ft. X 42 ft. inside, 
 and height to wall-plate 16 ft. D is a work-shop 
 fitted up with vice-bench, tools, &c., and is of the 
 same dimensions as the office ; height to wall-plate 
 10 ft. 6 in. E is a store-room for keeping and 
 slaking the lime for purifying the gas ; it is of the 
 same dimensions on the plan as the foreman’s kit- 
 chen ; height to wall-plate 10 ft 6 in. F is the house 
 for the purifiers, 20 ft. X 20 ft. inside (all the 
 dimensions given are inside ones on the plan) ; height 
 to the wall-plate 16 ft. The ^chimney is a column 
 70 ft. in height, inclusive of the cast-iron vase at 
 the top, which is 5 ft. diameter at its widest part 
 and 4 ft. in height. The whole of this front, as 
 well as the side and back elevations and the chim- 
 ney, is built of brick, finished partly with Portland- 
 cement and partly with stone for coping, mouldings, 
 &c. &c. 
 
 Plate III. is a vertical section of the works, in 
 which a front elevation of the retorts and elevations 
 of the purifying apparatus and valve are shown : the 
 other parts, having the same letters of reference as 
 corresponding parts in Plate II., do not require to 
 be referred to. 
 
 Plate IV. exhibits a back elevation of the fore- 
 man’s dwelling-house, the office, the retort-house, 
 
AT BURY ST. EDMUNDS. 
 
 443 
 
 and coke-store, the work-shop and the house for the 
 purifier already sufficiently described. It also shows 
 a front elevation of the coke-store, drawn from a 
 scale of one-eight inch to a foot, the wall-plate in 
 front of which is supported by four cast-iron columns 
 and two half columns, each 8 ft. in height. Four 
 cast-iron plates are placed between the columns as 
 shown, for the purpose of keeping up the coke; 
 these are each about 3 ft. 9 in. in height by 8 ft. 
 6 in. in length, and \ inch thick, and cast with 
 mouldings as shown. The internal dimensions of 
 the coke-store on the plan is 48 ft. x 10 ft. 
 
 Plate V. exhibits a side elevation of the foremans 
 dwelling-house and the retort-house : the doors to 
 the latter are folding, and made of cast-iron, the 
 louvering shown in the openings are of plate- iron. 
 O represents one of the gas-holders nearly full of 
 gas, it is supported from four points at the circum- 
 ference by the cast-iron columns «, a, described at 
 pages 305, 309, where figure 4, Plate XV., is ex- 
 plained. b, the back boundary wall, supported by 
 strong buttresses of brick-work, to sustain the pres- 
 sure upon its back of the ground, that being about 
 thirteen feet higher than the level of the ground 
 upon which the works are built. 
 
 Plate VI. is a ground-plan of the works which, 
 as far as relates to the office, the foreman’s dwelling^ 
 the retort-house, and coal-store, the vice-room, lime- 
 store, and house for purifier, requires no further 
 
444 
 
 DESCRIPTION OF THE GAS-WORKS 
 
 description. On this plan, however, it may be 
 noticed, that not only the flue from the bed of 
 retorts, but also the flues from the fire-places in the 
 office and foreman’s dwelling-house are carried under- 
 neath the floor of the retort-house and coal-store, 
 into the base of the chimney marked G. The base 
 of the chimney is divided into two parts by a nine- 
 inch brick-wall, as shown, to a height of about three 
 feet above the points at which the respective flues 
 enter, a precaution very necessary to be taken to pre- 
 vent the draught being checked by interfering flues, 
 as we have sometimes witnessed. When flues meet, 
 or act against each other, no dependence whatever 
 can be placed upon the draught ; for first one will fail 
 and then another, according to the quarter whence 
 the wind may blow. The pipe shown as leading 
 from the purifying-house towards the chimney is 
 for carrying off the vapour from the impure lime, 
 either whilst it remains in the 1 purifying vessel 
 through an aperture in the lid, which is opened after 
 it is thrown out of action, or, as has already been 
 described at page 246, from a receptacle made for 
 it after it is removed from the purifier, and having 
 a draught hole through it. H H is the plan of a bed 
 of eighteen elliptical retorts, dimensions twenty 
 inches by ten inches inside ; length, exclusive of 
 mouth-piece, six feet six inches. These are set on 
 precisely the same plan as the three large D retorts, 
 shown in figures 5, 6, 7, 8, 9 and 10, Plate VIII., 
 
AT BURY ST. EDMUNDS. 
 
 445 
 
 and described at pages 146 — 148 preceding. * * 
 represents the situation of the hydraulic main, a is 
 the pipe for conveying the tar and ammoniacal liquor 
 to the tar-cistern J, upon which is a branch leading 
 towards the washer I, which conveys into that 
 vessel the gas and such portions of tar and ammo- 
 niacal liquor as may, after it leaves the hydraulic 
 main, remain in a state of vapour. I is the washer, 
 similar to the one shown by figures 9 and 10, Plate 
 XI., and described at pages 217 and 218. J is the 
 tar-well, similar to the one shown at figure 9, 
 Plate XII., and described at page 227. c is a four- 
 inch pipe leading from the washer to the condenser, 
 upon which is an outlet for conveying any tar and 
 ammoniacal liquor produced by further condensation 
 in the washer and condenser K K K, by the pipe b 
 into the tar-well. The pipe b , and also the pipe «, 
 have each a dip-pipe for receiving them in the tar- 
 well, as described at page 227, where the tar-cistern, 
 shown at figure 3, Plate XII., is explained. KKK 
 represents the condenser, which is fixed in an oblong 
 tank made of masonry, the top of which rises about 
 six inches above the ground level of the works, and 
 is finished with a coping of three-inch Yorkshire 
 flagging. The inside dimensions of this tank are 
 eighteen feet by nine feet, depth about three feet. 
 It is built of brick, laid in Roman-cement, with a 
 coat of Roman cement inside the upright walls, of 
 
446 
 
 DESCRIPTION OF THE GAS-WORKS 
 
 about one inch in thickness ; the bottom, except 
 where the boxes we are about to mention are placed, 
 is well puddled, as are also the backs of the walls, 
 in the way already shown in our description of brick- 
 tanks for the gas-holders to work in. The con- 
 denser consists of four rectangular cast-iron boxes, 
 each about eight feet six inches in length, one foot 
 in width, and two feet in depth, cast with sockets 
 upon their sides for receiving four-inch cast-iron 
 pipes. The boxes are cast with partitions in them, 
 somewhat similar to that at the bottom of the con- 
 denser, showm at figure 3, Plate XI. The pipes 
 being jointed to these boxes, it is evident that if the 
 gas enters the condenser by the pipe c, it will be 
 compelled (there being but one pipe in the first box 
 communicating with that pipe, the partition in the 
 box shutting off all others) to proceed to the oppo- 
 site end of the condenser, where the partition in the 
 box there includes two pipes, and allows it to return 
 by the second pipe to the end at which it first 
 entered, and so on alternately from end to end, by 
 means of partitions in the end boxes, each including 
 two pipes, except the first and last (in the other 
 two boxes the partition-plates are placed between 
 each pipe of the range of which the condenser is 
 formed), till it comes to the single division in the 
 box communicating with the pipe d , which conveys 
 the refrigerated gas towards the purifier. The 
 
AT BURY ST. EDMUNDS. 
 
