r 
 
Scientific and 
 Medical Books 
 For Sale bv 
 A.E. FOdXE, M L. 
 
 1223 Belmoixji Ave., 
 Philadelptiia, P;\. 
 
 FRANKLIN INSTITUTE LIBRARY 
 
 PHILADELPHIA 
 
 Class.^.j&.G Book..-?\.Un~l Accession..6^4/ 0 
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A PRACTICAL TREATISE 
 
 PREPARATION, COMBINATION AND 
 APPLICATION 
 
 OF 
 
 CALCAREOUS AND HYDRAULIC 
 LIMES AND CEMENTS, 
 
 COMPILED AND ARRANGED FROM THE BEST AUTHORITIES, AND 
 FROM THE PRACTICAL EXPERIENCE OF THE COMPILER 
 DURING A LONG PROFESSIONAL CAREER, 
 
 »*o ^VIIieH-KS ALDf^D'MANY ' ' ' "* ' ' 
 
 USEFUL RECIPE^ ' -FOR VARIOOS' SCIENTIFIC, 
 MERCANTILE AND pOMESTlC :PUii:?,(^5ES. 
 
 JAMES G. AUSTIN, 
 
 ARCHITECT. 
 
 NEW YORK: 
 JOHN WILEY & SON, 
 15, ASTOR PLACE. 
 
 1871. 
 
OOA/S 
 
PEEFACE. 
 
 The following pages (which make but little pretensions to 
 originality) are presented to the notice of the Building Pro- 
 fession, as a concise and useful work upon the important subject 
 of Limes and Cements, and with a view to attract public 
 attention to their essential properties, analysis, combination 
 and application, as described in a rare, but highly esteemed 
 and valued work (long since out of print) by Dr. Brindley 
 Higgins, the theories and experiments therein enunciated and 
 defined having been practically confirmed by the compiler, 
 during a long professional career, and also as embodying the 
 best modern experience and information upon the subject, 
 derived from high authority (which is duly acknowledged) 
 interspersed with practical remarks by the Author, to w^hich 
 is added much that is useful to the engineer, geologist, and 
 American citizen, and now humbly and respectfully submitted 
 to the patronage of an enlightened public. 
 
 March, 1862. 
 
GENERAL REMARKS. 
 
 Cements are of two distinct classes, viz., Ca/ca?-eows(or those which 
 are used for works exposed to the air;) and Hydraulic^{ox such as are 
 used under water ,*)they are also further distinguished as Hot and Cold. 
 The former are those which are applied by the aid of heat or fire, and 
 which contain, rosin, resin, bees-wax, and such like substances ; and 
 the latter, those which are applied through the medium of alcohol, 
 water, or oil, and are chiefly composed of calcareous and other earthy 
 matters. 
 
 Calcareous Cement or mortar is a most important auxilliary in 
 the construction of every description of brickwork, and masonry, and 
 is universally known by the term mortar." 
 
 Hydraulic Cements are those whose property is to indurate or 
 to harden under water, and are consequently indispensable in the 
 construction of bridges, docks, quays, and other marine works. 
 
 Plastic Cements are such as are more particularly applied to the 
 stuccoing or incrustation of the exterior and interior surfaces of walls, 
 &c., the use of which is more applicable to the plasterer's art. 
 
 The above three classes or divisions will be separately treated and 
 explained, in consecutive order — ^but before entering into the descrip- 
 tion of the composition of either of them, it would be necessary first 
 to consider and to define the nature, properties, and qualifications of 
 the several ingredients of which ordinary mortar is composed, and to 
 describe the principal varieties in use, pointing out the relative use 
 and value of each, and then to describe the proportions of the several 
 ingredients, and afterwards to explain the mode of combining and 
 applying them to building purposes. 
 
COMPONENTS OF MORTAR. 
 
 Lime. — Of this important ingredient there are numerous varieties 
 possessing different qualities and merit. They are prepared from the 
 following minerals, viz. : marble, limestone (of which there are seve- 
 ral varieties), chalk, oyster and other shells, and also from other cal- 
 careous or carboniferous stones, which, when subjected to a red heat 
 and calcined, will dissolve and effervesce with acid ; and as a general 
 rule it may be remarked that the harder the stone or other material 
 is, the better will be the quality of the lime, and that which dissolves 
 the quickest, heats the most in slaldng, and falls into the finest pow- 
 der, is the best. 
 
 Lime is usually found in connection with an acid, and by subjecting 
 it to a red heat the acid is evolved, leaving the lime in a pure state, 
 ■»vhich is then termed caustic or quick lime, and is then fit for admix- 
 ture with the other ingredients to form mortar or cement. 
 
 Of the method of preparing lime from the crude material, it will be 
 irrelevant here to speak, but the operation will be found amongst 
 the "addenda" at the end of this treatise. 
 
 Lime should be used fresh from the kiln, or otherwise it must be se- 
 cured from the air, in close casks or other receptacles, till required for 
 use, or it will by exposure readily absorb the carbonic acid gas from 
 the atmosphere, to discharge which is the principal object of burning 
 or calcining it ; and lime, when once it is slaked, should be im- 
 mediately used or it would become effete or dead, or for all cementi- 
 tious purposes, perfectly useless. 
 
 Limestones lose about four-ninths of their weight in burning, though 
 they slirink but little, but when properly burnt and slaked to a 
 powder, they acquire nearly double their former bulk. 
 
 Chalk and lime stones if equally fresh and well burnt, differ but little 
 in their cementitious properties, but as slaked lime absorbs carbonic 
 
COMPONENTS OF MORTAR. 
 
 7 
 
 gas in proportion to its textui'e (solidity), so it yields its cementing 
 properties the more freely by exposure ; therefore, although stone and 
 chalk limes be equally good at first, yet there will exist a great diifer- 
 ence, subsequently ; because the latter becomes more readily affected 
 or injured by the atmosphere than the former, upon which fact, the 
 preference for stone limes has been, obtained. 
 
 Dr. Higgins in his work on Calcareous Cements" &c., section 2, 
 entitled Experiments and Observations on Limestone and Lime," 
 makes the following observ^ations (the result of practical experiments) 
 upon the properties of limestones, chalk and lime : — 
 
 Observation. 1. Limestone or chalk heated only to redness, in a 
 covered crucible, or a perforated one, through which the air circulates 
 freely, loses only about one-fourth of its weight, however long this 
 heat be continued. The sort of lime so formed, effervesces considera- 
 bly in acid, slakes slowly and partially to a gray or brown powder, 
 and heats but little in slaking ; by heat is meant that degree of it 
 which the bodies themselves (limestones, &c.) are made to conceive 
 equally through their whole mass during the operation of burning. 
 
 Obs. 2. Limestone or chalk exposed to a heat barely sufficient to 
 melt copper, whether in a perforated crucible or otherwise, loses about 
 one-third of its weight in twelve hours, and very little more in any 
 longer time. This lime effervesces but slightly in acids, heats much 
 sooner, and more strongly than the former when wetted, and slakes 
 more equally and to a whiter powder. In a variety of trials this 
 lime equalled the best specimens prepared in common lime- kilns, and 
 the amount of acidulous gas obtainable from each by a stronger 
 heat, or in solution, were nearly equal ; they slaked in like periods, 
 with the same phenomena, color, and condition of powder. 
 
 Obs. 3. The lime burned in perforated crucibles, or in the naked 
 fire, is whiter than that burned in common crucibles, covered, in 
 which latter case the air has not free access to it, although the loss 
 of weight be the same in both ; but this latter kind of lime, in slak- 
 
8 
 
 COMPONENTS OF MORTAR. 
 
 ing, affords as white a powder as any other which has lost equally of 
 its weight. Whatever portion of phlogiston it retains to produce the 
 dusky color, it is either detached in slaking, or does not sensibly affect 
 the lime in any use to which it may be applied. 
 
 Obs. 4. When dry chalk or limestone is used in the process above 
 described for making lime in close vessels, and for examining the 
 matter which is expelled by fire, the quantity of water obtainable 
 from it by heat is so inconsiderable as to deserve no notice in the 
 calculation of that matter. 
 
 Obs. 5. Chalk or limestone heated gradually in close vessels loses 
 very little acidulous gas until it begins to redden, after which the 
 elastic fluid issues from it quicker as the heat increases, and so 
 continues until the vessel attains a heat sufficient to melt steel. 
 
 Obs. 6. Forty-eight ounces of chalk yield twenty-one ounces of 
 elastic fluid, the first issues of which are turbid, but soon become 
 clear without loss of bulk, by the condensation of the aqueous fluid ; 
 the remaining portions being transparent and invisible, one thirty- 
 sixth part of this elastic fluid, and sometimes even more, is phlogistic 
 air, the residue, pure acidulous gas. 
 
 Obs. 7. The residuary lime of forty-eight ounces of chalk, heated 
 to the total expulsion of the elastic fluids, weighs only twenty-seven 
 ounces, when red-hot, but when cool it weighs more, by reason of the 
 air which it absorbs as the heat escapes from it. 
 
 Obs. 8. When no more heat is employed than necessary to expel 
 these elastic fluids, the residuary matter is sensibly diminished in 
 volume, and is good lime, though not so white as lime prepared in 
 the usual way ; it slakes readily with water, and grows very hot and 
 perfectly white. The slaked powder is exceedingly fine, except from 
 those parts of the lime which lay in contact with the retort, which are 
 always superficially vitrified, because clay and lime promote the vitrifi- 
 ation of each other. 
 
 Obs. 9. The lumps of this lime, immersed in lime-water, or boiling 
 
COMPONENTS OF MORTAR. 
 
 9 
 
 water, to expel the air which such spongy bodies imbibe in cooling, 
 dissolve in marine acid without signs of effervescence. 
 
 Obs. 10. Limestone or chalk, gradually heated in a crucible, or on 
 the bed of a reverbatory furnace, or in contact with the fuel in a 
 wind furnace, does not become perfectly non-effervescent, and similar 
 to the lime last described in slaking instantly, and in growing 
 hissing hot when water is sprinkled on it, until it has, after a strong 
 red heat of six or eight hours, sustained a white heat for an hour or 
 more — by a white heat, that which will melt cast iron is meant. 
 
 Obs. 11. Limestones heated sufficiently to reduce them to lime 
 which slakes instantly, and is perfectly non-effervescent, do not lose 
 in general so much of their weight as chalkstone does under the 
 like treatment. Some limestones lose little more than a third of 
 their weight ; those which lose the most slake the quickest, and to the 
 finest powder ; but those which lose the least slake the slowest, to a 
 gritty powder, composed of true lime, and particles, chiefly gypseous. 
 
 Obs. 12. The quantity of gypsum, or other earthy matter, in 
 well burned lime, is discoverable by weak marine acid, which dis- 
 solves and washes away the lime, leaving the gypsum to be meas- 
 ured when dry, the portion of which dissolved with the lime being too 
 small to notice, and if any other earthy or saline matter existed in 
 the limestone it vitrifies (with part of the calcareous matter) in the 
 heat necessary for making non-effervescent lime, and is separable by 
 the means last described, and in most instances, even by a fine sieve. 
 
 Obs. 13. When limestone or chalk is suddenly heated to the high- 
 est degree before mentioned, it vitrifies in those parts which touch 
 the furnace or fire- vessel, or the fuel, and such portions become incapa^ 
 ble of slaking freely, or making good lime, and limestone is the 
 more apt to vitrify in such circumstances in proportion as it contains 
 more gypseous or argillaceous particles ; and oysters, or cockle shells, 
 vitrify more easily than limestone or chalk, when they are suddenly 
 heated, which is imputed to their saline matter, for when they have 
 been long exposed to the weather they do not so easily vitrify. 
 
10 
 
 OF SAND. 
 
 Obs. 14. The agency of air is no further necessary in the pre* 
 paration of lime than as it operates in the combustion of the fuel. 
 
 Obs. 15. Calcareous stones acquire the properties of lime in the 
 highest degree when they are slowly heated in small fragments 
 until they appear to glow with a white heat, when this is continued 
 until they become non-effervescent, but is not augmented. The art 
 of preparing good lime consists chiefly in these particulars, and as be- 
 fore remarked, the agency of air is no further necessary than to pro- 
 mote the combustion of the fuel. 
 
 Obs. 16. That lime is to be accounted the purest and most 
 suited for experiment, whether it be the best for mortar or not, 
 which slakes the quickest, heats the most, is whitest and finest when 
 slaked, which, when wetted with lime-water, dissolves in marine acid 
 or distilled vinegar without effervescence, and leaves behind the small- 
 est quantity of residuary undissolved matter. 
 
 Obs. 17. The quick slaking, the color of the slaked powder, and 
 the former acid are the most convenient and perhaps the best tests 
 of the purity of the lime ; the whiteness denotes the lime to be free 
 from metallic impregnation, and the others show any imperfection in 
 the operation of burning, and the heterogeneous matter inseparable 
 from the calcareous earth by burning. 
 
 The mode of slaking lime, and the relative quantities to be em- 
 ployed in the composition of mortars will be hereafter explained. 
 
 OF SAND. 
 
 There are three distinct species in use for building purposes, viz. : 
 fiver sand, pit sand, and sea sand ; but of these the two former should 
 only be admitted into the composition of mortar, and the latter is 
 chiefly adapted for hydraulic cements, or such as will indurate under 
 water, as applied to the construction of marine works — it should be 
 pertinaciously excluded and rejected for any other purpose, and even 
 in the most pressing emergency should not be employed as an ingredi- 
 
OF SAND. 
 
 11 
 
 ent of mortar, unless it has been previously well washed in fresh 
 water to dissolve and dissipate all the saline and other objectionable 
 matter, otherwise the mortar made with it will never projoerly harden, 
 and will always imbibe the slightest humidity which may be present 
 in the atmosphere or elsewhere, and conduct it through the work to 
 its great damage and disfigurement. 
 
 There is, however, another ingredient used by many builders in heu 
 of either of the former, which, although when properly cleansed and 
 prepared, assimulates very closely thereto, viz. : road-drifts, or the 
 fractional particles of quartoze, granite, or other stones, broken off or 
 detached by abrasion, or attrition, or by the traffic of the road : this, 
 though, strictly speaking, not belonging to the category of building 
 sands, is yet a very fair substitute, and recommends itself upon the 
 score of economy ; and, in cases where the former two species cannot 
 be readily or cheaply obtained, is allowable. 
 
 But whatever variety of sand is employed in the composition of 
 mortar or cements, it should be of a hard, gritty, and granular 
 nature ; angular, and having a polished surface ; should be of nearly 
 uniform size, and perfectly freed by ample washings (in clean water), 
 and screenings from all organic matter, alluvium, salts and other 
 foreign and injurious substances, which interrupt the perfect cohesion 
 of its particles, and by their decomposition bring on a speedy destruc- 
 tion to the work. Sand when perfectly fit to be used in mortar, will 
 bear the test of being rubbed between the hands without soiling them, 
 and be free from any particular odor ; these are good criterions of 
 the purity of the sand — a most important matter to be attended to. 
 
 Dr. Higgins, in the 12th section of his treatise before referred to, 
 entitled, Experiments showing the best kinds and mixtures of sands, 
 and the best method of using the lime-water in making mortar," 
 writes thus upon the subject of sands, viz.: Pursuing the analogy 
 intimated in the 9th section, I thought that as large stones with 
 curvilinear faces, imbedded in common mortar, do not form so strong 
 a wall as they may when their interstices are filled with stones fittmg 
 
12 
 
 OF SAND. 
 
 together with a due quantity of mortar, so mortar made with sand 
 whose grains are nearly equal in size, and globular, cannot be so 
 strong at any period of induration, as that which is mixed with as 
 much fine sand as can easily be received into its interstices, in order 
 that the lime may cement the grains by the greater number and ex- 
 tent of their contiguous surfaces." And he further adds: *'It is to 
 be observed that the sand which can pass through a sieve in washing^ 
 is considered finer than that which may be sifted through the same 
 sieve when dry." 
 
 Sand is non-absorbent, that is, its volume is not increased by mois- 
 ture, nor contracted by drought or heat, and its nature is imperish- 
 able, as is daily visible on the sea-shore, in the pit, or elsewhere, and 
 its durability can be proved by a close inspection of specimens of mor- 
 tar which have withstood the wear and tear of ages, and its character 
 and purity are not less important than that of lime, in the composition 
 of mortar. Of the proportions of sand to be used for various building 
 purposes, due mention will be made when treating upon the prepara- 
 tion of mortar. 
 
 The following interesting experiments upon sand, are extracted 
 from Dr. Higgins' work before mentioned. In section 3, he says: "I 
 cleansed a large quantity of ' Thames' sand, by washing it in stream- 
 ing water, and sorted it into three parcels ; the coarsest which I call 
 rubble, consisted of small pebbles, fragments of weathered shells, and 
 grains of sand of divers sizes, which in washing had passed through a 
 sieve, whose apertures were one-eighth of an inch square, but could 
 not pass through a brass wired sieve whose meshes were one-sixteenth 
 of an inch square, or rather more ; the next parcel, which I called 
 fine sand, consisted of grains of divers sizes, which in washing passed 
 through a sieve whose meshes were one thirty-second of an inch square ; 
 the third parcel consisted of grains, the largest of which were washed 
 through the coarsest sieve, and the smallest of those which were re- 
 tained on the fine sieve ; these I call coarse sand. 
 
 Having dried these parcels on a sand plate, and provided a narrow* 
 
OF SAND. 
 
 13 
 
 mouthed glass bottle, capable of holding about two ounces, troy, of 
 water, and a cylindrical glass vessel, which contained twelve of these 
 measures, I found by repeated trials, that the large vessel, charged to 
 the brim with my rubble, might be made to hold somewhat more than 
 one additional measure of it, when the rubble was well-packed, by 
 striking the bottom of the vessel repeatedly against the table perpen- 
 dicularly. 
 
 "Charging the same vessel with coarse sand, I could, by the same 
 treatment, make it hold two-thirds of the thirteenth measure ; and 
 twelve measures of fine sand were so far contracted by this motion of 
 the vessel, that it could hold one measure and one-fourth more, or 
 thirteen and one-fourth in all. After noting how far the intersticial 
 spaces in each sized sand can be lessened by packing, I used water to 
 show what proportion these bear to the solids in these diiferent 
 sands. I found that the thirteen measures of rubble which I stowed 
 into the glass cylinder could take in five measures of water, without 
 any increase of bulk ; or rather with a striking decrease of bulk : 
 the twelve measures and two-thirds of stowed coarse sand imbibed 
 four and one half of water, and yet decreased sensibly in bulk : and 
 the thirteen measures and one fourth of fine sand, packed, could drink 
 in only four measures of water ; but the diminution of bulk was more 
 considerable in this than in either of the former, for the sand and 
 water together measured less by one-seventeenth than the packed 
 sand alone." 
 
 The importance of the foregoing experiments will be hereafter shown 
 and explained. The Doctor then proceeds to say: "When sand 
 was poured into the glass cylinder until it was filled, and the water 
 added before the sand was packed, by a slight agitation of the vessel 
 the sand contracted in a much greater degree than is above expressed. 
 Upon the whole it seemed that water, by poising the grains, facilitates 
 their sliding on each other, to fit well and fill the spaces. 
 
 "Until I had made these experiments I did not well understand, how 
 the beating of new mortar makes it much wetter, and more plastic 
 
14 
 
 OF SAND. 
 
 withal, than it can be made with the same proportions of water and 
 solids, by mere admixture. I now perceived that heating produces this 
 effect by closing the interstices of the sand, and rendering a small 
 quantity of lime paste as effectual towards filling them, and holding 
 the grains together to form a plastic mass, as a greater quantity is, in 
 sand whose grains cannot fit each other so well. 
 
 Seeing that the intersticial spaces in sand are so greatly lessened by 
 wetting it, I judged it expedient, for this reason alone, to expend all 
 the water I should henceforth use in making mortar, in wetting the 
 sand completely. I afterwards observed another advantage arising 
 from this practice : for in filling the spaces with the fluid, the air is 
 easily expelled, and the lime equally diffused in them by a little heat- 
 ing ; but when the water is added to a mixture of lime powder and 
 sand, the air is entangled in the lime paste, and cannot without 
 a great deal of heating, be totally pressed out of the plastic mass. I 
 likewise found that, as an excess of water is injurious to mortar, this 
 is an excellent method of regulating the quantity of it ; for the portion 
 of lime water which fills the spaces in sand, and can be held by capil- 
 lary attraction in a flat heap of it, is precisely the quantity which 
 makes well-tempered mortar with one part of the best slaked lime, and 
 seven of the best sand. 
 
 ''As I experienced some difficulty in expelling the air bubbles out of 
 the sand wetted in my deep cylindrical measure, even when I stirred 
 up the miiss with a slender instrument, I concluded that the spaces in 
 sand are rather in a higher proportion to the solid substance of it 
 than they appeared in these trials ; so that we may say they are at 
 least one-third and more of any measure of the fine sand, greater in 
 coarse sand, and more so in rubble. 
 
 "Suspecting on another ground that these experiments did not shovz 
 the whole of the spaces in sand, because water tends to insinuate itself 
 between the contiguous surfaces of the grains, and consequently to re- 
 move them asunder, even whilst it arranges them, I attempted to as- 
 certain the proportion of these spaces to the solids, by another method 
 
OF SAND. 
 
 15 
 
 founded on this supposition, that the measured portion of sand which 
 weighs the most, has the smallest quantity of intersticial space. 
 
 "By experiment I found that a well-packed measure of the rubble 
 weighed twenty ounces three pennyweights : the like measure of the 
 coarse sand, packed, weighed twenty-one ounces eighteen penny- 
 weights : and the same quantity, by measure of the fine sand, weighed 
 twenty-three ounces two pennyweights and three grains. 
 
 *'This trial corresponds sufiiciently with the former in showing that 
 the sum of the spaces in the rubble is much greater than that in the 
 coarse sand, and that the spaces in the latter, are larger in the sum 
 than those of the fine sand. 
 
 ''In order to learn whether this proportion is maintained in all kinds 
 of sand, I tried by water and by weight in the foregoing manner, a 
 great number of the sands used in London, such as the coarsest glass- 
 grinder's sand, Hampstead sand, Lynn sand, fine house sand, &c^ 
 The result of these experiments taught me that the spaces are always 
 smaller as the sand is finer, provided the comparison be made between 
 the sorted fine parts and the coarsest part of any kind of sand ; but 
 this does not hold true in the comparison of fine sand and coarse sand 
 of different districts. 
 
 ''On examining the several specimens of sand with a lens, I perceived 
 that, in some, the grains, however different in figure, were bounded 
 by flat faces meeting each other in angles, whilst in others the faces 
 were generally rounded, and their figures such as the foregoing grains 
 would be reduced to, by grinding off* their angles. The first kind I 
 call sharp sand, the other, round sand. Then taking into considera- 
 tion the measurement already described, together with the sharphess 
 or roundness of the sand, I found that the spaces are, in diffbrent 
 kinds of sand, as the size and roundness of them compounded, but 
 they don't appear to be smaller in any kind of sand that I have seen, 
 than in one fine parcel of Thames sand, which I think is owing to its 
 being sharper than any of the finer sands which I had compared it 
 with. The measure which contained twenty-three ounces two penny- 
 
16 
 
 OF SAND. 
 
 weights twelve grains of the fine Thames sand, contained only twenty- 
 two ounces ten pennyweights of the Lynn sand, which is a great deal 
 finer, but rounder. 
 
 **Ha\ing thus found the kind of sand which, by reason of the size 
 and figure of the grains, has the smallest intersticial space ; I next 
 endeavored to ascertain the mixture of coarse and fine sand, which 
 lessens this space in the greatest degree, which therefore requires the 
 less lime to cement the grains together, and for the reasons already 
 mentioned, promises to make the hardest and most durable cement. 
 
 *'I found that nine measures of the shingle, and an equal quantity 
 of the fine sand, both well packed, measured, when mixed and stowed 
 closely, sixteen measures and one eighth ; that eighteen measures of 
 the shingle, and nine of the fine sand, tried in the same way, 
 measured twenty-four ; and that on mixing the shingle and fine sand 
 in various proportions, nine measures of shingle took into its inter- 
 stices one measure and one-half of the fine sand without any increase 
 of bulk. 
 
 "I next learnt that nine measures of the coarse sand, and nine of 
 the fine, measured in like manner seventeen and a half; that eighteen 
 such measures of coarse sand, well mixed with nine of the fine sand, 
 measured twenty-six, and that on mixing these sands in various pro- 
 portions, eighteen measures of the coarse sand took into its interstices 
 one measure of the fine sand without any increase of bulk. 
 
 *' Lastly, I found that eighteen such measures of the coarse sand, and 
 nine of Lynn sand, which is much finer grained than the foregoing, 
 measured twenty-four when well mixed and stowed; and that on 
 mixing them in various other proportions, nine measures of coai*se 
 sand took into its interstices one and a half of the Lynn sand. 
 
 **By these and a variety of similar experiments made on different 
 sands, I found that the quantity of fine sand taken into the inter- 
 stices of the coarse sand was the greater without increase of bulk, as 
 the grains of the coarse differed more from those of the fine in bulk, 
 provided the diameters of the grains of coarse sand did not in general 
 
OF SAND. 
 
 17 
 
 exceed those of the fine in a proportion greater than five to one ; that 
 tlie greatest quantity of fine sand which could be taken into the inter- 
 stices of coarse sand was one-sixth of the bulk of the coarse sand, and 
 that in general the mixture of six measures of coarse sand with one 
 of the finest sand, reduced the sum of the intersticial spaces to nearly 
 one-half of the quantity of them in coarse only, or in fine Thames 
 sand or rubble only. 
 
 "Instructed by these observations, I proceeded to the following 
 experiments, in order to learn the advantages or defects attending each 
 kind of sand, and how far my expectations from the art of lessening 
 the spaces, were well founded. 
 
 "I made several parcels of mortar with my chalk-lime, lime-water, 
 and rubble in different proportions ; the quantity of lime being in one, 
 a fourth of that of the rubble, in another only one seventh, and in 
 the others intermediate : I also made other parcels of mortar with 
 my chalk-lime, lime-water, and the coarse sand ; and others with 
 this lime, lime-water, and fine Thames sand, in the last mentioned 
 proportions. 
 
 "I next made a great variety of specimens of mortar, some of 
 which consisted of rubble and coarse sand mixed in different propor- 
 tions, wetted with lime-water, and blended with one-fourth, or one- 
 seventh, or intermediate quantities of lime ; others were composed of 
 similar mixtures of rubble and fine sand, with lime and lime-water; 
 and others consisted of rubble, coarse sand, and fine sand, mixed in 
 different proportions, wetted with lime-water, and beaten up with the 
 different quantities of lime lately mentioned. 
 
 "I spread a part of each of these specimens of mortar, as soon as 
 it was made, on a tile soaked in lime-water, half an inch thick in 
 some places, and much thinner in others ; I placed the remainder of 
 it, formed into oblong pieces about an inch in diameter, on the part 
 of the tile which was not covered with mortar ; and I set all the tiles 
 (numerically marked) in the situation formerly described, where they 
 were equally exposed to the weather ; during the succeeding twelve 
 
18 
 
 OF SAND. 
 
 months I examined each specimen, and noted my obsen^ations, the 
 most useful of which I shall endeavor to relate in a few words. 
 
 "The specimens containing rubble and lime, mixed in any proportion 
 greater than five to one, were not fat enough, when fresh, to be conveni- 
 ently used in building or stuccoing ; but none of them, not even except- 
 ing those which contained the greater quantities of lime, cracked in dry- 
 ing. Those which had the least quantity of lime in them were very 
 rough on the surface, coarse in the grain, spongy, and easily broken ; 
 they showed a defect of lime, because those which contained more 
 lime were not so bad in these respects. By all of which it appeared 
 that whenever such rubble must be used for want of sand or finer 
 gravel, the lime mixed with it must not be less than one-fifth of the 
 quantity of rubble. 
 
 **0f the specimens consisting of coarse sand and lime, those which 
 had the smaller quantities of lime, were too short for common use, 
 and could not be made to assume a close and smooth surface whilst 
 fresh, but in drying and hardening, they were in every respect prefer- 
 able to the cements made with rubble and lime, in the same propor- 
 tions ; and of the same specimens those were the best which contained 
 one part of lime in five ot sand, the others containing less lime, being 
 faulty, like those made with rubble ; and those in which lime was 
 mixed in much greater quantity poslsessed the faults often observed to 
 attend the excess of lime. 
 
 **The specimens which consisted of fine sand and lime were in gene- 
 ral better than the foregoing, and that, particularly, which contained 
 one of lime in six and a half of sand, was in all respects much better 
 than those made with the same or any other quantities of rubble and 
 lime, and coarse sand and lime. The specimen which was formed 
 with seven parts of fine sand and one of lime, was not so compact and 
 hard as that last mentioned. The comparison of these two showed 
 that seven of sand are too much for one part of lime, when the sand 
 is fine and unmixed with coarse grains. The specimen made with 
 four parts of fine sand and one of lime, had the noted faults attending 
 
OF SAND. 
 
 19 
 
 the excess of lime ; for it cracked in drpng, and was sensibly injured 
 in the winter, by those alternations of drying, wetting, freezing and 
 thafwing, formerly noticed. 
 
 '*0n divers comparisons of those portions of mortar made of fine sand 
 and lime with the former, I was persuaded that a better cement can be 
 composed with such sand as I call finc^ than with a coarser sand, 
 whose grains are all larger than any of those in my fine sand, pro\dded 
 the coarser sand be not much sharper than all I have yet seen. If my 
 experiments had been made in slow succession, this last observation 
 would have led me to imagine that the mortar will be found the bet- 
 ter, as the sand is finer." 
 
 Of the observations made on the parcels of mortar, consisting of 
 mixed sands and lime, those which follow are the most pertinent to 
 our present inquiry : — 
 
 *' The specimens made with mixtures of rubble, coarse sand, and 
 different quantities of lime, resembled those made vdth rubble and 
 lime in similar proportions, when the rubble was predominant ; and I 
 could perceive no advantage derived from the mixture of the rubble 
 and coarse sand, except that the cement was somewhat better, as the 
 quantity of rubble was less, relatively to the quantity of sand and 
 lime ; but none of these specimens were in any respect so good as 
 those made with fine sand only. 
 
 "Of the specimens made with rubble and fine sand, that was the 
 best in which the fine sand was twice the quantity of the rubble. But 
 I could not perceive that any of these specimens were preferable to 
 those made with the like quantities of fine sand and lime, or that 
 any considerable advantage is gained by the mixture of rubble and 
 fine sand. 
 
 '^Of the specimens made of coarse sand, fine sand, and lime, those 
 were manifestly the best which consisted of four parts of coarse sand, 
 three of fine, and one part or a little more of lime ; for, while fresh, 
 they were more plastic than the others, and were easily made to as- 
 sume a smooth surface, they were not disposed to crack in this 
 
20 
 
 OF SAND. 
 
 method of drying, they were not at all injured by wet, or freez- 
 ing, or thawing ; they were pretty close in the grain, and they grew 
 so hard in the course of nine or ten months as to resist the chisel, or 
 any force tending to break the oblong pieces, much more powerfully 
 than any of the specimens lately mentioned ; I noted them as the best 
 specimens of mortar that I had ever made, and one part of lime, in 
 four of coarse and three of fine sand, to be a better proportion than 
 any other of the sands and lime, for incrustations. 
 
 *'0f the various samples of mortar made with mixtures of the rubble, 
 coarse sand, and fine sand, those were the best in which the fine sand 
 was equal or nearly so, in quantity, to the rubble and coarse sand, in 
 whick the rubble was not much more than one-seventh part of the 
 quantity of both sands, and in which the weight of the lime was one- 
 seventh of the weight of the sand and rubble, or a little more ; but 
 these specimens when fresh, were less plastic and less capable of as- 
 suming a smooth surface under the trowel, as the quantity of the rubble 
 was greater ; and I could not find that they were preferable in any 
 particular to those respectively which were made with similar quan- 
 tities of lime and the mixtures of coarse and fine sand lately recom- 
 mended. 
 
 ^ ' Upon the strictest comparison, I concluded that one part of rubble 
 in three of coarse and three of fine sand, makes as good mortar with 
 lime as can be made with the sand and lime without rubble, for any 
 purpose which does not require a finer cement, but there is no advan- 
 tage gained by the use of rubble when the coarse and fine sand can 
 be had equally cheap, unless a rough surface be required. 
 
 *'In stuccoing walls, the rubble promised to be useful in pointing, 
 and in the first coat, because a roughness of this coat raakes the finer 
 exterior coat adhere more firmly. 
 
 *'In the review of all these specimens, it appeared that the quantity 
 of lime which forms a mass somewhat plastic with sand and water, is 
 the smallest quantity necessary for making the best mortar which such 
 sand can afford, and that any further quantity of lime is useless in 
 
OF SAND. 
 
 21 
 
 the coarser sands, and injurious in the finer : that the necessary plas- 
 ticity is induced by the smaller quantities of lime, as the interstices of 
 the sand are smaller in the sum, and as the grains fit each other the 
 better in consequence of the due mixture of coarse and fine sands ; 
 but that the lessening of the intersticial spaces, by the admixture of 
 fine sand with the coarse, does not enable us to lessen the quantity of 
 lime so far as might be expected, in consequence of our notions of the 
 spaces measured by water. It seems that the grains of fine sand are 
 held asunder by the lime paste, to a greater distance than they are by 
 water, and that the reason why the finer sand requires more lime than 
 the coarser and mixed sand, is, that the spaces which are more nume- 
 rous in fine sand than in the coarse, are more augmented in the whole 
 quantity of them, by the particles of lime, which intercede alike, the 
 coarse and fine grains." 
 
 Further allusion to this matter will be subsequently made. Of 
 the several species of sand in general use for building purposes, that 
 which is obtained from the bottom of fresh water rivers, or from the 
 beds of rivulets and other water-courses, and known by the term 
 *'silt" is unquestionably the best; and next in quality is pit-sand, 
 but this is in general too fine, and not so sharp and gritty as the 
 former. 
 
 "Before closing these observations upon sand, it may be useful to 
 remark that, in cases of emergency where proper sands cannot be readily 
 obtained, ordinary gravel — if it be washed from all impurities, 
 clay, &c., and well freed from all large round pebbles, and its par- 
 ticles sub-di\ided through proper sieves into two or three gradations 
 of sizes, viz. ; coarse, medium, and Jine — may be used for construc- 
 tive purposes, but its particles being round, or less angular than ordi- 
 nary sand, do not so readily unite, and it consequently forms or pro- 
 duces mortar of an inferior quality." 
 
 The foregoing experiments are highly valuable and important, and 
 evince great judgment, clear perception, and an indomitable perse- 
 verance and pertinacity to ascertain facts and establish truth, and 
 
22 WATER. 
 
 prove to a demonstration that a careful selection and admixture of 
 coarse and fine sands in certain portions are preferable for mortar or 
 cements than any sizes employed individually, because the smaller 
 grains have the effect of filling up the interstices of the larger, there- 
 by tending to consolidate the mass and to lessen the quantity of lime 
 or other cementitious matter necessary to combine the whole. They 
 also teach that it is far preferable to apply the great bulk of the water 
 to the sand before incorporating it with lime, instead of mixing the 
 two ingredients together before slaking ; that by this method the air is 
 more readily and freely expelled from the mass, and the mortar con- 
 sequently becomes considerably improved. These results have been 
 fully confirmed by my personal experience and observation during a 
 series of many years professional practice in Em'ope and in distant 
 parts of the globe, and I have generally found that the qnality of 
 mortar (coeteris paribus) depends chiefly upon the purity of the sand, 
 the form of its grains, and a due admixture of two or more differing 
 sizes. The common practice of using unwashed sands, or road-drift, 
 argillaceous loams, and even alluvium or common soil, charged as it 
 is with vegetable and organic matter, cannot be too much repre- 
 hended, nor too speedily abolished. Builders are very apt to com- 
 pound their mortar with the soil removed from the foundations of the 
 sites of their buildings, alike regardless of its quality, or suitability 
 for the purpose, or of the natural consequences of its employment. 
 
 WATER. 
 
 The last ingredient necessary in the formation of mortar is the 
 aqueous element, the nature of which, being so well known to all, 
 needs no description : but not so with respect to its components, for 
 the value or quality of calcareous cements depends considerably upon 
 the purity of the water. It must in all cases be fresh, and obtained 
 from a river, pond, spring, well, brook, or any running water-course, 
 but never from any stagnant pond or pool, which is always sur- 
 
WATER. 
 
 23 
 
 charged with vegetative and organic matter ; nor should it be obtained 
 from any spring or well which is oxydized (i. e., containing mineral 
 properties, examples of which are often to be met with) ; nor should 
 the water contain any chalybeate or other chemical components ; and 
 sea- water is objectionable for the same reasons as explained in refer- 
 ence to sand, it being only allowable in the formation of hydraulic 
 cements or marine mortar. Rain water is good if not kept long 
 enough to vegetate or vivify. 
 
 Dr. Higgins has the following remarks upon the nature and use of 
 water in the composition of cements, aiid recommends the use ot 
 lime-water as being far preferable. In section 7 of his work, "On 
 the depreciation of mortar by the common method of using water, 
 and of the use of lime-water," he says: "Einding by reason and 
 experience the advantage of totally expelling the gas, and preventing 
 the return of it to lime, or even to mortar before it is used, and 
 knowing that common water, which is employed in great quantities, 
 first in slaking limes and then in making mortar, contains a great 
 deal of the noxious gas, it occurred to me that the vulgar process of 
 making mortar is, in this fresh instance, injudicious, as it tends to 
 injure materials otherwise good. 
 
 **Lime is slaked in such a manner that almost the whole of the 
 water is evaporated, and contributes nothing to the mortar except so 
 far as it deposits its gas in the lime, and injures it ; and then the 
 slaked dry lime and the sand require more water to make them into 
 mortar. I have found the quantity of water used for both these pur- 
 poses to be twice the weight of the lime at least. The quantities of 
 acidulous gas known to be contained in the waters commonly used 
 in making mortar, must greatly debase the lime which is thus ex- 
 posed to double its weight of such water ; and upon these grounds I 
 was assured, a priori, that it would be a considerable improvement in 
 mortar to use no water in it except what has been previously freed 
 from acidulous gas. 
 " This is done in making lime-water^ the use of which appeared ad van- 
 
24 
 
 WATER. 
 
 tageons in another point of view. One seven-hundredth part of lime- 
 water, being lime, (according to the experiments of Mr. Brandt, 
 which I find to be true) ; and the lime being introduced in a state of 
 solution, which favors the crystallization of it between the grains of 
 sand, assists in cementing them together by the utmost attractive 
 forces of its parts, if my notions of the polarity of these parts be 
 true. 
 
 ''I made divers experiments to try the practical validity of this 
 reasoning, and found it to be true ; for, on comparing specimens of 
 mortar made with my best lime, slaked with river water, and sand 
 and water, and spread on tiles soaked in water, with other specimens, 
 made with the same proportions of lime, slaked with lime-water, and 
 sand and lime-water, and spread on tiles previously soaked in lime- 
 water, the latter, at every stage of them, were sensibly harder, and 
 they adhered to the tiles better than the former. I must observe, 
 however, that such distinctions (discoveries) cannot easily be made, 
 except by those who have a great deal of experience in these trials and 
 comparisons. On repeated examinations of these and my other speci- 
 mens, I was highly encouraged in my pursuit, for those made with 
 lime-water were better near the surface than any I had ever made, 
 and I had good reason to be persuaded that the extraordinary indura- 
 tion would proceed in time, through the whole mass." 
 
 From the above experimental results, the superiority of 'Mime- 
 water" over crude water, in the composition of mortar, is apparent, 
 and the subsequent experience of many professional gentlemen fully 
 confirms the said theorem, and as lime-water is easily prepared, even 
 upon a large scale, by dissolving a quantity of lime in large casks or 
 tanks, it behooves every one engaged in the execution of extensive and 
 important works to adopt the plan. 
 
 Other ingredients are sometimes introduced into the compositions 
 of mortar for particular purposes or objects, such as cinders, scoria, 
 iron scales or filings, crude or burnt clay, pulverized potters' ware, or 
 tiles, or other porous substances ; they must, however, be pure and dry, 
 
VARIOUS KINDS OF MORTAR. 
 
 25 
 
 and rendered pretty fine by pulverization. Of these, however, we shall 
 have occasion to speak hereafter, in the description of hydraulic and 
 other cements for special purposes. 
 
 Of the Composition of various kinds of Mortar, their Ap- 
 plication AND Respective Values ; with Occasional Notes 
 OF the Experiments and Opinions of Dr. Higgins and 
 other first-class authorities. 
 
 Mortar as before mentioned, is generally compoj<ed of three in- 
 gredients, viz. : Lime (or cement), Sand, and Water, the respective 
 properties of which may be defined as follows, viz. : — 
 
 1st. Lime is the cementing ingredient. 2d. Sand is the substance 
 or matter (as relates to the mortar only) to be combined. 3d. Water 
 IS the element by which the combination of the lime and sand is to be 
 accomplished. 
 
 Such being the relative uses and properties of the above mentioned 
 ingredients, we must consider that lime being the cementitious med- 
 ium, and the particles of sand the material to be united, through the 
 agency or intervention of water, that it will require in the compostion 
 of the mortar no more of the aqueous element than wUl efiectually 
 slake or dissolve the lime into a liquid paste, or make it free and con- 
 venient for use ; and that of this cementitious paste, no greater quan- 
 tity wUl be necessary than sufficient to conjoin or unite the several 
 sides or angles of the sand together, or what is analogous, to fill the 
 mterstices between their bodies ; and that the more effectually this can 
 be done, the more compact and durable will be the mortar, the more 
 excluded will be all damps and other atmospheric influences, and con- 
 sequently the prevention of those destructive forces " expansion and 
 contraction." This important desideratum can only be obtained by a 
 judicious proportion and combination of the several component in- 
 gredients, and which Dr. Higgins and other qualified experimentors 
 
 have already shown to be, with pure materials (et caeteris paribus)^ to 
 2 
 
26 
 
 VARIOUS KINDS OF MORTAR. 
 
 be one part of lime to five, six, or seven parts of sand — the relative 
 proportion of the latter ingredient being dependent upon its descrip- 
 tion, and guage or size ; because pit sand will require more lime (to 
 make an equally good mortar) than sharp river sand, or clear road 
 drift, and coarse sand will take less lime than fine sand, although ob- 
 tained from the same source. This fact or knowledge resulted from 
 the experiments of Dr. Higgins, before quoted, and proves the practi- 
 cal value of them. But where an undue or unnecessary quantity of 
 lime is employed, the result will be, less compactness or solidity, im- 
 perfect induration, a disposition to imbibe and retain all moisture, and 
 to sympathize with every atmospheric change ; a constant disposition 
 to expand and contract, and consequent liability to a more speedy decay. 
 
 With a view to determine the question or fact. Dr. Higgins made 
 a series of impartial experiments, the result of which he gives as fol- 
 lows, in section 8 of his said treatise on calcareous cements, entitled, 
 * ' Experiments made with a view to approximate the best proportions 
 of lime, sand, and water for mortar" : — 
 
 "In reading over my notes, and examining the specimens of mor- 
 tar which I had hitherto made, I perceived that those were the best 
 which being made with common fresh lime, or with well-burnt lime, 
 contained the least of it ; that is, one ounce of lime in six or more of 
 sand ; and finding that this quantity of lime to be much less than 
 commonly used in making mortar ; and suspecting that as a wall may 
 be the weaker for its containing too much mortar (which widens the 
 joints), so mortar may be weakened by the introduction of more 
 lime than is necessary to cement the grains of sand together. I 
 thought another cause of the defect of common mortar opened to my 
 view, and that it was advisable to determine by experiment the best 
 proportion of lime and sand in making mortar in wliich lime water is 
 used. 
 
 I made five parcels of mortar with my best stone lime, recently 
 slaked with lime-water and coarse Thames sand, in the following pro- 
 portions, hy weight : — 
 
VARIOUS KINDS OF MORTAR. 
 
 27 
 
 No. 1, 
 " 2, 
 " 3, 
 " 4, 
 
 Slaked Lime. 
 
 1 
 1 
 1 
 1 
 1 
 
 Saiid. Water. 
 5 
 
 6 ^ quantity sufficient. 
 
 7 
 8 
 
 **This latter specimen was not sufficiently plastic for common use, 
 or as the workmen express themselves, it was too shor-t. I further 
 observed that the quantity of water required to make mortar to the 
 proper temper is 7nore as the quantity of lime is greater, relatively to 
 the proportion of sand. 
 
 * ' I spread these specimens on tiles in the month of J une, and ex- 
 posed them to the air and sun, which then was very hot. As my 
 former experiments taught me to expect that some of these in hasty 
 drying would crack considerably, and as mortar in building is not 
 liable to dry so quickly as these specimens, in order to render the 
 inferences from these experiments the more general, I made five 
 other parcels of mortar in the same manner, and exposed them in the 
 same way, in every respect, except that the direct rays of the sun 
 could not fall upon them, or heat the pavement on which they stood. 
 In three days I found this necessary, for the first of those which stood 
 exposed to the sun cracked considerably ; the second, less ; the third 
 sliowed three or four very slender fissures, visible only on a very close 
 inspection ; and the fourth and fifth showed no cracks at this time^ 
 nor in a month afterwards, when the fissures of the other were con- 
 siderably enlarged. 
 
 Of the specimens kept in the shade, and examined on the third 
 day like the former, the first was cracke'd in divers parts ; the second 
 showed two or three very slender cracks, and the rest were not cracked 
 in the least, and never cracked afterwards, although I was forced to 
 remove them to the place where the others stood. 
 
 *'Thus it appeared in a very short time that an excess of lime dis- 
 poses mortar to crack, and consequently injures it ; that the hishest 
 proportion of lime to such sand, which may be used without incurring 
 
9S VARIOUS KINDS OF MORTAE. 
 
 this risk depends on the circumstances in which the mortar is to be 
 exposed ; that no more than one part of lime to seven of coarse sand 
 ought to be used in mortar which is to dry quickly, and less lime may 
 not be used, because it does not render the mass sufficiently plastic for 
 building and incrustation ; and that if a greater proportion of lime to 
 such sand improves the mortar in any respect, it is to be used only 
 when the mortar cannot dry so quickly as it did in the specimens ex- 
 posed to the sun. 
 
 In the course of nine months I clearly perceived that those speci- 
 mens which stood in the shade for the first three days were harder 
 and better in other respect than those which were suddenly exposed to 
 the sun, the comparison being made between the specimens which 
 contained a corresponding proportion of lime, and which cracked the 
 least or not at all, and of all the specimens those were the best which 
 contained one part of lime to seven of sand ; for those which contain- 
 ed less\im.Q, and were too short*' while fresh, were most easily cut and 
 broken, and were pervious to water, and those which contained more 
 lime, although they were closer in the grain, did not harden so soon, 
 or to so great a degree, even when they escaped cracking by lying in 
 the shade to dry slowly. I therefore concluded, that hasty drying 
 injures mortar made in any proportions of such sand and the best 
 lime, and that the best proportion is one of lime in seven of sand, 
 whether the mortar is to be dried quickly or not. 
 
 *' I must observe, however, that these conclusions were made rather 
 with a view to my future experiments, in which an approximation to 
 the best proportions of lime and sand, and the best treatment of the 
 mortar would save a great deal of trouble, than to any general and 
 invariable rules for making mortar. 
 
 "I reserved it to be mentioned here, that I set apart four ounces 
 of each of the foregoing specimens of mortar, and spread them sever- 
 ally on plates of thin window glass, to the thickness of a quarter of an 
 inch or thereabouts, and noted the weight of each plate with its speci- 
 mens of mortar recently made. 
 
VARIOUS KINDS OF MORTAR. 
 
 29 
 
 " These being eqimlly exposed to the sun, and weighed at different 
 periods, were found to lose weight in equal times, nearly in proportion 
 to the quantity of lime and water used in making them ; and the 
 smallest loss of weight when the specimens were perfectly dry and con- 
 siderably hardened, was one-tenth of the weight of the same speci- 
 mens recently made. 
 
 "In my former experiments, I had observed that mortar which sets 
 without cracking, whether owing to the due proportion of sand, or to 
 the slow exhalation of the water from mortar containing less sand, 
 never cracks afterwards, whatever other faults it may have ; and the 
 specimens mentioned in this section, after a trial of eighteen months 
 afforded the same observation. 
 
 By the setting of mortar I mean that solidity which it acquires by 
 mere drying, and which differs widely from the induration that takes 
 place in time, by other means which we shall hereafter consider. 
 
 " Seeing then that the quantity of water is as the quantity of lime, 
 — that the fissures happen only in the drying or setting — that the 
 danger of cracking is greater, not merely as the quantity of water is 
 greater relatively to the sand, nor merely as the water is more ex- 
 peditiously exhaled, but in a rate compounded of these; I inferred 
 that mortar which is to be used where it must dry quickly ought to 
 be made as stiff as the purpose wiU admit, that is, with the smallest 
 practicable quantity of water, and that mortar will not crack, although 
 the lime be used in excessive quantity ; provided it be made stiffer, or 
 made to a thicker consistence than mortar usually is. 
 
 *'This inference was afterwards confirmed, for specimens made thus 
 with one part of lime and only six of sand, and others made with 
 greater proportions of lime, but as stiff as they could be used, did not 
 crack in any exposure, but they had faults which will be hereafter 
 noticed." 
 
 Thus far the above described experiments fully demonstrate the 
 advisability of employing a moderate proportion of lime and water to 
 the quantity of sand, and that theory I have found correct during 
 
80 
 
 VARIOUS KINDS OF MOETAR. 
 
 many years of professional experience in Europe, Australia and else- 
 where, and therefore confidently recommend it to the notice and trial 
 of all persons engaged in the building art, in further allusion to which, 
 the Doctor next proceeds (in Section 9,) to consider the "Theory of 
 induration dependent on the proportion of lime and sand in mortar, 
 and observations on the bad effects of the vulgar proportions of these." 
 Pie says : * ' It is sufficiently known that the aggregation of calcar- 
 eous bodies, which burn to lime, or are chiefly composed of the matter 
 of lime, is much weaker than that of the quartoze (sand), in so much 
 that the steel which easily cuts all calcareous stones or spars, is as 
 easily cut by the siliceous, and all stones and powders which are 
 chosen for cutting and grinding steel are found to have this effect 
 by reason of their siliceous or quartoze particles. This being consider- 
 ed, together with divers observations heretofore related, I reason in the 
 subsequent manner : — 
 
 As stones are cemented together in walls by the mediation of 
 mortar, so the grains of sand or gravel are made to cohere and form a 
 solid mass of mortar, by the intervention of lime. 
 
 **By the bare inspection, as well as by the experienced induration, 
 one part of lime paste appears sufficient to intercede the grains of 
 seven of sand without interruption of continuity, and in drying, to fill 
 the spaces between them, or to attract matter enough for this pur- 
 pose from the air. In this case the grains cohere at the smallest 
 distances of them, and by means of the thinnest laminae of cal- 
 careous matter ; and such mortar is the stronger as it consists of the 
 greater quantity of hard quartoze bodies, cohering by means of the 
 smallest practicable quantity of soft and brittle calcareous strata : just 
 in the same manner as a wall built with porphyry and bad mortar is, 
 (cceteris paribus) the stronger as the joints are made thinner ; for all 
 masses of such structures as mortar or cementitious walls resist frac- 
 ture and ruin, with the powers of aggregation which are, not merely 
 as the aggregate of the stones or brick, nor barely as the aggregate 
 of the softer cements, but in a ratio compounded of these, and vary- 
 
VARIOUS KINDS OF MORTAR. 
 
 3t 
 
 ing with circumstances which we need not attend to at present ; and 
 those masses therefore will resist the wind, in which the stronger ag- 
 gregates bear the greatest proportion to the weaker, so far as it is con- 
 sistent with the continuity of them. 
 
 Secondly. The small stones which compose a heap of sand do not 
 imbibe water, their volume is not increased by wetting them, nor less- 
 ened in drying ; neither does a measure of wet sand contract sensibly 
 in drying : this last I have repeatedly experienced ; but small pieces 
 of lime are considerably increased by wetting them ; and as the soft 
 paste of lime contracts greatly in drying, it must crack in every part 
 where the drying paste is prevented, by its adhesion to bodies or by 
 other causes, from contracting uniformly and concentrically. As the 
 contraction of mortar in drying, and its consequent cracking depends 
 on the lime paste, and not on the sand, they must take place in the 
 greater degree, and they must be lessened or prevented by a due pro- 
 portion of sand, which proportion experience shows (as before stated) 
 to be seven parts of sand to one of lime. Thus we understand the 
 cause of cracking, and how it happens that this defect is prevented by 
 using less than the customary quantity of lime, and, although the 
 lime should be used in excess, by using less than the customary quan- 
 tity of water. 
 
 ''Thirdly. The more perfect and expeditious setting and induration 
 of mortar, containing only one part of lime in seven of sand, than of 
 mortar made with greater proportions of lime, may be deduced from 
 several concurrent causes. Having less water in its composition, it is 
 sooner saturated with the matter which the air presents, and which 
 seems necessary to the induration of mortar ; and in this saturation, 
 the swelling of the lime is not so great as to put forth and derange 
 the grains of sand after they have once been placed, and in some 
 degree cemented together. 
 
 "This latter inconvenience arising from the excess of lime, cannot 
 easily happen in mortar compressed on all sides in massive buildings, 
 but it manifestly occurs in the exterior parts of the joints in walls. 
 
82 
 
 VARIOUS KINDS OF MORTAR. 
 
 where the mortar visibly swells, and afterwards crumbles ; it is lik<v 
 wise visible in the upper parts of walls of modern construction, where 
 the swelling is not prevented by a superincumbent weight. In these 
 cases the joints become hollow ; houses lately built look old and ruin- 
 ous, and the bricks themselves being bibulous in such position, soften 
 and moulder, in consequence of the alternate wetting, drying, freezing, 
 and thawing ; these being effectual agents in the dissolution of all 
 bodies which freely imbibe moisture. 
 
 " Without awaiting the event of those experiments which I have 
 lately made on the great scale, and shall point out before I conclude 
 this essay, we may on these grounds alone assure ourselves, that the 
 strength and duration of calcareous incrustations composed of lime 
 and sand, will be greater as we depart from the proportions of lime 
 and sand commonly observed, approaching to that of one part of lime to 
 seven of sand, because the stucco which hardens the soonest must be 
 the least injured, whilst it is new, by the beating rains and various 
 accidental impressions ; because that which adheres the most firmly to 
 the other materials of buildings, and which acquires the greatest degree 
 of induration, must contribute most to the strength of the walls, and 
 best withstand the shocks, attrition, and other trials to which the 
 stucco is exposed ; because that which contains the greatest proportion 
 of sand, is less liable to be injured by any saline matter with which 
 the air is sometimes impregnated, as its calcareous matter is best de- 
 fended by the sand ; but above all, because the stucco made with one 
 part of lime and about seven of sand is not disposed to crack, for in- 
 crustations perish sooner by reason of the fissures than of any other 
 defect, because the water imbibed into the smallest of them, as well 
 as those which appear on a cursory view, swells in the congelation 
 and dilates them, and frequent alternations of wetting and freezing, 
 gradually widen them, until the stucco is bulged and torn from the 
 walls.'* 
 
 In the early part of this treatize, allusion was made to the import- 
 ance of the acidulous gas being completely discharged from the lime^ 
 
VARIOUS KINDS OF MORTAR. 33 
 
 to effect which is the primary object in burning or calcining it, and 
 that its value or utility depends upon the method in which this opera- 
 ation is performed ; in support of which theorem, a further reference 
 will be made to the before-mentioned authority. In Section 4, he 
 says : "On divers considerations it appeared to me, that the perfec- 
 tion of lime for mortar consists chiefly in the total expulsion of the 
 acidulous gas ; but to be better satisfied of this opinion, I made sever- 
 al parcels of mortar, the description of which will be abridged by ob- 
 serving in this place, concerning all of them, that the sand employed 
 was coarse Thames sand, and that the lime was slaked as soon as it 
 cooled after being burned, and with the smallest quantity of water 
 necessary for this purpose, that it was sifted through a fine brass- wired 
 sieve as soon as it was fully slaked, and that each parcel of mortar was 
 beaten and briskly formed with the quantity of water which was 
 barely sufficient to give it the usual consistence, which quantity is ex- 
 pressed in the usual term, quan, suff. 
 
 Sample. 
 
 
 
 
 I Sand 3 parts 
 
 Purest Stone Lime, 1 
 
 . part. 
 
 2 
 
 6 " 
 
 it (( 
 
 L ^' 
 
 3 
 
 3 ** 
 
 " Chalk " ] 
 
 (( 
 
 4 
 
 6 " 
 
 
 L " 
 
 5 
 
 3 " 
 
 Stone Lime as Ob. 2, 1 
 
 (( 
 
 6 
 
 6 " 
 
 
 1 C( 
 
 7 
 
 3 " 
 
 Chalk Lime as Ob. 2, ] 
 
 <( 
 
 8 
 
 6 ** 
 
 (( (( 
 
 <c 
 
 9 
 
 3 " 
 
 Imperfect Limes as Ob. 1, of 
 best Limestone, ] 
 
 tc 
 
 10 
 
 6 " 
 
 U (( u 
 
 cc 
 
 11 
 
 3 " 
 
 Do. of inferior quality, ] 
 
 
 12 
 
 6 *• 
 
 
 il 
 
 "Mem 
 
 The lime of Nos. 9, 10, 11 and 12 samples 
 
 was slaked 
 
 whilst it was hissing hot, in a covered vessel, because it would not slake 
 sufficiently when it was suffered to cool before the water was sprinkled 
 on it, or when its heat was soon dissipated by a free exposure to the 
 air, and hasty evaporation of the water ; and as this lime required 
 
34 
 
 VARIOUS KINDS OF MORTAR. 
 
 Beveral hours to slake, I put it into a bottle as soon as it was cocl, 
 and kept it well stopped for twenty-four hours before using it. At the 
 same time I made two specimens of mortar with common chalk lime 
 and sand in the foregoing manner. 
 
 " Each specimen or sample was spread as soon as it was made, to the 
 thickness of half an inch, on a plain tile previously soaked in water ; 
 the tiles were numbered and kept close by each other in an airy part 
 of my laboratory until the mortar was dry, and then they were equally 
 exposed, standing upright in a place where the sun and rain had free 
 access to them. 
 
 *'In the course of fourteen or fifteen months these specimens 
 afforded me a great deal of information, which will be noticed in due 
 time ; even in the first six months they clearly indicated that lime is 
 the better for mortar as it is more perfectly freed from acidulous gas. 
 For when the comparison was made between specimens of mortar 
 consisting of the same quantities of lime and sand, I found that the 
 mortar made with well-burned non-eifervescent lime, hardened sooner 
 and to a much greater degree than mortar made with common lime, 
 or my stone or chalk-lime burned in the manner expressed in the 
 second observation of the second section ; and the specimens made 
 with the stone or chalk-lime which was least burned, were incompara- 
 bly worse than any others, for they never acquired any considerable 
 hardness, and they mouldered in the winter the sooner, as they con- » 
 tained more of the lime, and they also cracked more in the drying. 
 I also observed that the specimens which contained the smaller quan- 
 tities of well burnt lime cracked much less than the others, or not at 
 all ; that they adhered to the tiles more firmly, and were less injured 
 by freezing ; but as the specimens made with an excess of the well- 
 burnt lime were no more cracked than those made with equal quanti- 
 ties of the other kinds of lime, and as I could distinguish the imper- 
 fections arising from the excess of lime, from those which proceeded 
 from the bad quality of it, I was satisfied that the lime which is most 
 completely burned is the best for mortar. 
 
VARIOUS KINDS OF MORTAR. 
 
 35 
 
 ** Considering the heat which I found necessary to extricate the last 
 portions of acidulous gas from chalk or limestone to be much greater 
 than even adopted in making lime, so far as I had observed or learnt 
 from others ; I suspected that the lime, commonly in use, is seldom 
 or never sufficiently burned. 
 
 **0n repeated trials of several specimens of such lime, I found this 
 suspicion to be weU-founded, for they all effervesced and yielded acidu- 
 lous gas, more or less, during the solution of them, and slaked slowly 
 in comparison with well-burned lime ; and in order to render the 
 effervescence conspicuous, a strong acid ought to be used, because the 
 quantity of water in a diluted acid retains a proportional share of the 
 acidulous gas, and a certain quantity will retain the whole of it and 
 prevent the eflfervescence, because the effervescence depends on the 
 escape of the elastic fluid out of the solution. This is exemplified in 
 the mixture of diluted vitriolic acid with the diluted solution of salt 
 of tartar — for these solutions mix without effervescence, although a 
 more concentrated solution of the alkali, mixed with vitriolic acid, 
 effervesces violently. 
 
 "By several experiments I found that chalk-lime, when taken as 
 fresh as it can be had from the wharf, consisting of pieces which, being 
 well-burnt, contain, especially in their central parts, about one-twen- 
 tieth of their weight of acidulous gas, of others which contain more, 
 and of others which retain near half their original quantity ; that 
 these last are easily discoverable by their specific gravity and hardness, 
 and that this is the part of our common lime which slakes the latest, 
 and of the darkest color, or which never slakes at all. On a peck of 
 this lime I sprinkled water, endeavoring to slake it equally by throw- 
 ing the most water on those pieces which required it most. After the 
 lime had stood a quarter of an hour to slake, I sifted it through a 
 sieve whose apertures were one-sixteenth of an inch square, and then 
 measuring the part which could not pass through the sieve, I found it 
 to be one-fifth of a peck, upon which I sprinkled boiling water, and 
 put into a close vessel, in a warm place, to accelerate the slaking of it. 
 
36 
 
 VARIOUS KINDS OF MORTAR. 
 
 ** I made a parcel of mortar with one part of the sifted lime and 
 three of sand, with a sufficient quantity of water ; and another par- 
 cel with one part of the lime, six of sand, and the necessary quantity 
 of water, and dried them upon tiles in the manner already related, in 
 the month of April, the weather being dry. The foregoing coarse 
 portion of the lime, after three hours, was slaked in several parts to a 
 greyish powder, and I could perceive that more of it would slake in a 
 longer time ; I anticipated this by reducing the unslaked part to pow- 
 der and mixing them together. 
 
 With this powder and sand and water in the foregoing propor- 
 tions, I made two specimens of mortar, and exposed them as I had 
 done the former. In a few months it appeared that the specimens 
 last mentioned scarcely deserved the name of mortar, whilst those 
 made with the first slaked part of the lime were but little inferior to 
 the best specimens made with the same proportions of chalk, lime, 
 and sand. 
 
 ** These experiments confirmed me in my opinion that lime is better 
 for mortar, as it is free from acidulous gas ; they showed one of the 
 causes of the inferiority of common mortar, and how to manage ill- 
 burnt lime when better cannot be had. 
 
 "Workmen usually slake lime mixed with sand or gravel in great 
 heaps, and do not* screen it until the most useful part is debased by 
 that which slakes after five or six hours or more, and which is little 
 better than so mucli powdered chalk. But if they would screen the 
 lime in about half an hour after the water is thrown upon it, the 
 mortar would be much better, although the quantity of lime in it 
 should be much less ; for I observed in all tlie foregoing specimens 
 that those which contained the smallest quantity of lime were the 
 best, and this quantity is much less than is usually employed in 
 mortar. 
 
 ** These remarks are applicable to mortar made with stone-lime, 
 which is generally better than the chalk-lime, because it is obliged to 
 be burned better, as it will not slake otherwise. 
 
VARIOUS KINDS OF MORTAR. 37 
 
 **In the brief relation of these experiments I have taken no notice 
 of the flinty kernels which frequently occur in chalk-lime, or of other 
 stony masses which differ from calcareous, and which are found in 
 lime-stone, in order to avoid being led into errors. 
 
 When first I noticed the quantity of chalk-lime which slakes late 
 or not at all, I suspected that this difference might in some degree be 
 owing to the admixture of argillaceous or other matter, but on try- 
 ing these portions in acids, and after burning several specimens of 
 them, I was convinced that the only impediment to their slaking con- 
 sisted in their not being sufficiently burned in the kiln. " 
 
 From the results of the foregoing experiments it is clearly demon- 
 strated that much of the imperfection of mortar is owing to careless 
 or imperfect manufacture of the lime, to say nothing of the loss in 
 waste. All therefore interested or concerned in the building art 
 should look well to this most important matter, as the durability of 
 tlieir works depends greatly upon the character of the mortar and 
 other cementitious substances employed therein. 
 
 Before proceeding to describe the mode of slaking lime and prepar- 
 ing mortar, it may be well to record some further experiments made 
 by Dr. Iliggins, in reference to the chemical properties of lime, and 
 of several effects produced upon lime and mortar by atmospheric or 
 other agencies. His observations upon phlogisticated (inflammable) 
 air, whicli abounds in all lime, are very pertinent to our subject, and 
 we quote his words in Section 3 of his valuable treatise, entitled, 
 "Remarks on the phlogisticated air which appeared in some of the 
 foregoing experiments" : — 
 
 "As phlogisticated air had not been noticed in any former experi- 
 ment made on chalk or lime-stone, I resolved to examine the elastic 
 fluid detached from them in the usual method. I extracted several 
 gallons of elastic fluid from chalk, during the solution of it in marine 
 acid, diluted largely with water, and after agitating this fluid with 
 the necessary quantity of water, and sometimes with lime-water, until 
 all the acidulous gas was imbibed by them, I found a residue consist- 
 
38 EXPEKIMENTS WITH LIME. 
 
 ing of common air, which was about one- twenty-eighth of the. bulk 
 of the acidulous gas, in some trials, in others it was much less. 
 
 As I have not had time to examine lime-stone in the same man- 
 ner, or to prosecute this subject by other experiments, I must content 
 myself with offering a conjecture concerning it. 
 
 The air which is extracted during the solution of chalk seems to 
 be that which chalk, like other porous bodies, imbibes by capillary 
 attraction, and it retains its proper character, because all the phlogis- 
 tic matter of chalk is held in the solution. It may happen likewise 
 that some air escapes from the water while it imbibes the acidulous 
 gas, which it attracts more forcibly ; and this air from the water may 
 contribute to the bulk of that which appears in the solution of cal- 
 careous bodies. But whilst chalk is deprived of its acidulous gas by 
 the action of fire, the air which was held in its pores, and which 
 attracts phlogiston, is expelled therewith, and consequently in the 
 form of phlogistic air. This conjecture appears the more proba- 
 ble when we consider that the quantity of air imbibed by porous 
 bodies is much greater than it appears in any experiments made with 
 the air-pump, as shown by the great increase of weight, which red- 
 hot charcoal acquires in cooling in vessels into which nothing ponder- 
 able but air was admitted. The same attractive powers which draw 
 air into bodies, and then condense it, resist the expansion and escape 
 of it in the void, and detain in such' a situation of the bodies that 
 quantity whose repulsive powers are counterposed by the attractive 
 ones." 
 
 Experiments showing how quickly Lime imbibes Acidulous 
 Gas, and is injured by Exposure to the Air. 
 
 - " It was generally known that lime exposed to air loses those charac- 
 ters which chiefly distinguish it from whiting or powder of chalk, and 
 that it resumes the acidulous gas which had been expelled from it in 
 burning. But being desirous to know in what measure or time these 
 
EXPERIMENTS WITH LIME. 
 
 39 
 
 changes take place, and in what circumstances they are accelerated or 
 retarded, I made the following experiments : — 
 
 "Exp. 1. I exposed two pounds (avoirdupoise) of well-burned non- 
 effervescent chalk lime, in fragments of the size of a walnut, spread 
 on a board, in a dry unfrequented room ; I exposed the same quan- 
 tity of this lime at the same time, and in the same manner, in a pas- 
 sage through which there was a constant current of air, and I put the 
 same quantity of this lime, in fragments of the same size, in a box 
 which might hold as much more of it, and placed the box loosely 
 covered with its lid, close by the first portion of the lime. 
 
 **In twenty-four hours the superficial lumps of the first parcel crack- 
 ed in some parts a little, those of the second cracked mdre, but those 
 of the third were not visibly altered. In forty-eight hours the first 
 parcel cracked so much as to fall into smaller fragments on being, 
 moved, and these were reducible to powder by pressing them between 
 the fingers ; the second parcel underwent the like, or rather greater 
 change, for it was more cracked and friable ; and the third now began 
 
 to crack in the superficial parts. On weighing them, I found the 
 
 » 
 
 first parcel weighed two pounds five ounces, the second, two pounds 
 six ounces and one drachm, and the third, two pounds one ounce and 
 ten drachms ; I then returned them to their former stations. 
 
 *'In six days the first parcel weighed two pounds ten ounces and 
 seven drachms; the second, two pounds twelve ounces and one 
 drachm ; and the third, two pounds four ounces and eight drachms. 
 In twenty-one days, the first weighed three pounds and one drachm ; 
 the second, three pounds two ounces and one drachm and a half ; and 
 the third, two pounds six ounces and eight drachms. During this 
 increase of weight, the fragments split into smaller pieces, but did 
 not fall into powder, except in a small part of them, or when they 
 were handled. 
 
 "By similar experiments made on well-burned stone lime, I found 
 that it imbibes matter from the air nearly in the same manner as 
 chalk lime, but rather more slowly, which I think is owing to its 
 
40 
 
 EXPERIMENTS WITH LIME 
 
 closer texture ; and on exposing common chalk or stone lime in the 
 same way, it was found to increase in weight much less, and more 
 slowly. 
 
 Exp. 2. In order to discover the quantity of water which the lime 
 imhibed from the air, and which contributed to this increase of weight, 
 I put each parcel into a glass retort, and adjusting to it my apparatus 
 whereby all that is condensed, is saved, whilst elastic fluids are at 
 liberty to escape, I found that the quantity of water contained in each 
 parcel of lime was nearly in some; and in others exactly one twenty- 
 fourth of the gained weight, the remainder of which was acidulous 
 gas, mixed with a little air ; which latter was not reckoned, having 
 been already weighed in the lime. 
 
 If a glass bottle be filled with fragments of well-burned chalk lime, 
 or stone lime, and well closed with a ground glass stopple, waxed 
 where it fits the neck of the bottle, the lime will remain unaltered in 
 weight, or in any other particular for a year or two, as I have repeat- 
 edly experienced ; even the phosphorescence of lime is thus preserved 
 in its full lustre, for a year or more. 
 
 Thus it appeared that well-burned lime imbibes acidulous gas from 
 the air, the sooner as it is the more exposed to it ; that Hme absorbs 
 this matter from the open air, the more greedily as it is the more per- 
 fectly deprived of it, previously to the exposure ; that lime cannot be 
 ong preserved unaltered in any vessels which are not perfectly air- 
 tiffht, but may be kept uninjured in air-tight vessels filled with it ; 
 that chalk lime by reason of its sponginess, or by some other condition 
 of it, requires to be kept less exposed than stone lime, and well-burn- 
 ed lime less exposed than common lime, to render the depravation 
 of them equal in equal times ; that if acidulous gas imbibed in lime 
 previous to its being used in mortar, be as injurious to mortar as the 
 acidulous gas retained in an equal quantity of ill-burned lime is, lime 
 becomes more unfit for mortar every hour that it is kept exposed to 
 air, whether in a heap, or in casks pervious to air. Moreover these 
 experiments show that lime undergoes these changes much quicker 
 
EXPERIMENTS WITH LIME. 
 
 41 
 
 than has been suspected, since well-burned chalk lime kept in a dry 
 room, imbibes near a pound of acidulous gas in three weeks, in the 
 summer season. 
 
 " Not trusting to theory, what I could prove by experiment^ I did not 
 rest satisfied with the observations and reasons which might persuade 
 one, that lime which has imbibed some acidulous gas, is as unfit for 
 the uses now under consideration as lime which retains an equal 
 quantity of the like matter by reason of the deficiency of heat in 
 burning it ; I tried parcels of well-burned chalk and stone-lime, some 
 of which were used fresh, others exposed two days, others six days, 
 others twenty-one days ; by making several specimens of mortar with 
 them, and exposing these specimens in the manner already related ; 
 and in a few months I was satisfied that the specimens made with 
 fresh lime were the hardest and best, and that the others were worse 
 as the lime of them had been longer exposed, for those made with 
 the lime which had been exposed three weeks, and had gained four or 
 five ounces to each pound, were so easily cut or broken, so much effect- 
 ed by moisture and drying, and so liable to break off" from the tiles, 
 as to be utterly unfit for the ordinary uses of mortar. 
 
 "After this there remained no doubt that lime grows worse for mor- 
 tar every day that it is kept in the usual manner, or in crazy casks ; 
 that the workmen are mistaken in thinking that it is sufficient to keep 
 it dry ; that lime may be greatly debased without slaking sensibly, 
 and that the superficial parts of any parcel of lime, which fall into 
 fragments or powder without being wetted, and merely by exposure 
 to air, are quite unfit for mortar, since this does not happen until 
 they have imbibed a great deal of acidulous gas. 
 
 ''I now saw more clearly another cause of the imperfection of our 
 common cements. The lime being exposed a considerable time before 
 it is made into mortar, and drinking in acidulous gas all the while, 
 the quicker as it is the better burned, is incapable of acting like good 
 lime, when it is made into mortar, and often approaches to the con- 
 
42 
 
 EXPERIMENTS WITH MORTAR. 
 
 dition of whiting, which with sand and water makes a friable, perish- 
 able mass, however carefully it be dried. 
 
 **In London, particularly, they use lime which is burned at a dis- 
 tance of ten or twenty miles or more, with an insufficient quantity of 
 fuel. This lime remains in the kiln to which the air has access, for 
 many hours after it is burned ; it is then exposed for some days in the 
 transportation and on the lime wharves, and it undergoes further ex- 
 posure and carriage before it is slaked into mortar. It is, therefore, 
 no wonder that mortar is bad, if its imperfection depended solely upon 
 the badness of the lime, since the lime is not only bad when it comes 
 from the kiln, but becomes worse before it is used, and when slaked is 
 as widely different from good lime as it is from powdered chalk." 
 