 447 
 
 boxes are placed upon piers of brick-work of dif- 
 ferent heights, and so that the box at the entrance 
 and exit end is about six inches lower than that at 
 the opposite end ; consequently the pipes have a 
 regular fall of about six inches in the entire length, 
 and thereby cause the condensable products to fall 
 into the lowest box, and be thence conveyed by the 
 pipe b to the tar-cistern J. L 1, L2, L 3, and L 4 
 are the dry-lime purifiers, of very nearly the same 
 construction as the purifier shown at figure 1,2, and 
 3, Plate XIV., and described at pages 247 — 259 ; 
 the principal difference is in the internal cylinder, or 
 lifting part of the valve M, which is constructed with 
 the partitions in the reverse order, which of course 
 reverses the order in which the purifiers are thrown 
 out of action, so that the centre valve, shown at 
 figure 2, Plate XIV., represents figure 4 there 
 shown, and vice versa. Plate XIV. represents the 
 action as from right to left ; here LI, L 2, &c., 
 show it is from left to right, e is a four-inch pipe 
 for conveying the purified gas to the gas-holders N 
 and O, the inlet and outlet pipes of which e andy*, 
 and e and g, and also the gas-holders, valves attached 
 to them, and the pipe g g , and f leading to the 
 governor P have all been fully explained, along 
 with figure 4, Plate XV., at pages 305 — 309. 
 P is the governor, shown at figures 10, 11, 12, and 
 13, Plate XXII., and described at pages 389 — 393. 
 
448 
 
 DESCRIPTION OF THE GAS-WORKS 
 
 Q Q is a plan of the coke-store, the dimensions of 
 which were given when describing its front eleva- 
 tion, R and S are the privies, h a five-inch main 
 pipe for conveying the gas from the governor to the 
 street-mains, the leading one of which is of that 
 diameter. 
 
 Having now given very lengthened and full 
 descriptions of every part of the apparatus used in 
 the gas manufactory from the retort to the governor, 
 and also furnished detailed plans, &c., of a gas-work 
 now in actual existence, we have little more to add 
 beyond observing, that the arrangement of a gas- 
 manufactory must always depend very much upon 
 the plan of the ground it has to be built upon. In 
 our practice we have had plans of almost all shapes 
 to erect works upon — some very irregular ; but when 
 uniformity of arrangement is considered, the ground- 
 plan of the works ought to be always rectangular. 
 In choosing a site for a gas manufactory, it will 
 always he well to recollect that a low situation is 
 preferable to one more elevated, because, from the 
 levity of the gas, its passage through the pipes will 
 he effected with less pressure. Such a situation, 
 near a river or canal from which the coals required 
 are delivered, is very desirable, as thence will arise 
 a great saving in the expense of carriage of that 
 article. We may remark that, in several instances, 
 we have placed the purifiers in a room over the 
 
AT BURY ST. EDMUNDS. 
 
 449 
 
 lime-store, which we find very convenient in prac- 
 tice ; for, under such an arrangement, the entire of 
 their bottoms, and the various pipes connected there- 
 with, are easily accessible. We also recommend 
 that the gas-holders, on all occasions, should be 
 fixed in the open air (and not have houses built 
 round them, or be covered in, as is the case in some 
 places), as the least expensive and decidedly the 
 safest method. An arrangement similar to that 
 given in Plate VI. presents a uniformity of ap- 
 pearance, and saves room. However, the arrange- 
 ment of the apparatus must vary with local circum- 
 stances, and therefore no general rule can be given 
 for the purpose. It will be obvious, notwithstand- 
 ing, that it will always be well to place the gas- 
 holders at as great a distance from the retort-house 
 as the premises will allow. 
 
 After what we have said, we expect there is now 
 no occasion to recapitulate the different parts of the 
 apparatus, or to point out how and where the gas is 
 first produced in the manufactory, or how it passes 
 from the washer to the condenser, from the con- 
 denser to the purifier, and thence to gas-holders, 
 &c., ready for supplying the demand. And having, 
 for the third time, led the reader through the dif- 
 ferent stages of the process for generating, collect- 
 ing, and distributing coal-gas, and, we hope, intro- 
 duced to his notice such plans, &c., as are at the 
 present period most worthy of his consideration, we 
 
 2 G 
 
450 DESCRIPTION OF THE GAS-WORKS, ETC. 
 
 again take our leave, with a firm conviction that, 
 though much has been achieved tending to promote 
 the progress of gas-lighting, still there is a wide 
 field open for improving and simplifying that appa- 
 ratus by means of which coal-gas is now obtained. 
 
 THE END. 
 
INDEX. 
 
 A. 
 
 Page 
 
 Air, a proper supply of, necessary for supporting combustion 6 
 Ammoniacal Liquor , quantity of, produced from a ton of 
 
 coals ........ 224 
 
 Argand Gas-Burner , whence the idea of it arose . . 35 
 
 Argand Lamp , how the idea of it was first suggested . . 6 
 
 ,, advantages attending the use of . . 6 
 
 Artificial Light , how produced at the least expense . . 5 
 
 B. 
 
 Bend- Pipe , description and use of . . . .341 
 
 Bend-Pipes , wrought-iron, where used . . . .351 
 
 Branch Pipe , description and use of ... 340 
 
 Brande , Mr. T. W., obtains carburetted-hydrogen gas from 
 coal, from the dried wood of the common willow, from 
 white birch-wood, from hazel-wood, and from writing- 
 paper . . . . . . . .411 
 
 Brass-Cross , description and use of . . . .35? 
 
 Brass T-Piece , description and use of . . . 358 
 
 Burners , Gas , best size for obtaining a large quantity of light 25 
 ,, Argand more economical than single jets . 25 
 
 ,, fifteen-hole, consumption of gas per hour . 28 
 
 „ ditto mould candles equal to .28 
 
 „ Argand should always be used with glass 
 
 chimneys ........ 36 
 
 Bury St. Edmunds Gas-Works, description of . . .441 
 
 C. 
 
 Candle- Light , reading by, why injurious to the eyes . . ? 
 
 „ how to obviate its variability as suggested by 
 
 Mr. Ezekiel Walker .... . . 7 
 
 Candle , for what purpose the wick is used . . .12 
 
 2 g 2 
 
452 
 
 INDEX. 
 
 Page 
 
 13 
 
 14 
 
 15 
 15 
 
 15 
 
 13 
 
 16 
 16 
 
 16 
 
 9 
 
 17 
 
 Candle , wick of, why it becomes black .... 
 
 „ whence smoke from it is produced 
 „ with a wick of a single thread, effect of 
 „ remarks on the thickness of the wick of 
 „ wick of a wax one may be made much slighter than 
 that for tallow, and why ..... 
 