 Experiments and Observations made to determine whether 
 Mortar becomes better for being kept long before it is 
 
 USED. 
 
 " I am generally disposed to think that there is some good reason 
 for any practice which is common to all men of the same trade, al- 
 though it may not be easily reconcilable to the notions of others ; and 
 seeing that the builders slake a great quantity of lime at once, more 
 than they can use for some days, and that all those with whom I con- 
 versed, esteemed mortar to be the better for being long made before 
 it is used, and that plasterers in particular follow this opinion in mak- 
 ing their fine mortar or stucco for in-door work ; I was desirous to 
 discover the grounds of these measures so repugnant to the notions 
 gathered from the foregoing experiments, and others. I therefore 
 made about a peck of mortar with one part of the freshest and best 
 chalk lime, slaked, six parts of sand, and water quart, suff. ; for in a 
 great number of experiments I observed that this proportion of lime 
 was better than any larger which I had tried, or which the workmen 
 observe in making mortar. The mortar was formed into an hemi- 
 spherical heap on the paved floor of a damp cellar, where it remained 
 untouched twenty-four days. At the expiration of which time, it was 
 
EXPERIMENTS WITH MORTAR. 43 
 
 found hardened at the surface, but moist, and rather friable or * short 
 than plastic in the interior parts of it. I beat the whole of it with a 
 little water to its former consistence, and with this mortar and clean 
 new bricks, built a wall eighteen inches square, and half a brick in 
 thickness, in a workmanlike manner. On the same day I made mor- 
 tar of the same kind and quantities of fresh chalk lime and sand^ 
 tempered in the same manner, and built a wall with it, like the for- 
 mer, near it, and equally exposed to the weather. I examined the 
 mortar in the joints of these walls every fortnight, by picking it with 
 a pointed knife, and could perceive a very considerable difference in 
 the hardness of them, the mortar which was used fresh being invaria- 
 bly the hardest. 
 
 "At the expiration of twelve months, in pulling these walls to 
 pieces, and by several trials of the force necessary to break the cement 
 and separate the bricks, I found the mortar which had been used 
 quite fresh to be harder and to resist fracture and the separation of it 
 from the bricks in a much greater degree than the other experiment. 
 
 "Considering that mortar exposed in the foregoing manner must 
 imbibe some acidulous gas, though not so much perhaps as the dry 
 and spongy lumps of lime drink in during the same time ; that the ad- 
 ditional quantity of water necessary in beating it up the second time 
 must have introduced more of the like matter, as all native waters 
 contain some quantities of it ; that the fresh exposure in the last 
 mentioned agitation of the mortar must have contributed something 
 to the same effect ; and lastly, that the result of this experiment coin- 
 cided with the notions already derived from others, I concluded that 
 mortar grows worse every hour that it is kept before it is used in the 
 building, and that we may reckon as another cause of badness of 
 common mortar, that the workmen make too much at once, and 
 falsely imagine that it is not the worse, but better, for being kept. 
 
 Having in consequence of these observations had a great deal of 
 conversation with workmen on this subject, I could perceive the origin 
 of this error. 
 
44 
 
 PLASTERERS' LIME. 
 
 **Some portions of every kind of lime used do not slake freely, by 
 reason of their not being sufficiently burned, or by the admixture of 
 gypseous or argillaceous matter, and these, like marl, slake in time, 
 though not so quickly as the purer lime. 
 
 The plasterers, who use a finer kind of mortar made with lime 
 and sand, observe that their plaster or stucco blisters when it con- 
 tains such particles of unslaked lime : and as their purpose is to work 
 their stucco to a smooth surface, and to secure from cracking, or any 
 such roughness as would be occasioned by the slaking or moulding of 
 bits of calcareous matter in the face of it ; and as the hardness of the 
 stucco is not their chief object, they very properly keep their mortar a 
 considerable time before they use it, in order that the imperfect pieces of 
 lime which passed through the screen may have time to slake thoroughly. 
 
 " It appears that there is another reason which the workmen do not 
 notice for their process, which is, that lime imbibes so much acidulous 
 gas from the air, as to become increased in bulk, and in weight be- 
 yond the half of its former quantity ; and as stucco for inside work, 
 for the sake of a fine grain and even surface, must have a greater 
 quantity of lime in its composition than is necessary for cementing 
 the grains of sand together, the incrustation would, by the access of 
 acidulous gas after it is laid on, be apt to swell and chip, and lose the 
 even surface if the lime were fresh when it is used in this excessive 
 quantity ; but this inconvenience is obviated by their processes, in which 
 the lime, whether slaked into water or otherwise, imbibes a considerable 
 quantity of the gas, and is, therefore, less apt to blister and swell, 
 after the stucco is laid on. The builders, considering the plasterers* 
 mortar or stucco as a finer and better kind of mortar, think it not 
 amiss to imitate them in those particulars which are not attended 
 with any expense, and especially in the practice of slaking a great 
 deal of lime at once, and of keeping the mortar made some time ; and 
 they do not seem to know that such mode prevents the mortar from 
 ever acquiring that degree of hardness in which the perfection of mor* 
 tar truly consists.* 
 
PRACTICAL INFERENCES. 
 
 45 
 
 Experiments and Observations showing the Agency or 
 Acidulous Gas in the Induration of Mortar, and cir- 
 cumstances WHICH IMPEDE OR PROMOTE IT. PRACTICAL IN- 
 FERENCES. 
 
 * ' The observations made on divers specimens of mortar at different 
 periods, led me early into the opinion that the setting of mortar de- 
 pends chiefly on the exsiccation of it, but that the induration is prin- 
 cipally owing to the accession of acidulous gas in certain circum- 
 stances, and not to the drying, as the workmen generally imagine. In 
 order to place this opinion beyond a doubt, and to discover the cir- 
 cumstances which favor or impede this induration, I made the sub- 
 sequent inquiries : — 
 
 *' Exp. 1. I made mortar with seven parts of Thames sand, om 
 part of the best slaked chalk-lime, and the necessary quantity of lime- 
 water, and forming a part of it into oval pieces, I put these into a 
 gallon bottle, stopped closely with a ground glass stopple, waxed ; and 
 I noted the gross weight of the bottle and mortar, and placed it ex- 
 posed to the sun. Having examined it frequently during the first 
 month, I could perceive no alteration in the weight, nor anything 
 worth notice, except that some water exhaled out of the mortal, and 
 condensed in bright drops on the sides and the upper parts of the 
 bottle. At divers times during six months afterwards, I shook and 
 weighed the bottle, and found the mortar quite soft, and the weight 
 of the whole unaltered. 
 
 "Exp. 2. Another portion ot the same mortar was spread briskly 
 as soon as it was made, on oblong pieces of dry and warm tile, and 
 these were immediately placed over a sand bath, where they were 
 gradually heated to about 100^ Fahrenheit for six hours, and then to 
 150° for two hours more, when the mortar was dried thoroughly. 1 
 took particular notice of the solidity which it acquired in this hasty 
 dr}dng, and then put the pieces of tile with the adhering mortar into 
 a bottle, stopped in the manner already described, marking down the 
 
46 
 
 PRACTICAL INFERENCES. 
 
 gross weight. At the expiration of seven months the whole was 
 found unaltered in weight, and the mortar as easily cut or broken as 
 it was when put into the bottle. 
 
 **ExF. 3. Another part of the same mortar was spread whilst fresh 
 on a large tile, to the thickness of half an inch, aud the tile was im- 
 mediately placed in a tub, in which water was put to the depth of 
 three inches over the mortar, and which was placed in the open air to 
 receive the rain. At different periods I broke the calcareous pellicle 
 which formed on the water and defended it from the air during the 
 tirst fortnight : afterwards the wind and rain rendered this precaution 
 unnecessary. In the course of six months, the mortar, instead of 
 acquiring any solidity, was deprived of the greater part of its lime 
 and what remained on the tile was not much different from a layer of 
 wet sand. 
 
 "Exp. 4. Another portion of the same fresh mortar was spread on a 
 board strewed with slaked lime to prevent adhesion, and placed in the 
 open air, but sheltered from the sun. When this mortar became suffi- 
 ciently solid, which was on the second day, the pieces were raised, 
 which were about a quarter of an inch thick, and placed upright, 
 fully exposed to the weather, which was about this time dry and 
 warm. 
 
 **In seven weeks after this exposure they were indurated to a con- 
 giderable degree. They resisted a cutting instrument as much as 
 Portland stone does, but not so well any force tending to break them 
 across at once. I then placed them under water as I had done by the 
 former portion of this mortar. 
 
 After they had lain in water four months, I examined them 
 attentively, and found them, if at aU altered, to be ratTier softened 
 than indurated further. I replaced them in the water, to be better 
 i^tLsfied about them, but by mistake they were removed in my absence 
 and lost. 
 
 *♦ Exp. 5. Soon after the foregoing parcel of mortar was made I 
 prepared another in the same manner, and spread a part of it on a 
 
PRACTICAL INFERENCES. 47 
 
 tJJe soaked in lime-water, and placed tbe tile in the open air, sheltered 
 from the sun and rain ; and after it had remained there one month, 
 it was placed where sheltered from the rain only. 
 
 **Exp. 6. Another portion of the same mortar was spread fresh 
 on a warm, dry tile, which I placed over a sand bath heated to about 
 100° Fahrenheit for six hours, and then to 150° for four hours more, 
 at the expiration of which it was solid and hard. The next day they 
 were placed in the open air, exposed to the sun and weather, which 
 was dry and warm for a considerable time afterwards. 
 
 " On comparing these two last specimens at the expiration of seven 
 months, and again after six months more, I could easily perceive that 
 the latter was inferior to the former, for it was much more easily cut. 
 and scaled from the tile, and broken. 
 
 *'Exp. 7. With mortar made the day after the former, of the 
 same materials and in the same manner, and with new bricks, which 
 I had heated almost to redness, and suffered to cool almost to the 
 temperature of my hands, I briskly erected a little waU, half a 
 brick thick, on a stone bench raised for the purpose, and fully exposed 
 to the weather. 
 
 **Exp. 8. On the same day, and with the like mortar, and with 
 cold new bricks previously soaked in lime-water, I built another waU 
 equal to the former in dimensions, and placed it in same manner on a 
 stone bench in the open air. 
 
 After nine months, in puUing these walls to pieces, and in divers 
 comparisons of the cement of them, I found that the latter cement 
 adhered better to the bricks, and was harder than the former, inso- 
 much that I had not a doubt about it. 
 
 *'Exp. 9. In a few days after I had made the experiment with the 
 warm bricks, I considered the walls erected in variable weather, and 
 the fence walls which are wetted frequently and deeply, while new, by 
 rain or by moisture from the ground, and as often dried as quickly: 
 and being desirous to learn the effects of such alternations of wetting 
 and drying, I spread mortar made like those parcels lately mentioned, 
 
48 
 
 PRACTICAL INFERENCES. 
 
 on a large tile soaked in lime-water, and as often as it bad dried m 
 fair weather, and generally at the interval of three days. In the 
 course of nine months I found it was much less indurated than the 
 spe'cimen made in the same manner, and defended from the rain ; it 
 moreover grew green by means of a vegetation which took place upon 
 the surface of it, and which thrived the more as the mortar was fre- 
 quently wetted, or the tile longer permitted to lie flat on the stone 
 bench already mentioned. 
 
 **I have often observed such a vegetation on mortar which I had 
 made a few months before, especially when, in the summer season, 
 I had laid tiles flat on the wooden border of a dust-hole, or when, from 
 want of room to preserve the specimens in, I piled many of them to- 
 gether in a damp corner on the pavement ; I likewise saw that when 
 the vegetation took place, the induration did not proceed as it does 
 elsewhere ; on the contrary, semi-indurated mortar softened them. 
 
 All these being considered, I was satisfied that frequent wetting 
 or constant moisture, together with exposure to the air, injures mortar 
 to a great degree, if it be not perfectly indurated by great age before 
 it is exposed to such trials, and that the vegetation chiefly depends on 
 moisture. 
 
 " Exp. 10. By the kind of analysis mentioned in the 10th section, 
 I repeatedly examined the proportion of the acidulous gas to the 
 lime, in the hardest of the old cements which I had collected, and 
 finding it in the best of them to be, at the lowest, in the proportion 
 of three to five, I rate the quantity of acidulous gad imbibed by good 
 mortar, during the induration of it, to be sixty pounds at least for 
 every hundred pounds of lime. 
 
 **Exp. 11. Such mortar as that of the first experiment of tliis 
 section, was formed into slender pieces, each an inch broad, a quarter 
 of an inch thick, and three inches in length. These were placed in 
 an airy passage, sheltered from the sun and rain, and were turned ag 
 soon as they could bear it without danger of cracking, ttiey were then 
 set upright and fully exposed on all sides to the air. On the fourth 
 
PRACTIC^iL INFERENCES. 
 
 49 
 
 day I slid four of the pieces entire into a small wide-nccked glass re- 
 tort, which I set deep in a sand-bath, with its nozzle immersed in 
 quicksilver, which stood cool whilst the charge was gradually heated ; 
 in the course of forty-eight hours, to about 75° Fahrenheit, which is 
 under the temperature of incrustations of this kind exposed to the 
 sun in summer; and in the course of forty-eight hours more, was 
 slowly heated to about 100° Fahrenheit, to which degree incrustations 
 are frequently heated by the sun in summer. As the retort cooled, 
 I admitted the necessary quantity of air, and then left it, with the 
 nozzle immersed deeply in the mercury during three months. I then 
 gently slid the pieces out of the retort, after having wiped away a few 
 drops of water which adhered to the vessel in their way, and immedi- 
 ately made the comparison which I shall presently mention. 
 
 Close to the retort, and in a situation where the heat was equal to 
 that described, or nearly so, I placed four other of the pieces above 
 described, on the fourth day after they were made, and encompassed 
 them with sand, but with a free access, and even a circulation of air to 
 them. When the sand bath was cooled, I put these pieces which 
 were thus perfectly dried, into a bottle stopped closely in the manner 
 heretofore mentioned. 
 
 "On the seventh day after the pieces were made, also on the 
 twenty-first, and at the expiration of three months, I examined four 
 pieces taken from different quarters of the remaining parcel, and 
 found the quantity of acidulous gas which they yielded to correspond 
 with the degree of induration, and the depth to which it had advanced 
 in them respectively. 
 
 "On comparing and examining the pieces dried in the retort and 
 kept three months in it ; the pieces dried in the same heat and freely 
 exposed to the air during four days, but afterwards kept in a close 
 vessel ; and the pieces which dried and hardened in the free air, with- 
 out being heated ; I found that the first were friable in comparison 
 with the second, and the last were by much the hardest and best. 
 
 "As the second, tenth, and eleventh experiments, together with 
 3 
 
50 
 
 PRACTICAL INFERENCES. 
 
 observations formerly made, show that the induration peculiar tc 
 mortar is not caused by exsiccation ; that it is greater as the calcare- 
 ous matter of cements approaches nearer to be saturated with acidu« 
 lous gas ; that it is retarded or prevented as the accession of acidu- 
 lous gas is interrupted or obviated ; we may conclude that this matter 
 is a principal agent in the induration of calcareous cements, and in- 
 dispensably necessary to it. 
 
 "By observations formerly made, but especially by the comparison 
 of the fifth and eighth experiments of this section, with the sixth and 
 seventh, I learned that hasty drying prevents good mortar from ever 
 acquiring the hardness which it otherwise would have ; and that the 
 more slowly the proper water of the mortar is exhaled or absorbed 
 from it, in incrustation or brick-work, the more perfect will be the 
 induration. 
 
 * * By the first, third, and ninth experiments of this section, com- 
 pared with the fourth, fifth, and others, and by observations which 
 led me to make these experiments, I discovered that mortar which is 
 not sufi*ered to dry, or which is supplied vsdth moisture as fast as its 
 proper water exhales, does not harden, or hardens only to a small de- 
 gree by an accession of acidulous gas. 
 
 " The fourth experiment indicates that mortar, whose lime has not 
 yet imbibed its complement of acidulous gas, although the mass be 
 considerably hardened, is liable to be injured by soaking in water, if 
 it be pervious to water so freely as these thin pieces were. 
 
 ' ' All these experiments and observations conspire to point* out the 
 circumstances in which mortar becomes indurated the soonest, and in 
 the highest degree, and operates most effectually as a cement. To 
 this end it must be suffered to dry gently and set, the exsiccation 
 must be effected by temperate air, and not accelerated by the heat of 
 the sun or fire. It must not be wetted soon after it sets, and subse- 
 quently it ought to be protected from wet as much as possible, until it 
 is completely indurated ; the entry of acidulous gas must be prevented 
 as much as possible until the mortar is finally fixed and quiescent, and 
 
PRACTICAL INFERENCES. 
 
 51 
 
 then it must be as freely exposed to the open air as the work will 
 admit, in order to supply acidulous gas, and enable it sooner to sus- 
 tain the trials to which mortar is exposed in cementitious buildings 
 and incrustations. 
 
 ''From these considerations we learn other causes besides those al- 
 ready mentioned of the speedy ruin of our modern buildings. 
 
 ''The mortar made with bad lime and a great excess of it, and 
 debased in watering and long exposure, is used with dry bricks, and 
 not unusually with warm ones. These immediately imbibe or dissi- 
 pate the water and not only induce the defect above noticed, but, as 
 the cement approaches nearer to dry, whilst it is liable to be disturbed 
 by the percussions of the workmen, render it more nearly equivalent 
 to a mixture of sand and powdered chalk. 
 
 "But in order to make strong work, the bricks ought to be soaked 
 in lime-water, and freed from dust, which in common bricklaying, 
 intercedes between the brick and mortar in many parts. By this 
 method the bricks would be rendered closer and harder ; the cement, by 
 setting slowly would admit the motion which the bricks receive when 
 the workman dresses them without being impaired, and it would ad- 
 here and indurate more perfectly. The same advantages would attend 
 the soaking of bibulous stones in lime-water, and the use of grouts, 
 provided this were made with good lime, sand and lime-water. 
 
 "In plastering, the workmen always brush away the dust, and wet 
 the wall on which they are to lay the cement, because it will not 
 otherwise adhere. From what has already been said, it is manifest 
 that this ought to be done with lime-water, and repeated as long as 
 the wall is thirsty. 
 
 "To perceive more clearly how much our slight buildings are 
 weakened by the agitations and percussions to which they are exposed, 
 first in erecting the walls, and setting the timbers, and then driving 
 those wedges (plugs) to which they fasten the wainscot, cornices and 
 other ornaments, we must observe that the accession of acidulous gas 
 to mortar, was found to contribute nothing to the strength of it. 
 
52 
 
 EXPERIMENTS ON OLD CEMENTS. 
 
 when it entered the composition before it was finally fixed in a quies- 
 cent state, and a little experience is sufficient to teach us, that the 
 same matter which assists in the induration of mortar, never serves 
 to repair the fissm'es, or solution of continuity between the bricks and 
 cement which happen after it is set. When mortar is set, and before 
 it is indurated, it may easily be severed from the bricks and crumbled, 
 and for want of softness it cannot bend into the fissures, or resume its 
 former condition in any time. Therefore, by heavy blows, and in 
 wedging, our walls must be greatly weakened, and the more, as the 
 houses are slight, quickly built and slightly finished." 
 
 jtfXPERIMENTS ON OlD CeMENTS, AUTHORISING THE PROPORTION 
 LATELY RECOMMENDED OF LIME AND SAND. 
 
 To discover the quantity of lime and sand originally used in many 
 hard and old cements, which was found by a previous analysis to con- 
 sist of lime, and sand or clear gravel, I break a pound of it into 
 small fragments, but not into powder, and with diluted warm acid I 
 dissolve and wash away the calcareous part from the gravel or sand. 
 I measure the acidulous gas obtainable during the solution, and know- 
 ing the weight of any quantity of it, in any temperature or weight of 
 the atmosphere, I substract this weight of acidulous gas and that of 
 the sand or gravel, from the whole weight of the mortar, and state the 
 residuary weight as that of the lime originally employed, knowing 
 that it could not have made so hard a cement, if it had not been so 
 far burned as to retain very little acidulous gas. I did not adopt this 
 method of examination before I found it to exhibit the lime and sand 
 of my oldest and hardest cements, in the same proportions in which I 
 had mixed them. 
 
 "By this kind of analysis, and by other trials, I found that the 
 quantity of lime in old cements made with clear, sharp sand, and 
 noted for their hardness, was much less than is now commonly used in 
 mortar, and that in the hardest of them, it was very near to that 
 
EXPERIMENTS ON OLD CEMENTS. 
 
 53 
 
 wMch my experiments indicated to be the best. By sharp sand I 
 mean those whose grains are bounded by flat surfaces. Thus I found 
 the inferences made from my compositions to be authenticated by 
 long experience so far as they related to the proportion of lime and 
 such sand." 
 
 The foregoing practical experiments of Dr. Higgins, undoubtedly 
 prove, 1st. That the value or quality of lime for mortar depends upon 
 its freedom from acidulous gas ; 2d. That it should be well or perfectly 
 burnt ; 3d. That it should be used immediately after it is burned ; 
 4th. That its quality is greatly debased or deteriorated by exposure to 
 the atmosphere ; 5th. That the nature or quality of the sand employ- 
 ed is important in the composition of mortar, and that when used 
 should be perfectly clean and free from any foreign or objectionable 
 matter ; 6th. That sand of a mixed size or gauge is preferable for 
 general purposes; 7th. That sea sand, or any other sand which con- 
 tains saline impregnations, is objectionable for mortar; 8th. That 
 the best proportion of lime to sharp, clear sand, where strength and 
 durability are concerned, is that of one part of lime to six or seven of 
 sand ; 9th. That the water used to amalgamate the other ingredients 
 of mortar should be pure : sea or any salt water, or any that are im- 
 pregnated with mineral or chemical proportions are not only objection- 
 able but injurious ; 10th. That as little water as possible should be 
 used in the preparation of mortar, and that an excess thereof, and 
 especially a second application, after the mortar has been once pro- 
 perly made, is debasing to the mortar, as it dissipates the cementitious 
 properties of the lime, and leaves a large residuum of acidulous gas, 
 which is imbibed or absorbed by the lime ; 11th. That lime-water is 
 far preferable to crude water for making mortar, as the solution of 
 lime has the effect of disengaging or discharging the acidulous gaa 
 from the water ; 12th. That the perfect induration of mortar depends 
 upon a moderate temperature and a protection from rain, frosts, &c., 
 and that (coeteris paribus) those mortars are the hardest and most 
 durable that require the longer time to dry ; 13th. That the bricks 
 
54 
 
 EXPERIMENTS ON OLD CEMENTS. 
 
 should never be used when warm, and that they be free from dust, 
 never used in a dry state, but should be previously wetted or soaked 
 with water, lime-water being preferable ; 14th. That brick or stone 
 work when once laid, should be disturbed as Httle as possible, for when 
 a joint of mortar is broken, after it is once set, it becomes very prob- 
 lematical whether it will ever properly unite again. 
 
 Having now described the several ingredients forming the composi- 
 tion of mortar, and exhibited sundry experiments thereon, with their 
 results and inferences, from the inquiries and labors of the celebrated 
 Dr. Higgins, whose work and reputation upon this, stand preeminently 
 and deservedly high, and who ranks as one of the chief authorities 
 upon the subject, we shall in due course proceed to lay before the in- 
 quiring reader, the mode of preparing the several ingredients of mor- 
 tar, their combination and application, interspersing our remarks 
 with the opinions and practice of other professional men of note, who 
 have recorded the issue of their labors for the benefit of the present and 
 future generations ; after which, we purpose to complete our notice of 
 other experiments of Dr. Higgins upon the eifects of combining sundry 
 foreign matters in the composition of mortar or cements for particular 
 purposes, to which will be appended some account of the cements used 
 by the ancients ; also an account of hydraulic cements, their nature, 
 properties, use, combination and application, together with the experi- 
 ence, opinions, and experiments of some of the first authorities there- 
 on ; and the whole to conclude with a detailed account of the 
 lime-kiln, and various modern methods of burning or preparing 
 lime, fee- 
 Such being the ' ' programme" of the entertainment now contemplat- 
 ed, we will proceed to perform the several "parts" in their consecutive 
 order, trusting the finale" will be satisfactory. 
 
PREPARATION OF COMMON MORTAR. 55 
 
 On the Preparation of Common Mortas. 
 
 The Lime when perfectly prepared or burnt in the kiln should be 
 speedily withdrawn, and packed for transportation to its intended des- 
 tination, in sound casks or air-tight vessels well closed down, and 
 should be kept entirely free from all moisture ; and when received by 
 the builder should be deposited until required for use (which should be 
 as early as possible) in a shed or other dry building, or if left out of 
 doors should be closely covered with a tarpaulin, or boards, and each 
 cask should be unheaded or opened only as required. 
 
 Lime in this state is termed caustic or quick lime, and in order to 
 make it fit to be incorporated with the other ingredients it must be 
 reduced to *^ hydrate," a change which is effected by the application 
 of water, which process is termed ' slaking" and after which opera^ 
 tion the lime is called slaked lime. Of this operation, there are three 
 methods in use. The 1st. and most usual is by pouring or throwing 
 the necessary quantity of water over the lime after it is spread out into 
 a shallow heap, surrounded by the whole or a portion of the sand with 
 which it is to be incorporated. 2dly. By immersion, or plunging the 
 lime when deposited in a basket or other suitable receptacle for a few 
 moments into water until the surface lime begins to effervesce or boil 
 and then turned out into heaps to afford time and opportunity for the 
 slaking to be completed. And 3dly., by mere exposure to the atmo^ 
 sphere, the lumps of lime having been previously broken up to about the 
 size of a pigeon's egg, or somewhat smaller, so as to secure a more 
 speedy and effectual calcination of the whole, but this operation must 
 not be performed in wet weather, nor in too damp an atmosphere ; it 
 must be carefully watched, and so soon as the slaking is complete, the 
 quick lime must be immediately used or deposited in close casks till 
 required. This method is seldom adopted except for plasterers, who 
 consider lime so prepared preferable for their work, as it is said to 
 make the lime stronger. This mode suits fat limes (such as slake 
 freely) better than poor limes. Lime slaked by the second process will 
 
56 PKEPAKATION OF COMMON MORTAR. 
 
 keep well for months in a dry, sheltered spot. But in every case where 
 water is employed for slaking lime or mixing the mortar subsequently, 
 care must be taken not to drown" the lime for the reasons before 
 explained, and also not to go to the opposite extreme, but to put the 
 quantum su ff. at once, which is usually computed at about one and a 
 quarter of the weight of the lime, or from four to five gallons to a 
 cubic foot of lime, which weighs upon an average from 28 lb. to 35 lb., 
 for if the water be applied tardily or sparingly, the lime will be be- 
 numbed, or imperfectly calcined, and gritty. 
 
 But the exact quantity of water required will be proportionate to 
 the nature and quality of the lime — ^the fat or richer sorts will require 
 or absorb more than the lean or poorer sorts, so that in this matter 
 no absolute or definite rule can be laid down, but the architect or 
 builder must exercise his observation and judgment — always bearing 
 in mind that it is most essential that mortar should be used fresh, 
 that it will consequently be necessary to apply a sufficiency of water 
 at once, so as not to expose the lime unnecessarily long to the atmos- 
 phere. 
 
 Limes become effete (difficult to slake) after much exposure to the 
 air, so that speedy calcination is important to their subsequent use 
 or value. 
 
 Limes, when slaked, increase considerably in bulk and weight by 
 their absorption of both moisture and air, as hath before been alluded 
 to, and which increase varies in different specimens of lime. 
 
 The slaked lime must be passed through a seive or screen, the 
 meshes or orifices of which should be small, not exceeding one hun- 
 dredth part of an inch, so as to give passage only to the powdry par- 
 ticles of the lime or that which is perfectly calcined, leaving all the 
 core or indissoluble portions of the lime behind, which must be thrown 
 out ; and if, after a further addition of water and lime, it should 
 prove obdurate, and will not slake, it must be abandoned altogether ; 
 however, this refuse will be found serviceable to use in concrete, or to 
 fill round the sides of walls, piers, drains, &c., or to lay under floor 
 
PREPAKxVTION OF COMMON MOETAR. r,7 
 
 next the earth, where it would check damps by partially absorbing 
 any rising moisture. The operation of screening the lime is some- 
 times performed before its admixture with the sand, and at other 
 times with it ; of these two methods we prefer the latter for the fol- 
 lowing reasons, viz. : because it eifects a saving, of time, and because 
 it insures a better and more equable amalgamation of the ingredients, 
 and because the lime is thereby not so much exposed to injury from 
 the atmosphere. 
 
 Upon the perfect completion of the above-described operation, th« 
 combined mass should be spread out in the form of a hollow cone, 
 and the final complement of the aqueous fluid should be speedily but 
 uniformly added ; the whole mass being at the same time effectually 
 stirred up and about, to promote a proper combination thereof ; oi 
 what is better, the mass should, so soon as it is brought to a proper 
 consistency, be passed through a "pug mill," which is a machine 
 well known, and employed in the preparation of clay for the manu- 
 facture of bricks ; but where this desideratum cannot be obtained, it 
 should be well-tempered with wooden beaters, and also well-turned 
 over and incorporated together, as it is also very important for the 
 solidity of the work for which it is to be used, that the mortar be well 
 mixed and quite unifbrm throughout. 
 
 Mortar should be prepared of a medium consistency, not too tough, " 
 that is, not too dry, nor yet too short," that is, not too wet — for in the 
 former case the beds and joints will be rigid and difficult to regu- 
 late, from the absence of sufficient moisture, and what there is will 
 be speedily absorbed by the brick or stone, and the mortar will indu- 
 rate too speedily, and in the latter case, the joints will settle too much, 
 and the quality of the mortar be deteriorated. 
 
 The induration of mortar is dependent upon its due absorption of 
 carbonic acid gas from the atmosphere, and it is necessary in order to 
 effect the re-union of carbonic acid with the lime, that the latter 
 should have received, previously, not less than one-third its weight of 
 water, and which is proved by the fact that if dry-slaked lime be put 
 
58 PREPARATION OF COMMON MORTAR- 
 
 into a jar or vessel of carbonic acid alone, there will be no absorption 
 whatever. 
 
 Mortar^ stuccoes, or cements, prepared from ill-burnt lime, con- 
 tinue soft and dusty for a long time after being made; whereas, when 
 they are compounded of well-burnt and slaked lime, they readily im- 
 bibe the carbonic acid and soon become thoroughly indurated. 
 
 Rich limes emit a strong hissing noise and great heat during the 
 process of slaking, but the poor or meager limes, which nevertheless 
 are the most valuable, undergo the operation with less apparent ex- 
 citement; and in proportion to the extraneous or foreign matter 
 wliich they contain, and with some varieties of hydraulic limes, no 
 visible effect will be observable in them until after the lapse of several 
 hours. 
 
 The purest limes require the largest proportion of sand, and require 
 the most water in slaking, and harden in less time than the common 
 limes. 
 
 Hydrate of lime, or the powdered state of lime produced by slaking 
 whilst in a damp state, soon faUs away and is dissolved in water, and 
 the same result is produced by alumina, manganeze, silica, &c., but 
 not to so great an extent. 
 
 In the before-mentioned experiments. Dr. Higgins determined that 
 the best proportion of lime and sand is one measure of the former 
 to six or seven of the latter ; but in England the tradesmen usually 
 combine one hundred and a half, that is, 150 pecks, or 37/^ striked 
 bushels of chalk-lime with two loads of sand, that is, 60 bushels of 
 sand ; and with the like quantity of stone lime they usually put two 
 and a half loads of sand, or 75 bushels, which are very erroneous 
 proportions, as the sand experiments clearly show, and as our own 
 experience has often testified. 
 
 The above-mentioned quantities are each sufficient to do a rod of 
 brick-work, which is equal to 212% feet of one and a half brick thick, 
 or 408/^ feet of one brick thick ; to this standard the calculation of 
 all brick- work, of whatever thickness it may be, is reduced, and by 
 
EXPERIMENTS AND RESULTS, 59 
 
 fthis, the architect, in his specification of works, usually limits or de- 
 termines the quantity of lime and sand to be used. 
 
 Various substances are sometimes added to mortar to increase the 
 tenacity, and they impart thereto the principles of hydraulic cements 
 to a greater or lesser degree. 
 
 These chiefly consist of burnt clay, ashes, scorisB, iron scales and 
 filings, pulverized broken potter's ware, bricks, tiles, &c., all of which 
 are very useful for mixing with lime or mortar to increase their hard- 
 ness, but these must be veiy pure and dry, and reduced to a fine 
 powder before being mixed with the lime. To enable lime to harden 
 by the absorption of carbonic acid, it must be divided as minutely as 
 possible so as freely to admit the air, and for which purpose these sub- 
 stances are available. Any of these compositions are very useful for 
 the purpose of bedding, chain-bond, wall-plates, templates, common 
 bond or bearers upon walls, instead of lime mortar, the properties of 
 which are highly injurious to wood, and on that account ought never 
 to be brought into close contact therewith. 
 
 Common mortar of ashes is prepared by mixing two parts of fresh 
 slaked lime with three parts of wood ashes together, and when cold, 
 to be well beaten, in which state it is usually kept for a considerable 
 time ; and if beaten two or three times previous to using it, will be 
 found to improve by keeping. In resisting the alternate effects of 
 moisture and dryness, this mixture is by some persons thought to be 
 superior to terras mortar, but not nearly equal to it when applied quite 
 under water. 
 
 We will now proceed to quote further from Dr. Higgin's work; — 
 
 ExPERmENTS SHOWING THE EFFECTS OF FiNEST SaND AND 
 
 QuARTOZE Powder in Mortar ; Observations on the finest 
 Calcareous Cements ; Practical Precepts. 
 
 **The last-mentioned notion led me to suspect, soon after the fore- 
 going experiments were made^ that although the fine Thames sand 
 
60 
 
 EXPERIMENTS AND RESULTS. 
 
 made better mortar than the coarse sand or rubble afforded, the 
 mortar will not always be the better as the sand is finer, however 
 sharp it may be. I therefore procured a large quantity of the very 
 fine pit sand, used in London under the name of "house sand." I 
 washed away the clay with which it abounds, and dried it. Viewing 
 it when thus cleansed, with a lens, I estimated the size of the grains 
 to be, at a medium, about one-ninth of that of any fine Thames sand ; 
 this I shall call, finest sand. At the same time I was favored by Mr. 
 Bentley, the ingenious manufacturer of ornamental Staffordshire 
 ware, with the necessary quantity of the fine powder of calcined flints, 
 which is prepared for his manufactory. With divers mixtures of these 
 with lime-water and lime, in a variety of proportions, and with each 
 and both of these ingredients blended with coarse and fine sand, lime, 
 and lime-water in similar proportions, I made a great number of 
 specimens of mortar, which I tried in the manner already described ; 
 and noting my observations on them I found the following to be the 
 most eligible, for the concise recital intended in this essay : — 
 
 *'lst. Mortar containing the quantity of lime necessary to the plas- 
 ticity and other desirable properties of it, or a greater quantity of 
 lime, is the more liable to crack in drying, as the sand of it is finer. 
 
 Mortar made with this finest sand and lime, does not grow so 
 hard, or resist fracture so forcibly, as that made with the fine Thames 
 6and and lime, in the same proportions, or any others nearest to these. 
 But the former mortar, when composed of about six parts of sand, 
 one of lime, and the necessary quantity of lime-water, and slowly 
 dried, becomes much harder than many of the calcareous stuccoes com- 
 monly used by the plasterers. 
 
 "3d. Mortar composed of lime, fine Thames sand, and the finest 
 sand, is worse as the quantity of the finest sand is greater, and this 
 holds true in every tried proportion of the sands and lime. 
 
 "4:th. Mortar consisting of lime, coarse Thames sand, fine Thames 
 sand, and finest sand, is the worse as the quantity of the latter ia 
 greater, when the comparison is made between it and the cement 
 
EXPERIMENTS AND RESULTS. 
 
 61 
 
 made with the same quantities of lime, and the best mixture of coarse 
 and fine Thames sand. 
 
 **5th. Mortar made with flint powder, lime, and lime-water, in 
 any proportion, is more liable to crack in drying, than mortar com- 
 posed of any sand and lime ; it is moreover incapable of hardening to 
 so great a degree, whether it be tested by a chisel, or by breaking it 
 across. But mortar made with about five parts of flint powder, one 
 of lime, and the necessary quantity of lime-water, is neverthelcLb pre- 
 ferable to any stucco now used for inside work, for the finishing coat, 
 because it has a more lively whiteness, and assumes a finer surface, 
 which I think might be made to imitate that of marble ; it requires, 
 however, to be dried very slowly. 
 
 "6th. Mortar made with coarse Thames sand, fine Thames sand, 
 flint powder and lime, or with fine Thames sand, finest sand, flint 
 powder, and lime, or with the finest sand, flint powder and lime, is 
 worse as the quantity of flint powder is greater, relatively to that of 
 the sand. 
 