 „ with a thick wick, effects of under various circum- 
 stances ........ 
 
 ,, made of wax, its action ..... 
 
 „ ,, is snuffed spontaneously 
 
 „ made of tallow, what is required for making it equal 
 to such as are made of wax ..... 
 
 ,, not requiring snuffing, why advantageous 
 Candles , mould and ill-snuffed dips, cost of obtaining light 
 from respectively, compared with light afforded from 
 wax, sperm-oil, whale or seed-oil, and coal-gas . 26 — 29 
 
 „ how to ascertain and compare the illuminating 
 powers of with other luminous bodies 
 ,, on the variability of light they afford when burnt 
 vertically ........ 
 
 „ so placed as neither to produce smoke nor require 
 snuffing, effects of ..... 
 
 Candles and Lamps , theory of the action of 
 Carbonization , when carried on disadvantageously . . 
 
 ,, how to be managed, so as to produce the 
 greatest quantity of gas in the least time from equal 
 quantities of coal .... 125 and 188 
 
 Carbonizing , importance of the process of . . .163 
 
 „ mode adopted for, in the earlier stages of the 
 manufacture of gas . . . . .164 
 
 ,, consequences resulting from such mode . .165 
 
 ,, opinion of some as to the per centage at which it 
 might be carried on . . . „ .165 
 
 ,, the per centage it has been reduced to . .175 
 
 ,, best temperature for . . , , .166 
 
 „ whence arose the idea of working short charges 169 
 
 ,, considerations relative to short charges . .172 
 
 ,, why six hours’ charges are not so profitable as 
 those of eight hours’ . . . . . .176 
 
 7 
 
 11 
 
 190 
 
INDEX. 
 
 453 
 
 Page 
 
 Carbonizing , a week’s experiment stated when working six 
 
 hours* charges . . . . . . .176 
 
 „ a week’s experiment stated when working 
 eight hours’ charges . . . . . .177 
 
 „ balance struck between the above two processes 180 
 
 „ further experiments on the eight hours’ process 181 
 
 ,, balance between the above process and that of 
 six hours . . . . . . . .180 
 
 ,, when carried on at the six hours’ process dis- 
 advantages of ...... 181 
 
 „ annual balance in favour of the eight hours’ 
 process when working with cylindrical retorts . .183 
 
 „ absurdity of working short charges with cylin- 
 drical retorts . . . . . . .184 
 
 „ to be carried on advantageously, the coal must 
 be submitted in thin strata . . . . .129 
 
 ,, carried on by cylindrical or small D -retorts, set 
 on the oven-plan, remarks upon . . . .173 
 
 ,, when carried on by semicircular, kidney- 
 shaped, or elliptical retorts, remarks upon . . .175 
 
 „ coals for, recommended to be introduced into 
 the retorts in sheet-iron trays . . . . .186 
 
 ,, a week’s experiment stated when working 
 
 elliptical retorts at four hours’ charges . . .190 
 
 ,, balance in favour of working elliptical retorts . 192 
 
 Carburetted- Hydrogen Gas , produced from pit-coal . • 405 
 
 „ qualities of, differ with circum- 
 stances . . . . . . . . 406 
 
 „ found ready formed on the 
 
 surface of stagnant waters and in marshes . . . 407 
 
 „ how procured from charcoal . 407 
 
 „ ditto spirits of wine 408 
 
 ,, may be obtained from most 
 
 animal and vegetable substances .... 408 
 „ procured from ether, or alcohol 408 
 
 „ specific gravity of . . 409 
 
 „ how the greatest proportion of 
 
 may be obtained in the least time . . . .411 
 
 ,, obtained from coal-tar . . 409 
 
454 
 
 INDEX. 
 
 Page 
 
 Carburetted-Bydrogen Gas , quantity obtained from a pound 
 
 of coal-tar ........ 409 
 
 „ obtained from wood, by Messrs. 
 
 Sobolowsky and Horrer, of St. Petersburg . .411 
 
 „ obtained from coal, oxygen 
 
 required for burning . . . . . .412 
 
 „ obtained from wax or lamp-oil, 
 
 oxygen required for burning . . . . .412 
 
 Cement , Iron , bow made and mode of using . . . 339 
 
 Clayton's , Dr., account of obtaining gas from pit-coal . 77 
 
 Clegg , Mr. Samuel , communicates to the Society of Arts his 
 
 method of lighting up manufactories with gas . . 91 
 
 „ his rotary retort described . . .121 
 
 „ ditto performance of . .122 
 
 „ ditto why not used . .123 
 
 „ his revolving gas-holder described . 298 
 
 „ his collapsing gas-holder noticed . .298 
 
 his gas-meter with reciprocating motion 36 1 
 ditto patent, with a rotary 
 
 motion ........ 
 
 ,, patent governor described . 
 
 Coal, description of, and where found . 
 
 „ varieties and composition of, viz : — jet . 
 
 „ cannel ........ 
 
 „ common and spurious . 
 
 „ Anthracite, Kilkenny, and Culm . . . . 
 
 „ sulphureous and Bovey . 
 
 „ theory of the combustion of, considered for the purpose 
 of explaining the nature of gas-light and its production 
 „ products expelled from by the action of heat . 
 
 „ statement of successive discoveries made in decom- 
 
 363 
 
 383 
 
 38 
 
 38 
 
 39 
 
 40 
 
 41 
 
 42 
 
 60 
 
 60 
 
 posing ........ 68 
 
 „ composed of carbon, hydrogen, azote, oxygen, sulphur, 
 hygrometric water, and earthy matter . . . 405 
 
 „ produced from when distilled in close vessels at a 
 heat equal to 1077° Fahrenheit .... 406 
 
 Coal, Pit, not the only substance producing carburetted- 
 
 hydrogen gas ....... 407 
 
 Coal, Fire, observations on the process of its combustion . 62 
 
INDEX. 455 
 
 Page 
 
 Coal-Gas , cost of obtaining light from, compared with cost 
 of obtaining light from wax-candles, mould, and ill- 
 snuffed tallow-candles, whale, seed, or sperm-oil . 26 — 29 
 
 „ economy of, compared with the economy of oil- gas 106 
 ,, how distributed for use . . . .61 
 
 „ heaviest obtained during the early parts of the 
 distillatory process ...... 409 
 
 ,, average specific gravity of . . . 409 
 
 „ specific gravity of, how to ascertain . .435 
 
 „ how mixed with atmospheric air so as to form an 
 explosive compound . . . . . .413 
 
 „ smell of, a fortunate circumstance . . .413 
 
 „ light afforded by, can be applied in any direction 414 
 
 ,, deprived of its smell, would render its application 
 dangerous ....... 413 
 
 ,, explosions from, when mixed with atmospheric 
 air, not of frequent occurrence . . . .414 
 
 ,, used for cooking . . . . .416 
 
 ,, used for heating churches, chapels, shops, count- 
 ing-houses, warehouses, &c. . . . .415 
 
 „ cannot be manufactured economically on a small 
 scale ........ 416 
 
 „ for what purposes most advantageously used . 416 
 
 ,, price of, not depending upon the price of coals . 417 
 
 Coal-Gas Establishments , their extent and power in London 66 
 
 Coal-Mines , of Durham and Northumberland, the number 
 
 of years capable of affording a supply ... 57 
 
 Coals , classification of, as regards their uses in the gas-light 
 
 manufactory ....... 42 
 
 „ of the first class under this arrangement, of what they 
 consist ........ 43 
 
 ,, of the second class, ditto ditto . 47 
 
 „ of the third class, ditto ditto . 50 
 
 „ analyzing of, considerably extended by the introduc- 
 tion of the manufacture of gas .... 66 
 
 „ distilled in London daily for the generation of gas . 67 
 
 Coal-Tar , quantity of, produced from one ton of coals . 224 
 
 ,, carburetted- hydrogen gas obtained from one 
 
 pound of ....... 409 
 
456 
 
 INDEX. 
 
 Coal-Tar , how proposed to be converted into gas, by the 
 Marquis Montauban ...... 
 
 ,, how proposed to be converted into gas, by the 
 Comte de Yal Marino .... 
 
 Coke , the base of coal ..... 
 
 „ how made to answer the purpose of the maltster, or 
 for metallurgical operations 
 Coke-Ovens , retorts heated by means of 
 
 „ for heating retorts, where beneficially used 
 ,, directions for working 
 
 Combustion , spontaneous, whence occurring . 
 
 „ result of, when carried on favourably . 
 
 ,, result of, when incomplete 
 
 ,, imperfect, soot a sign of . 
 
 Condensation of Gas , various modes of effecting 
 
 ,, by mains from retort-house to purifier 
 ,, by worm pipe in tank of gas-holder 
 ,, by parallel lines of main pipes in the works 
 ,, remarks upon the modes above mentioned 
 
 „ by main pipes, why objectionable 
 
 „ by the patent condenser of Mr. Perks 
 ,, by Mr. Malam’s condenser 
 Condenser , now generally used .... 
 
 ,, such as fixed in several places by the Author 
 
 „ of plate-iron, fit for a small manufactory 
 
 described ...... 
 
 ,, proper for a large gas-manufactory 
 
 Connecting Pieces , wrought-iron, described 
 Croll, Mr. A. A ., his patent for depriving coal-gas of am- 
 monia ........ 
 
 Page 
 
 409 
 
 410 
 61 
 
 149 
 
 137 
 
 138 
 149 
 
 4 
 
 4 
 
 5 
 5 
 
 207 
 
 207 
 
 207 
 
 207 
 
 207 
 
 209 
 
 210 
 212 
 214 
 216 
 
 219 
 
 221 
 
 351 
 
 262 
 
 D. 
 
 Daniel , Professor , invents an apparatus for converting resin 
 
 into gas ........ 104 
 
 De Carolles , M. Blondcau , proposes purifying coal-gas 
 
 from ammonia therein contained . . • .261 
 
 De Val Marino , the Comte , proposed method for obtaining 
 
 carburetted-hydrogen gas from coal-tar . .410 
 
INDEX. 
 
 457 
 
 Diminishing Pipes , description and use of 
 Dip Pipes , description of section of 
 Doors , sliding, for furnaces, with slide, &c. 
 
 Door and Frame , for furnace and ash-pit 
 Double Sockets , wrought-iron, where used 
 Down's, Mr. James , patent for improvements in making 
 gas noticed, and mode of operation described 
 
 Page 
 
 341 
 
 196 
 
 151 
 
 159 
 
 351 
 
 418 
 
 E. 
 
 Ess- Pipe, description and use of . . . .341 
 
 Explosion, from coal-gas, not to be expected under ordinary 
 
 circumstances . . . . . . .413 
 
 ,, from coal-gas when mixed with atmospheric air, 
 what combination of circumstances required to produce 413 
 Eye, human, not fitted for judging of the intensities of 
 
 different lights . . . . . .17 
 
 „ particularly adapted for judging of the strength of 
 shadows . . . . . . .17 
 
 Fire, has been known in all ages 
 ,, used as an emblem of the Deity, &c. 
 
 „ various means of obtaining 
 „ when made from crude materials, how to be managed to 
 produce complete combustion 
 Fire-Bar, for retort- furnace, description of 
 Filtings-up, tubing to be used for, described . 
 
 „ directions relative to ... 
 
 Flame, of what it consists .... 
 
 ,, when perfect and brilliant 
 
 ,, matter for producing it should be at a proper heat 
 
 ,, how to be thrown into the atmosphere, so as to be 
 
 wholly decomposed ..... 
 
 ,, how weakened ..... 
 
 ,, small one proportionally brighter than a large one 
 ,, bodies capable of producing it, what they contain 
 
 2 
 
 3 
 
 3 
 
 6 
 
 160 
 
 352 
 
 358 
 
 4 
 4 
 6 
 
 6 
 
 6 
 
 7 
 
 9 
 
458 
 
 INDEX. 
 
 Flame , may be tinged of various colours, and by what means 
 ,, remarks on the colours of, when produced from coals 
 and wood .... ... 
 
 „ of a common candle, remarks on the shades of 
 colour it exhibits ..... 
 
 ,, transparent ..... 
 
 „ of gas-burner, remarks on the lengths of 
 Flames , for producing light, if brought into contact wit 
 each other, why beneficial .... 
 Flanch Pipe, description of ... 
 
 Fluids , movable every way .... 
 
 ,, surfaces of, rest in horizontal planes . 
 
 ,, press equally on every part of the base of the vesse 
 containing them ..... 
 
 ,, all parts of, press equally at the same depth . 
 
 ,, press equally in all directions whatever 
 „ pressure of, on the base of a vessel, is as the has 
 and perpendicular height .... 
 Franklin's , Dr. B ., suggestions relative to using two candles 
 so near each other as to allow the flames to unite . 
 
 Page 
 
 10 
 
 11 
 
 11 
 
 35 
 
 36 
 
 35 
 
 339 
 
 275 
 
 275 
 
 276 
 276 
 276 
 
 279 
 
 34 
 
 ton of coals in 
 
 G. 
 
 Gas , Portable , Mr. David Gordon obtains a patent for 
 vessels to contain . ..... 
 
 „ procured from turf 
 ,, average quantity of, produced from 
 
 London, in 1837 ... ... 
 
 „ average quantity of, produced from a ton of coals at 
 sundry places ....... 
 
 „ why to be condensed (or refrigerated) before being 
 submitted to the purifying process .... 
 
 „ impure, the use of it to be avoided .... 
 
 „ purity of, depends very much upon condensation 
 „ the levity of, particularly observable in theatres. 
 
 „ requires to be thoroughly purified to produce a good 
 light . . . • • • • • 
 
 „ coal, price of, not depending altogether upon the price 
 paid for coals ....... 
 
 104 
 
 107 
 
 123 
 
 167 
 
 205 
 
 206 
 206 
 351 
 
 412 
 
 417 
 
INDEX. 
 