 " Upon the whole it appeared, that the finest sand is injurious in 
 mortar which is exposed to the weather, and that flint powder is still 
 worse, but that this last may be advantageously used in composing 
 stucco for inside work, in which a fine texture, pleasing color, and 
 smooth surface are preferred before extreme hardness, and in which 
 the drying may be regulated so as to prevent the incrustation from 
 cracking. 
 
 " Instead of resting satisfied with the bare discovery of the fact, that 
 very fine sand or quartoze powder is incapable of making so good a 
 cement as may be formed with coarser sand, although fine Thames 
 sand and lime make a better cement than can be composed with the 
 coarse sand and lime, and that the mixture of the very fine sand, or 
 siliceous powder, with the Thames sand, is rather injurious than use- 
 ful, although the mixture of the coarse Thames sand with the finer, is 
 better for mortar, than either of them, unmixed. I took a great deal 
 of pains to learn the cause of this, in order to confirm or correct the 
 
62 EXPERIMENTS AND RESULTS. 
 
 foregoing notions, and render the precepts which flow from this fact, 
 the more satisfactory. 
 
 *'By sorting my finest sand into divers parcels, in sifting it through 
 different sieves, by measuring the meshes of these, and by viewing the 
 grains of each parcel ranked closely on a scale, I perceived, more 
 clearly than I had done before, the roundness of this sand ; I more- 
 over found that the grains of the coarsest parcel were, at a medium 
 of their respective bulks, upwards of sixteen times larger than those 
 of the finest parcel ; the grains of the other parcels being of divers in- 
 termediate sizes. As this sand therefore has every advantage attain- 
 able by the admixture of coarse and fine grains, and every disadvan- 
 tage resulting from the smallness and roundness of its grains, I 
 learned the reason why the defects attending such fine round sand 
 in mortar are not corrected by any mixture of coarse sand. How 
 these defects are induced by the finest sand and flint powder, we may 
 conceive in the following manner : — 
 
 Having already shown how the roundness of sand tends to render 
 the mortar made with it defective, I may, without any further illus- 
 tration of this matter, reckon on this figure of the grains of finest 
 sand, as one cause of the imperfection of the mortar in which it is 
 used. 
 
 " There is nothing to prevent the laminas of lime-paste, which inter- 
 cede the grains of finest sand, from being as thick, in the mass of 
 mortar made with it, as they are in mortar made with coarse sand, 
 but they are likely to be thicker in general, as the faces of the finer 
 grains are rounder. 
 
 The number and extent, moreover, of these laminae, must be 
 greater, in the sum, in the finest sand, than in the coarser, and it is 
 for these reasons that more lime-paste is required to make mortar 
 with the former than the latter, since the mortar is not formed until 
 the paste developes every grain and fills the interstices. In this view 
 of the subject we discover another cause of the defect lately men- 
 tioned. If we use lime with a sparing hand it will not extend be- 
 
EXPERIMENTS AND RESULTS. 
 
 63 
 
 tween all the grains or fill the spaces ; we find the mortar too "short" 
 whilst fresh, and it is as defective in strength when indurated as it is 
 deficient of the cementing matter. When we use the necessary quan- 
 tity of lime, the calcareous matter bears a greater proportion to the 
 quartoze grains, in this finest mortar, than in the coarser, and this 
 renders the former defective, according to the principles of aggregation 
 already expressed. 
 
 *' A third cause of the imperfection of mortar, made with finest 
 sand, or containing a larger quantity of it, appears on the considera^ 
 tion of the quantity of lime. 
 
 "We have repeatedly seen that mortar contracts the more in 
 drying, and is the more apt to crack, as it contains a greater quantity 
 of lime-paste, and as the finest sand requires an extraordinary quan- 
 tity of the paste to form it into mortar, the aggregate of such a 
 cement is likely to be impared by fissures, although they do not 
 always appear, by reason of their smallness. 
 
 "Other causes of the experienced imperfection of fine mortar 
 might be added, which have no relation to the figure of the grains of 
 sand, or the quantity of calcareous matter, but to avoid an excess of 
 theory, I forbear to mention them, and shall only add a conjecture 
 concerning the finer cements. 
 
 "When a cementitious mass, like mortar, is cut with an edged 
 instrument or broken across, we may observe that the fracture happens 
 in the shortest line, along the laminse of the weaker cementing mat- 
 ter, and seldom or never in the shorter right line passing through 
 the harder grains and the cement alternately, although the impressed 
 force tends to cause the solution of continuity in the shortest or in a 
 right line. By the principle of mechanics, the resistance to such forces 
 is greater (coeteris paribus) as the line of fi^acture is longer, whether 
 it be straight or winding in any course ; and it is for this reason that 
 a wall built with any large stones, is less liable to crack, although the 
 foundation should fail near one extremity of it, than a brick wall built 
 with the same kind of cement on the like ground ; or that a wall. 
 
64 
 
 EXPERIMENTS AND RESULTS. 
 
 whose bricks are jointed in the present fashion, is more secure from 
 cracking, that that which should be built, on the like infirm ground, 
 with the same kind of bricks standing over each other, not jointed, 
 but with their sides and ends flushed, as the workmen express it. 
 
 ''As cements are cut and broken in the direction of the cement, 
 and not in the shorter line, as the cracks in ill-founded walls run 
 winding along the joints, instead of going in the shortest course, 
 through the bricks and joints alternately, and the resistance of such 
 cementitious masses, estimated by mechanical theory, is greater, as 
 the line of fracture is necessarily elongated, by the stronger aggrega- 
 tion of certain parts of them. I am inclined to think that calcareous 
 cements made with lime, and quartoze powder will always be found 
 weaker under trial by the chisel or by fracture, as the quartoze sand 
 or powder is finer, because the line of fracture, which takes the course 
 of the cementing matter, is shorter, in any equal depth of such masses, 
 as the hard quartoze grains are finer and rounder. 
 
 "As flint powder consists of exceedingly fine grains of silicious 
 stone worn to roundness in the grinding, what has been said of the 
 finest sand is sufficient to show why the cements which contain flint 
 powder are the worst of all those we have mentioned. 
 
 '' The customary method of washing sand, even for stucco, which is 
 to be exposed to the weather, consists in passing it through a sieve, by 
 a circular horizontal motion of it, in a tub filled with water, which 
 flows over and carries away with it any light matter which can be 
 long suspended in water, as fast as the sand runs through the sieve 
 into the vessel. But this process is inadequate to our views, because 
 the finest sand subsides along with the best, and those in the precipita- 
 tion entangle and carry down with them a great deal of finer powder 
 and dirt. Where such a method must be pursued for want of other 
 utensils, or through the scarcity of water, the sand ought to be agitat- 
 ed again in small parcels, with a part of the water which has cleared 
 by subsidence, and immediately after the agitation, the muddy water 
 ought to be poured off" before the light parts have time to subside in it. 
 
EXPERIMENTS AND RESULTS. 
 
 65 
 
 But the useful part of sand is more effectually freed from the finer and 
 noxious parts, by sifting it in streaming water, whose current is to be 
 so managed that it shall carry away the mud and the sand which is 
 too fine, whilst the better part subsides in a proper receptacle. 
 
 **In the subsequent pages I purpose to show the integrant parts of 
 gravel, and their several properties in mortar ; for the present purpose 
 it will be sufficient to observe that the gravel commonly employed in 
 building consists chiefly, after it is screened, of rubble, coarse sand, 
 fine sand, and finest sand, similar to those used in our experiments. 
 This is obvious on the bare inspection of it, and leads us to discover 
 another cause of the weakness of our modern cements, in the composi- 
 tion of which no other precaution is used, respecting the gravel, 
 except to separate the stones and coarsest rubble from it by screen- 
 ing. 
 
 **When it happens that the screened gravel contains more than a 
 certain quantity of rubble, relatively to that of coarse and fine sand, 
 similar to those described, the mortar made with it, must, according 
 to our experiments, be defective. It will be so likewise, whenever the 
 coarse sand of it predominates over the fine sand, to a greater degree 
 than that which was found consistent with the perfection of mortar ; 
 and when the quantity of finest sand happens to be considerable in 
 gravel, the mortar made with it must be faulty in a greater degree. 
 
 " Now supposing the gravel to be freed, by the screening, from 
 everything more injurious than finest sand and quartose powder, we 
 perceive that the artist who is ignorant of the advantages of sizing his 
 gravel, and uses it in its native state, as chance presents it, has the 
 odds greatly against his making good mortar, although he may some- 
 times do it, without knowing the reason, as we shall find hereafter, 
 for his chance is, that the native gravel shall consist of coarse and fine 
 sand mixed in the proportion of three to four, or of the rubble, coarse 
 and fine sand mixed in the proportions above recommended ; and that 
 it shall contain little or no sand like our finest sand, but the chancea 
 against him are as numerous as there are other distant proportions of 
 
66 
 
 EXPERIMENTS AND RESULTS. 
 
 rubble, coarse and fine sand in gravel, and as the kinds of gravel used 
 are, vi^hich contain the finest sand, or still finer quartoze grains in 
 efficient quantities. 
 
 '*In great cities where gravel cannot be procured so cheap as tne 
 rubbish of old walls, which the workmen lay in the streets to be ground 
 to powder by the passing carriages, they use this rubbish, screened, in 
 the place of sand or gravel, in making mortar. It consists of the 
 gross powder of bricks, and of mortar indurated, as much as bad mor- 
 tar can be, by time, and some builders affirm that it is better than 
 sand or gravel for mortar. It is certainly eligible when the price is 
 chiefly considered, in any other view, it is not so. 
 
 *'From my past experience, I judged the calcareous powder of an 
 old cement, and that of the bricks, to be a brittle, perishable and weak 
 substitute for grains of sand, and the quantity of dust in such ground 
 rubbish, to be highly injurious, but as the opinion of the workmen was 
 against me, I made some trials of it. 
 
 "I found that less lime was required to make fat mortar with this 
 ground rubbish, than with my best mixtures of sand, which is no 
 small recommendation of it in certain jobs, and is owing, in my 
 opinion, to the ground calcareous part, which, so far as it is finely 
 powdered, is equivalent to whiting, but the mortar made with the 
 rubbish appeared, in every stage of induration, and in every compari- 
 son, except that of plasticity, to be greatly inferior to that made with 
 mixed sand and lime in the same proportions. 
 
 * ' If the workmen would confine their opinion to the comparison of 
 such rubbish mortar, with that in which clayey gravel is used, or with 
 the cements made with the ashes and ordure of the town, dug out in 
 preparing foundations of houses, in those places which were formerly 
 receptacles of such matter, they might maintain it on divers grounds 
 which will be examined hereafter, but otherwise it is erroneous." ^ 
 
EXPERIMENTS WITH SAND, &c. 
 
 67 
 
 Experiments made on a larger scale with our Best Mix- 
 ture OF Sands, Lime-water and Lime. 
 
 ** At a subsequent period, I repeated a great number of the forego- 
 ing experiments, particularly those which exhibit mortar in the im- 
 proved state to which I had brought it ; and finding my former obser- 
 vations to be true, when the circumstances were not varied, I resolv- 
 ed to try my best cements in larger quantity, and in other circumstan- 
 ces. 
 
 *'I applied them in the way of stucco, on the brick walls of houses 
 in different aspects, but chiefly in that of the meridian sun ; covering 
 a square yard at least with each specimen, after I had repeatedly 
 wetted the wall with lime-water. 
 
 "By these trials I found that mortar made with four parts of coarse 
 sand, and three of fine, wetted with lime-water, and beaten up with 
 one of my lime, slaked with lime-water, although it could be easily 
 spread on a horizontal plane, or used in building with bricks, was 
 rather too * short' for plastering on the perpendicular surface of a wall. 
 It might, however, be laid on in small successive portions, by a dex- 
 terous management of the trowel, and especially by sliding the tool on 
 it upwards. 
 
 "When the weather continued temperate and dry for eight or ten 
 days after the incrustation was made, and no great quantity of rain 
 fell for three or four weeks afterwards, this stucco answered my ex- 
 pectations, for it did not crack in the least, and in three months was 
 almost as hard as Portland stone at the surface, where the induration 
 first takes place for the reasons formerly mentioned, but it was too 
 coarse to represent a fine grained stone. 
 
 "Having made two pieces of incrustation of this kind, on the same 
 wall, and knowing that calcareous cements cannot harden so soon as 
 necessary in outside stuccoing, unless they be pervious to acidulous gas 
 in which case they may drink in water likewise. I frequently wetted 
 one of the pieces, in about three months after it was formed, with 
 
68 
 
 EXPERIMENTS WITH SAND, &c. 
 
 iime-water, expecting that the calcareous matter of it would crystal- 
 lize in the cement, and render it harder and closer. I was not dis- 
 appointed, for, in the course of a month I found this piece of stucco 
 harder and closer than the former, and at the surface as much supe- 
 rior in these particulars to Portland stone, as the other was inferior to 
 it. I have since found that lime-water has not this effect, if the in- 
 crustation be wetted with it before it is quite dry and indurated slowly, 
 to vie with Portland stone in that kind of strength which is tried by 
 grinding Portland stone on it, or scraping it with a chisel, for any 
 other trial of incrustations is unfair, until the induration has proceeded 
 equally throughout the mass. 
 
 When the incrustations made of the same cement, were wetted 
 by rain in two or three days, or sooner, after they were applied, and 
 especially when the wind blew the rain forcibly upon them, they were 
 sensibly injured, for they never afterwards looked or hardened so well 
 as the former specimens of stucco. 
 
 **In these particulars the large incrustations agreed with those 
 made on tiles, but the same agreement did not appear in the incrus- 
 tations which I had made with the same composition on a wall which 
 fronted the meridian sun, at a time when the weather was very hot, 
 for these showed a few slender cracks in the course of three days. 
 When in the same situation and weather, and on a coarse stucco of 
 this kind, I spread in about two hours, after it was laid on, a thinner 
 coat of cement made with finer sand in order to represent a finer 
 grained stone, the incrustation consisting of these two layers cracked 
 more than the former. 
 
 After many repetitions of these experiments in the hottest weather 
 with the same result, I perceived that the trials of such cement on 
 tiles are not so severe as those to which they may be exposed some- 
 times in incrustations on walls. In the latter case, the stucco is very un- 
 equal in thickness, for in the hollow joints and depressions of the bricks 
 it is near an inch thick, when over the prominences it has not more 
 than one-eighth of this thickness ; and as it dries soonest in the thin 
 
EXPERIMENTS WITH SAND, &c. 
 
 69 
 
 parts, the unequal contractioti seems to be the cause of those cracks, 
 which would not happen to the same cement laid on the flat surface 
 of a tile ; it seems, moreover, that such a composition may more easily 
 contract in drying, without cracking, as the crust is made narrower 
 or less extensive. But I impute the cracking chiefly, to the foregoing 
 unequal contraction, accelerated not only by the heat of the sun and 
 the wall, but by the thirsty bricks, for if we form our judgment accord- 
 ing to the quicker or slower progress of the exsiccation, and the stiff- 
 ness which the cement acquires in the act of spreading it on the brick 
 wall, and the wetting of this last, superficially with lime-water, is 
 not equivalent to steeping the tiles for a few minutes in the same 
 liquor. 
 
 <'When with a view of preventing fissures, I stuccoed a part 
 of the same wall (wetted with lime-water) with cement containing 
 the mixed sands and limes in the proportion of fifteen to two, in the 
 same kind of weather, I found the difiiculty and waste in applying it 
 greater than in the former instances, and that it was defective in 
 strength and closeness for want of lime, although it did not crack. 
 When through distrust of my former experiments, I used more 
 than one-seventh of lime, the cracks were still larger and more nume- 
 rous. 
 
 "To guard a recent incrustation from the rain, and to secure it 
 from cracking in the circumstances last described, I proposed the ex- 
 pedient of hanging sail-cloth on the cornices and scaffolding, but the 
 expense of this measure, and the danger arising from it in windy 
 weather, were strong objections. Embarassed by this unexpected 
 difficulty, I resolved to change my ground, and try what might be 
 done by a new series of experiments, in which I intended to use every 
 known cheap substance, whether it could be reasonably supposed to 
 have any considerable effect towards securing a recent incrustation 
 against the above-mentioned impressions of rain or hot weather, or 
 could be suspected of rendering the stucco defective. I prosecuted this 
 Inquiry with great alacrity, because I was certain that, although I 
 
70 
 
 EXPERIMENTS WITH GRAVEL. 
 
 should fail in the attempt towards improvement, I should learn how 
 in future to avoid those things which being naturally blended in cer- 
 tain kinds of lime-stone, sand or water, tend to render the mortar 
 made with them, faulty. I had already conceived a notion, which I 
 shall submit before I conclude, concerning the excellence of some 
 ancient cements ; but lest I should be misled by it, I proceeded in all 
 my experiments which I am to relate, on the supposition that the ex- 
 cellence is owing to some matter accidentally introduced in the 
 materials which the ancients found in the districts contiguous to 
 the most durable cementitious works, or designedly blended with their 
 mortar." 
 
 Experiments showing the integrant parts of Gravel, the 
 
 CHOICE AND preparation OF IT, AND THE EFFECTS OF ClAY, 
 
 Fuller's Earth, and Terras in Mortar. 
 
 **0n inspecting different kinds of gravel used in London, and in 
 divers parts of England, in making mortar, I observed that they 
 all contained some clay, and that this was generally colored with 
 martial matter. In consideration of the frequency of which matter 
 m mortar I made it the first subject of my present inquiry. 
 
 **By theart already described, I sorted three bushels of screened 
 gravel dug up near Portland place, in Marylebone parish, into five 
 parcels ; one equivalent to our rubble, another to coarse sand, another 
 to our Jine Thames sand, another to our finest sand, and the remain- 
 der was set aside as clay or bolar earth, I dried all these, and reduced 
 the lumps of clay to an impalpable powder. 
 
 "Having treated divers other specimens of gravel in the same 
 manner, I found that gravel, freed from the larger pebbles, may 
 generally be considered as a native mixture of rubble, sand and clay ; 
 and that when the clay is washed out, the residuary parts of different 
 kinds of gravel differ in size, sharpness, color, and hardness, those 
 being the hardest which consist chiefly of quartoze matter. Judging 
 of gravel according to the precepts derived from my trials of sand, I 
 
EXPERIIVIENTS WITH GRAVEL. 
 
 71 
 
 rank that dug in Marylebone amongst the better kinds of gravel, 
 and used no other in mortar. 
 
 "After a great number of trials of cements made with my best 
 chalk-lime, lime-water and the gravel, or certain parts of the gravel, 
 and applied on tiles, and on a wall, I found that those made with the 
 coarse and fine sand of the gravel, separated from the rest of it, and 
 mixed in their native proportions, were the best ; that those made 
 with the rubble, coarse sand, and fine sand mixed in their original 
 proportions, but containing no other part of the gravel, were the 
 next in hardness, and the other desirable qualities ; that those con- 
 taining all the parts of the gravel, except the clay, in their native 
 proportions, differed in nothing that I could discover from these last, 
 for the finest sand of this gravel was not a fiftieth part of the mass of 
 it; that those containing the rubble, sands and clay, in the same 
 proportions, and those made with the unwashed gravel, appeared on 
 close examination to be the worst of all these, and those containing 
 the native, unwashed gravel, mixed with twice its proper quantity of 
 the clay of such gravel, showed most clearly that clay is highly injuri- 
 ous, by disposing the mortar to crack in drying, to soften in wet 
 weather, and to moulder when the quantity of clay is one-eighth of 
 that of the sand, but in much smaller quantities it only prevents the 
 cement from acquiring the hardness peculiar to good mortar, and 
 consequently disposes it to perish in a few years. 
 
 "With my best mixtures of sands, lime-water and lime, I blended 
 fine fat tobacco-pipe clay, in different proportions, and exposing these 
 specimens, I perceived that the efiect of the clay is greater as it is 
 purer and fatter ; the specimens in which the quantity of fat clay was 
 one-seventh, or one-eighth of that of the sands, mouldered early in the 
 winter like marl. 
 
 "These appearances were not altogether unexpected, for in experi- 
 ments formerly made with a view to the improvement of fire- vessels, 
 I had observed that clay adheres but weakly to any hard bodies, how- 
 ever slowly it is dried on them, and that masses composed of clay and 
 
72 
 
 VARIOUS EXPERIMENTS. 
 
 Band in divers proportions, never acquired any considerable hardness 
 by the mere drying and exposure to the air. It was not, therefore, 
 likely that clay should add to the strength of mortar ; but as dried 
 clay greedily imbibes water and swells with it, and in drying, con- 
 tracts greatly and cracks, if anything prevent it from contracting 
 equably; and as marl-stones, which consist of clay and calcareous 
 earth, moulder in the weather, it was to be expected that clay would 
 be hurtful. 
 
 " These experiments point out another cause of the defects of the 
 common mortar, and show that the gravel or pit sand to be used in 
 any valuable building ought to be freed from the clay by washing, 
 which will be found a very cheap operation, >even in cities, if the water 
 which carries off the clay be directed into a place where it may be 
 depurated by subsidence, for repeated use ; they likewise direct us in 
 the examination and choice of these, and show that the viler kinds 
 may be made equivalent to our best mixtures of Thames sand, or 
 nearly so, by washing or sorting, and then rejecting the excess of 
 rubble, or fine sand. 
 
 "I must observe, however, that some kinds of gravel cannot be 
 made fit for mortar by this process, for the grains of them, which 
 resemble those of rubble and coarse sand, consist of smaller grains ce- 
 mented by clay, which is so far indurated that it cannot difiiise itself 
 in, the water speedily. 
 
 Fuller'' s earth tried in the same manner was found to operate 
 in the mortar like clay in every respect, as I might have presumed, 
 except that the former was less injurious than the clay, when the 
 quantities of them were equal. 
 
 « Terras, which is a volcanic production consisting chiefiy of clay 
 and calx of iron, indurated together, when it was ground to an im- 
 palpable powder, produced the effects of Fuller's earth, in mortar the 
 more sensibly as it approached nearer to be one-seventh of the quan- 
 tity of sand. The coarser powder of terras has the same effect. 
 
 "A mortar made of terras powder and lime, was used in wato. 
 
VARIOUS EXPERIMENTS. 
 
 73 
 
 fences by the Romans, and has generally been employed in such struc- 
 tures ever since their time. It is preferred before any other, for this 
 use, because it sets quickly, and then is impervious to water, whence 
 some people hastily conclude that it is the best kind of mortar for any 
 purpose. But by experience I know that mortar made of lime and 
 terras powder, whether course or fine, will not grow so hard as mortar 
 made with lime and sand, but on the contrary is apt to crack and 
 perish quickly in the open air. The efficacy of it in water fences is 
 only experienced where it is kept constantly wet, and seems to de- 
 pend upon the property which the powder of terras has, in common 
 with other indurated argillaceous bodies, and especially the boles (but 
 in a higher degree), of expediting the crystallization of the calcareous 
 matter, by imbibing the water in which it is diffused in the mortar, 
 and of swelling during the absorption, so much as to render the ce- 
 ment impenetrable to any more water; it seems also, that an acid 
 of the vitriolic kind, which is contained in terras, as well as in boles, 
 contributes to the speedy setting of this cement, by reducing a part 
 of the lime to the condition of gypsum." 
 
 Experiments showing the effects op Plaster-powder, Alum, 
 Vitriolic Acid, and of some Metallic and Earthy Salts 
 AND OF Alkalies in Mortar. Practical Inferences. 
 
 "In my best mixtures of coarse and fine Thames sand, with one- 
 seventh, and with larger quantities of lime, I tried the gypseous pow- 
 der of which plaster-of-paris is made, and found it to be injurious 
 in proportion to the quantity of it. The particular effects of gypsum 
 in mortar were such as might be expected in consequence of our 
 knowledge of the saline nature of it, gypsum being in a compound of 
 calcareous earth and vitriolic acid, which is soluble in water, not so 
 freely as neutral salts, but rather like lime, it disposed the mortar to 
 set faster than it could be applied in stuccoing ; it contributed very 
 little to the plasticity of it, and the cement was the more apt to soften 
 4 
 
74 
 
 VARIOUS EXPERIMENTS. 
 
 in wet weather, and to perish in time, as the quantity of plaster-pow- 
 der in it was greater. The greater quantity tried was only one-seventh 
 of that of the sand. 
 
 ^' Alum was found very injurious. The acid of alum formed silen- 
 ite or gypsum with a part of the lime, and thus operated like gypsum 
 or plaster-powder, whilst the earth of the alum induced the imperfec- 
 tions which attend the use of clay. The greatest quantity of alum 
 used was one part in ten of the best mixture of sand and lime, and 
 this specimen mouldered, in nine or ten months, like marl. 
 
 " Vbtriolic acid, which formed silenite or gypsum with a part 
 of the lime, produced the effect of a quadruple quantity of plastic pow- 
 der. 
 
 Vitriols of lead and tin, being decomposed by the lime, operated 
 like smaller quantities of vitriolic acid. Martial vitriol or copperas had 
 the same effect, and induced an olive color, which was soon turned to 
 that of rust. 
 
 " Vitriol of zinc, or white vitriol, and Epsom salt, did not dispose 
 the mortar to set hastily, nor injure it in any particular discoverable 
 during the application and drying of it, for these vitriols are not easily 
 decomposed by lime ; but afterwards I perceived that they impeded 
 the induration of the stucco, and disposed it to suffer by the weather, 
 the more as the quantity of either came near to be one-tenth of the 
 quantity of sand. 
 
 Vitriolated tartar, Glauber's salts, and the salts which are found 
 in most of our waters, such as sea-salt, nitre, marine calcareous salt, 
 calcareous nitre, and that composed of magnesia, and marine acid, 
 were found, like Epsom salt, to injure the best mortar ; so were caustic 
 mineral alkali, caustic vegetable alkali, and liquor silicum. Caustic 
 volatile alkali, which soon exhales by reason of its volatility, had no 
 sensible effect, I did not try argol, or mild alkalies, because they re- 
 duce the lime to whiting, neither did I use any acid which forms a 
 very soluble salt with lime, for obvious reasons. 
 
 "Knowing that the lime which has been employed by soap-boilers 
 
VARIOUS EXPERIMENTS, 
 
 75 
 
 to render their barilla and pot-ash, caustic, contains, (even after the 
 repeated elixations,) a little alkali and vitriolated tartar, blended 
 with the calcareous earth, and that the greater part of this last is 
 restored to the condition of chalk, by the acidulous gas imbibed from 
 the alkaline salts ; I had, in consequence of the foregoing experiments, 
 sufficient reason to presume that this refuse matter of soap-boilers 
 cannot answer the purposes of lime, or improve our mortar. But as 
 a pretence to the contrary is made by some, and as its cheapness is a 
 temptation towards the use of it, I resolved to decide this question by 
 direct experiment. 
 
 ' * After trying in my usual manner, specimens of mortar made with 
 the refuse of soap-lees, and my best sand, in different proportions, 
 and others made with this sand, lime, and the refuse matter, in 
 various proportions, I found the first destitute of the most useful 
 properties of good mortar; and the others were defective in pro- 
 portion to the quantity of the refuse matter relatively to that of the 
 lime. Whether this matter improves mortar made with gravel and 
 the common chalk lime, or increases the defects of it, is a question 
 not worth our notice. 
 
 The experiments lately related show that lime is the more unfit 
 for building and external incrustations as it contains more gypsum, 
 and I must now remark that most kinds of limestone used in England 
 contain considerable quantities of this matter, which is not much cor- 
 rected in the burning ; but as I have in the second section enabled my 
 readers to discover this imperfection, I hope I shall be excused from 
 the inviduous office of deprecating or recommending any particular 
 lime-stone, or manufactory of lime. 
 
 "The cautions which our last-mentioned experiments suggest in 
 regard to the use of water are especially necessaiy where wells and 
 springs abound with one or more of the above-mentioned salts, and it 
 is not to be presumed that the quantity of these contained in water 
 which is used for culinary purposes cannot be injurious to mortar, for 
 I know that silenite, Epsom salt, the very deliquescent salts, com- 
 
76 
 
 VARIOUS EXPERIMENTS. 
 
 pound of magnesia, and marine acid, and of calcareous earth and the 
 same acid, may, together with a little sea salt, be natively dissolved 
 in water, to the quantity of half an ounce in a gallon, without effect- 
 ing the taste of it sensibly. 
 
 When we consider the quantity of water necessary in slaking the 
 lime, making the mortar, and wetting the thirsty bricks, and the 
 smallness of those portions of salts whose injurious effects were dis- 
 coverable in the course of one year, or in a shorter time, we find suffi- 
 cient grounds for concluding that such saline waters will be found 
 hurtful in mortar, before many years elapse, particularly where it is 
 exposed to moisture. Indeed this has been already experienced of sea 
 salt, even in the small quantity of it introduced in mortar, when the 
 sand is taken from the sea-shore. 
 
 **The easiest method of discovering the quantity of saline matter in 
 water, consists in evaporating it slowly to dryness, and weighing the 
 residue. Water which deposits calcareous earth as soon as it is heat- 
 ed ought to be cleared by subsidence or filtering, before the evapora- 
 tion is completed. 
 
 * ' When a choice can be made, rain water is to be preferred, river 
 water holds the next place, land water the next, spring water the last, 
 and waters noted medicinally or otherwise for their saline con- 
 tents ought not to be used at all in mortar, for the salts contain- 
 ed in them are those which were tried, the vitriolated tartar ex- 
 cepted." 
 
 Experiments showing the effects of Skimmed Milk, Serum 
 OF Ox-blood, Decoction of Linseed, Mucilage of Lin- 
 seed, Olive Oil, Linseed Oil, and Resin in Mortar, and 
 the effect of painting Calcareous Incrustations. 
 
 " At the same time and in the same mixtures of the best sand 
 and lime, I tried skimmed milk, serum of ox-blood, decoction of lin- 
 seed (strained), and thick mucilage of linseed, in the place of lime-' 
 water. 
 
VARIOUS EXPERIMENTS. 77 
 
 "The mortar made with any of these was fatter as the liquor was 
 more glutinous, but was as liable to crack as mortar made with 
 water. In the course of a year it appeared that each of these 
 liquors encourages a vegetation to take place on the surface, which 
 gives it an ugly appearance and tends to ruin it, and that they all 
 • prevent the cement from acquiring the experienced hardness of our 
 best compositions, or indeed from having any competition with them 
 in this particular. 
 
 The notion, therefore, that is entertained by some builders con- 
 cerning the use of skimmed milk and blood is erroneous, unless it 
 be confined to the viler kinds of mortar, which may perhaps be im- 
 proved by them, because a composition of sand, whiting and mu- 
 cilage grows harder than that of whiting and sand kneaded with 
 mortar. 
 
 It seems that glutinous liquors and good lime act reciprocally on 
 each other, in the time of mixing them, to the destruction of their 
 respective characters, and particularly to the conversion of a part 
 of the quick lime into whiting; and that if any kind of mortar 
 is is improved by them, it is then especially, when the workmen 
 takes advantage of the fatness induced by them, and using less 
 than his customary quantity of lime, secures his work from crack- 
 ing. 
 
 Olive oil, mixed with good mortar or substituted in the place of 
 a part of the lime-water, rendered the cement defective, as the quan- 
 tity of oil was greater. The greatest quantity used was half that of 
 the lime 
 
 Linseed oil, used in the same manner, makes the mortar fatter, 
 retards the drying of it, and prevents it from acquiring in any time, 
 so great a degree of hardness as it otherwise would have. It was the 
 more hurtful as the quantity of it was nearer to that of half the lime, 
 in much smaller quantities it was less injurious than olive oil. From 
 roy observation on this subject, and on the compositions called oil ce- 
 ments, I have reason to conclude that no oil ought to be used in a 
 
78 
 
 VARIOUS EXPERIMENTS. 
 
 cement which consists chiefly of sand, lime and water, nor any 
 water, or watery liquor, in a cementitious mixture, which is moistened 
 or kneaded with oil chiefly. 
 
 As linseed oil, whiting and sand, make a cement which hardens 
 to a great degree in dry situations, and abides the weather a long 
 time before the hardened oil relents, it is not improbable that linseed 
 oil may meliorate mortar made with bad lime. But good lime and 
 linseed oil seem to injure each other, in forming a kind of saponaceous 
 compound, with the lime-water of the mortar. 
 
 From the experienced effects of saline, gelatinous and oleaginous 
 matter, I infer that cow-dung, which I have not tried, would impair 
 good mortar. It makes the common mortar fatter, and in that re- 
 spect more convenient for " pargetting " the interior surface.of chimney 
 flues ; it seems likewise to prevent the parget made with bad lime from 
 drying so quickly, and from cracking so much, as it otherwise would 
 do ; the fibrous part of the dung contributing largely to this latter 
 eflect. On these grounds it may be useful in bad mortar thus applied, 
 whether it increases the hardness of it or not, although it is likely to 
 impair good mortar. 
 
 ^'•Powder of resin intimately blended with mortar by grinding it 
 with a part of the lime, and lime-water, was hurtful according to 
 the quantity of it, the greatest quantity tried being one-fourth of that 
 of the lime. 
 
 Before I knew the event of these experiments I made an incrusta* 
 tion on a wall fronting the south, but shaded from the sun after mid- 
 day, with a cement composed of seven parts of my mixed sand, one 
 of the best stone lime, and the necessary quantity of lime-water. As 
 soon as the incrustation was dry, which happened in four days, I 
 painted one-third of it with linseed oil, prepared for painter's use, an- 
 other tl^ird with white lead paint, and the remainder was separated 
 from these by a channel cut between them. 
 
 " After fourteen months, the last-mentioned portion was very hard 
 near the surface, and the induration extended very deeply into the 
 
VARIOUS EXPERIMENTS. 
 
 79 
 
 mass of it, though not in so great a degree of perfection as that of the 
 surface. The painted portions were also very hard at the surface, but 
 internally much weaker than the other. 
 
 *'From my observations of these specimens, and of divers incrusta- 
 tions in this city, which, being made of bad calcareous cement, have 
 been painted and sanded, in order to fill the cracks and fence them 
 from the weather, I have had sufficient reason to conclude that an 
 incrustation, made as good as it may be with lime and sand, and 
 lime-water, is not better by painting it as soon as it dries ; that this 
 covering retards the induration of it, by cutting off its communication 
 with the air ; that it therefore renders it liable to be irreparably in- 
 jured in wet weather whenever the water can get behind the paint ; 
 and that if paint or oil ought ever to be applied on such stucco, it 
 ought not to be used in less than a year after the incrustation is made. 
 I likewise found that the painting and sanding of the common 
 incrustations, contributes very little to their duration, although it 
 hardens them at the surface, for it does not effectually prevent them 
 from cracking, and it avails very little to paint the cracked stucco 
 again, because cracked stucco is always * hollow,' as the workmen term 
 it, that is, it parts from the wall in the parts contiguous to the cracks, 
 sounds hollow on being struck with the knuckle, and falls off in a few 
 years, if it be so thick and large in extent as to break the adhering 
 portions by its weight." 
 
 Experiments showing the effect of Sulphur introduced 
 INTO Mortar by different methods. 
 
 " In my first trials of sulphur, it seemed to be useful, and this lea 
 me to try it in so many different ways, and in so many mixtures 
 of limes and sands, and of these with flint-powder and divers other 
 substances, as would render the recital of all my observations on the 
 effects of it, inconsistent with the plan of this essay ; I must, there- 
 fore, content myself with communicating those which I think most 
 
80 
 
 VARIOUS EXPERIMENTS. 
 
 useful, in such terms as may give some intimation of the manner in 
 which the experiments were made. 
 
 **When the powder of sulphur was mixed with mortar already 
 made of good materials, and did not exceed one-thirty-second part of 
 the mass, is seemed to improve it, in the first and second month, and 
 sometimes during a longer time of comparison with mortar made of 
 all the same materials (except sulphur) in the same proportions, but 
 in ten or twelve months the sulphur was found to be injurious, and 
 the more so as it exceeded the foregoing proportion. The most 
 hurtful effect of it, was, its disposing the mortar to relent in long con- 
 tinued rains, and become quite friable after a few alternatives of freez- 
 ing and thawing. It had the same effect in mortar containing seve- 
 ral of the ingredients already named, and of those hereafter to be 
 mentioned. 
 
 When the sulphur was mixed with fresh powdered lime, and these 
 were ground briskly with lime-water, a calcareous liver of sulphur 
 was formed, proportionate to the quantity of sulphur used ; and the 
 mortar made with this mixture and sand, or with this and 
 sand and other ingredients, was worse than mortar contaning an 
 equal quantity of the sulphur mixed in it in the former method. 
 
 The transparent liquor called liquid calcareous liver of sulphur, 
 which consists of sulphur dissolved in water by the intervention of 
 lime, being used instead of water in making mortar with sand and 
 lime in any proportions, was found more injurious than three times 
 the quantity of undissolved sulphur was, in the first-mentioned method 
 of using it, and this liquor had the like efiect in mixtures of mortar 
 with divers other ingredients ; whence I infer that sulphurous miner- 
 al waters ought not to be used in mortar. 
 