 459 
 
 Page 
 
 Gas-Burner , how to ascertain the illuminating power of . 22 
 
 „ Argand, not to be used without a chimney- 
 glass ........ 36 
 
 ,, account of improvements in the manufacture of, 354 
 „ t Argand, shank described .... 353 
 
 „ ditto 12-hole, dimensions of . . . 353 
 
 „ ditto 15-hole, ditto . . . 354 
 
 „ one sometimes used as a street-light, description 
 and dimensions of ..... 355 
 
 „ bat’s-wing, description of . . . .355 
 
 ,, fish-tail, or swallow’s-tail, description of . 356 
 
 „ ditto or bat’s-wing, upright socket for . 357 
 
 „ ditto ditto elbow socket for . .357 
 
 „ with a single jet of flame .... 356 
 
 „ yielding three jets of flame. . . . 356 
 
 „ yielding eight jets of flame. . . . 356 
 
 „ improved Argand, manufactured by Messrs. 
 
 Platow and Co., described ..... 355 
 
 Gas-Conductors , remarks upon the diameters of . . 203 
 
 Gas-Cooking Apparatus , adverted to, and where manu- 
 factured ........ 416 
 
 Gas-Heating Stoves , for warming churches, &c., described . 415 
 Gas-Holder (gasometer), its use ..... 265 
 
 „ how the gas is prevented from escaping out of it, 266 
 ,, to produce a proper light, at what pressure to 
 be worked ....... 267 
 
 „ an equilibrium can be effected between it and 
 the balance-weight ...... 268 
 
 „ how to ascertain the pressure at which it works 268 
 
 pressure of, how to be regulated . 
 
 one of its uses is to regulate the emission of the 
 
 „ weight of, increases as it rises 
 „ some contrivance necessary for making the 
 pressure equal at all heights of its rise 
 ,, equality of pressure, how obtained in the early 
 period of gas-lighting ...... 
 
 „ equality of pressure effected by the chain of 
 suspension. ....... 
 
 269 
 
 269 
 
 269 
 
 270 
 
 270 
 
 271 
 
460 
 
 INDEX. 
 
 Page 
 
 Gas-Holder , rule for ascertaining the weight of the sus- 
 pension-chain for effecting an equal pressure, with ex- 
 amples thereon . . . . . . .211 
 
 „ of 15,000 cubic feet capacity, how constructed 292 
 „ formerly encumbered with wooden frames or 
 iron stays ........ 293 
 
 „ Mr. Clegg’s revolving one, noticed . . 298 
 
 „ cylindrical, on the ordinary principle, described, 266 
 „ ditto Mr. Malam’s mode of constructing, 
 
 with upright centre column ..... 302 
 
 „ collapsing one of Mr. Clegg’s invention, 
 noticed ........ 298 
 
 „ patent obtained for one by Mr. William 
 Stratton, for doubling its capacity in the ordinary tank 299 
 „ suspended from four or more points at the cir- 
 cumference, description of .... 305 
 
 ,, suspended from three points at the circum- 
 ference, description of . . . . . . 309 
 
 „ telescope, remarks upon its action . .315 
 
 M ditto description of one . . .311 
 
 „ pressure at which it works, how to calculate . 294 
 Gas-Holders , proposed to be worked with air-vessels for 
 
 equalizing pressure of, noticed ..... 298 
 
 „ should always be placed in the open air, and 
 as far from the retort-house as circumstances will 
 permit ........ 449 
 
 Gas-Light , does not produce any smoke or emit sparks . 85 
 
 „ not so dangerous as candles and lamps . . 85 
 
 not liable to be put out by sudden gusts of wind 
 or heavy rain ....... 85 
 
 „ to whom the merit of bringing it into notice as a 
 substitute for other lights is due . . . .88 
 
 „ its superiority over other artificial light, whence 
 it arises . . . . . . • .414 
 
 „ how managed, so as to produce different inten- 
 sities of light . • 414 
 
 „ exceedingly applicable for use in light-houses . 415 
 „ cannot be manufactured with economy on a small 
 scale ........ 416 
 
INDEX. 
 
 461 
 
 Page 
 
 Gas-Light Companies , on what they rest their claims to 
 
 public notice ....... 62 
 
 Gas-Light Manufactory , arrangement of, must always 
 
 depend upon local circumstances .... 448 
 
 ,, low situation of, near a river or 
 
 canal, why to be preferred « 448 
 
 Gas-Meter, history of its origin ..... 361 
 
 „ Mr. Clegg’s first (or reciprocating), described . 361 
 „ ditto patent rotary one, described. . 363 
 
 „ Mr. John Malam submits one to the Chartered 
 Gas-Light Company, Westminster .... 364 
 
 „ its usefulness for ascertaining the quantity of 
 gas generated . . . . . . .360 
 
 Mr. Malam’s first, description of . . . 368 
 
 ,, ditto improved, description of . . 373 
 
 ,, would be a check upon the stokers. . .375 
 
 „ dial of, should be accessible to the manager of the 
 gas-works only. . . . . . .376 
 
 „ its use advantageous to the manufacturer . 376 
 
 „ ditto consumer of gas . 376 
 
 „ use for economizing the consumption of gas . 378 
 
 ,, remarks on its use in private houses, shops, &c. 376 
 
 „ dry ones noticed . . . . .379 
 
 „ Mr. John Malam’s patent wet meter, noticed . 379 
 
 „ Mr. John Hemming’s patent protector gas- 
 meter, described . . . . . . .380 
 
 „ float-valve of, for keeping water at a proper level . 382 
 .„ may be relied upon as a correct measurer . 382 
 
 Gas-Moderator , manufactured by Messrs. Platow and Co., 
 
 described ........ 394 
 
 Gas- Regenerators, patented by Mr. John Malam . . 420 
 
 „ description of, and furnaces . .421 
 
 „ operation of, and results produced from 
 
 working them ...... 424 
 
 „ advantages they hold out to the gas ma- 
 nufacturer ....... 427 
 
 ,, advantages further stated . . . 432 
 
 Governor, why first thought of, and the object it was intended 
 
 to accomplish ....... 383 
 
462 
 
 INDEX. 
 
 Page 
 
 Governor , Mr. Samuel Clegg obtains a patent for one . 383 
 
 „ description of one . . . . .384 
 
 ,, large one to be used in the gas manufactory, de- 
 scription and use of . . . . .389 
 
 ,, where usefully employed . . . .395 
 
 Ground Plan of the gas-works at Bury St. Edmunds, de- 
 scribed ........ 443 
 
 H. 
 
 Hales , Dr ., made chemical experiments upon pit-coal . 1 2 
 
 Heat , best for working retorts at, and why so . .411 
 
 Heated-medium , for passing gas through after it had left the 
 hydraulic main, tried by the author many years ago, and 
 abandoned ....... 418 
 
 Henry's , Dr. IV., account of Mr. Murdoch’s discoveries 
 
 and experiments on pit-coal . . . . 81 
 
 ,, results of experiments on the quantity of 
 
 oxygen required for burning different species of carbu- 
 retted-hydrogen gas . . . . . .412 
 
 Hydraulic Main, description and use of . * .196 
 
 ,, advantages arising from the use of .198 
 
 „ remarks relative to the pressure thereon . 200 
 
 ,, with the dip-pipes forms a series of hy- 
 draulic joints . . . . . . .201 
 
 ,, importance of its being well constructed . 202 
 
 ,, gas therein has exploded . . . 202 
 
 ,, to be kept as distant from the retorts as 
 
 possible ........ 203 
 
 I. 
 