 " If the plan of these experiments had not comprehended the noxi- 
 ous as well as the useful ingredients, and I had not resolved to distrust 
 every theory, I might have foretold the event of these mixtures, in 
 consequence of my certain knowledge of the operation of sulphur, 
 lime, and air on each other. 
 
VARIOUS EXPERIMENTS. 81 
 
 "When sulphur and lime are moistened with water, and exposed 
 to air, the acid of sulphur being attracted by the lime, whilst the 
 phlogiston of the sulphur is attracted by the air, a decomposition of 
 the sulphur takes place, and new compounds are formed. The acid 
 and lime gradually form selinite, or gypsum, whilst the air combined 
 with the phlogiston is wafted away. Therefore, lime, by so much of 
 it as is thus expended in forming gypsum, is not only unable to act as 
 a durable cement of the grains of sand, but is capable, according to the 
 experiments of the sixteenth section, of counteracting the cementing 
 power of the residuary part of it, when the mass of sulphurated 
 cement is exposed to the weather. 
 
 "The pleasing warm color which sulphur induces in calcareous 
 stucco, whilst it is fresh, and the promising appearance of such incrus- 
 tations in the first year, have, if I am rightly informed, already mis- 
 led some to apply it freely at their own risk. I wish these observations 
 may serve to undeceive them. 
 
 " About this time, the imitation of colored stones, by incrustations, 
 became an object of my attention, and some of the subsequent experi- 
 ments were made with a view to it, as well as to the purposes already 
 expressed." 
 
 Experiments showing the effects op Crude Antimony, Reg- 
 uLus OP Antimony, Lead Matt, Potter's Ore, White Lead, 
 Arsenic, Orpiment, Martial Pyrites, and Slaked Mundic, 
 IN Mortar. 
 
 " Crude antimony reduced to an impalpable powder, and then ground 
 with the lime, and lime-water, operated in mortar as sulphur does 
 when it is used in the same manner and in the quantity which the 
 crude antimony contains. 
 
 **The antimonial powder, moreover, induced a disagreeable bluish 
 color, which in a little time became brown, and afterwards, yellowish. 
 When the powder of antimony was mixed in the mortar after it was 
 made it was less injurious. 
 
82 VARIOUS EXPERIMENTS. 
 
 ** Regulus of antimony, tried in the same way, seemed to have no 
 other effect than that which is produced by the admixture of flint 
 powder, or other fine powders of hard bodies. 
 
 Powdered lead matt, QXi(i potter'' s ore of lead acted like crude anti- 
 mony but more slowly and weakly in equal quantities of them. 
 
 White leadwsLS found exceedingly injurious, which I expected, for 
 I had long before discovered and shown in my public courses on chem- 
 istry, that a great part of white lead is acidulous gas, into which vine- 
 gar is easily convert able in the process for making white lead, and in 
 many others ; and I foresaw that the lime, attracting this matter, 
 would be reduced to the condition of whiting in the time of making 
 the mixture, and that the mortar would consequently be defective. 
 The white lead, as fast as its acidulous gas is drawn from it by the 
 lime, becomes yellow, like masticot. As white lead improves the oil 
 cements, these experiments show that there is no true analogy be- 
 tween the calcareous watyer cements and those which are called oil 
 cements. 
 
 Arsenic operated in mortar like the neutral salts, and orpiments 
 produced the injurious eflfects experienced of sulphur and of arsenic, 
 which effects were greatest when the orpiment was ground with the 
 unslaked lime and lime-water. Orpiment imparted a dark brown 
 color at first, which soon became yellow and afterwards disappeared. 
 
 The martial pyrites, called mundic, heated to redness, and then 
 slaked by moistening it with water whilst it was hot, operated like 
 crude antimony, with this difference only, that a greater quantity of 
 it was required to produce the same effect ; for this reason, as I con- 
 ceive it, that the quantity of sulphur in martial pyrites is less than in 
 crude antimony, and being held in it by a more forcible attraction, is 
 prevented from acting as freely in the lime of the mortar. The color 
 induced by the slaked mundic was at first bluish, and afterwards 
 turned to that of iron rust. 
 
 ** The mundic which was from Cornwall, used in its native state^ in 
 mortar, kept me in suspense upwards of twelve months. It was tried not 
 
VARIOUS EXPERIMENTS. 8? 
 
 only on tiles but in large incrustations on walls, because it promised 
 great advantages at first. When the quantity of it did not exceed 
 one-twenty-fourth of that of the mortar, it manifestly increased the 
 induration of the cement during the first nine months, but after 
 fourteen or fifteen months it disposed the incrustation to relent, the 
 more as it was oftener wetted, or as the place was damp, and from be- 
 ing exceedingly hard, to become penetrable to a pointed instrument, 
 pushed only with the hand, and as brittle as chalk-stone. The color 
 and changes of color of the mortar containing native mundic, are 
 similar to those produced by the slaked mundic, and are not at all 
 pleasing to the eye. The effects of much smaller quantities of this 
 matter in mortar do not yet appear so clearly, but there is no reason 
 to presume that they will not be of the same kind, though in a 
 smaller degree. 
 
 "These and the preceeding experiments, indicate that all bodies 
 soluble in water, not excepting arsenic, and all those which are capa- 
 ble of efflorescing, or of being decomposed by air and moisture, are 
 hurtful in mortar ; and they teach us to avoid those kinds of gravel 
 which are impregnated with pyritous matter, whether it be arsenical, 
 metalic, aluminous, or calcareous. 
 
 ' ' The effects of regulus of antimony, and the speedy decay of the 
 cheaper metals, however perfectly they are de-sulphurated, give strong 
 grounds for presuming that calcareous cements, which are to be ex- 
 posed to the weather, are more likely to be injured than improved by 
 metallic matter introduced in any form." 
 
 Experiments shovting the effects of Iron Scales, Washed 
 CoLCOTHAR, Native Eed Ochres, Yellow Ochres, Umber, 
 Powder op Colored Fluor, Colored Mica, Smalt and 
 other colored bodies, in Mortar. Advice concerning 
 Colored Incrustrations, Inside Stucco, and Damp Walls. 
 
 '■^ Iron scales from a smith's forge, which consist of iron semi-cal- 
 cined, and are thought by many to improve mortar, were tried 
 
84 COLOURED MORTARS. 
 
 eighteen months ago, (by grinding them to fine powder,) and mixing 
 them in mortar, to half the quantity of lime, and in smaller proportions. 
 
 **The larger quantities, in the course of twelve or fourteen months, 
 appeared to be hurtful ; and by these I judge of the smallest, which do 
 not yet appear to produce any remarkable effect in incrustations made 
 in any situations. But in those which reached near the ground, and 
 in others made on tiles which were laid flat on the ground in a shaded 
 damp corner, in both of which instances the incrustations were always 
 moist, the iron powder seemed to render the cement a little harder 
 than it would otherwise become in the same time in such circum- 
 stances, and it certainly made it closer in the grain. 
 
 *'By these experiments, I am inclined to think, that iron powder, 
 which, during its conversion to rust, imbibes a good deal of acidulous 
 gas and air, and swells considerably, may be used with success, where 
 the proper induration of good mortar is prevented by continual moisture, 
 and the chief purpose of the cement is to exclude water perfectly, by the 
 closeness of its texture, to which the swelling of the iron contributes 
 not a little. If it is capable of producing any desirable effects in ce- 
 ments otherwise circumstanced, these are to be expected only when 
 the quantity of it does not exceed one-eighth of that of the lime, or 
 one-fiftieth of that of the mortar. 
 
 ' ' Washed colcothar of iron, native red ochres, yellow ochres, and 
 umber, had the effects of smaller quantities of terras, or of equal 
 quantities of flint powder. 
 
 " Colored fluor and micaceous stones, colored marble, smalt and 
 divers other colored substances, which are insoluble in water, reduced 
 to fine powder, imparted their respective tints to the incrustations, 
 but acted like flint powder. 
 
 "From the experienced effects of colored calces of iron, and of 
 divers sulphurated and perishable metallic powders, I learned that these 
 ought not to be used in external incrustations, since they render them 
 more defective, as they color them deeply ; and I turned my thoughts 
 
COLOURED MOKTARS. 
 
 85 
 
 to the discovery of some other expedient for inducing permanent 
 color, without injuring the cement. 
 
 soon found that this may be done, with regard to the lighter and 
 pleasanter tints, by the use of colored sands, or the coarse, gritty sorted 
 powder of hard and durable colored bodies. Lynn sand affords a white 
 cement, which is the better as more of the finest part of the sand is 
 sifted out. Thames sand makes a grey cement, not unlike Portland 
 stone, and this color is agreeably varied by the use of grey bone-ash, 
 of which we shall presently treat. 
 
 * ' A rich yellow tint is obtained by using the golden yellow sand, 
 of which kind there is one near Croydon, in Surrey, and a small 
 quantity of which mixed with Lynn sand gives a warm white, and 
 with Thames sand, an exact resemblance of Bath stone. These are 
 the most eligible tints for the fronts of houses. 
 
 Until I had tried the glistening scaly talcs, I imagined that 
 they would serve to impart all other tints, as they may be had of any 
 color, and are as durable as they are pleasing to the eye ; but they 
 were found to weaken the adhesion of the cement to the wall, and to 
 make it so rough and * short ' that it was almost impossible to form a 
 smooth, compact incrustation with it, unless the lime was used in an 
 excessive quantity, and in the course of eight or nine months, it ap- 
 peared that the cements in which they were mixed in the quantity 
 necessary to produce stone tints, were rendered spongy, and greatly 
 weakened by them. 
 
 " Scaly glistening mica, strewed equally on an incrustation, pre- 
 viously wetted with a thin mixture of lime-water and lime, and gently 
 compressed, to lay the scales flat, imparts the color with the fullest 
 effects. In this way, colored mica may be used, where it is cheap, on 
 external incrustations, if the perspective appearance of a building can 
 be improved by different colors of any members of it, and this 
 kind of coloring greatly excels painting, in the fickle weather of 
 our climate, because it lasts, unfaded, as long as the micaceous 
 crust. 
 
86 
 
 COLOURED MORTARS. 
 
 **To tinge a cement sufficiently for prospect or contrast, of any 
 color which is not found in sand, so that the incrustation shall not be 
 impaired, and that the color shall be as durable as the cement, I 
 found nothing more advisable than to use, in the place of the sand, or 
 of a part of it, colored glasses or colored stones of the hardest kind, 
 beaten to coarse powder, the finer parts of which are to be washed 
 away, not merely because they are injurious to the cement, but because 
 I observed that they contribute but very little to the intended color. 
 
 *'The drying, induration and the texture of incrustations made on 
 brick walls, and other irregular surfaces, are always so far unequal as 
 to exhibit visible traces, which deform the work, and cannot be 
 effectually obliterated by any known method so convenient as that of 
 covering the first coarse incrustation, after it has dried, with another 
 coat which may be finer and smoother. Thus the expense of fine 
 grained, smooth or colored stucco is rendered moderate, because the 
 finer, or the coloring materials may be reserved for the exterior coat, 
 which will last for ages if the cement be good, as we shall show when 
 we come to considerthe experienced duration of the best calcareous 
 cements. 
 
 •'As the mouldings and paintings which are expended on the soft 
 stucco now used, and which contribute so much to the magnificence 
 of our apartments, can be equalled in their ornamental efiects by the 
 double incrustations which I have described, and greatly exceeded by 
 these last, in the hardness and durability of them, I do not doubt 
 that plasterers will adopt this improved method, when they find that 
 it is consistent with their own interest, as well as that of their em- 
 ployers. I am not sufficiently acquainted with their business to form 
 a just estimate of this subject, but I will submit to their consideration 
 a few observations which would influence me very much in the choice 
 of stucco for a house of mine. 
 
 **The compositions heretofore used for stuccoing in-doors are 
 capable of hardening considerably, and when they are laid on the 
 naked walls, soon became tarnished, unsightly, and inconvenient, by 
 
COLOURED MORTARS. 
 
 87 
 
 the damps which workmen call * sweating, ' and which are in ray opin- 
 ion of two kinds, one I will call damp by * transpiration,' and the 
 other damp by 'condensation.' The damp by transpiration occurs 
 when the principle walls are stuccoed before they have dried, or when 
 the materials of them are so spongy as to imbibe the rain, and the 
 circulation of the air within the house is not sufficient to waft away 
 the moisture which transudes from the wet wall into the stucco, and 
 especially when the exhalation of this moisture from the stucco is im- 
 peded by the closeness of its texture, for all such bodies retain moisture 
 the more forcibly as their pores are smaller and as the air meets 
 more difficulty in pervading them. I see no reason to doubt that this 
 inconvenience would be obviated by making the incrustation of a tex- 
 ture similar to that of the materials on which it is laid, and that the 
 cement made with about seven parts of sand, one of lime, and the 
 lime-water, and improved as we shall teach hereafter by the admixture 
 of bone-ash, would continue dry in such circumstances, because mois- 
 ture quickly exhales from it, by reason of its texture. 
 
 ''The damp which seizes incrustations when the walls are badly 
 constructed, when the joints of the facing bricks become hollow by the 
 decay of the mortar, or when the copings or gutters are defective, do 
 not fall under our consideration. 
 
 "The damp by 'condensation' appears most in the finest and 
 closest incrustations, however perfect and old the walls may be. To 
 find the proximate cause of it, we need only to advert to that which 
 gathers on glass windows, whilst the wainscot and other spongy bodies 
 which serve to enclose the same rooms, remain dry, or to the moisture 
 which gathers on walls faced with the closer kinds of ornamental 
 marble, in sumptuous buildings, at the same time when the walls and 
 incrustations contiguous to them, and are of a coarse texture, are 
 quite dry. In these and other instances we may perceive that the 
 damp is owing to the closeness of these bodies, and that a stucco per- 
 vious in a certain degree to air and moisture, will be free from it, as 
 well as from the other lately mentioned. 
 
88 
 
 COLOURED MORTARS. 
 
 ** The plasterers, finding their stucco which is as fine and close as 
 they can make it, liable to contract these damps, especially on the 
 principal walls of houses, case them with lath-work, on which the in- 
 crustation is laid, distant from the wall. In this way they obviate the 
 appearance of damp, but they at the same time contract the rooms, 
 and narrow passages, and stair-cases sensibly, at a great expense. 
 This is enhanced by the repeated plastering necessary to fill the slen- 
 der cracks which disfigure their incrustation during the drying, and 
 Dy the oiling or painting which is finally required to hide this defect 
 completely, if not to give color. Thus the work becomes costly, al- 
 though the plasterer's profit is moderate. 
 
 *^0n these considerations I am inclined to the opinion that it will 
 be found as advantageous to the plasterer as to his employer, to prefer 
 our cement before any other, for internal incrustations, especially 
 when no other color is required, besides those which may be imparted 
 by colored sand, or materials which do not greatly exceed it in price. 
 I would not interfere with the workman in forming an exact com- 
 parative estimate of the expenses, if I could do it, but I will venture 
 to affirm that an incrustation made as I have described, or in the im- 
 proved method hereafter to be shown, will be found ultimately cheaper 
 than any other yet discovered, for the following reasons, viz. : It will 
 be more durable by reason of its greater hardness ; it will retain its 
 color longer unfaded, because the coloring materials do not tarnish, 
 or perish the paint ; it will preserve the sharpness of the moldings, 
 and the elegance of its appearance longer, because it will not require 
 the frequent painting, which soon blunts the figures and moldings of 
 ordinary stuccoes ; it may be finished with less labor, because it is 
 not apt to crack in these circumstances, and does not need many 
 coats and repeated plastering ; and, as it is not likely to contract 
 damp, it will save all the expenses and inconveniences of lath-work, 
 whether it be laid on partitions or on principal walls, provided the 
 cement applied on the former be made of the finest materials. 
 
 If a polished and white surface of our stucco should be required, 
 
WOOD ASHES, ETC., IN MORTAR. 
 
 89 
 
 it ought to consist of two layers ; the first of which is to be coarse, 
 and capable of hardening to the highest degree, the second is to con- 
 sist of flint powder, lime, and lime-water, and is to be laid on very- 
 thin, and finely smoothed. To give a rich color together with a 
 smooth surface to our best incrustations, we must use tin the place of 
 flint powder for the finishing coat, the colored powder of sands, or 
 stones, or glasses, and introduce as much of the coloring ingredients 
 used in painting as will be sufiicient to givQ the required appearance, 
 avoiding those which are spoiled by lime, 
 
 "To my eye, the warm white, or colored stucco, which is not quite 
 smooth, is the pleasantest, but those who prefer the smoothest, may 
 have it made at a moderate expense, in this last-mentioned method, 
 in which the useful and solid part of it, contributes to the support and 
 duration of the weaker ornamental coat, which thus circumstanced is 
 likely to preserve its beauty for a very long time, although it might in 
 the weather be impaired in three or four years." 
 
 Experiments showing the effects of common Wood Ashes, 
 
 CALCINED OR PURER WoOD ASHES, ElIXATED AsHES, CHAR- 
 COAL Powder, Sea-coal Ashes, and Powdered Coke, in 
 . Mortar; and Observations on their integrant parts, and 
 the differences between them and the powders of other 
 
 BODIES. 
 
 " The ashes of wood and sea-coal, are frequently mixed with mor- 
 tar, or used in the place of sand, in laying tiled floors, and even in 
 external incrustations. Some workmen say they are used in the for- 
 mer case to save sand, others that they serve to resist moisture, and 
 those who seem to be the best informed afiirm that they hasten the 
 drying and induration, and prevent the cracking of mortar which is 
 laid very thick in order to fill the depressions of walls which are to be 
 stuccoed ; and that they are used in finer incrustations with the sole 
 riew of preventing cracks. 
 
90 WOOD ASHES, ETC., IN MORTAR. 
 
 " The ashes of the same kind of wood, differ, according to the cir- 
 cumstances in which they are formed, even upon the same hearth, not 
 only in color, but in other particulars known to chemists, which I shall 
 attend to presently. As the separation of these different sorts of ashes 
 is not practicable at a moderate expense, and is never attempted by 
 the workmen, I contented myself, at first, with procuring the ashes 
 of cleft pollards, burned on the hearth, and with sifting the whole 
 quantity of them, to free the finer parts from the fragments, and 
 coarse powder of charred wood, which formed a great part of the 
 bulk of them. The sifted ashes were gray, inclining to brown, 
 strongly alkaline to the taste, and viewed through a convex lens, 
 were found to contain a considerable quantity of fine charcoal powder, 
 which I estimated at one-sixth or more of the bulk. 
 
 "To learn the effect of the purer ashes, or of the more dephlogis- 
 ticated earthy and saline parts, separated from the charcoal, I took 
 about a gallon of the sifted ashes, and burned them on a test in a re- 
 verberatory furnace, with a heat not exceeding that of a culinary fire, 
 taking care to accelerate the combustion of the charcoal powder con- 
 tained in them, and render it equable through the whole heap by 
 stirring it, and presenting fresh surfaces to the air, until the whole 
 was rendered incombustible. After this process, the powder which I 
 shall call calcined wood ashes, was rather brown than gray, and re- 
 tained its saline taste. 
 
 ''On trying the sifted wood-ashes in my best mortar, and in other 
 mixtures of sand and lime, I found that they gave the cement a 
 spongy texture, and enabled it to dry without cracldng, when the 
 lime was not used in excessive quantity, but that they prevented it 
 from acquiring the hardness of mortar made of lime and sand only ; 
 so that the advantages they promised to afford in certain circum- 
 stances appeared to be counterbalanced by the permanent weakness in- 
 duced by them ; which latter effect was the greater, as the quantity 
 of the ashes, came nearer to equal that of the lime. 
 
 "The calcined wood-ashes likewise prevented the mortar fi'ora 
 
WOOD ASHES, ETC., IN MORTAR. 91 
 
 2racking, without making it so spongy, but they materially impeded 
 the induration of it, and disposed it to be injured by rain, in 
 the same manner as small quantities of alkali were found to do. 
 
 *'0n a strict comparison, the calcined wood-ashes, which wc may 
 consider as ashes freed from the charcoal powder, appeared to be 
 much more injurious than the uncalcined. This I imputed to the 
 greater quantity of alkali in the former, which is hurtful in a double 
 capacity, first, as a saline body, and secondly, as a compound which 
 yields its acidulous gas to lime, in the instant of mixture, and con- 
 sequently impairs the cement. 
 
 Mortar made with bad lime in the usual proportions may never- 
 theless be improved by sifted wood-ashes ; for the coal and earthy 
 parts of these, if they were only equivalent to so much sand, render it 
 less liable to crack ; and the bad effect of the alkali, may be greatly 
 overbalanced by this advantage, in an incrustation which is required 
 to be rather uniform and secure from clacking, than hard and durable 
 in the highest degree. 
 
 must not omit this opportunity of observing that calcined wood- 
 ashes, and even the sifted fresh wood-ashes, improve p(aster-of-paris, 
 in hardness, to a very great degree, if it be kept in a dry place. The 
 solution of this phenomenon is not difiicult. 
 
 "Any person who intends to repeat my experiments on calcined 
 wood-ashes ought so take care that they be not calcined with a 
 stronger heat than I described, for if he exceeds this, the ashes, after 
 the signs of their combustion have ceased, will smoke strongly, a part 
 of the saline matter being sublimed in the meantime, and the remain- 
 ing earthy and saline portion will form a light gray or brown, semi- 
 vitrified, gritty powder, or will concrete in lumps. This matter will 
 then be found insipid, and equivalent to sand, in mortar, as I have 
 experienced, for it differs as much from wood-ashes, as the* powder of 
 potter's stoneware differs from the raw clay. 
 
 '•Whilst I was employed in these experiments the following 
 thoughts occurred to me. The ashes used by workmen being passed 
 
92 WOOD ASHES, ETC., IN MORTAR. 
 
 througli a coarse sieve may consist for the greater part of charcoal 
 which afterwards is beaten finer in making the mortar. 
 
 **The ashes used by builders, whose durable works authorized this 
 practice, might have been the refuse of manufactories of potash, into 
 which the saline matter is always carefully extracted from them ; and 
 charcoal powder, or elixated ashes may greatly improve mortar, al- 
 though ashes finely sifted and replete with salts would impare it. I 
 therefore boiled my calcined wood-ashes in water, and repeated this 
 operation twice in fresh water, knowing that one elixation does not 
 free the ashes perfectly from the saline matter. I then dried the in- 
 sipid ashes thoroughly and used them in this state, under the name oi 
 elixated wood-ashes. At the same time I pro\ided charcoal powder 
 sifted through the same sieve which I used for the wood-ashes. 
 
 "After a great many experiments made in the usual manner with 
 the elixated ashes, I found that they rendered the mortar spongy, dis- 
 posed it to dry and harden quickly, and prevented it from cracking, 
 more eifectually than the like additional quantity of sand would do it. 
 They did not appear to induce the defects attending saline bodies in 
 mortar, they only made it weaker, as the quantity of the elixated 
 ashes was greater relatively to that of the sand and lime. 
 
 " This weakness, however, was not such as the unwashed ashes or 
 saline bodies produce, but rather of the kind which I pointed out in 
 those parts of the foregoing sections, wherein I endeavored to show 
 that cementitious masses resist edged instruments, or any force tend- 
 ing to break them, the more weakly as they contain more of the 
 softer and brittle calcareous matter, or as softer grains are substituted 
 for a part of the sand. 
 
 *^In every comparison of the specimens containing unwashed wood- 
 ashes, with those in which the elixated ashes were mixed in the same 
 proportions, it clearly appeared that the latter are to be preferred, and 
 that neither of them ought ever to exceed half the quantity of lime, 
 in good mortar. 
 
 As flint powder and other earthy powders were found to dispose 
 
WOOD ASHES, ETC., IN MORTAR. 
 
 93 
 
 mortar to crack, I could not conceive how the elixated wood-n lies 
 operated so elFectually in preventing this defect, until I examined them 
 attentively, and found them to differ from the other powders in two 
 particulars. Elixated wood-ashes contain very little powder of the 
 finer kind, they feel gritty between the fingers, and appear to consist 
 of ragged, spongy, small grains, compressible to a considerable degree 
 in the heap. How a powder thus conditioned prevents the crack- 
 ing of mortar or otherwise improves it, I shall attempt to explain 
 after stating other facts upon which my notions of this subject are 
 founded. 
 
 " Charcoal powder had the same effects as elixated wood-ashes, 
 with these differences only, that the cements containing the larger 
 quantities of charcoal powder could be more easily cut, and were of a 
 bluer color, than those containing the like quantities of elixated wood- 
 ashes. The powder which I used when sifted like the ashes, and viewed . 
 through a microscope, answered to the description lately given of elix- 
 ated ashes. 
 
 The screened ashes of Newcastle coal consist chiefly of charred 
 coal or coke, and as they contain very little saline matter, are insipid. 
 When I reduced them to powder, and passed them through the sieve, 
 they answered to the description given of elixated wood-ashes and 
 produced nearly the same effects in mortar. They did not weaken it 
 BO much as charcoal powder had done, which I impute to the greater 
 hardness of the small grains of coke. 
 
 *'In all these comparisons, it is to be understood that I made 
 them at the same periods of the induration of the several specimens. 
 
 **From these experiments, I conclude that, where a choice can be 
 made, these powders are eligible in this order : 1. Elixated wood-ashes 
 freed from the finest powder in washing ; 2. Powdered coke or sea- 
 coal cinders ; 3. Charcoal powder ; 4. Rough wood-ashes, powdered. 
 But well-burned fine unwashed wood-ashes, ought not to be used at all 
 in external cementitious work, or incrustation. 
 
 **The last of these gives a disagreeable gray or dusky color to the 
 
94 
 
 WOOD ASHES, ETC., IN MORTAR. 
 
 cement ; and the others a bluish or slate color, still more offensive to 
 the eye, for which reason they are unfit for any work that is not hid 
 iTom the view. 
 
 As my reader may not fully understand what I briefly mentioned 
 concerning the sensible difference between these last examined pow- 
 ders and others noticed in the preceding sections, I will thus exem- 
 plify my notions. 
 
 Wood consists of watery and volatile parts which are expelled by 
 heat, and of fixed parts which constitute the charcoal ; and charred 
 wood, which greedily imbibes air or water in great quantity, may 
 be considered as an assemblage of capillary tubes of divers figures 
 and sizes. So we may likewise consider the fragments of charcoal, 
 each a visible grain of its powder. But as the most brittle bodies 
 are flexible when they are made sufficiently thin, the charcoal pow- 
 der is an assemblage of small flexible or compressible tubulated 
 bodies. 
 
 " As the charcoal which is the fixed and more solid basis of wood, 
 is spongy after the juices are expelled in charring ; so the ashes of 
 charred wood are, after the elixation, an assemblage of spongy or 
 tubulated grains out of which the phlogistic matter has escaped during 
 the combustion, and the texture of these grains differs from that of 
 the grains of fine sand, or of flint powder, in the same manner, if not 
 in the same degree, as the texture of sponge differs from that of flint, 
 And we may conceive the unwashed wood-ashes as a heap of small 
 spongy bodies clogged with alkaline salt. 
 
 "Upon the same grounds, the relation of coke or sea-coal cinders 
 to the raw coal is analagous to that which charcoal bears to wood, or 
 spongy pumice stone to porphyry ; and transferring these observations 
 to bones, and considering the smaller vessels and finer texture of 
 them, than of wood, we shall find the powder of charred bones 
 to consist of tubulated or spongy bodies like those of charcoal 
 powder, but pervious by slenderer and harder tubes, and bone- 
 ash, which is the gritty powder of well-burnt bones, to have the same 
 
/ BONE ASHES IN MORTAR. 95 
 
 relation to the charred bones as eJixated wood-ashes have to cliarcoal 
 powder. 
 
 ^'Thuslhave thought of these substances after having observed 
 what happens to them in the preparation ; examined them hy sl mi- 
 croscope, experienced their effect to be so different from those of iinest 
 sand, or pov^dered stones in mortar, and finally discovered by repeated 
 experiments, the detail of which is not now necessary, that semi- vitri- 
 fication, which destroys the spongy texture, and levigation which 
 breaks these spongy grains down to the particles of which they are 
 constructed, render charcoal powder, wood -ashes, powdered sea-coal 
 cinders and others of the like kind, incapable of acting in the man- 
 ner described in calcareous cements. 
 
 **A11 these things being considered, I impute the effects of these 
 ashes, or powders, to the tubulated structure and compressibility of 
 the integrant parts of them, and in the next section I shall offer all 
 that I have attempted further, theoretically or practically, relative to 
 this subject." 
 
 Experiments showing the effects of White and Gray Bone- 
 Ashes, AND the Powder of Charred Bones, and Theory 
 OF the Agency of these in the best Calcareous CEMENXii. 
 
 "Long before I had tried all the powders heretobefore mentioned, 
 I used bone-ashes in many experiments, and saw the effects in 
 mortar. For the sake of brevity and perspicuity, I reserved the rela- 
 tion of them for this section : and in order to show more clearly the 
 analogy in texture between bone-ashes and the powders lately men 
 tioned, and to suggest the means of procuring them in any part of 
 this country, I will premise a sketch of the most profitable processes 
 by which they are prepared, at a moderate price not exceeding that of 
 good lime. 
 
 "The bones collected in great cities are broken to small fragments 
 in a mill, and boiled in water, in order to extract and save the oil of 
 
96 
 
 BONE ASHES IN MORTAR. 
 
 them. They are tlien put into a large iron * still,* through an aper- 
 tiire which is stopped up closely after the charge is made, The still, 
 which opens into an apparatus of refrigeratory vessels, is h(jated grad- 
 ually to redness, until all the volatile alkali, commonly called spirit, 
 find salt of hartshorn, is expelled from them, together with the empy- 
 reumatic oil, water, and certain elastic invisible fluids. The alkali 
 being the only valuable article amongst these, is retained and con- 
 densed in the refrigeratory tubes and vessels, with all possible care, 
 whilst the lactic fluids, lest they should burst the vessels, are sufFerea 
 to escape in places distant from the fire, or the flame of candles, be- 
 cause they are combustible, and if they catch fire whilst air remains 
 in the condensing vessels, explode like gunpowder. 
 
 *'The bones thus heated, without being exposed to the air, are 
 charred to blackness, but still remain combustible. When they are 
 required in this state, the iron still is kept closed until they are 
 cool, and then the blackest of them are ground to fine powder, which 
 is used as a substitute for ivory black, which is prepared in the same 
 way from ivory. The coarser powder of these is what I understand by 
 powder of charred bones. But when this is not the manufacturer's 
 design, the door of the iron still is left open whilst it is hot, and the 
 charred bones which flame and burn when they meet the air are 
 thrown into a kind of kiln, at the bottom of which the air can freely en- 
 ter, and maintain the combustion until the bones are burned to 
 whiteness for the greater part. The white fragments are picked, and 
 rather bruised than ground to a gritty powder by a millstone, which 
 rolls over them vertically on an inclined circular plane. This powder, 
 passed through a sieve, is called bone-ashes^ which are much used in 
 metallurgy, and fitter for our purposes in incrustations than the pow- 
 der of burned bones, ground as pigments are. The fragments which 
 have not been thoroughly burned in the kiln form a dark grey powder, 
 and the mixtures of white and grey burned bones afford bone ashes of 
 the lighter grey colors. 
 
 " The whole quantity of bone -ashes, which is to be used in the same 
 
BONE ASHES IN MORTAR. 
 
 97 
 
 incrustation, ought to be well-mixed, for it is impossible to sort the 
 well burnt or the gray bones so accurately as to secure an unity of 
 color in the parcels of powder which are successively prepared, and a 
 very small variation in the color will be apparent in the incrustation. 
 
 Knowing that bone-ashes consist chiefly of calcareous earth, and 
 may be reduced to lime by dissolving them in acids, precipitating the 
 solution by alkalies, washing the precipitate perfectly, and then burn- 
 ing it. I tried them with sand in different ways, in order to learn 
 how far they resemble lime in their cementing properties, and found 
 that the sorted bone-ashes had very little effect, but that the composi- 
 tions made with the levigated powder of these, and sand and water, 
 were nearly equal in hardness to those made with whiting and 
 sand, kneaded with water, in the same proportion, and were not so 
 liable to crack. Hence I inferred that bone-ashes, of which five-sixths 
 are calcareous earth, could not improve mortar by any augmentation 
 of the cementing powers of the lime, although they might be useful in 
 other respects, and that they could not supply the defect of lime, in 
 quantity or quality. 
 
 *'In the course of two years I made so many experiments with 
 bone-ashes, mixed in mortar composed of lime, sand and lime-water, 
 in different proportions, and of these with divers other ingredients, 
 that I may venture to say, I attained a thorough knowledge of their 
 effects, and need not hesitate to relate them in the style of precept. 
 
 "The sorted bone-ashes, mixed with mortar, in any quantity not 
 exceeding that of the lime, dispose the cement to set speedily, without 
 cracking, and effectually secure it from cracking, if it does not con- 
 tain lime in superfluous quantity. They likewise give a texture 
 which is the more spongy as the quantity of bone-ashes is greater, and 
 they accelerate the induration of it, through the whole mass. 
 
 *'The sorted bone-ashes increase the plasticity of fresh mortar 
 which is made with the smaller quantities of lime, in order to secure 
 the woi-k from fissures, and thus they are useful in a triple view, in 
 external incrustations, by facilitating the operation of plastering, b^ 
 
98 
 
 BONE ASHES IN MORTAR. 
 
 preventing cracks, and by bringing the incrustations quickly to a state 
 in which it is not easily injured by rain. 
 
 "When the sorted bone-ashes exceed the lime in quantity, they sen- 
 sibly injure the cement by rendering it weaker. How these ashes, 
 which are not equivalent to sand in the hardness of their grains, nor 
 to lime in their cementing powers, operate to weaken the cement may 
 be easily conceived, in consequence of the observations made in the 
 ninth, twelfth, and thirteenth sections. And when they are mixed in 
 mortar, in the quantity of one-fourth of the lime, they improve the 
 plasticity, if the mortar be * short,' and they produce the desirable elfects 
 above-mentioned in a sensible degree, without weakening the cement 
 in the same proportion. As a smaller quantity of them seem to be 
 useless, and a greater quantity than that of the limes, injurious, the 
 following rules are to be observed : — 
 
 *'When it is required more to secure an incrustation from the 
 effects of hot weather, to finish it quickly, to hide the traces of brick- 
 work, which are apt to appear through it, and to guard it against 
 rain, than to make it hard and durable in the highest degree, as much 
 sorted bone-ashes must be used as lime. When the season, exposure, 
 and other circumstances permit to attend solely to the true excellence 
 and duration of the work, there must be used in our best calcareous 
 cement only one part of the sorted bone-ashes for every four parts of 
 lime. By these rules the operator may choose intermediate quantities 
 adapted to his purposes. 
 
 *'The coarser bone-ashes used in making cupels, and tests, do not 
 go so far (so the workmen express themselves) or do not operate so 
 effectually as the sorted ashes in equal quantities of them, by weight ; 
 and finer or levigated bone-ashes are rather injurious than useful in 
 the coarser cements. 
 
 "The black powder, of charred bones, and gray bone-ashes 
 have nearly the same effects as sorted bone-ashes have, when the 
 powder of them is sorted in the same manner, excepting what relates 
 to color. 
 
BONE ASHES IN MORTAR. 
 
 99 
 
 '* These observations on bone-ashes were made on specimens of mor- 
 tar laid on tiles, and small pieces of incrustations made on the v/alls 
 of my house, and on the fence-walls behind it. But they v/ere not 
 confirmed thoroughly, until a comparison was made between large 
 incrustations laid in trying aspects, and containing bone-ashes, 
 \vith those close by them, of my best mortar, some months afterwards, 
 when I discovered the difficulty (expressed in the fourteenth section) 
 of making extensive incrustations, in certain circumstances so 
 free from defects as the smaller ones were, which I had made at 
 home. 
 
 "By the analogy of bone-ashes to cinders, or ashes of other bodies 
 by the effects of them in my experiments, and by the observa- 
 tions I have made on houses and garden walls which have been 
 fronted or entirely stuccoed with my cement, I have been led into the 
 following opinions, concerning the agency of bone-ashes in calcareous 
 cements : — 
 
 " The mortar which contains bone-ashes, partakes in some degree 
 of the elasticity and sponginess of their grains, and is the less liitble 
 to crack in setting, for the same reason that sponginess is, in any 
 other body, and effectual preventive of fissures in drying, or because 
 any contraction of the lime-paste, in consequence of the exhalation 
 of its w^ater, is combined to the circuit of the spongy grains compress- 
 ed in beating, trowelling, and floating the cement, and is thereby 
 prevented from running longitudinally to form fissures. The same 
 texture of bone-ashes, contributes to this effect, or causes it, upon 
 other principles, which are less exceptionable, and there is no reason 
 to doubt that bone-ashes, whose grains are tubulated in all possible 
 directions, which greedily imbibe water, and emit air, and which 
 render the mortar in which they are mixed, manifestly bibulous ; fa- 
 cilitate the entry of acidulous gas into the cement, and that this mat- 
 ter entering, so fast as the water exhales, occupies the place of the 
 water in the cement, and by preventing the contraction of it, avoids 
 fissures. The speedy induration of the cement which implies a quick 
 
100 
 
 BONE ASHES IN MORTAR. 
 
 and copious accession of acidulous gas, according to our opinion and 
 experience, is a proof of this agency of bone-ashes, as well as an effect 
 deducible from their texture, and from these premises, we may easily 
 conceive how they accelerate the setting of calcareous incrustations, 
 and tend to secure them from the injuries of variable weather. 
 
 These properties of bone-ashes render tbem peculiarly useful in 
 incrustations made within doors, on principal walls, and the admix- 
 ture of them in half the quantity of the lime, or in a greater quantity, 
 is the improvement I pointed out in the twentieth section, whereby 
 the damp that disfigures the common incrustations made in the cir- 
 cumstances there described, may be obviated without incurring the 
 expenses of lath-work. 
 
 * ' Those who know that one-sixth part of charred bones, or about 
 one-tenth part of well-burned bones, is phosphoric acid, may have 
 some doubt concerning the duration of a cement in which they are 
 mixed in large quantity, unless they consider that the strength of the 
 cement does not depend on them, and that it is impossible for the phos- 
 phoric acid to quit the lime of bone-ashes, in order to dissolve the 
 saturated lime of the cement. Though the bone-ashes should perish 
 in a century, which is not probable, the cement is not likely to fail on 
 this account, provided the quantity of them is not excessive. 
 
 Thus I surmounted the difficulties mentioned in the fourteenth 
 section, and made my best calcareous cement applicable in all cemen- 
 titious and crustaceous works, external or internal, without inducing 
 in it any disagreeable color or other imperfection. 
 
101 
 
 SPECIFICATION OF THE AUTHOR'S PATENT 
 CEMENT. 
 
 ''To ALL TO WHOM THESE PRESENTS SHALL COMB, &C., 
 
 "Now know ye, that in compliance with the said proviso, I, the 
 said Brindlet Higgins, do hereby declare that my invention of a water 
 cement or stucco, for building, repairing and plastering walls, and for 
 other purposes, is described in the manner following (that is to say) : 
 Drift or quarry sand, which consists chiefly of hard quartoze, flat- 
 faced grains with sharp angles ; which is the freest, or may be most 
 easily freed by washing, from clay, salts, and calcareous, gypseous, 
 or other grains less hard and durable that quartz ; which contains the 
 smallest quantity of pyrites or hea\^ metallic matter, inseparable by 
 washing, and which suffers the smallest diminution of its bulk in 
 washing in the following manner, is to be preferred before any other. 
 And where a coarse and a fine sand of this kind, and corresponding 
 in the size of their grains with the coarse and the fine sand hereafter 
 described, cannot be easily procured, let such sand of the foregoing 
 quality be chosen, as may be sorted and cleansed in the following 
 manner. 
 
 *'Let the sand be sifted in streaming clear water, through a sieve 
 which shall give passage to all such grains as do not exceed one-sixteenth 
 of an inch in diameter, and let the stream of water and the sifting be 
 regulated so that all the sand which is much finer than the Lynn sand 
 commonly used in the London glass-houses, together with clay and 
 every other matter specifically lighter than sand, may be washed 
 away with the stream, whilst the purer and coarser kind of sand which 
 passes through the sieve subsides in a convenient receptacle, and 
 whilst the coarse rubbish and rubble remain in the sieve to be re- 
 jected. 
 
 **Let the sand which thus subsides in the receptacle be washed in 
 
102 
 
 IIIGGINS'S PATENT. 
 
 clear streaming water, through a finer sieve, so as to be further 
 cleansed and sorted into two parcels : a coarser, which will remain in 
 the sieve, which is to give passage to such grains of sand only as are 
 less than one-thirtieth of an inch in diameter, and which is to be saved 
 apart under the name of coarse sand ; and a finer, which will pass 
 through the sieve and subside in the water, and which is to be saved 
 apart under the name of fine sand. 
 
 "Let the coarse and the fine sand be dried separately, either in 
 the sun, or on a clean iron plate, set on a convenient furnace, in the 
 manner of a sand-heat. 
 
 **Let lime be chosen, which is stone-lime, which heats the most in 
 slaking, and slakes the quickest when duly watered ; which is the 
 freshest made, and closest kept, which dissolves in distilled vinegar 
 with the least effervescence, and leaves the smallest residue insoluble, 
 and in this residue, the smallest quantity of clay, gypsum or martial 
 matter. 
 
 **Let the lime chosen according to these important rules be put in a 
 brass wired sieve, to the quantity of fourteen pounds. Let the sieve 
 be finer than any of the foregoing, the finer, the better it will be . 
 Let the lime be slaked by plunging it in a butt filled with soft water, 
 and raising it out quickly, and suffering it to heat and fume, and by 
 repeating this plunging and raising alternately, and agitating the 
 lime until it be made to pass through the sieve into the water, and let 
 the part of the lime which does not easily pass through the sieve be 
 rejected, and. let fresh portions of the lime be used, until as many 
 ounces of lime have passed through the seive as there are quarts of 
 water in the butt. 
 
 * * Let the water thus impregnated stand in the butt closely covered, 
 until it becomes clear ; and through wooden cocks, placed at different 
 heights in the butt, let the clear liquor be drawn off, as fast and as 
 low as the lime subsides, for use. The freer the water is from saline 
 matter, the better will be the lime-water or cementing liquor. 
 
 "Let fifty-six pounds of the aforesaid chosen lime be slaked by 
 
HIGGINS'S PATENT. 
 
 103 
 
 gradually sprinkling on it, and especially on the unslaked pieces, the 
 lime-water, in a close, clean place. Let the slaked part be immediate- 
 ly sifted through the last mentioned fine brass wired sieve. Let the 
 lime which passes be used instantly, or kept in air-tight vessels, and 
 let the part of the lime which does not pass the sieve be rejected. 
 This finer, richer part of the lime, which passes through the sieve, I 
 caJl purified lime. 
 
 *'Let bone-ashes be prepared in the usual manner, by grinding the 
 whitest burnt bones, but let it be sifted so that it be much finer than 
 the bone-ashes commonly sold for making cupels. 
 
 *' The most eligible materials for making my cement being thus pre- 
 pared : take fifty-six pounds of the coarse sand and forty-two pounds 
 of the fine sand : mix them on a large plank of hard wood, placed 
 horizontally, then spread the sand so that it may stand to the height 
 of six inches, with a flat surface on the plank ; wet it with the lime- 
 water, and let any superfluous quantity thereof, which the sand in the 
 condition described cannot retain, flow away off the plank. To the 
 wetted sand add fourteen pounds of the purified lime, in several suc- 
 cessive portions, mixing and beating them up together in the mean- 
 time with the instruments generally used in making fine mortar ; then 
 add fourteen pounds of the bone-ashes in successive portions, mixing 
 and beating all together. The quicker and the more perfectly these 
 materials are compounded, and the sooner the cement thus formed is 
 used, the better it will be. 
 
 " This I call the * water cement,' coarse grained, which is to be applied 
 in building, painting, plastering, stuccoing, and other work, as mortar 
 and stucco now are, with this difference chiefly, that as this cement is 
 ' shorter ' than mortar or common stucco, and dries sooner, it ought to 
 be worked expeditiously in all cases, and in stuccoing it ought to be 
 laid on by sliding the trowel upwards on it ; that the materials used 
 along with this cement in building, or the ground on which it is to be 
 laid in stuccoing, ought to be well wetted with the lime-water at the 
 instant of laying on the cement, and that the lime-water is to be used 
 
104 
 
 HIGGINS'S PATENT. 
 
 when it is necessary to moisten the cement, or when a liquid is required 
 to facilitate the floating of the cement. 
 
 *' When such cement is required to be of a finer texture; take 
 ninety-eight pounds of the fine sand, wet it with the lime-water, and 
 mix it with the purified lime and the bone- ashes, in the quantities and 
 in the manner above described, with this difference only, that fifteen 
 pounds of lime or thereabouts, are to be used, if the greater part of the 
 sand be as fine as the Lynn sand. 
 
 This I call the ' water cement,' fine grained. It is to be used in 
 giving the last coating or the finish to any work intended to imitate 
 the finer grained st-ones or stucco. But it may be applied to all the 
 uses of the coarser grained water cement, and in the same manner. 
 
 When for any of the foregoing purposes of painting, building, &c., 
 such a cement is required much cheaper, and coarser grained, then, 
 much coarser, clean sand, or well washed fine rubble is to be provided^ 
 Of this coarser sand or rubble take fifty-six pounds ; of the foregoing 
 coarse sand, twenty-eight pounds ; and of the fine sand, fourteen 
 pounds; and after mixing these and wetting them with the lime- 
 water, in the foregoing manner, add fourteen pounds or somewhat less 
 of the bone-ashes, mixing them together in the manner described. 
 
 "When the cement is required to be white, then white sand, white 
 lime and the whitest bone-ashes are to be chosen. Gray sand and 
 gray bone-ashes formed of half-burnt bones, are to be selected to make 
 the cements gray, and any other color of the cement is obtained, either 
 by choosing colored sand or by the admixture of the necessary quan- 
 tity of colored talc, in powder, or of colored vitreous or metallic 
 powders, or other durable coloring ingredients commonly used in 
 paint. 
 
 . "To the end that such a water cement as I have described may be 
 made as useful as possible in all circumstances, and that no person 
 may imagine that my claim and right under these ^ Letters Patent * 
 may be eluded by divers variations which may be made in the foregoing 
 process, without producing any notable defect in the cement, and to 
 
HIGGINS'S PATENT. 105 
 
 the end that the principles of this art, as well as the art itself of mak- 
 ing my cement, may be gathered from the specification, and perpet- 
 uated to the public, I shall add the following observations: — 
 
 *'This, my water cement, whether coarse or fine grained, is applica- 
 ble in forming artificial stone, by making alternate layers of the 
 cement and the. flint, hard stone or brick, in molds of the figure of the 
 intended stone, and by exposing the masses so formed to the open air 
 to harden. 
 
 " When such cement is required for water fences, two-thirds of the 
 prescribed quantity of bone-ashes are to be omitted; and in place 
 thereof, an equal measure of powdered terras is to be used, and if the 
 sand employed be not of the coarsest sort, more terras must be added, 
 so that it shall be (by weight) one-sixth part of the weight of the 
 sand. When such a cement is required of the finest grain, or in a 
 fluid form, so that it may be applied with a brush, flint powder, or the 
 powder of any quartoze or hard earthy substance may be nsed in the 
 place of sand, but in a quantity smaller, as the flint or other powder 
 is finer, so that the flint powder, or other such powder shall not be 
 more than six times the weight of the lime, nor less than four times 
 its weight. The greater the quantity of lime, within these limits, 
 the more will the cement be liable to crack by quick drying, and 
 vice versa. 
 
 "Where such sand as I prefer cannot be conveniently procured, or 
 where sand cannot be conveniently washed and sorted, that sand 
 which most resembles the mixture of coarse and fine sand above pre- 
 scribed, may be nsed as I have directed, provided due attention is 
 paid to the quantity of lime, which is to be the greater, as the sand is 
 the finer, and vice versa. 
 
 "Where the sand cannot be easily procured, any durable stony 
 body, or baked earth, grossly powdered, and sorted nearly to the sizes 
 above prescribed for sand, may be used in the place of sand, measure 
 for measure, but not weight for weight, unless such gross powder be as 
 heavy, specifically, as sand. 
 
106 
 
 HIGGINS'S PATENT. 
 
 <<Sand may be cleansed from every softer, lighter, and less 
 durable matter, and from that of the sand which is too fine, by 
 various methods preferable in certain circumstances to that which I 
 have described. 
 
 Water may be found naturally free from fixable gas, silenite, or 
 clay ; such water may witliout any notable inconvenience be used in 
 the place of the lime-water ; and water approaching this state will not 
 require so much lime as I have ordered, to make the cementing liquor 
 or lime-water, and which, sufficiently useful may be made by various 
 methods of mixing lime and water in the described proportions, or 
 nearly so. 
 
 When stone-lime cannot be procured, chalk, or shell-lime which 
 best resembles stone-lime in the characters before described, may be 
 substituted, except that fourteen pounds and a half of chaik-lime will be 
 required in place of fourteen pounds of stone-lime. 
 
 ^ ' The proportion of lime which I have prescribed above may be in- 
 creased without inconvenience, when the cement or stucco is to be 
 applied where it is not liable to dry quickly; and in the contrary 
 circumstances, this proportion may be diminished, and the defect of 
 lime in quantity or quality may be advantageously supplied by caus- 
 ing a considerable quantity of lime-water to soak into the work, in 
 successive portions and at distant intervals of time, so that the calcare- 
 ous matter thereof, and the matter attracted from the open air, may 
 fill and strengthen the work. 
 
 The powder of almost every well-dried or burnt animal substance 
 may be used instead of bone-ash, and several earthy powders, especially 
 the micaceous and the metallic, and elixated ashes of divers vegetables, 
 whose earth will not burn to lime, and the ashes of mineral fuel, which 
 are of the calcareous kind, but will not burn to lime, will answer the 
 ends of bone-ash in some degree. 
 
 '*The quantity of bone-ash described may be lessened without in- 
 juring the cement in those circumstances especially, which admit ^he 
 quantity of lime to be lessened, and in those wherein the cement is not 
 
HIGGINS'S PATENT. 
 
 107 
 
 liable to dry quickly. And the art of remedying the defects of lime 
 may, be advantageously practiced to supply the deficiency of bone- 
 ash especially in building and in making artificial stone with this ce- 
 ment. 
 
 B. — For inside work, the admixture of hair with this cement 
 is useful. 
 
 "The excellency of my cement depends, first, on the figure, size, 
 and purity of the sand ; secondly, on the purity of the lime, obtained 
 in the choice of lime-stone, and in the perfect burning, and security 
 in preserving it from the air, in my method of slaking, and in the 
 separation of heterogeneous parts ; thirdly, on the use of strong and 
 pure lime-water, in the place of common water; fourthly, on the pro- 
 portions of sands, lime-water and lime; fifthly, on the manner of 
 mixing them ; sixthly, on the knowledge of ingredients and circum- 
 stances which are injurious or useful ; seventhly, on the use of bone- 
 ashes of determinate size; eighthly, on the art of suiting some 
 of these to the several purposes; and finally, on so many other 
 particulars as render it very diflicult to give a more candid specifica- 
 tion in the usual compass, than this which I have enrolled, or to guard 
 otherwise against evasions, than by anticipating them. 
 
 "In witness whereof, I, the said B. H.," &c. 
 
 In allusion to the foregoing specification, the author (or patentee) 
 makes the following remarks :— 
 
 "As the specification of these letters-patent comprehends the most 
 useful practical instructions deduced from the foregoing experiments 
 and observations, and may serve as a concise recapitulation^ I subjoin 
 a transcript of it. " 
 
108 
 
 Experimental Comparison of Chalk-lime with Stone-lime. 
 Advice to Manufacturers of Chalk-lime concerning the 
 Art of making it equal, if not superior, to Stone-lime, 
 
 FOR the purposes OF BuiLDERS, SOAP-BOILERS. AND SuGAR- 
 BAKERS. 
 
 ''All the authors whom I have consulted, who have treated of ce- 
 mentitious buildings and of lime, from the time of Vitruvius, who 
 wrote on these subjects in the reign of the Roman emperor, Titus, or 
 before it, down to the present hour, and all the artists with whom I 
 have conversed, agree in the opinion that lime prepared from the 
 closest lime-stone makes a stronger cement than that which is made 
 of spongy lime-stone, and that the lime of chalk particularly is inca- 
 pable of acting as effectually as the best lime-stone, in cementitious 
 works or incrustations, which are exposed to the weather. 
 
 " This universal and undisputed notion had great influence with me 
 in the course of my experiments, until I had discovered not only the 
 fallacy of it, but the grounds which gave rise to it ; both which I shall 
 now expose, in the pleasing hope of rendering great service to many 
 of my friends, and all who are proprietors of chalk-pits, or are obliged 
 to use chalk-lime in their buildings. 
 
 " The experiments already mentioned afforded me a great many 
 opportunities of comparing cements made of lime and sand, or with 
 those and other ingredients in various proportions, and differing only 
 in the kind of lime. Jn these comparisons I could not perceive that 
 chalk-lime, judiciously prepared and used, was in any respect inferior 
 to the best stone-lime ; but I did not content myself with these. I 
 made a great number of cements, with the sole view of collecting the 
 respective merits of these kinds of lime, in small and great incrusta- 
 tions, in masses made to resemble cut stone, in all exposures and 
 seasons of the year ; and after the strictest comparisons of those which 
 contained lime in equal quantities, and were treated alike in all re- 
 spects, I was thoroughly convinced that my chalk-lime was as good 
 
CHALK-LIME AND STONE-LXME. 109 
 
 for any purpose of this kind as the best stone-lime in the kingdom ; 
 for I nsed the well-burned lime of Plymouth stone, which I reckon 
 among the most excellent of our lime-stones. 
 
 ' * This stone loses seven-sixteenths of its weight in conversion into 
 lime, and becomes as white as chalk. Chalk loses a little more in the 
 perfect burning. Plymouth lime leaves a small gypseous residue in 
 the solution, described in the tenth page, which is preferable to that 
 directed in the specification ; chalk lime leaves none. Therefore, the 
 chalk lime, chemically or technically tried, appears to be equal if not 
 superior to stone-lime, in its cementing powers, when it is properly 
 used. 
 
 "The prejudices entertained against chalk-lime may be traced to 
 three sources. The first is that which is mentioned in the fourth sec- 
 tion. The vulgar criterion of the due preparation of lime consists in 
 the slaking ; and as chalk which has undergone a slight calcination 
 and thereby lost only a part of its acidulous gas, is capable of slaking, 
 by reason of its sponginess, the manufacturers of chalk-lime content 
 themselves with the degree of calcination which renders it tracticable 
 or vendible, and thus bring it into disrepute. 
 
 The second source is mentioned in the fifth section. Chalk-lime 
 imbibes acidulous gas, during its exposure to the air, much faster 
 than stone-lime, and is consequently more impaired or worse, at the 
 time of using it in mortar, than stone-lime kept in the same circum- 
 stances. As the lime may be greatly injured in this way, without 
 slaking sensibly, and as there was no suspicion or measure of such in- 
 jury, beyond what the slaking afforded, the acquired imperfection of 
 ehalk-lime was considered as the very nature of it. In our foregoing 
 remarks, it appears that a pound of chalk-lime, placed in the quiescent 
 air of a chamber, imbibes two ounces and a half of acidulous gas in 
 two days ; which is the shortest time in which lime is usually exposed, 
 if we count from the moment of its being red-hot to that of its being 
 mixed in mortar, during which interval it is in the state of ab 
 sorption. 
 
110 
 
 CHALK-LIME AND STONE-LIME. 
 
 "The third source I have discovered in the structure of the lime- 
 kilns. The cavity of a lime-kiln has the figure of a truncated cone, 
 inverted. When the charge, consisting of lime-stone and fuel, alter- 
 nately stratified, has burned for some time, the fuel is exhausted at 
 the lower narrow extremity of the cavity, the lime in this part cools, 
 and serves as a grate to the fuel and lime-stone above it, which con 
 tinue to burn briskly, for eighteen hours longer, after the lime beneath 
 begins to cool. Duiing this time, the last-mentioned part of the lime 
 is exposed to a strong current of air, and the whole charge of lime 
 stands in the like current of air until the lime is cooled, or with- 
 drawn; which in common practice is seldom or never done till 
 the sixtieth or seventieth hour after the combustion of the fuel com- 
 menced. 
 
 ''The injury which lime-stone sustains in these circumstances, 
 which I have often imitated in my laboratory, is not great, because 
 this lime is much more compact than the chalk-lime. But when we 
 observe that the best pieces of chalk-lime of the common kilns, and 
 those which, after beating them sufficiently, I had left in the fire- 
 place, exposed as they are in the usual process, are always effervescent ; 
 that good chalk-lime, in a weaker current of air, imbibes more than 
 three ounces of acidulous gas into each pound of it, in two days, ac- 
 cording to our former experiment, and that my chalk-lime, which I 
 remove from the fire-place as soon as it is sufficiently burned, is per- 
 fectly non-effervescent ; we find that the long experienced imperfec- 
 tions of fresh chalk-lime are owing more to the faulty construction of 
 the kilns, and the ignorance of the manufacturer, than to any incapa- 
 city of chalk to yield excellent lime. 
 
 " The means of preparing chalk-lime to equal stone-lime, and of 
 making the best stone-lime, may be gathered from what I have said, 
 and the following intimations : — 
 
 "The kilns are to be made broader and shallower in the cavity 
 which receives the charge ; the circular waU enclosing this cavity, is 
 to be continued tapering upwards, until it terminates in a lofty flue, 
 
CHALK-LIME AND STONE-LIME. 
 
 Ill 
 
 in order to accelerate the combustion, and increase the heat by a quick 
 current of air, to be regulated by opening or closing the doorway, 
 which is to be left in the circular wall, at a convenient height for the 
 introduction of the charge. The massive walls of the lower cone are 
 to be lined with fire-brick, or a pyrous stone set in the best fire-loam, 
 and are to be girded with iron. The fuel is to be stratified with the 
 lime-stone, or chalk, and the combustion is to be so conducted, that 
 every part of the charge shall be sufficiently ventilated and heated, 
 and that the lowest shall remain red-hot, until the whole is well-burn- 
 ed. Then the current of air through the kiln is to be stopped by 
 closing the apertures at the bottom, or the red-hot lime is to be re- 
 moved out of it, to cool in quiescent air, until it is fit to be enclosed 
 in air-tight vessels. 
 
 "A cask of chalk-lime is not to be opened until the moment when 
 the workman is ready to slake the lime ; and the greatest expedition 
 is to be used in the slaking, in making the mortar, and in applying it 
 to use. By this treatment, the chalk-lime will answer every end 
 of the best stone-lime, and stone-lime may be prepared and pre- 
 served in the highest perfection which the nature of the lime-stone 
 can admit. 
 
 "The manufacturer of chalk-lime who adopts this plan will profit 
 by it, for good lime is not only better, but goes further in building, 
 than bad lime ; good chalk-lime will answer the purposes of the soap- 
 boiler, in half the quantity which they use of common chalk-lime, the 
 greater part of which serves only to waste their lees, and clog their 
 vats ; and the sugar-bakers will not hesitate about the price of good 
 chalk-lime, when they find that it is totally soluble in pure water, and 
 introduces no selenitic matter into the sugar. The exportation of 
 lime to the West India islands will be a further incitement towards 
 the improvements which I have s%gested, when they understand the 
 principles by which fee, duly admmm^red facilitates, hut injudicious^ 
 ly used, impedes the granulation of tRe saccharine parts of their cane 
 juices." ' ■ 
 
112 
 
 POZZOLANA OR PUZZOLANA. 
 
 "This mineral being a very essential ingredient in the composition 
 of hydraulic cement, a brief account of it here, may not be considered 
 out of place, or uninteresting. 
 
 Pozzolana is a greyish kind of earth, much used in Italy and else- 
 where, for building under water— the best variety of which is found 
 about Pozzuola, (Puteoli,) Cumaj, Baias, &c., in the kingdom of 
 Naples ; and from the former of which places it derives its name. 
 
 "The mineral, of itself, is a pale greyish powder, composed of 
 particles so very minute, as to escape distinction even by the aid of 
 powerful glasses, and when viewed through a microscope appear only 
 a loose, fine irregular powder, and containing small quantities of talc 
 spangles, and when mixed with water in a glass vessel, and well- 
 shaken up, leaves a white muddiness in it, which requires a long time 
 to subside ; and when wetted with sea-water, immediately dries into 
 a firm, compact mass, similar to stone, hence its value for marine 
 works ; it will do the same when mixed with fresh water, but not in 
 80 great a degree. 
 
 "Mixed with lime, Pozzohna makes the best possible mortar, it 
 hardens and petrifies in water. 
 
 " The ancients were well acquainted with this substance, and its 
 properties, and employed it extensively in the construction of moles, 
 piers, &c. of bridges and all works exposed to direct contact with sea- 
 water, or subject to saline atmosphere or impregnation. Vitruvius, 
 Pliny, De Lorme, &c., set great value on it, and the latter is reported 
 to have used it largely in France. Some have considered it to be of 
 an aluminous and sulphurous nature. 
 
 "It is said to have been first no^ed on the sea-shore of its native 
 place, where having drifted do\^^om the hills by the force or action 
 of the wind, aided by the law ^Pavitation, or by the mountain tor- 
 rents, it lodged on the beach or sea-side, and becoming mixed with 
 
POZZOLANA. 
 
 113 
 
 the sea-water, dissolved, and speedily acquired extreme induration 
 and solidity, so much so as to be by many mistaken for masses of 
 Dative stone. 
 
 *'The remarkable property which it possesses of coalescing so 
 quickly with water, is probably owing to its having in its composition 
 a large proportion of a certain earth very common on the sides of 
 hills throughout Italy, and known to the ancients by the name of 
 gypsum tymphiacum, and by the moderns as calx nativa, and which 
 possesses the quality of forming a kind of plaster, without being 
 burnt. 
 
 *^Puzzolana is also found in other parts of Italy than those before 
 enumerated, as Viterbo, Bologna, &c., and frequently in the vicinity 
 of burning mountains, from which it has been ejected in the form of 
 ashes — in the crater or belly of which volcanoes it had been previously 
 burnt or calcined; and which fact will reasonably and satisfactorily 
 account for its highly cementitious properties (in its native state) 
 without further preparation. It is said to exist in large quantities, 
 sometimes covering the face of the country, and even whole districts 
 to a considerable depth ; and it is sometimes found in small detached 
 pieces of an earthy and porous texture ; classed by mineralogists under 
 the genus "lava," and is considered a volcanic product. 
 
 " It is magnetic, and readily melts stone into a dark slag; it quickly 
 hardens when mixed with one-third of its own weight of lime and 
 water, forming a cement more durable under water than any other 
 yet known. 
 
 ''Upon analysis it has been found to contain the following com- 
 ponents, viz., (out of one hundred parts, )from fifty-five to sixty of 
 siliceous earth, twenty of argillaceous, five or six of calcareous, and 
 from fifteen to twenty of iron. This last constituent is thought to be 
 the principal cause of its peculiar property of hardening under water . 
 The iron decomposes the water, thus producing in a short time a new 
 compound. 
 
 Another examination of a specimen of puzzolana gave the follow 
 
114 
 
 ARTIFICIAL PUZZOLANAS. 
 
 ing results: 44*5 of silica, 15-0 alumina, 8*8 lime, 4*7 magnesia 
 1*4 potash, 4*1 soda, 12 oxide of iron and bitumen, and 9*2 water iu 
 100 parts. 
 
 "The Greeks were not acquainted with this substance, and the 
 Romans had in this respect a great advantage over them, on account 
 of the solidity it imparted to their buildings. When used for struc- 
 tures in or under water, the Romans mixed (according to Vitruvius) 
 two parts of Pozzolana to one of mortar. The ruins of edifices near 
 Baiae attest the solidity of this cement. 
 
 **Puzzolana was called by the Romans ^ terra puteolana^ from the 
 place where it was chiefly obtained, and was employed by them with 
 great advantage in the construction of their pubUc ways at Rome, 
 and its vicinity. 
 
 "Artificial puzzolana is made by reducing to a red heat, three 
 parts of clay to one of slaked lime by measure. 
 
 "A species of puzzolana has been found in England and France, 
 but it is not equal in quality to the Italian. 
 
 Puzzolanas are either natural or artificial, the former are found in 
 situations which have been acted upon by subterraneous heat, such as 
 is contained in volcanos, &c. They all consist of silex, alumina, oxide 
 of iron, and a little lime ; the proportions of which greatly vary in 
 different specimens, the silex or clay, in all cases, predominating, 
 while the lime and iron are sometimes, though rarely, wanting. 
 
 "The scoria of forges and furnaces, broken pottery, and pulverized 
 brick or tile, are artificial substances analogous to puzzolanas. One 
 class of puzzolanas, containing a large portion of clay or argil, resist 
 the action of sulphuric acidf another class, with a less proportion of 
 clay, readily dissolve with this acid, abandon the clay, which imme- 
 diately separates and subsides. 
 
 " Since the quality of natural hydraulic lime depends on the mixture 
 of various ingredients, with only a certain proportionate quantity of 
 3lay, combined with heat, it is natural to suppose that an artificial 
 mixture of the like materials submitted to heat, would produce a 
 
ARTIFICIAL PUZZOLANAS. 
 
 115 
 
 compound of equal efficacy. Experience has abundantly confirmed 
 this opinion, and it is now known that an artificial hydraulic lime 
 may be prepared in almost any place, at a moderate price, and equal 
 to the natural. 
 
 An artificial puzzolana is made by heating of slaked lime, one 
 part to three of clay, and keeping them at a red heat for several hours ; 
 after which cover the top of the kiln with sand or earth, and when 
 cool, pack it up close in casks for use. 
 
 **It is well known that puzzolana in itself has no cementing prop- 
 erties, having been found upon analysis to consist of the same compo- 
 nent parts as the colored clays of nature, that is, chiefly of silica and 
 alumina, with a small portion of the metallic oxides, and sometimes 
 with a little lime ; but when mixed with the weaker hydraulic limes, 
 or even with common lime, it constitutes a hydraulic mortar, that 
 sets under water, but more slowly than either the natural or artificial 
 water-cements. 
 
 John Smeaton, C. E., who erected the Eddystone lighthouse in 
 the English Channel, is accredited as having been the first to bring 
 puzzolana into public notice in England, and used it extensively, both 
 in a pure state and also mixed with Watchet or Aberthaw lime, and 
 other hydraulic ingredients in the construction of that far-famed struc- 
 ture, and also made several experiments upon its peculiar properties. 
 
 *'Mr. Stevenson, C. E., also employed puzzolana, with a mixture 
 of Aberthaw lime and sand, at the building of the Bell Eock light- 
 house, opposite to the mouth of the river Tay (Scotland) ; his propor- 
 tions were one measure of slaked lime-powder, one measure of puzzo- 
 lana, one measure of sand. 
 
 The most ancient sort of artificial puzzolana is composed of brick- 
 dust or tile-dust, or fragments of broken pottery ground to powder, and 
 being mixed with lime, produced a cement more impervious to water 
 than common mortar made of lime and sand, and which in all probabil- 
 ity was in common use in the time of the Romans, as may be inferred 
 from some passages of Vitruvius. Puzzolana and brick-dust not only 
 
116 EXPERIMENTS ON AETIFICIAL PUZZOLANA. 
 
 resemble each other in appearance, but chemistry prove that they con- 
 tam the same component parts, both being originally clays, and both 
 being moderately calcined or burned, the one by volcanic agency, and 
 the other in a kiln or clamp. 
 
 This primitive sort of artificial puzzolana has been in constant 
 use from time immemorial in the south of Europe, and especially in 
 France, where the term ' cement ' has been applied to it, which, when- 
 ever it occurs in any French work on practical architecture, may be 
 taken invariably and exclusively to signify brick or tile-dust mixed 
 with lime for the purpose of forming a hydraulic mortar, but which 
 term has been supplanted by M. Vicat, who employs the phrase * arti- 
 ficial puzzolana,' which is now almost universally adopted by modern 
 authors. 
 
 **The Dutch, to whom hydraulic mortars have long been known, 
 and of great importance, accustom themselves to burn a clay found 
 under the sea of their coast, for the purpose of forming an artificial 
 puzzolana, which is said to be a close and good imitation of the natu- 
 ral ' trass * of Andernach on the Rhine, and which is often sold and 
 exported as such. 
 
 A series of experiments undertaken by Col. Pasley (at Chatham) 
 on artificial puzzolana, produced the following restdts: — 
 
 1st. That the calcined blue clay of the river Medway forms bet- 
 ter artificial puzzolana than the calcined brown pit clay of Up- 
 nor, but in its water-setting properties it is rather inferior to natural 
 puzzolanas. 
 
 2d. That the finest clays make the best, and pounded bricks the 
 worst, artificial puzzolana. 
 
 " 3d. That no hydraulic mortar, except cement, will set on the 
 outside of walls, exposed to the violent action of the water. 
 
 «<4th. That puzzolana mortars, as well as those of the strongest 
 hydraulic limes, require to be protected by cement in all the external 
 joints. 
 
 *<5th. That the mortar of walls built with weak hydraulic limes 
 
ANALYSIS OF TRASS AND PUZZOLANA. 117 
 
 ;vill not set nnder water, unless improved by puzzolana as well as be- 
 ing guarded aU round with cement 
 
 ANALYSIS OP TRASS AND PUZZOLANA. 
 
 "The chemical component parts of Trass and Puzzolana are so 
 nearly alike, that the one cannot possess any property not belonging 
 to the other, though it may be in a lesser or greater degree, but ii; 
 ought to be understood, that the puzzolanas and trasses even of the 
 same locality, may somewhat differ from each other in the proportions 
 of their component parts, and those from different localities still more^ 
 and the same remark will apply to hydrauHc limes and water cements^ 
 The trass used by Mr. Stevenson on commencing the Bell-rock light" 
 house, for want of puzzolana, is stated to have contained in 100 parts^ 
 silica 57, alumina 28, lime 6*5, and oxide of iron 8*5. 
 
 "The puzzolana used by him for the same lighthouse contained, 
 silica 55 parts, alumina 20, lime 5, and oxide of iron 20. 
 
 "The following shows the component parts of the trass and puz 
 zolana used by General Treussart at Strasburgh, as analyzed by M. 
 Berthier : — 
 
 
 TEASS, 
 
 PUZZOLANA. 
 
 
 
 445 
 
 Alumina, 
 
 120 
 
 150 
 
 
 
 88 
 
 Magnesia, 
 
 10 
 
 47 
 
 Oxide of Iron, 
 
 50 
 
 120 
 
 Potassa, 
 
 70 
 
 14 
 
 
 10 
 
 40 
 
 Water, . , , , 
 
 96 
 
 92 
 
 
 * 952 
 
 996 
 
118 
 
 NOTES FROM THE 
 LATE GENERAL SIR C. W. PASLEY'S (K.C.B., R.E.) 
 WORK ON LIMES. 
 
 Pure limes are those which consist entirely of caroonate of lime ; 
 that is, lime combined with carbonic acid gas or fixed air, in the pro- 
 portion of five parts by weight of the former and four of the latter — 
 they are all white, such as pure chalk ; the Carrara marbles used by 
 statuaries being the purest limestone in nature, and are entirely soluble 
 in muriatic or nitric acid, which expels the carbonic acid gas with 
 great effervescence which is a certain test of their properties and 
 character ; and when chalk or white marble is exposed to a strong red 
 heat, as in a lime-kiln, the carbonic acid gas is driven off and the 
 stone is converted into quick-lime, and ia which state, if a piece be 
 dropped into either of the above mentioned acids (diluted), no effer- 
 vescence will occur ; the quick-lime, when slaked with water, speedily 
 falls to pieces into a fine powder with great heat, and is then termed 
 * hydrate of lime, ' in which condition it is, by admixture with certain 
 proportions of sand and water, converted into building mortar. Sixty- 
 three pounds of pure native chalk will produce, upon an average, 35 
 pounds of lime, and when slaked with a proper quantity of water will 
 occupy a space of about 1 § cubic foot. A cubic foot of solid chalk 
 weighs 95 pounds. The process of slaking wiU increase the weight of 
 a cubic foot of lime from 35 to about 50 pounds, or in the proportion 
 of 7 to 10. The carbonic acid gas driven off by the process of burning 
 the Ume-stone is gradually recovered after slaking the lime. 
 
 Thirty-five pounds of fresh-burnt chalk-lime, mixed with 3 \ 
 cubic feet (87 pounds to the cubic foot) of river sand, and about 1 J 
 cubic foot of water, produces about 3 \ cubic feet of good mortar, or 
 one-fourth of a cubic foot less bulk than the sand alone previously oo- 
 cupied, which is owing to the solidifying effect of the water upon the 
 dry materials. 
 
NOTES, &c. 
 
 119 
 
 Pounded quick-lime measures less, and slaked powder of lime 
 measures more in bulk than it originally occupied. 
 
 *'Pure carbonates of lime are suitable for mortar to be used in dry 
 situations or for inside work, but are unsuited for wet or damp posi- 
 tions, and consequently quite unfit for hydraulic mortar. In works 
 which are much exposed to damps or to occasional floodings, when 
 iime-mortar is chiefly to be employed, it is a good method to p(»nt all 
 the external joints with Koman or hydraulic cement. 
 
 Walls built with chalk-limes are most liable to * settle*; those 
 built with hydraulic limes settle less, and such as are built with ce- 
 ment, not at all." 
 
 OF WATEE LIMES OR HYDRAULIC LIMES. 
 