 Iron-founder , coke produced in ovens for heating the re- 
 torts, fit for use of . . . . .130 
 
 L. 
 
 Lamp , shadowless overflowing, or meteor lamp . . 9 
 
 „ ditto consumption of oil per hour . . 28 
 
INDEX. 
 
 463 
 
 Lamp, solar ........ 
 
 „ ditto consumption of oil per hour 
 
 Lamps , quality of combustible material for 
 „ use of the wick of . 
 
 Liebig , Professor , aids Mr. Thomas Richardson in examin- 
 ing the exact proportions of each ingredient contained 
 in various specimens of coals .... 
 
 Light , procured by the agency of fire .... 
 
 „ proportions of, afforded by candles when newly 
 snuffed, and when requiring snuffing 
 ,, evolved by artificial means, whence derived 
 „ strength of, decreases in what proportion with the 
 distance from the point of divergency 
 „ remarks on ascertaining its intensity when obtained 
 from candles, lamps, &c. . 
 
 „ travels in straight lines, and in every direction from 
 its point of divergency . 
 
 „ emitted from any luminous body, how it becomes 
 dilated, explained by a diagram 
 „ afforded by candles of different sizes, or other lu- 
 minous bodies, rules for ascertaining comparative pro- 
 portions of ...... 
 
 „ comparative cost of as obtained from different sub- 
 stances ........ 
 
 „ from coal-gas to be good, the gas must be thoroughly 
 purified ........ 
 
 Light, Artificial, from whence it arises 
 
 ,, how much of its effect is lost 
 
 „ resources in this country for supplying it 
 
 Lights, strength of various, how compared 
 Light-Houses might be furnished with a better light from 
 gas than in the ordinary way of lighting, and at less 
 expense ....... 
 
 Llandaff, the Bishop of, examines the qualities of the pro- 
 ducts obtained from coal ..... 
 
 Lowe, Mr. George , uses double retorts set end to end, and 
 how worked ....... 
 
 Lowe, Mr. George, and Mr. John Kirkham , take out a 
 patent for a mode of combining and working retorts 
 
 Page 
 
 9 
 
 28 
 
 12 
 
 12 
 
 405 
 
 2 
 
 7 
 
 10 
 
 18 
 
 18 
 
 18 
 
 18 
 
 20 
 
 28 
 
 412 
 
 5 
 
 5 
 
 35 
 
 30 
 
 415 
 
 80 
 
 430 
 
 431 
 
464 
 
 INDEX. 
 
 Page 
 
 Lowe , Mr. George , and Mr. John Kirkham , patent retorts, 
 
 mode of operation thereof described . . .431 
 
 Lowther , Sir James , coal-mine of, shaft takes fire . . 73 
 
 M. 
 
 Maiben’s , J/r., o/ Perth, observations on the distillatory 
 process, his retort, &c. ..... 
 
 Main Pipes , when to be laid, steps necessary to be taken . 
 
 „ how diameters of should be arranged . 
 
 „ socket described ..... 
 
 ,, do. how jointed together 
 
 „ Roman-cement used for making good the 
 
 joints of socket pipes ...... 
 
 „ flanch described ..... 
 
 „ do. cement for forming joints of 
 
 „ branches, description and use of 
 „ outlets, description and use of 
 „ bend, description and use of 
 
 „ ess, description and use of ... 
 
 „ description and use of thimble-joint used upon 
 
 „ for conveying gas, might be lighter than those 
 
 for water ....... 
 
 „ rule for ascertaining the diameter of, for sup- 
 plying a given quantity of gas .... 
 
 ,, Dr. Ure’s formula for ascertaining the diameters 
 of, for supplying a given quantity of gas, the length of 
 pipe being taken into consideration 
 ,, rule (practical one) for ascertaining the diameter 
 of, for supplying a given quantity of gas 
 „ to be laid with a certain declivity 
 ,, better supply of gas from, in elevated than in 
 low situations ....... 
 
 Malam , Mr. John , condensing vessels of his invention de- 
 scribed ........ 
 
 ,, invents a treble wet-lime purifier 
 
 „ description of his treble purifier 
 
 121 
 
 343 
 
 344 
 
 335 
 
 336 
 
 337 
 339 
 
 339 
 
 340 
 
 341 
 341 
 
 341 
 
 342 
 
 343 
 346 
 
 346 
 
 347 
 
 349 
 
 350 
 
 212 
 238 
 23 S 
 
INDEX, 
 
 465 
 
 Page 
 
 Malam , Mr. 
 
 John , description of the action of his treble 
 
 
 purifier 
 
 . . . ..... 
 
 241 
 
 )> 
 
 patent dry lime purifier described 
 
 247 
 
 
 double hydraulic valve described 
 
 324 
 
 
 ditto ditto pressure it will sustain . 
 
 326 
 
 » 
 
 pneumatic valve described 
 
 326 
 
 )> 
 
 ditto is of a small size, and 
 
 
 got up at a trifling expense ..... 
 
 328 
 
 
 exhibits a model of a gas-meter . 
 
 364 
 
 
 gas-meter invented by, disputed by Mr. 
 
 
 Clegg 
 
 . 
 
 365 
 
 
 has the gold Isis medal of the Society of 
 
 
 Arts voted to him for his gas-meter 
 
 366 
 
 
 his first gas-meter on the principle of 
 
 
 Archimedes’ screw ...... 
 
 367 
 
 >■> 
 
 g’as-meter of, described 
 
 368 
 
 
 improved gas-meter of, described 
 
 373 
 
 S3 
 
 dry gas-meter noticed 
 
 379 
 
 33 
 
 wet-meter, for which he obtained a 
 
 
 patent in 
 
 1835, noticed ..... 
 
 379 
 
 ?» 
 
 regulator of, described 
 
 386 
 
 33 
 
 dimensions of, for supplying four lights 
 
 388 
 
 33 
 
 regulator of, capable of sustaining a very 
 
 
 5> 
 
 heavy pressure ..... 
 
 388 
 
 >3 
 
 takes out a patent for gas -^generators 
 
 420 
 
 33 
 
 gas-regenerators of, and furnaces described 
 
 421 
 
 33 
 
 ditto operation of. 
 