 " These are composed of carbonate of lime, generally mixed with 
 silica, alumina, and the oxide of iron, and with frequent indications 
 of other matter ; if the carbonate of lime be removed the residuary 
 parts are of a clayey nature, from which fact the occasional term of 
 (vgiUaceous lime-stones is derived ; they possess the peculiar and valu- 
 able property of setting in wet or damp situations, and are therefore 
 very useful in the construction of marine works, and dock and river 
 walls, especially when protected in front with such superior cements as 
 puzzolana, trass, or English cement. 
 
 Of all the English lime-stones the Blue Lias stones are reckoned 
 the best and strongest ; they are found in the British Channel, also 
 near Watchet in Somersetshire, at Aberthaw in Glamorganshire 
 (Wales), and at Lyme Regis in Dorsetshire. The former of these was 
 mixed with puzzolana and used by Smeaton in the construction of the 
 Eddystone lighthouse. 
 
 The Dorking or Mersham lime, and also the Hailing lime (Eng- 
 land), are much valued as hydraulic cements, especially the former, 
 and are much employed in London. 
 
 All the water lime-stones are of a bluish gray, or brown color, 
 which they derive from oxide of iron, and are usually termed stone- 
 
120 
 
 NOTES, &c. 
 
 limes, in contradistinction to chalk-limes. Colored chalks are com- 
 monly termed gray chalks ; they are usually free from flints, and are 
 more or less possessed of hydraulic properties. 
 
 " Most of the water lime-stones, when burned into quick-lime, so 
 as to expel the carbonic acid gas, are of a yellowish or light brown 
 color, so that any calcareous stone, which, after calcination, assumes 
 a kind of buff color, may be considered to have hydraulic properties. 
 Water limes will not bear so much sand as common chalk lime. 
 
 Three measures of sand and one of Dorking or Hailing lime make 
 a good mortar, but blue lias stone lime requires only twice its meas- 
 ure of sand to produce good mortar. 
 
 " Magnesian lime-stones possess some amount of hydraulic proper- 
 ties, but do not make a good water lime or water cement.* 
 
 WATER CEMENTS, USUALLY TERMED ROMAN CEMENTS. * 
 
 " The best varietiesof these are produced from the isle of Sheppy, Har- 
 wich, Yorkshire, &c., and they differ chemically from water limes in 
 having less carbonate of lime, and more silica and alumina, and prac- 
 tically, in not slaking with mortar unless previously pulverized ; that 
 powder balls made of these cements, calcined and mixed with water, 
 will not swell and burst, but will set not only in air but under water, 
 even if instantly immersed ; and that these cements are always weak- 
 ened by the addition of sand ; and also in the necessity for their im- 
 mediate use after being mixed, before they begin to heat, or they must 
 be thrown away, as they will not bear to be re-mixed." 
 
 ON ANALYSING LIME-STONES, AND TESTING THEIR SEVERAL 
 PROPERTIES. 
 
 A Stone supposed to be a water cement, ought to be of a bluish 
 gray, or brown, or some darkish color, as white indicates pure lime- 
 
 • Note. The propertiea of the Sheppy cement were first discovered by Mr, 
 Parker, who took out a patent for it under the name of ' Roman Cement,* but it 
 is better known as Parker's cement. Mr. Frost discovered the Harwich cement, 
 and Mr. Atkinson (architect) that obtained from Yorkshire. 
 
ANALYSIS OF CEMENTS. 
 
 121 
 
 stone or gypsum. From their containing silica and alumina, which 
 are the component parts of clay, the natural cement stones, on being 
 touched with the tongue, indicate sensibly the presence of clay, which 
 is also detected by the smell after wetting them. They only dissolve 
 partially in diluted acids, having a more copious sediment than any 
 of the lime-stones. 
 
 ' ' The first test, therefore, is to pour a little diluted muriatic or 
 nitric acid into a glass, and drop a fragment of the stone into it. If 
 no action takes place^ it is neither a lime-stone nor cement ; but if it 
 effervesce and fall to pieces with a muddy sediment, it is probably a 
 water-cement. To ascertain this point, break the stone, if necessary, 
 into compact fragments, not exceeding one inch and a half in thick- 
 ness, and put two or three of these into a common fire-place, first 
 heating them gradually, that they may not burst into too many 
 small pieces, and keep them exposed to a full red heat for about three 
 hours. At the end of this time, take one of your specimens out of the 
 fire, and put a small fragment of it into a glass of diluted muriatic 
 or nitric acid. When the stone is burned enough, that is, when all 
 the carbonic acid gas has been driven off by the heat, no effervescence 
 will take place in the acid. A moderate effervescence will show that 
 it is a little under-burned, but violent effervescence will prove that it 
 is very imperfectly burned, and it should therefore be put into the fire 
 again. 
 
 Care must be taken not to over-burn the cement, which would 
 always injure if not entirely spoil it ; this fact may be known by its 
 changing to an unnatural dark color, and which is a proof of incipient 
 vitrification ; for, by excess of heat, all the natural cement stones may 
 be fused into a dark-colored glassy substance resembling the volcanic 
 product called obsidian. 
 
 *'If, therefore, the calcined cement stone does not effervesce with 
 acids, and if at the same time its proper color be not changed to a 
 darker one on taking it out of the fire, it will prove that it is properly 
 burned. 
 
 6 
 
122 
 
 ANALYSIS OF CEMENTS. 
 
 ** The next process is to pound the perfectly calcined specimens to 
 an impalpable powder, which state is ascertained by its not feeling 
 gritty when rubbed between the fingers and thumb. This is an im- 
 portant condition of natural and artificial cements, for their properties 
 are much deteriorated by not being finely powdered after calcination. 
 You must then proceed to mix a small quantity of the powder with a 
 moderate quantity of water, upon a slate or slab, into a paste, with a 
 spatula or knife, and then form it into a ball by turning it between 
 the palms of the hands, when it will become warm, and if it be a good 
 water-cement it will not only set or harden in the heating, but if 
 put into a vessel of water will become more indurated. Good ce- 
 ment will harden under water, even if put in while wet, but it is 
 better to wait and let it cool a little before you put it in. 
 
 The setting of these cement balls will be greatly retarded by using 
 an excess of water in their mixture, the best proportion of which ap- 
 pears to be one-fourth part of water to one of cement. During the 
 process of setting, they always throw out a vapor so long as the heat 
 continues. 
 
 * ^ The Sheppy cement stone is usually found in boulders or round 
 nodules, and when dry is of a light brown color. 
 
 The Harwich cement stone is obtained in larger masses, and is 
 of a dark bluish brown color. When properly burned, the former is 
 of a light brown, and the latter of nut brown color. When the cal- 
 cined powder of each is mixed with water for use, both mixtures are 
 brown, but the former is much lighter than the latter, which approaches 
 to blackness. 
 
 Since cement from the kiln will not slake even with water, much 
 less by the action of the air alone, it might be preserved for a long 
 time in a dry room as I have proved by experiment ; but calcined ce- 
 ment being useless until pulverized, which process is always performed 
 by the manufacturer in a mill, in which state water and the atmo- 
 sphere is enabled to act upon it. 
 
 Calcined cement powder, when mixed up for use, recovers (like 
 
AiN^ALYSIS OF CEMENTS. 
 
 123 
 
 the lime mortars) in time the whole of the carbonic acid gas, pre 
 viously thrown off by the fire, and is brought back to its original chemi- 
 cal state. And old cements and mortars if re-burnt, calcined, and 
 pulverized to powder, will produce a material nearly as good as from 
 the natural stone. 
 
 ' ' Cement powder exposed to the air, especially if damp, also gradu- 
 ally recovers the carbonic acid gas, and becomes injured and eventually 
 spoiled ; for which reason it is always kept in tight casks or bags, but 
 when the cement becomes damaged or stale, it may be recovered or 
 converted into good cement by re-burning it, the practicability of 
 which may be ascertained by burning some stale cement powder in a 
 crucible, in a common fire-place ; but if any considerable quantity 
 should be required to be restored, it must be first mixed up with water 
 into balls or convenient sized lumps, and allowed .sufficient time to 
 set, or harden before being re-burnt. If, however, the cement-powder 
 should be too stale for this purpose, let a small portion of fine clay, 
 not exceeding one-tenth part (by measure), be added to it, in making 
 these lumps, which will cause them to hold together in the kiln, with- 
 out materially injuring the quality of the cement. 
 
 ''The most powerful water cements are like limes, partially decom- 
 posed by and soluble in water when first prepared for use, but the in- 
 jury is too insufficient to affect the solidity of structures in which it is 
 employed. 
 
 " Cement, soon after it is mixed or applied, throws out an efflores- 
 cence at first, as is observable in the fronts of buildings, when first 
 stuccoed therewith, and is considered a criterion of good quality. 
 This efflorescence, when viewed in the sun or a strong artificial light, 
 presents the appearance of bright crystals. 
 
 "Whilst water cements, and water limes are analogous in their 
 component parts, and general properties, there is great distinction 
 between them for the purposes of hydraulic architecture, inasmuch as 
 the settmg process at the surface comes so much sooner to perfection 
 in the former than m the latter, that the water which after this period 
 
124 
 
 ANALYSIS OF CEMENTS, 
 
 ceases to act perceptibly upon either, has not time to irjure the ex- 
 ternal joints of the cement, while it makes a considerable impression 
 upon the lime ; in this consists the chief difference between them, and 
 it constitutes their relative use and value. 
 
 " There are two properties of cement which ought to be fully under- 
 stood. 1st. That it only sets rapidly when made up in small parcels 
 or thin joints, as rapid induration takes place near the surface only, 
 extending slowly towards the centre, where it may remain imperfect 
 to a very long time. This property it has in common with lime mor- 
 tars and concrete. 2d. Cement is always weakened by sand, no 
 matter how small the proportion of that ingredient may be, so that 
 if both materials were equally cheap, it would be best to dispense with 
 sand altogether in using cement as mortar for building walls, but not 
 in using it as a stucco for incrustations. 
 
 ' ' With reference to the quantity of sand which should be mixed 
 with cement for constructive purposes, where strength and durabihty 
 are desired, both experience and experiments clearly show, that not 
 more than two measures of sand to one of cement powder ought to be 
 employed on any work, and that when very important operations are 
 involved, five parts of sand to four of cement powder ought to be used, 
 or what is better, an equal proportion of each ingredient, as too much 
 sand injures the cement by retarding its drying or setting, and ren- 
 ders it too friable ; but with limes it is different, for they will bear two, 
 three, or even more measures of sand to one of lime, without much 
 deterioration. Upon the whole, cement sets most quickly and unites 
 itself more powerfully to bricks or stones, when it is perfectly pure or 
 unmixed with sand, provided the joints be thin, that is, not exceeding 
 half an inch in thickness. 
 
 * ' The construction of the Thames Tunnel satisfactorily established 
 the character and superiority of the cement, and without the aid of 
 which the work could never have been carried on to completion, or 
 any lengthened period of durability assured. The foundation and 
 lower portions of the brick-work, having been laid in a compost 
 
ANALYSIS OF CEMENTS. 
 
 125 
 
 of equal proportions of cement and sand ; and the piers were built 
 with one measure of sand to two of cement, and the arch work with 
 pure cement only. 
 
 ^'Lime expands by admixture with water, and readily attaches 
 itself to the particles of sand, which increase the bulk and add much 
 to the strength, whereas cement does not expand, and is weakened by 
 the addition of sand ; and whilst one measure of good calcined lime 
 powder will take seven or eight measures of gravel to form a good 
 concrete, the cement will require three measures of it, to mix with 
 the above quantity of gravel or sand to produce concrete of an equal 
 property. Hence cement should never be used for making concrete. 
 But for the purpose of building brickwork, it is as well to mix the 
 cement with a moderate quantity of sand, as the cost of the work is 
 thereby diminished, and the joints will become quite as hard as the 
 bricks themselves. Pure cement should always be employed for the 
 most important works, or in particular portions of them, and it is in- 
 dispensable for the linings of cisterns or tanks, and the coating of 
 casemates, as it prevents leakage, and renders the latter perfectly 
 dry, but it cannot be depended upon for such like purposes if mixed 
 or adulterated with sand ; and great care must be taken in the appli- 
 cation of the cement, to have it firmly compressed and consolidated 
 when laid on, to prevent cracks or fissures ; the neglect of plasterers 
 in this precaution being the chief cause of the defects in exterior and 
 other incrustations where this cement is employed. This material 
 mixed with a due proportion of sand, and applied in a liquid state, 
 forms a most excellent groat." 
 
 ON BLACK ROCK OF QUEBEC. 
 
 '*At the suggestion of Capt. Baddeley, E.E., the author of the 
 treatise now under notice (Col. Pasley, K.E.), by order of the British 
 Government, made some experiments upon its character and qualifi- 
 cation as a water (or hydraulic) cement, and found its properties to 
 be very satisfactory, although it was comparatively very slow in sett- 
 
126 
 
 ANALYSIS OF CEMENTS. 
 
 ing, but in the end it acquired a very stony hardness. For tide work 
 he considered it would be necessary to mix it with boiling water to 
 expedite the setting." 
 
 ON ARTIFICIAL WATER CEMENTS AND ON THE ESSENTIAL 
 COMPONENTS THEREOF 
 
 "Natural water cements being chiefly composed of carbonate of 
 lime, silica, alumina and the oxides of iron, it appeared that 
 next to the carbonate of lime or chalk, which is indispensable, 
 silica and alumina were the most important ingredients, for these 
 together made a water cement without the iron, whereas the iron 
 never succeeded without them, notwithstanding which, it was of great 
 use, since it caused them to set more quickly, and at the same time 
 imparted a superior degree of compactness and hardness ; but in all 
 cases it is imperative that all the solid ingredients be well burned, 
 calcined and reduced to an impalpable powder, and the moist 
 ones must also be reduced to the finest possible state before being 
 burned." 
 
 In order to establish these facts the author undertook the following 
 experiments: — 
 
 Experiment 1st. Carbonate of lime, silica, alumina, with 
 other metallic oxides, with the addition of the peroxide of iron — these 
 occasionally formed a good cement, but the success of this mixture is 
 very precarious. The addition of the oxides of manganese or of red 
 lead always formed good cements with the same ingredients. 
 
 Exp. 2d. Carbonate of lime, silica, alumina, with the carbonate 
 of magnesia. On mixing measures of pounded chalk, two measures 
 of pipe-clay, aud from one to five measures of the carbonate of mag- 
 nesia together — the result was an excellent artificial cement. This 
 cement when moderately burned was of a handsome white color ; but 
 when burnt rather more, it assumed a darkish slate color, but in 
 either case it was equally good. 
 
ANALYSIS OF CEMENTS. 
 
 127 
 
 " Carbonate of magnesia is a highly favorable ingredient in water 
 cement, producing the same effect as protoxide of iron, or it may be 
 said to be superior to it, or to any other metallic oxide, inasmuch as 
 the carbonate of magnesia will sometimes combine with the carbonate 
 of lime, alone, into a good water cement, which none of the metallic 
 oxides are capable of effecting. 
 
 "Exp. 3d. Chalk and blue alluvial clay. This mixture of pounded 
 chalk and blue clay; of which the former ingredient supplies the 
 carbonate of lime, and the latter, the silica, the alumina, and 
 the protoxide of iron, was successful, and is here placed among the 
 quadruple compounds. Having tried various proportions of the above 
 ingredients, the following, which most resembles the Sheppy cement in 
 its qualities, was adopted, viz., five measures of chalk to two measures 
 of moist clay. Three measures of chalk to one of clay will also make 
 a good water cement, but not equal to the former proportions. An 
 excess of chalk such as three and a half, four or five to one, spoils 
 the mixture as a water cement," but converts it into a *^ water 
 lime." A smaller portion of chalk, on the contrary, such as two to 
 one, makes a very good water cement, and even one and a half meas- 
 m-e of chalk to one of clay, makes a good cement, but one that sets 
 slowly and with moderate heat, for as the quantity of chalk is diminish- 
 ed, so is the heat of setting, whilst the period required for that pro- 
 cess is prolonged." 
 
 CONCLUSIONS DRAWN FROM OTHER EXPERIMENTS. 
 
 That alluvial clay is brown at the surface, where it is exposed to 
 the air, and that this brown part will not form a water cement. That 
 blue clay fresh from a river, which forms an excellent ingredient for 
 an artificial water cement, loses this property when it becomes stale 
 by exposure to the air, which also deprives it of its color. 
 
 "That repeated washings spoil alluvial clay. 
 
 "That chalk and fine brown pit clay make a good cement. 
 
 **That tile-dust, slate-dust, and Euller's earth failed; and that as 
 
128 
 
 ANALYSIS OF CEMENTS. 
 
 none of these are plastic, which property seems necessary in clay as an 
 ingredient for a water cement — 
 
 *' That Fuller's earth is much improved, and rendered plastic by re- 
 peated washing. 
 
 "That hard stone if used as an ingredient for a water cement, 
 must be burned twice, first in its natural state, and afterwards mixed 
 with clay. 
 
 * ' That lime and clay burned separately failed in making an artifi- 
 cial cement, on immediate immersion, but may be useful for many 
 hydraulic purposes, though inferior both to the natural and artificial 
 cements." 
 
 Then follows a series of experiments to ascertain by what additional 
 substances, the best natural cements may be spoiled, from which the 
 following conclusions are deduced, viz. : — 
 
 "That salt is very prejudicial to brick earths. 
 
 "That the carbonate of magnesia was the only substance which 
 did not spoil the Sheppy cement. 
 
 " That the latter ingredient is itself a water cement, but a slow 
 setting one. 
 
 "That all the author's experimental cement which had succeeded 
 in setting under water, also resisted the severest frosts, quite as well 
 as the natural cements, after rigorous tests to which they were ex- 
 posed in the winter of 1829— 30. 
 
 "That the best cements, though perfectly 'frost-proof,' may be 
 injured by frost, if applied as stucco in an injudicious manner.'* 
 
129 
 
 VARIOUS RECIPES FOR CEMENTS, MORTARS, ETC. 
 
 FOR BUILDING AND INCRUSTATIONS. 
 
 A Strong mastic cement for coating walls, &c., is prepared as fol- 
 lows : 20 parts of clean river sand, 2 parts of litharge (red lead), and 
 1 part of quick-lime, mixed into a thin putty with linseed oil. 
 
 Dalits cement for covering fronts of buildings consists of linseed 
 oil, rendered dry by boiling with litharge, and mixed with porcelain 
 clay in fine powder, or pipe-clay well ground, and colored with ground 
 bricks or pottery. A little oil of turpentine added, to thin this ce- 
 ment, aids it in its cohesion to brick, stone, &c., 
 
 Hamlin's cement is composed of fifty measures of siliceous sand 
 fifty of lime marl, and nine of litharge, ground up with linseed oil. 
 This material has been in much use and repute in England and else- 
 where. 
 
 Leardefs (or, as it is commonly called, Adam's") oil cement or 
 stucco, is prepared in the following manner : for the first coat, take 
 21 pounds of fine whiting, or oyster shells, or any other sea shells cal- 
 cined, or plaster of Paris, or any other suitable calcareous material, 
 calcined and pounded; add white or red lead at pleasure, deducting 
 from the other absorbent materials in proportion to the weight of 
 the red or white lead added, to which put four quarts (beer measure) of 
 oil, and mix them together in a grinding mill, or in any levigating 
 machine, and afterwards mix and beat up the same, well, with 28 
 quarts of sand or gravel, or of both, mixed and sifted, or of 
 pounded stone or marble, or any solid and suitable material. 
 
 For the second coat, 16 ^ pounds of superfine whiting, or oyster 
 
 shells, &c., as for the first coat, 16 ^ pounds of white or red lead, 
 
 6 \ quarts of oil, and mix them together as before described ; add 30 
 
 quarts of fine sand, gravel, &c., as before noted, and mix and beat them 
 
 up well together ; varying the proportion of sand or gravel, &c., as the 
 6* 
 
130 
 
 VARIOUS RECIPES. 
 
 nature of the work may require. In preparing this composition the best 
 linseed or hempseed or other proper oils, suited for the purpose, must be 
 employed, either boiled or raw, with such drying ingredients as the 
 nature of the work, climate, season, or other circumstances may de- 
 mand ; and in some cases, bees-wax may be substituted for oil. All 
 the absorbent and solid materials must be kiln-dried. 
 
 Tliis cement is applied in the usual manner, but previous to laying 
 it on, it may be proper to wet the surface on which it is to be laid, 
 with the same sort of oil and other ingredients which have passed 
 through the levigating machine, reduced to a more liquid state and 
 applied with a brush, in order to make the composition adhere the 
 better. 
 
 This composition admits of being modeled or cast in molds in the 
 same manner as statuaries, plasterers, &c., model or cast their stucco 
 work. It also admits being painted upon, and adorned with land- 
 scapes, figures, &c. 
 
 A good cement is prepared from equal quantities of powdered glass, 
 sea-salt, and iron filings, mixed with burnt loam, which becomes very 
 hard and durable. 
 
 Beavari's mortar, or building cement, is composed of marble, flint, 
 chalk, lime and water, and when dry is capable of a high polish. Its 
 proportions are, equal parts of marble, flint and chalk ; pulverized, 
 mixed together, and passed through a very fine sieve ; add to this one 
 part of lime which has been slaked three months, and sufiicicnt water 
 to make the whole into a thin paste ; and in this state it is to be ap- 
 plied over a coai'se ground (or previous coat), as thin as possible, and 
 rendered smooth on the surface ; and when dry may be polished by 
 Venetian talc. If buildings are to be covered with it, a preparatory 
 rough ground should be attached, formed of river sand and lime. 
 
 Venetian cement, used in the Italian provinces for covering floors, 
 terraces and roofs of houses, the secret of which is not precisely known, 
 is believed to be compounded of plaster of Paris, sulphur, resin, pitch, 
 and spirit of turpentine, or wax, mixed and applied hot. 
 
VARIOUS RECIPES. 
 
 131 
 
 Smeatori's cement, used in the construction of the far-famed Eddy- 
 stone lighthouse, in the British Channel, was composed of equal quan- 
 titias of Puzzolana and Aberthaw lime ; this mixture was calculated 
 as best able to withstand the utmost violence of the wa\es which are 
 continually beating, and oftentimes with violent shocks, the substruc- 
 ture of the building ; and truly has that conjecture been verified by 
 the test and experience of many years and sundry storms. 
 
 Two bushels of slaked Aberthaw lime, one bushel of Puzzolana, and 
 three of clean, sharp sand, will form a good water-cement. 
 
 Dutch trass, terras, or tarras, or as sometimes called in Holland, 
 wakke, is a basaltic mineral, found in the Low countries, and abun- 
 dantly used in the construction of mounds, weirs, and other aquatic 
 works. This celebrated mortar is made by covering a previously pre- 
 pared mass of quick-lime of about a foot in thickness (and sprinkled 
 with water), with an equal quantity of powdered terras, and then left 
 for two or three days, after which, the quantity required for imme- 
 diate use is separated from the bulk, and beaten up to a pro]:>er 
 consistency. 
 
 One measure of quick-lime, and two of slaked-lime, in powder, and 
 one of terras, well mixed and beaten together to the consistence of 
 paste, with as little water as possible, forms the terras mortar in 
 general use ; and a cheaper kind is made by mixing two parts of 
 slaked lime, one of terras, and three of coarse sand together. These 
 cements indurate very quickly under water and remain very firm. 
 
 The trifa stone, which, when ground, forms trass or terras, con- 
 tains 57.0 silica, 16.0 clay, 2.6 lime, 1.0 magnesia, 7.0 potash, 1.0 
 soda, 5.0 oxide of iron and titanum, and 9.6 water; it is found abun- 
 dantly in the north of Ireland, among the schistoze formations on the 
 banks of the Rhine, and at Manheim in Bavaria. 
 
 The fatter the lime, the less of it must be added to the trass to 
 make hydraulic cement ; the mixture should be made extempora- 
 neously, and kept dry till used. When it hardens too soon (as in twelve 
 hours) it is apt to crack, but if it takes six or eight days to indurate, it 
 
132 
 
 VARIOUS RECIPES. 
 
 is better ; through the medium of water, silicates of lime, alumina, 
 clay, and the oxide of iron are formed, which soon become hard . 
 
 " Beside the two volcanic products just described, all lime-stones 
 which contain from 20 to 30 per cent of silica are fitted for hydraulic 
 cements ; but much depends upon the proportion of silica present, and 
 the physical structure of all the constituents. 
 
 Meagre or poor lime-stones are best suited for hydraulic mortar, 
 such as contain from 8 to 25 per cent, of foreign matter, such as sili- 
 ca, alumina, magnesia, &c. ; these, though calcined, do not slake when 
 wetted ; but when pulverized, will absorb water without heat or swell- 
 ing, and form a paste which will harden under water in a few days, 
 but will never become greatly indurated by simple exposure to the air. 
 
 All sorts of lime can be made hydraulic by mixing slaked lime with 
 solutions of common alum, or sulphate of alumina; but the best 
 method consists in employing a solution of silicate of potash (called 
 liquor of flints, or soluble glass), to mix with the lime, or lime and 
 clay. Also by adding silica and alumina, or merely the former to 
 good fat lime, a water-cement may be artificially formed ; and like- 
 wise by adding to lime or other natural productions which contain sili- 
 cates — puzzolanas, trass, pumice-stone, basalt, trifa, slate clay, &c. 
 
 Ground felspar, or clay, if previously calcined with the lime, will 
 form an hydraulic cement. 
 
 Beton (French), used for constructing marine works, consists of 12 
 parts of puzzolana, or Dutch trass, 6 parts of sand, 9 parts of un- 
 slaked lime, 13 parts of stone fragments, about the size of an egg, 3 
 parts-of tile dust, cinders or scales from a forge ; the whole well worked 
 and beaten together. 
 
 A composition for incrustations may be formed of lime-stone, road- 
 drift, sand, or similar substances, with the powder of burnt-bones ; 
 these ingredients are to be powdered, mixed together and heated in 
 an oven, and while hot to be mixed with one-fourth part of tar^ 
 pitch, or resin, and applied warm ; this will be found a good covering 
 for ro(;fs, floors, terraces, &c. 
 
VARIOUS RECIPES. 
 
 133 
 
 Plaster of Paris, with an admixture of one tenth part of rust of 
 iron, or iron scales or filings, makes a water-cement which sets very 
 quickly and is of great hardiess, and if boiled potatoes be incorpora- 
 ted mth mortar of lime and sand or with mortar containing burnt 
 clay, these compositions will be much improved. 
 
 A composition said to equal Roman cement is made by dissolving 
 three pounds and a half of sulphate of iron, and mixing them with a 
 bushel of lime, and half a bushel of fine gravel sand, previously made 
 into mortar. 
 
 Parker's Roman cement, for incrustations and general building pur- 
 poses, is a composition forming an artificial stone, and being imper- 
 vious to water is very valuable. This material, when incorporated 
 with an equal quantity of clean sharp grit sand, well beaten up with 
 a suflficiency of water, and applied quickly, forms a handsome and 
 durable covering for fronts of houses ; and one bushel of the cement, 
 with the addition of sand, &c., is considered sufficient to cover about 
 four square yards of surface. 
 
 Ancient MaUha. The Roman and Greek architects gave the term 
 of maltha to a calcareous cement used as stucco, and this and the 
 term mastic are given to various compositions. 
 
 The mixture of milk with lime and sand is said to have constituted 
 the maltha of the Greeks ; and we learn from Pliny, that Roman 
 maltha was made by mixing fresh-burnt lime, slaked with wine, and 
 beaten in a mortar, with hog's lard and figs. This composition is re- 
 ported to possess great tenacity, and acquires the hardness of granite. 
 
 Another kind was made of powder of slaked lime, mixed with bul- 
 lock's blood and powdered scales of the gray oxide of iron. 
 
 Previous to applying the maltha, the surface of the wall or ceiling 
 was smeared over with oil to make the composition adhere. 
 
 Dr. Shaw gives the following particulars of a species of maltha 
 which the inhabitants of Tunis and of other places in Africa use for 
 incrustations, &c. One measure of sand, two of wood-ashes, and 
 three of sifted lime powder are mixed together with a very little water, 
 
134 
 
 VARIOUS RECIPES. 
 
 and after this mixture has been well beaten, a little oil is added ; the 
 beating is then resumed, and continued for three or four days occas- 
 sionally, during which, the proper degree of softening is preserved by 
 alternately adding small quantities of water and oil. In a short time 
 after its application it acquires the hardness of stone. 
 
 A cement of a gray color, found upon examination to be composed 
 of an admixture of unslaked lime, pulverized charcoal, and powdered 
 sandstone, was discovered in the construction of a mausoleum of some 
 of the Tartar princes. The spaces between the bricks were about an 
 inch broad, and the cement had acquired such a solid consistence 
 that it was found easier to break the well-burnt bricks than to separ- 
 ate or detach the cement. 
 
 A composition for mouldings, &c., is prepared from two pounds of 
 powdered whiting, one pound of glue, mixed with half a pint of oil, 
 and thoroughly incorporated in a metal vessel by means of heat, and 
 then well beaten on a stone with whiting, till it has acquired the 
 necessary consistence and toughness. It is kept under moist cloths 
 until used. The ornaments or mouldings when cast and dry are 
 affixed to the surfaces by means of glue or white lead. 
 
 A delicate cement for small work, is made by heating a pint of 
 milk to the boiling point, and adding vinegar till the curd separates, 
 then straining off the whey, which must be beaten up with the whites 
 of four or five eggs, gradually adding the whey again. When the 
 whole is well mixed, sifted quicklime is to be stirred in until the 
 consistence becomes like a thick paste. The prepared liquid 
 alone may be kept, if closely corked up, but the lime must only 
 be added when required for use. This composition resists the ac- 
 tion of fire and water, and is chiefly used to replace deficiencies 
 in small works, and to fasten fragments together, which it unites 
 firmly. 
 
 A cement for stopping holes and cracks in marble or stone, and for 
 veneering marble, for inlaying and mosaic work, is made of a pound 
 of bees-wax, sliced, melted with a quarter of a pound of resin, powder- 
 
VARIOUS RECIPES. 
 
 135 
 
 ed, to which add an ounce, each, of chalk and brick-dust, both finely 
 powdered, the whole to be well boiled and mixed up together. This 
 cement must be used hot, and the substance to which it is applied 
 must be previously heated. 
 
 The cold cement for the like purpose or for mending earthenware, 
 &c., and which is reckoned a great secret among workmen, is made 
 by grating a pound of old Cheshire cheese, with a bread grater, into 
 a quart of milk, in which it must remain fourteen hours, stirring it 
 frequently, a pound of unslaked lime in powder must then be added, 
 and the whole well-beaten up, and finally add the whites of twenty or 
 thirty eggs, beaten up with any coloring matter desired, and let the 
 whole be well mixed and beaten up together. 
 
 The hot cement is made of resin, beeswax, brick-dust, and 
 chalk boiled together. The bricks or other substance to be united, 
 must be heated, and their surfaces rubbed together with the cement 
 between them, as carpenters make a glued joint in boards. 
 
 FrosVs water cement is composed of carbonate of lime, calcined at 
 a heat not exceeding that at which cast-iron softens, and cooled 
 without access of atmospheric air or moisture, acquires the property 
 of quickly hardening under water, and mixed with silicious sand and 
 water, forms an artificial Puzzolana, or Roman cement. 
 
 Dohhs' ce77ient for water-proof purposes, is composed of carbonate 
 of lime (burnt as for common plaster) mixed up with water, clay 
 loam, shale, road drift, metallic oxides, ores, sand, or any other 
 earthy substance which will bear a sufficient heat for calcination. The 
 whole of these ingredients are then to be reduced to a fine powder, 
 mixed with a water, and left in proper vessels till it has subsided. 
 The water is then to be poured off and the plastic materials formed 
 into square pieces and dried, after which they are to be subjected to 
 the heat of a lime-kiln or stove, and lastly mixed with the lime and 
 water for the intended purposes. 
 
 A good incrustation cement is made with one hundred parts of 
 quick lime, five of white or colored clay, and two of yellow ochre; it 
 
136 
 
 VARIOUS RECIPES. 
 
 forms a cement which is tenacious, and remains unchangeable when 
 exposed to the weather. The process of its manufacture is thus : The 
 lime must be first slaked with a small quantity of water, more of 
 which must afterwards be added till of the consistence of cream. 
 White clay is at the same time mixed to a similar condition, and 
 after remaining some time apart, the two solutions are carefully 
 mixed together. During the continuance of this mixture in a tub 
 for twenty-four hours, it should be frequently stirred, and a portion 
 of yellow ochre added to give it an agreeable color. Walls covered 
 with this cement have remained exposed to the weather for years, 
 without injury. 
 
 M. Berthier is of opinion that with one part of common clay, and 
 two parts and a half of chalk, a very good hydraulic lime may be 
 made which will set as quickly as Parker's cement. He concludes 
 that a lime-stone, which contains six per cent of clay, affords a mor- 
 tar precisely "hydraulic." 
 
 Lime possessing from fifteen to twenty per cent of clay, is very 
 hydraulic, and when from twenty-fiA^e to thirty, it sets almost instant- 
 ly, and may therefore be held to be a perfect Roman cement. But 
 an argillaceous lime-stone, which, when slaked, increases its bulk from 
 one to three parts in ten, and which when in the form of slaked paste, 
 will take from one hundred to one hundred and sixty measures 
 of sand, will afford at a moderate cost, a cement well fitted to 
 resist atmospheric changes, and constant exposure to a running 
 stream. 
 
 A little manganese added to mortar imparts the property of hard- 
 ening under water, and lime-stone is frequently found combined 
 with this mineral, which gives it a brown color when burnt. 
 
 The essential constituents of all good hydraulic mortars are caustic 
 lime and silica, the hardening of which under water merely consists 
 in their chemical combinations, through the medium of water, pro- 
 ducing a hydrated silicate of lime. Quartoze sand, however finely 
 powdered wiU form no water mortar with lime, but if the powder be 
 
VARIOUS RECIPES. 
 
 137 
 
 ignited by the lime, it will be rendered fit for hydraulic works. 
 
 Bituminous Ime-stone dried, ground, sifted, and mixed, with about 
 its own weight of melted pitch or coal tar, may, when in a semi-fluid 
 state be moulded into blocks or slabs, and be applied for floors of ter- 
 races, balconies, roofs of houses, or linings of tanks and reservoirs, 
 conduits, drains, &c., but when laid, the joints must be run together 
 with hot irons. The terrace floor must be previously covered with a 
 layer of plaster-of-paris or common mortar, laid to the required slope 
 or level, about an inch to the yard. It weighs about 144: lbs. to the 
 cubic foot, consequently one foot square, and one inch thick will 
 weigh 12 lbs. 
 
 RECIPES 
 
 FOR MANUrACTURING AND DOMESTIC PURPOSES. 
 
 Iron-rust cement : 100 parts of iron borings or filings, powdered 
 and sifted, and mixed with one of sal-ammoniac, and when applied 
 must be mixed and well incorporated together, with as much water as 
 will give it a pasty consistency ; or 4 parts of fine borings, 2 parts of 
 potter's clay and 1 of powdered potsherds, mixed as above. This ce- 
 ment is good for making joints &c., to ironwork, and if allowed to 
 concrete slowly becomes very hard. 
 
 Plumber's cement : 1 part of black resin and 2 parts of pulverized 
 and sifted brick-dust, well incorporated together with a melting heat. 
 
 Coppersmith's and engineer's cement: Boiled linseed oil and red 
 lead, mixed into a putty ; or bullock's blood and quick-lime. 
 
 Diamond cement, for mending china, glass, porcelain, &c., is com- 
 posed of isinglass, soaked in water till soft, then dissolved in proof- 
 spirit, to which are added a little gum-resin, ammoniac, or galbanum, 
 and resin mastic, each being previously dissolved in a minimum of 
 alcohol ; and when applied must be gently heated, in order to liquify 
 it^ and when not required should be kept in a well-corked bottle. 
 
 Other cements for the like purpose : Gum shellac dissolved in alco- 
 hol^ or in a solution of borax, makes a good cement. 
 
 White of eggs (albumen), mixed with finely powdered quick-lime^ 
 
138 
 
 VARIOUS RECIPES. 
 
 forms a good cement for joining substances which are not exposed to 
 much moisture. 
 
 Skim milk cheese^ cut in slices, and boiled to a gluey consistence in 
 a quantity of water, and then incorporated with quick-lime on a slab 
 with a muller ; is applied to mend broken stone-ware, and when cold 
 unites very firmly. 
 
 Melted brimstone (sulphur) used either alone or mixed with resm 
 and brick-dust, makes a tolerably good and cheap cement. 
 
 Jeweller s cement is composed of resin, beeswax, and finely sifted 
 brick dust, and is in use amongst goldsmiths, jewellers and engravers, 
 to fix metals, stones, &c., to be engraved or operated upon, firm to 
 the block. 
 
 Carpenter^s cement : Take equal quantities of pounded resin and 
 beeswax, mixing them together over a slow fire, during which pro- 
 cess add as much powdered chalk, yellow ochre, or burnt ochre, as will 
 produce the required color, and when well incorporated together, ap- 
 ply hot ; or — 
 
 Take fine saw-dust of the wood you wish to imitate, and macerate 
 it in water for two or three days ; then pour ofi* a part of the water, 
 and boil the residue until it becomes smooth and pulpy. Keep it well 
 covered up for use, and when required, mix as much glue with it as 
 necessary. These cements are very useful for stopping up flaws in 
 wainscotting, and for other purposes. 
 