 424 
 
 3» 
 
 ditto advantages they hold out 
 
 
 to the manufacturer of gas . . . .427 
 
 Malting , coke produced in oven for heating retorts, answers 
 
 „ Exceedingly well for . . . .130 
 
 Montauban , the Marquis of, proposed method of converting 
 
 coal-tar into carburetted-hydrogen gas . . . 409 
 
 „ takes out a patent for a distilla- 
 
 tory vessel in addition to the retort ordinarily used, 
 which he calls “ a decomposer” .... 429 
 „ decomposer of, described . 429 
 
 Murdoch’s, Mr., experiments on pit-coal at Old Cumnock, 
 
 in Ayrshire. . . . - . . 82 
 
 2 H 
 
466 
 
 INDEX. 
 
 Page 
 
 Murdoch s , Mr., experiments on pit-coal at Redruth, in 
 
 Cornwall ....... 83 
 
 „ gas apparatus at Soho foundry . . .83 
 
 „ account of lighting the whole of Mr. Lee’s 
 
 cotton-mill with gas, in which the saving of expense 
 is noticed ........ 96 
 
 N. 
 
 Northern’s , Mr., account of applying coal-nn for the pur- 
 pose of producing light ... 89 
 
 O. 
 
 Oil , burnt in lamps with different sized wicks, experiments 
 
 relative to the expense of . . . .34 
 
 Oil-gas, apparatus for making, protected by a patent . . 101 
 
 „ from what obtainable . . . . .101 
 
 „ bulk of, stated to be equal in illuminating power to 
 more than thrice its bulk of coal-gas . . .102 
 
 ,, scheme why abandoned . . . . .103 
 
 cost of obtaining light from, compared with 
 cost of obtaining light from wax-candles, 
 mould or ill -snuffed tallow-candles and coal- 
 gas ....... 26 — 28 
 
 Olejiant-gas , produced from pit-coal .... 408 
 
 „ coal producing greatest proportion of, most 
 profitable ........ 408 
 
 Outlet-Pipe , description and use of . 341 
 
 P. 
 
 Palmer , Mr., candles of, with metallic wicks ... 8 
 
 Perks , Mr. John, patent condenser of, described . .210 
 
 Phillips , Mr. R., obtains a patent for purifying coal-gas by 
 
 means of dry lime ...... 242 
 
 ,, dry-lime purifier described, and how used 243 
 
 „ ditto advantages attending use of 246 
 
 Oil , seed, 
 
 „ sperm , 
 „ whale, 
 
INDEX. 
 
 46? 
 
 Pipes , connecting, for retorts, described .... 
 
 „ dip and H, for retorts, described .... 
 
 Portable Gas , London Portable Gas-light Company noticed 
 Pressure , frequently confounded with weight . 
 
 „ of fluids on vessels having equal bases, but of 
 different capacities, exemplified by an experiment 
 „ upon every square inch of the top of the gas- 
 holder how ascertained ...... 
 
 Protector Gas-Meter , Mr. Hemming’s patent one . 
 Purification of Coal-Gas , why it should be properly per- 
 formed ........ 
 
 „ general modes of performing the 
 
 „ by lime in mechanical solution, 
 
 how first effected . 
 
 wet-lime purifier 
 
 heated metal tubes 
 
 effected by Mr. Malam’s treble 
 
 by lime in a semi-fluid state 
 effected by dry lime . 
 attempted by passing it through 
 
 „ from ammonia, how proposed to 
 
 be effected by M. Blondeau de Carolles . 
 
 ,, (patent for) from ammonia, &c., 
 
 obtained by Mr. A. A. Croll, describing his mode of 
 procedure to effect that object .... 
 
 „ lime to, be used for effecting it . 
 
 Purifiers , description of dry-lime ones, patented by Mr. R. 
 Phillips ........ 
 
 „ description of dry-lime ones, patented by Mr. 
 John Malam ....... 
 
 „ Mr. John Malam’s patent dry-lime purifiers, ad- 
 vantages attending the use of . 
 
 „ remarks as to where sometimes placed, in order 
 that all the connexions to them might be accessible 
 Purifying Vessel, the pressure it is worked at explained 
 
 „ necessity of means being adopted for 
 
 giving notice of any impediment therein . 
 
 „ square, or parallelopipedal why not equal 
 
 to round one ....... 
 
 Page 
 
 196 
 
 196 
 
 104 
 
 275 
 
 281 
 
 295 
 
 380 
 
 230 
 
 231 
 
 233 
 
 238 
 
 232 
 243 
 
 232 
 
 261 
 
 262 
 
 263 
 
 243 
 
 246 
 
 259 
 
 448 
 
 200 
 
 201 
 
 237 
 
 2 h 2 
 
468 
 
 INDEX, 
 
 R. 
 
 Receiver , for inlet and outlet pipes to and from gas-holder, 
 described ........ 
 
 Regulator , for correcting inequalities of pressure upon 
 burners ........ 
 
 „ large one, for supplying a town or district, de- 
 scribed ..... -v . . 
 
 Retorts , different kinds of, used ..... 
 
 „ circular (or cylindrical), description of . 
 
 „ circular, performance of, when set two to one fire . 
 „ ditto ditto set three to one fire 
 
 ditto ditto set four to one fire . 
 
 „ circular, when set four to one fire the top ones fail 
 first ......... 
 
 „ ovens for heating them first adopted . 
 
 „ advantages of elliptical or large D -shaped over cy- 
 
 lindrical ones ....... 
 
 „ elliptical, proposed to be used .... 
 
 „ ditto, advantages arising from the use of . 
 
 „ large D- shaped ...... 
 
 „ semicircular, observations upon .... 
 
 „ kidney-formed ...... 
 
 „ square (so called) ...... 
 
 „ ditto, their action ...... 
 
 „ on the kind of workmanship which should be at- 
 tended to in setting them ..... 
 
 ,, as of day, fire-tiles, &c., of various kinds submitted 
 to the public ....... 
 
 „ square, description of mode of setting them . 
 
 „ method of setting five elliptical ones, in one oven, 
 
 to be heated by two coke-ovens described . 
 
 „ kidney-shaped, plan for setting one over one fire 
 described ........ 
 
 „ large D-shaped, description of setting three over an 
 oven (with descending flues) and in such a way as 
 will admit of the oven being worked either as a furnace 
 or for making coke ...... 
 
 Pag*? 
 
 331 
 
 383 
 
 389 
 
 109 
 
 110 
 110 
 111 
 112 
 
 114 
 
 115 
 
 118 
 
 125 
 
 126 
 127 
 
 129 
 
 130 
 
 131 
 
 132 
 
 135 
 
 139 
 
 141 
 
 142 
 144 
 
 146 
 
INDEX. 
 
 469 
 
 Page 
 
 Retort a, small D-shaped, description of setting three over 
 
 one furnace . . . . . . .156 
 
 ,, the most advantageous heat to work them at, and 
 why so ...... 410, 411 
 
 Richardson , Mr Thomas , aided by Professor Liebig, ex- 
 amines the exact proportions of each ingredient con- 
 tained in various specimens of coals . . . 405 
 
 Rickets, Mr. C ., manufactures gas-heating stoves and ap- 
 paratus for cooking by gas . . . . .416 
 
 Rosin , gas procured from . . . . . .103 
 
 Rumford’s , Count , experiments on the quantity of materials 
 necessary to produce a light of a certain intensity, for 
 a given time ....... 26 
 
 S. 
 
 Seed-Oil , compared as to cost for procuring light with cost 
 of obtaining light by means of wax or tallow-candles, 
 sperm or whale-oil, and coal-gas . . . 26 — 28 
 
 Service Pipes, description and use of . . . .351 
 
 „ to be laid sloping .... 352 
 
 Shadowless Lamp, overflowing, or Meteor Lamp, noticed . 9 
 
 „ cost per hour for burning . . .28 
 
 Shadows, produced by two or more luminous bodies, how 
 
 to judge of the strength of . . . . .19 
 
 Shirley's, Mr. Thomas, description of a burning well near 
 
 Wigan, Lancashire ...... 69 
 
 Short-lengths, wrought-iron, described, and where used . 351 
 
 Sight-hole and Frames, description of . 144 and 151 
 
 Soholowsky and Horrer, obtain carburetted-hydrogen gas 
 
 from wood . . . . . . .411 
 
 Socket Pipe , described ...... 335 
 
 „ turned and bored, much used, and where used 
 advantageously ...... 338 
 
 Solar Lamp , noticed ...... 9 
 
 „ consumption of oil, and consequent cost of 
 using it per hour ...... 28 
 
 Specific Gravity , of coal-gas, average of ... 409 
 
470 
 
 INDEX. 
 
 Page 
 
 Specific Gravity of coal-gas obtained when working the 
 
 gas-regenerators . . . . . .426 
 
 „ of coal-gas, directions and rules for ascer- 
 taining ........ 435 
 
 Sperm-Oil , compared as to cost for procuring light with 
 light obtained from burning wax and tallow-candles, 
 whale and seed-oil, and coal-gas . . . 26 — 28 
 
 Station Gas-Meter , dial of, should be accessible to the 
 
 manager of a gas manufactory only . . .376 
 
 ,, sometimes has mechanism attached 
 
 thereto for marking down with a pencil, or other tracer 
 upon paper, the quantity of gas made every hour . 375 
 
 Stratton s, Mr. William , gas-holder, described . . 299 
 
 „ ditto, action of . .301 
 
 ,, ditto, compensation of pres- 
 sure well effected ...... 302 
 
 Sulphuretted-Hydrogen , produced from pit-coal . . 406 
 
 Syphon , difficulty of accounting for the name of that (so 
 
 called) used in the gas-light manufactory . . 328 
 
 ,, the different kinds of, noticed . . . 328 
 
 ,, description of gun-barrel and bottle syphon . 330 
 
 „ gun-barrel, or bottle, where used . . . 330 
 
 T. 
 
 Table of comparative illuminating power and expense per 
 annum for burning coal-gas, tallow and wax-candles, 
 and spermaceti oil . . . . .37 
 
 „ showing the quantities of gas obtainable from several 
 varieties of coals of the first class . . .45 
 
 „ ditto, from coals of the second class . 49 
 
 ,, showing the relative proportions of gas obtainable 
 from coals of various kinds . . . .51 
 
 „ exhibiting the ratio at which gas is evolved when 
 working the retorts at eight hours’ charges . .170 
 
 ,, last mentioned, use of exemplified . . .171 
 
 Tanks for Gas-Holders , remarks on their construction , 285 
 
INDEX. 
 
 471 
 
 Page 
 
 Tanks for Gas-Holders , when of cast-iron, how to ascertain 
 the proportional strength of each tier of plates 
 
 ,, when of brick or masonry, detailed 
 
 instructions for making ..... 
 
 „ cast-iron one of thirty-four feet 
 
 diameter described 
 
 „ double one noticed 
 
 ,, circular preferable, to square . 
 
 Tar Cistern , where it should be situated 
 
 „ shape and construction of one of cast-iron 
 „ ditto ditto of one of brick 
 
 „ method of preventing the gas entering into it 
 
 Tar Well , described, and where used . . 330 and 
 
 Tee-Pieces , wrought-iron, description and use of 
 Telescope Gas-Holder , mode of constructing described 
 Tests, necessity of taking, and why so . 
 
 „ a self-acting test-card described, with remarks thereon 
 „ most correct and satisfactory mode of taking . 
 
 „ a great number described in Dr. Henry’s Chemistry, 
 and also in Dr. Reid’s Chemistry .... 
 
 Test, for detecting sulphuretted-hydrogen gas, 1st 
 
 
 ditto 
 
 ditto 
 
 2nd * 
 
 JJ 
 
 ditto 
 
 ditto 
 
 3rd . 
 
 
 ditto 
 
 ditto 
 
 4th r 
 
 
 ditto 
 
 ditto 
 
 5th . 
 
 
 ditto 
 
 sulphuretted-hydrogen 
 
 gas, or carbonic 
 
 
 acid gas . 
 
 . 
 
 
 
 ditto 
 
 carbonic acid gas 
 
 . . 
 
 
 ditto 
 
 ammoniacal gas 
 
 • 
 
 Theory of the production of gas-light compared with the 
 theory of procuring artificial light by means of candles 
 or lamps ....... 
 
 Thimble-Joint , description and use of . 
 
 U. 
 
 286 
 
 289 
 
 286 
 
 288 
 
 288 
 
 224 
 
 226 
 
 227 
 
 227 
 
 331 
 
 351 
 
 317 
 
 397 
 
 398 
 
 399 
 
 404 
 
 399 
 
 400 
 
 401 
 
 401 
 
 402 
 
 402 
 
 403 
 
 403 
 
 63 
 
 342 
 
 Union- Joint, description and use of 
 
 . 356 
 
472 
 
 INDEX. 
 
 V. 
 
 Valves , why necessary ...... 
 
 „ ordinary slide valves now used for most purposes in 
 the gas-light manufactory ..... 
 
 Valve , double hydraulic, described .... 
 
 ,, pneumatic, described . . . . 
 
 ,, ditto, rule for its dimensions 
 Vats , Wooden , for gas-holders to work in, remarks upon . 
 
 Page 
 
 324 
 
 324 
 
 324 
 
 326 
 
 326 
 
 288 
 
 W. 
 
 Walker , Mr. Ezekiel , on a mode for preventing the fluctua- 
 tion of light afforded by candles ... 7 
 
 Washer, description of one . . . . .217 
 
 Watson, Dr., afterwards Bishop of Llandaff, publishes re- 
 sults of his experiments for obtaining gas from pit-coal 80 
 Wax-Candles, cost of obtaining light from, compared with 
 the cost of obtaining light from sperm-oil, whale or 
 seed-oil, mould or ill-snuffed tallow-candles, and coal- 
 gas ....... 26 — 28 
 
 Whale-Oil, cost of obtaining light from, compared with the 
 cost of obtaining light from wax and tallow-candles, 
 sperm-oil, seed-oil, and coal-gas . . . 26 — 28 
 
 Winsor, Mr. F., some account of his labours for bringing 
 the subject of lighting streets, houses, &c. &c., by 
 
 London : Priliited by William Clowes and Sons, Stamford-street- 
 
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