 A cement for fixing mouldings, fillets, ornaments, &c., can be made 
 by dissolving isinglass, and adding glue to it which has been soaked 
 twenty-four hours, and straining the compound through a fine sieve, or 
 coarse cloth. 
 
 A cement for closing and repairing pipes of subterraneous aqueducts, 
 is composed of pulverized tobacco-pipe clay, mixed with a large quan- 
 tity of pulverized flocks, tempered with linseed oil, and well beaten 
 into a stiff" paste. 
 
 A cement for fastening the receiver of an air-pump to a metallic 
 plate, is made with equal parts of beeswax and turpentine (for winter 
 
VARIOUS RECIPES. 
 
 139 
 
 use), or three parts of beeswax to two of turpentine, for summer use. 
 
 ChemisVs cement, for repairing chemical glasses or vessels, and 
 which will bear the fire, is made with equal quantities of wheat flour, 
 fine powdered Venice glass, pulverized chalk, with half the quantity 
 of fine brick-dust, a little scraped lint, and the whites of eggs, well 
 and properly incorporated together. This mixture is to be spread 
 thinly but evenly on linen cloth, and then applied to the fractured 
 parts of the glass, and the whole should be well dried before subjected 
 to fire ; or old varnish is said to answer the same purpose. 
 
 Electrical cement, for electrical purposes, is compounded of two 
 pounds of resin, two of beeswax, and one of powdered red ocher, the 
 whole mixed and melted together, and kept close for use; or five 
 pounds of resin, one of beeswax, one of red ocher, and two table-spoon- 
 fuls of plaster of Paris, well melted together. 
 
 A bituminous cement : Sixteen parts of whiting, sifted and 
 thoroughly dried by a white heat, the like quantity of black resin, and 
 one part of beeswax, to be added to the former ingredients while cool, 
 stirring the whole together while cooling, 
 
 A cement for uniting voltaic plates and wooden troughs, is com- 
 posed of six pounds of resin, one of red ochre, half a pound of plaster 
 of Paris, and a quarter of a pound of linseed oil. The ochre and 
 plaster of Paris must be previously calcined, and added to the other 
 ingredients when in their molten state, and the thinner the stratum 
 of cement applied, the stronger will be the joint. 
 
 Statuary^s cement, for joining alabaster, marble, porphyry and 
 other stones, is prepared as follows : Melt two pounds of bee's wax 
 and one pound of resin together ; add one pound and a half of the 
 same material, pulverized, as the body to be cemented is composed 
 of, and stir them well together ; let the mass be warmed together, and 
 when applied, the body or matter to be cemented, should be heated. 
 The required color can be obtained by varying the proportions of the 
 powdered matter, and the mass of bee's wax and resin. 
 
 Steam cement. This is not only useful for cementing different 
 
140 
 
 VAKIOUS RECIPES. 
 
 parts of hydraulic and steam engines, but also for repairing broken 
 stone, &c. It consists of boiled linseed oil, litharge, and red and 
 white lead, mixed to a proper consistence, aud applied on each side of 
 a piece of flannel previously cut to the shape of the joint of iron or 
 other substance, and put between the pieces before being screwed to- 
 gether, or hammered, or brought home" as the workmen term it. 
 By this means a close and durable joint is made. Care must be taken 
 not to leave the mixture too thin with oil, and as the white lead does 
 not dry so quickly as the red, more of the latter ought to be used. 
 When the fittings will not admit the substance of flannel, linen, paper 
 or thin pasteboard, may be substituted. 
 
 The following cement answers well for joining broken stones of the 
 largest kind, and stone joints set with this, never leak or want future 
 repairs ; and if the stone be thick, not more than an inch next the 
 water need be filled with the cement, the rest may be done with com- 
 mon mortar : Two ounces of sal-ammoniae, one ounce of flower of 
 sulphur, and sixteen ounces of cast-iron filings or borings; mix them 
 in a * ' mortar, " and keep the powder dry. When this cement is 
 wanted, take one part of the above, to twenty parts of clean iron 
 filings or borings, and mix them intimately, and beat to a powder in 
 a mortar. When mixed to a proper consistence with water, apply it 
 with a wooden or iron spatula. 
 
 This is the cement used in the filling-up and clasping the joinings 
 of Southwark cast-iron bridge, built over the river Thames (Lon- 
 don) by the late Sir John Rennie. The chemical action of all these 
 ingredients on one another causes the whole to unite in a hard homo- 
 genous mass. 
 
 Flooring cement may be made of two-tlyrds of lime, and one of 
 coal-ashes, well sifted, added to a small quantity of clay; then mix the 
 whole together with water, temper well, and make into a heap, let it 
 remain for a week or ten days, then temper again, heating it until it 
 acquires a proper tenacity and consistency. 
 
 The surface upon which it is to be applied being made perfectly 
 
VAKIOUS RECIPES. 
 
 Ul 
 
 level or smooth, lay the composition on, about two and a half or three 
 inches thick, working it smooth with a trowel. If a better floor be 
 required for superior apartments, cover this first layer with another, 
 made of the lime of rag-stones, well tempered with whites of eggs, 
 laid on about half an inch thick, before the first covering or layer be- 
 comes too dry. 
 
 When the whole is thoroughly dried, and rubbed with a little oil, 
 it will be as smooth as polished marble. This cement is also adapted 
 for roofs and walls. 
 
 RECIPES. 
 
 The following recipes are from Colonel Fanshawe's memoranda, 
 and remarks on hydraulic mortars, descriptive of different sorts used 
 at Water Point, Gibraltar, in the year 1790 — 1 : — 
 
 1st. Coal-ash mortar. This consisted of lime two and a half 
 measures, sand two and a half, coal-ashes two and half, Puzzolana 
 one and a half, and smith's cinders one and a half, the proportion of 
 lime to the other ingredient, thus being one to three and a half. 
 
 2d. Dutch terras mortar. This was formed of equal parts of 
 lime and trass, by measure. 
 
 3d. Puzzolana mortar, which consisted of the like propor- 
 tions of lime and Puzzolana. 
 
 4th. Puzzolana mortar for lining cisterns and coating 
 the roofs of casemates. This consisted of slaked lime sixteen 
 measures, Puzzolana eight, sand five and a quarter, beaten glass four, 
 and smith's cinders four, the proportion of lime to the other ingredi- 
 ents being as one to one and two-thirds nearly. 
 
 notes on puzzolana. 
 
 Col. Pasley draws the following inferences from various experiments 
 upon the effects of Puzzolana, when mixed with other cementitious 
 matters. 
 
 1st. That Puzzolana is very injurious to cement. 
 
142 
 
 PUZZOLANA, 
 
 2d. It imparts to chalk-lime the important property of setting un- 
 der water and to increase its adhesiveness to a moderate extent when 
 mixed in the proportion of two measures of Puzzolana powder to one 
 of lime paste ; but it increases the resistance of this lime in a most 
 extraordinary degree, nearly six-fold, rendering it in seventeen days 
 nearly double of the resistance of the best concretes and mortars made 
 of the same lime, mixed with gravel and sand alone, though eight to 
 twelve months old and upwards. 
 
 3rd. That the effect of Puzzolana on common chalk lime, mixed 
 with sand, is highly beneficial, the usual proportion of the powder 
 employed is one measure to one of lime, combined with various pro- 
 portions of sand, for which Smeaton's rule, that the latter shall not 
 exceed two measures, when the lime alone, without the Puzzolana, 
 will bear three measures of sand, is probably the most judicious. By 
 our experiments, it appears that one measure of sand to one of Puzzo- 
 lana powder, and one of chalk-lime paste, produces the strongest 
 Puzzolana mortar with that species of lime ; that one additional 
 measure of sand diminishes the adhesiveness of this mortar in a slight 
 degree, not exceeding 10 per cent., but that it diminishes the resist- 
 ance by 60 per cent. 
 
 4:th. Its effect upon a strong hydraulic lime, such as Blue Lias lime, 
 is to increase its adhesiveness, and when mixed in the proportions of 
 two measures of the Puzzolana powder to one of lime, it increases its 
 resistance also, but one measure of each would be the utmost propor- 
 tions that could be recommended in practice. 
 
 5th. Its effect upon a weak hydraulic lime is favorable, and for 
 works under water it would not be prudent to use such limes without 
 an admixture of It. 
 
 M. vicat's rules for judging of the quality of natural 
 
 OR ARTIFICIAL PUZZOLANAS. 
 
 He recommends testing them by acids, and in water, and observes : 
 1st. That those which are not acted upon by acids, and have no action 
 
PUZZOLANA. 
 
 143 
 
 on lime-water, are inert. 2d. That those which are moderately acted 
 upon by acids, and which act very moderately in lime-water, have 
 little energy. 3rd. Those which are powerfully acted upon by acids, 
 and which are very active in lime-water, are energetic. 
 
 M. Baggi, of Gottenburgh, made use of a very hard, black, 
 schistous rock, which he burned until it lost its hardness, and after- 
 wards pulverized it, in which state it made, when mixed with lime, a 
 good hydraulic mortar. 
 
 Count Chaptal calcined the ochrey clays of Languedoc, (France,) of 
 which he made an excellent artificial Puzzolana ; and subsequently 
 M. Mason experimented upon the same description of clay, and con- 
 verted them into Puzzolanas, which were tried as "betons," by sink- 
 ing casks filled with them in the Seine, and which, after six months' 
 submersion, were found to be extremely hard. 
 
 General Treussart states that a mixture of common lime with 
 sand and brick-dust (pounded brick is probably meant), in equal parts, 
 forms a hydraulic mortar requiring a breaking weight of from 221 to 
 331 lbs. avoirdupoise, which he considers sufficient for general pur- 
 poses, but for more important works he thinks that a resistance of 
 from 331 to 441 lbs. is desirable, for which purpose the clays suited for 
 potteries should be selected, which are to be treated by burning, &c., 
 as before described. 
 
 He also remarks that artificial Puzzolana, formed of bricks exposed 
 to a draft of air while being burnt, will set in three or four days, 
 whereas, that formed of similar bricks, equally well burned, but not so 
 exposed, may not set for ten, twenty, or even thirty days, and yet 
 may form good hydraulic mortars in time. He says that he has ob- 
 served, that the strength of artificial Puzzolana may generally be 
 judged by its quickness in setting. 
 
 He also tried other experiments upon trdss^ and found that mortar 
 made of one measure of common lime, mixed with two measures of 
 sifted trass, was nearly twice as strong as the mortar made of the 
 same lime, mixed with coarse trass in the same proportion, their re- 
 
144 
 
 COMPOSITION OF MORTAR. 
 
 sistence being 463 and 232 lbs. respectively ; and he also ascertained 
 that wetting trass did it little or no harm, and he is of opinion, that 
 neither trass nor any sort of artificial Puzzolana nor natural Puzzolana 
 can possibly be injured by exposure to the weather. 
 
 M. vicat's opinion of the best combination of various limes 
 
 WITH other ingredients FOR THE COMPOSITION OF 
 MORTAR. 
 
 In order to obtain hydraulic mortars capable of acquiring great 
 hardness under water, or in situations always moist, he recommends 
 weak hydraulic limes to be combined with energetic Puzzolanas, and 
 that hydraulic limes may be combined with Puzzolanas of little energy, 
 but that first-class hydraulic limes may be mixed with inert substances 
 such as sand, whether siliceous or calcareous, and also with the slag 
 of forges, &c. 
 
 To obtain mortars or cements capable of acquiring great hard- 
 ness in the open air, and to resist rain, heat, and severe frosts, ne is 
 of opinion, that fat limes are unsuited for such purposes, nor can weak 
 hydraulic limes accomplish it in a satisfactory manner, but that or- 
 dinary and eminently hydraulic limes will succeed if mixed with any 
 clean sand, quartoze dust or with the powder of hard lime-stones or 
 other inert substances. 
 
 Of mortars to be used under water he says that the proportions 
 of sand and other ingredients used with different sorts of lime, must 
 vary according to circumstances, but as a general rule he states that 
 arenes psammonites and clai/s will do with a smaller proportion of lime 
 than other substances generally, for in measuring them in the state 
 of dry powder, they require of fat lime-paste, slaked by the common 
 method, from 15 to 20 per cent ; of moderate hydraulic lime from 20 
 to 25 per cent ; and of hydraulic lime, from 25 to 30 per cent. That 
 the energetic or very energetic Puzzolanas require, under the same 
 circumstances, of fat lime from 30 to 50 per cent, and of moderate 
 
VICAT'S MODE OF MAKING LIME. 
 
 145 
 
 hydraulic lime from 40 to 60 per cent ; and that silicious any calcare- 
 ous sands require of hydraulic or eminently hydraulic lime from 50 to 
 66 per cent. As a general rule it is better to err by using too much, 
 than too little lime in such mixtures, for excess of lime causes them 
 to adhere better to stone, but if to be used alone, then the just propor- 
 tions attain the greatest induration. 
 
 M. vicat's mode op preparing artificial hydraulic 
 
 LIMES. 
 
 Wherever good hydraulic limes are to be found on the spot, or can 
 be procured at a moderate expense, M. Vicat recommends using 
 them, but when only common limes or inferior hydraulic limes 
 are to be found, he converts them into water-setting limes, by the fol- 
 lowing process: — 
 
 Burn the lime in the usual manner, and let it slake or fall down 
 into powder by spontaneous slaking in the air under cover, then mix 
 the slaked lime with a certain quantity of gray or brown clay, or sim- 
 ply with brick earth into a paste with water, and form it into balls, 
 which are to be first dried and then baked in a kiln. He gives the 
 following proportions of clay to be used . — 
 
 Very fat common limes, such as absorb a great quantity of water 
 in slaking, and which are pure or nearly so, as common chalk, will bear 
 20 per cent of clay ; for middling limes 15 per cent is enough, but for 
 limes having hydraulic properties 10 or even 6 per cent may suffice. 
 When the proportion of clay is increased to 33 or 40 per cent, the 
 lime obtained does not slake, but it is easily pulverized, after which 
 when moistened, it forms a paste which sets very quickly under water. 
 When the clay is mixed V^ith stones or gravel, it must be washed, and 
 the fluid mixture stirred up and made to flow over the vessel into an- 
 other receptacle to subside ; and when sufficiently dry, mix the 
 liquid clay with slaked lime powder, in which state it will be found 
 more convenient than if it were stiffer. 
 
 7 
 
146 
 
 ROOFS AND FLOORS. 
 
 RESULTS AND INTEREWCES OBTAINED FROM EXPERIMENTS, 
 
 From the experiments on lime and lime mortars (before de- 
 scribed), combined with those previously tried on cement, the follow- 
 ing inferences may be drawn : — 
 
 1st. Of the effects of sand and of Puzzolana on cement. Sand 
 in all cases dimishes the strength of cement, whether as estimating 
 its adhesiveness, its resistance or its water setting powers. Puzzolana 
 is still more injurious to it than sand, as was found by a series of ex- 
 periments to ascertain this point. In short every extraneous sub- 
 stance, excepting the carbonate of magnesia, which is far too expen- 
 sive to use for building purposes in this country, (found abundantly in 
 one part of India, and consequently, cheap) injures, and when added 
 in a certain excess, entirely ruins cement. 
 
 2ndly. Of the effects of sand on common chalk lime, or weak 
 hydraulic limes, such as the Hailing lime. Sand appears rather to 
 diminish the adhesiveness of chalk lime, but slightly to increase that 
 of Hailing lime, in either case the difference being insignificant. Its 
 effect upon their resistence is more marked, especially upon that of 
 chalk lime, which it nearly doubles, whilst it only increases that of 
 Hailing lime by one-half. 
 
 3rdly. Of the effects of sand on strongly hydraulic limes, such as 
 the blue lias. It appears to increase both their adhesiveness and 
 their resistance in a slight degree, and blue lias lime does not appear 
 to be materially injured by an admixture of three parts of sand to 
 one of lime, although two of sand to one of lime is found to make 
 the best mortar. 
 
 ON THE CONSTRUCTION OF WATER-TIGHT ROOFS 
 AND FIRE-PROOF FLOORS. 
 Water-tight roofs are constructed with two or three courses of plain 
 tiles, which are about lOJ inches long, 6 J broad, and f of an 
 inch thick, and weigh about 2 J lbs. each ; they are laid in cement 
 
ROOFS AND ELOORS. 
 
 147 
 
 upon flat beams or rafters, placed about 4 feet apart, crossed by trans- 
 verse battens, 2 inches by three inches, at intervals of 11 inches, from 
 centre to centre; the joints of each course of tiles are broken, and the 
 upper covering should be about an inch thick. The roof must have 
 sufficient fall to carry off the rain, &c., and if iron bearers are substi- 
 tuted for timber, it would be better. 
 
 Mr. Frost contrived an ingenious method of forming fire-proof 
 floors and roofs with square earthenware tubes measuring external- 
 ly 2 J inches square and 1. foot long. Two courses of these were 
 laid in pure cement at right angles to each other, and formed a floor 
 from 8 to 10 feet wide, and which was considered safe for any number 
 of persons to walk upon. In consequence of its tubulated form it is 
 reckoned much stronger than if made of plain tiles, or any sort of 
 plain flat tiles of equal weight. The tubes are so arranged as to break 
 joint with one another in both courses, and a coat of cement stucco is 
 applied both above and below, which completes and strengthens it- 
 They are turned in flat arches on iron beams or bearers, at 8 or 10 
 feet apart. 
 
 Fire-proof ceilings or roofs are constructed in like manner with arch 
 pots, which are made square at top and round at bottom, the side of 
 the upper square and the diameter of the lower circle being equal, 4 
 f inches, and from 5| to 8 inches high, having the sides and bot- 
 tom screwed, and a small hole in the top to receive the cement and 
 form a key thereto : the smaller ones weigh about 2 1 lbs., and the 
 larger about 4J lbs. 
 
 Ceilings of this description were formed over the basement of the 
 Treasury buildings, Whitehall, at Buckingham Palace, the Senior 
 United Service Club, and the National Gallery, London. Various 
 experients, such as pieces of bricks, or half pots broken down the 
 middle, alternating with the regular arch-pots, were used, in order to 
 obtain proper bond at the springing of the arches, which generally 
 abutted against stone skew-backs, on each side of the iron girders, 
 
148 
 
 MEASUREMENT OF LIME. 
 
 which were placed usually about 6 feet apart, seldom more than 7i 
 feet, and never less than 4J feet, and their rise seldom exceeded 6 
 inches. 
 
 ON THE MEASUREMENT OF LIME. 
 
 Lieut.-Col. Pasley found, by experiment, that a very important difference 
 in the apparent quantity of lime (and coals) exists under various con- 
 ditions, particularly in reference to the size of the lumps or particles 
 thereof, and it being of the utmost importance for both the interest of 
 trade and purposes of experiment to ascertain and determine the real 
 quantity contained in any apparent measure, he devoted much time 
 and study to the subject which resulted in the following facts : — 
 
 1st. He found that 1 cubic foot of solid coal was broken into about 
 30 pieces, together with the rubbish and dust produced in the break- 
 ing, occupied 2 J cubic feet of fair level measure, but that on further 
 breaking the same coal into a tythe part of the size, or 300 pieces, 
 which produced a greater quantity of rubbish, it filled If foot ; but 
 on being pounded entirely into rubbish and dust, it only filled 1 J 
 cubic foot. He also found that a compact 10 cubic feet measure con- 
 tained a greater quantity, by about 5 per cent., than ten times the con- 
 tents of a single cubic measure, in all which states the real quantity 
 of the coal was the same, though the estimates of it by measure were 
 so very difierent ; and as lime is usually sold by the same measure, the 
 difierence of the actual quantity supplied would, in like manner as with 
 coals, vary in proportion to the size of the component parts of a cubic 
 foot, cubic yard, or any other measure, so that for the purposes of use 
 in building, or for experiment, great deception and error may arise 
 He further observes, however, that this difference in the uncertainty 
 of measure is not so great in lime as in coals, inasmuch that the pieces 
 of lime-stone are necessarily obliged to be broken into one uniform 
 size for the convenience of burning, and accordingly the builder, in 
 
MEASUREMENT OF LIME. 
 
 149 
 
 purchasing his lime in lumps, by the cubic yard, may depend upon 
 receiving nearly the same average quantity of the same sort of lime 
 from the same kiln ; the variation of different sorts of lime from dif- 
 ferent kilns seldom exceeds 10 per cent., the excess of real quantity 
 being in favor of small pieces of kiln-burned lime, about 9 cubic yards 
 of which will equal 10 cubic yards of the same sort of lime, when 
 burned in a flame kiln. 
 
 DIFFERENT MODES OF MEASURING LIME. 
 
 1st. In lumps as it comes from the kiln. This is the customary 
 mode, which, if any large compact measure, such as one containing a 
 cubic yard, or even 10 cubic feet only, be used, will afford a tolerable 
 fair estimate of the quantity, but not so if much smaller measures be 
 used. 
 
 2d. In slaked lime powder. This mode was first adopted by Smea- 
 ton, at the building of the Eddystone lighthouse, and recommended 
 by him for all hydraulic mortars ; and the term applies to lime broken 
 small and slaked by a moderate quantity of water, sprinkled over it 
 with a watering pot, after which it should be covered up, until it falls 
 down into a powder, for which more or less time will be required, ac- 
 cording to the quality of the lime, but from 18 to 24: hours will be 
 sufficient, as even the blue lias limes, which are the slowest slaking of 
 all our English limes, from possessing the strongest hydraulic proper- 
 ties, do not usually require more than 18 hours. 
 
 3d. In quick-lime powder. For this purpose the lime is reduced to 
 a fine powder, by being pounded in a mill, or by manual labor ; this 
 mode, is, however, but seldom adopted. 
 
 4th. In slaked lime putty or paste, This mode was adopted in 
 preference by Col. Pasley in his experiments at Chatham, and applies 
 to quick-lime fresh from the kiln, pounded in a mortar, and after- 
 wards thoroughly slaked with a moderate quantity of water, gradually 
 applied, until the lime, throwing out more or less heat, shall become 
 
150 
 
 LIMEKILNS. 
 
 quite cool, and then re-mixing it with more water into a stifilsh paste, 
 in which state it is to be measured. 
 
 Lime in lumps, as in the first case, is always computed by fair leyel 
 measure, rather full than otherwise. Lime in powder, as in the second 
 and third cases, is reckoned by strike measure. In the fourth case, 
 of putty or paste, it is also measured in the latter mode. A more ac- 
 curate method of ascertaining the quantity of lime would be by weigh- 
 ing it, provided it be well burned and fresh from the kiln. 
 
 The average weight of well burned blue lias, Hailing, and chalk- 
 lime, when well burned and broken into rather small pieces, suited to 
 the common lime-kiln, may be estimated at 49, 37 and 31 J lbs. 
 per cubic foot, respectively. 
 
 A MODERN LIME KILN. 
 
 As an example of a modern lime-kiln of the most approved form 
 and construction, with a full description of the structure, and of the 
 modus operandi of lime-burning, a better cannot be selected than that 
 given by Mr. Samuel Clegg, Junr. (of London), in his "Notes on 
 Construction," published November, 1851, which is now quoted with 
 the illustration, for the advantage and interest of all concerned in the 
 trade. 
 
 iVide plates at end of book.] 
 ON THE BURNING OF LIMESTONE. 
 
 In England the operation of calcination is left almost entirely to 
 the lime-burner, and the engineer receives his material in the state of 
 quick-lime, the virtue of which is generally so well known, that he 
 mixes it up for extensive use without previous trial of its virtues. 
 This, however, would not be the case in new countries, or in those 
 districts removed from spots where lime-burning is carried on as 
 a trade ; he must then be his own lime-burner, and the knowledge of 
 the best processes followed, both as to fuel and form of kiln, must be 
 studied by him. 
 
LIMEKILNS. 
 
 151 
 
 The art of lime-burning consists in calcining the greatest quantity 
 of material with the least expendituie fuel, of time and of manual 
 labor. To gain this end, the preparation of the lime-stone its ar- 
 rangement in the kiln, the disposition of the fuel, the regulation of the 
 heat and draught, and the proper coloring of the lime must be attended 
 to. The general process will probably be more easily understood by 
 first giving a description of a kiln and the manipulation necessary, 
 and then proceeding to more minute matters. 
 
 THE KILN. 
 
 The kiln shown in the wood-cut called a "flare or dome kiln," 
 is used by the most extensive lime-burners in Dorking, and is similar 
 to all those used in the vicinity of London, only they are sometimes 
 placed in pairs or three or four together ; this arrangement, by expos- 
 ing a less surface of wall to the cold air, slightly diminishes the expendi- 
 ture of fuel ; but is probably adopted more with a view of saving labor 
 than fuel, as the fireman has all the fires under his immediate control. 
 The interior of the kiln is of a circular bottle shape, the diameter at 
 the bottom being 10 feet 6 inches, the wall is carried up plumb to a 
 height of 7 feet, at which point the dome is commenced, which closes 
 in the kiln, leaving only an opening at the top 1 foot 8 inches dia- 
 meter and 2 feet high as a chimney ; the total height from the hearth 
 to the top of the chimney being 19 feet 6 inches. The thickness of the 
 brickwork, to a height of 11 feet, is 14 inches, which is the level of the 
 top of a surrounding wall of rubble work ; from this height to the top, 
 the thickness is nine inches, including the lining of fire-brick. 
 The surrounding wall is of a horse-shoe form, the circular part 20 
 feet in diameter, and the depth from front to back 19 feet ; it is about 
 18 inches thick, batters, about 6 inches, and the space between it and 
 the brickwork of the kiln, is filled in with rubbish. At the back of 
 the kiln and 3 feet 6 inches above the grate bars, a doorway is made, 6 
 feet 6 inches high, and 4 feet 8 inches wide, arched over with 9 
 inches brick-work, through which the kiln is filled. On the opposite 
 
152 
 
 LIMEKILNS. 
 
 side to this opening are two furnace doors, the grates 18 inches wide, ex* 
 tending to the back of the kiln. The furnace mouths are funnel shaped, 
 and are 3 feet 6 inches high above the grates in the inside. This 
 construction makes it convenient for turning the rough arches of the 
 limestone when filling the kiln. A shed is built on this side to 
 protect the workmen and the fuel from the weather. 
 
 CHARGING THE KILN. 
 
 In charging the kiln, brushwood is laid over the grates, with a 
 stratum of coals upon it to form the fire. Large lumps of lime- 
 stone, or chalk, are then brought in at the door-way, and a rough 
 arch, about 3 feet high and 2 feet wide, is firmly built over each grate, 
 that the superincumbent weight of the stone may not crush them. The 
 lumps are generally trimmed to shape that they may bed properly 
 upon these arches. The general mass of stone to be burnt is then 
 thrown in, care being taken to keep the largest stones at the bottom, 
 and where the greatest heat will be, and gradually to diminish the 
 size towards the top, where the small pieces are placed. The top of 
 the charge is about on a level with the surrounding rubble wall. 
 Some care is taken to have the interstices between the lumps of stone 
 as large as possible, by placing the angles in contact ; the object of 
 this is to facilitate the calcination of the large lumps, for if the smaller 
 pieces were mixed with larger, they would be *^ over-burnt" * before 
 the latter were nearly calcined ; there is a greater draught also when 
 the spaces between the stones are greater, and this likewise assists to 
 burn the large lumps as quickly as the small. When compact lime- 
 stone is to be burnt, it should be broken into pieces not exceeding a 
 fist in size. Chalk lumps may be much larger. If the stones are 
 
 * Pure lime is incombustible, and therefore cannot be over-bnrnt, but lime 
 containing the impurities necessary to render it a weather lime, easily fuses and 
 becomes covered with a kind of enamel ; it slakes with gi-eat difficulty, sometimes 
 it will not slake at all, but becomes reduced to a harsh powder, altogether in^t^ 
 and is called dead lirae. 
 
LIMEKILNS. 
 
 153 
 
 broken into too small pieces, the spaces between them will not give 
 free passage enough to the draught and flame. The stone thro\m 
 into the kiln should not be too dry : its state just as taken from the 
 quarry is the best ; if it has lost much of its natural moisture by lying 
 by. Water should be sprinkled over it with a rose. The reason of 
 raoistm'e being useful, is, that the vapor from it facilitates the disen- 
 gagement of the carbonic acid gas, by reason of its great affinity for 
 water ; the stones, however, must not be wet. 
 
 THE BUKNING. 
 
 In commencing the operation of burning, the fire must be lighted, 
 and the heat of tlie kiln very gradually raised; from 15 to 20 hours 
 being suffered to elapse before the whole intensity of the fuel and 
 draught is allowed to be felt. To keep the fire down, as little air as 
 possible must be allowed to pass through the grate bars ; and if there 
 are not shutters or dampers to the ash-pits, lumps of stone may be 
 built up before them, to be gradually removed as greater draught is 
 required. The effect of raising the heat too suddenly would be to 
 destroy the rough arches over the grates, when the mass above them 
 would fall and smotlier the fire ; also the lumps of stone would splin- 
 ter, and the splinters fillhig the air spaces between them would de- 
 stroy the draught. This attention to the gentle increase of the heat 
 is more especially necessary in a new kiln, when the sudden heat 
 would burst the green work ; hooping the kiln with iron, to prevent 
 this kind of danger, is therefore practiced. When the calcination is 
 complete, the color of the flame from the chimney will be either of a 
 pale, yellow or a white, with no smoke ; the stone in the kiln ^\t11 
 have settled down to an extent of a fifth or a sixth of the entire mass, 
 and the whole will present a glowing red heat, or a whitish rosy tint. 
 The experienced lime-burnei well knows by these indications that 
 his charge is worked out ; but those who have not had much practice, 
 should take out a piece of the stone from the kiln, remove the outer 
 coating, and slake the inside portion in water; if no effer- 
 
154 
 
 LIMEKILNS. 
 
 veecence ensues upon the applicatioa of an acid having a stronger 
 aflSnity for the base than the carbonic acid (nitric or sulphuric acid, 
 for instance), the calcination is complete. When this is ascertained 
 to be the case, the fire may be raked out, and the kiln suffered to cool 
 gradually. If the ash-pits and air-vents are closed, the effect will be 
 favorable to the lime, which will be harder, and will keep longer ex- 
 posed to the air, so that it can be conveyed to greater distance with- 
 out deterioration ; but for a long journey, or if the lime is not to be 
 used for some time, it should be put into tight casks. 
 
 A flare kiln, containing 45 yards of Dorking gray chalk takes 48 
 hours to burn, and consumes about 7 tons of coal, the quantity de- 
 pending somewhat upon the dryness of the chalk, but the varia- 
 tion is very inconsiderable, never exceeding five or six sacks (10 or 12 
 cwt.) 
 
 The cost of such a kiln of lime is about the following : — 
 
 f, 7 American 
 
 i- S. a. Currency. 
 
 Blasting and digging in the quarry, . . 0 1 2 0 or $2 88 
 
 Carting (dependent on the distance) say . . 0 10 6 2 52 
 
 Turning rough arches, and filling, . . 0 16 0 3 84 
 
 Labor for burning, 0 18 0 4 32 
 
 Emptying at Sd, per cubic yard, . . . 0 11 3 2 70 
 
 £3 7 9 or $16 26 
 
 To this must be added the price of seven tons of coal used as 
 fuel, and the value of the land from which the limestone is taken. 
 The price in London for Dorking lime is ten shillings per cubic yard, 
 or $2.40. 
 
 A kiln in constant use v/ill not last more than eighteen months 
 or two years, without it be re-lined. It is economy, therefore, to use 
 the best Stourbridge bricks or other fire-bricks, set in fire-clay, in the 
 original construction. 
 
 In selecting a position for the kiln, the spot should be chosen as 
 near to the quarry as possible, for as the stone loses about 45 per cent 
 
CEMENT KILNS. 
 
 155 
 
 in burning, it is a saving in the carriage of the remaining 55 per cent. 
 A sloping bank should also be chosen, that the natural ground may 
 be on a level at the back of the bottom of the hatchway, and at the 
 front with the bottom of the ash-pits. 
 
 DESCRIPTION OF THE CEMENT KILN USED AT 
 SHEERNESS DOCKYARD. 
 
 The form differs in nothing from the inverted, conical frustum- 
 shaped lime-kilns ; and the size may be varied according to circum- 
 stances ; but when not built upon the side of a cliff or hill, as is 
 usually the case, they are sometimes built in the external form of 
 small cylindrical brick towers, with strong iron hoops, and sometimes 
 also with vertical bars, to prevent tb .i fire splitting the brickwork. 
 
 The kiln designed and built by Mr. Rennie, C. E., at Sheemess 
 dockyard (and which is considered of a very convenient construction) 
 is a mass of brickwork, measu ing 17 feet in external diameter and 
 21 J feet in extreme height. The hollow inverted conical frustum 
 is 8 feet clear diameter at top and 5 J feet at bottom, a 9-inch ring 
 of brickwork incloses this space, surrounded by the brickwork in mass. 
 At the bottom of it there is a sort of small solid dome, 2 feet 3 inches 
 high, for the purpose of throwing off the calcined cement, and to 
 cause it to fall down through the ash-holes of four openings, or 
 **eyes," as they are technically termed, at the bottom of the kiln, 
 formed in recesses which are arched over, and increased to 6 feet 3 
 inches in width, and 7 feet 6 inches in height, at the outside. These 
 ash-holes are 2 feet 6 inches wide, and 1 8 inches high to the crown 
 of the flat arch which covers them, and over each, at the interval of 
 15 inches higher, there are fire-holes 12 inches square, within the 
 same recesses, having iron bars at top, to support the brickwork above 
 them. 
 
156 
 
 CEMENT KILNS. 
 
 Plate 2 (see end of the book), Figs. 1, 2 and 3, represents the con- 
 struction of the above-described kiln, with the exception of the paror 
 pet wall or railing which is attached around the top of the kiln to pre- 
 vent the workmen falling over. 
 
 There are four wrought iron hoops inclosing the brickwork, as 
 shown in Eig. 2, each 3 inches wide, and 3-8 of an inch thick, which 
 are formed in several pieces, connected together at the joints by strong 
 vertical iron bolts, similar to a hinge. The plan, Eig. 3, represents a 
 horizontal section, taken on the level of the ash-holes (or eyes), in 
 which the voids are left blank and the solid parts shaded. This kiln 
 will contain nearly 30 tons of broken cement-stone, averaging 26 cubic 
 feet to the ton, exclusive of the fuel necessary to burn the cement 
 stone. 
 
 THE OPERATION OF BURNING. 
 
 The bottom of the kiln is first filled with shavings and wood, after 
 which the coals and cement-stone are added in alternate layers, the 
 former being broken so small that they occupy little more space than 
 necessary to fill the interstices betAveen the strata of the latter, each 
 of which is usually one foot in height or thickness. 
 
 Three days after the kiln is lighted, the calcined cement should be 
 drawn, whilst laying on more coals and raw cement-stone at the top, 
 so as to keep it continually burning ; the kiln may be drawn every 
 twenty-four hours. Each ton of cement-stone produces about about 
 21 bushels of cement-powder. 
 
 Sometimes two such kilns are built near to each other, and con- 
 nected by a bridge at top, and a crane or derrick fixed there to raise 
 the cement-stone and fuel, and to deposit it where and when required. 
 It is not always customary to make the inclosing brickwork so thick 
 as before described, but the width at the top is increased by a project- 
 ing balcony, the ascent to which is by an outside stairway. 
 
 Mr. Mitchell recommends the introduction of chains in addition to 
 the external hoops, the better to resist the tendency of the fire to split 
 
AETIEICIAL CEMENT. 
 
 157 
 
 the brick-work ; and Col. Pasley suggests a kiln of the form shown in 
 Plate 3, which is a vertical section thereof. It is of rather an oval 
 form, instead of the inverted frustum of a cone, having its greatest 
 diameter some little distance from the top ; this kiln is of the same 
 height as the one before described, and of the same diameter at bot- 
 tom, and from thence increasing to 8 feet at about two-thirds of the 
 way up, and again diminishing to 6 feet in clear diameter at top. 
 
 The calcined cement is afterwards to be ground in a proper mill, 
 and passed through dressing sieves similar to flour, and immediately 
 packed in tight casks or bags for use. 
 
 RULE FOR MAKING AN ARTIFICIAL CEMENT, WHEN 
 HARD LIME-STONE ONLY CAN BE PROCURED. 
 
 Supposing that no chalk can be procured, but only hard lime-stone, 
 which must be bm-ned and slaked before it is mixed with the clay, as 
 it would be too expensive to grind, and supposing further that it is as 
 hard as marble (or nearly a pure carbonate of lime), the same propor- 
 tion of chalk to clay, by weight, which made the best cement mixture 
 will also fix the proportion of lime-stone to the clay ; but instead of 
 weighing the former in its natural state, it will be better to weigh it 
 as quick-lime after it comes from the kiln, in which state 40 lbs. of 
 lime to 100 lbs. of blue clay, or 30 lbs. of lime to 1 cubic foot of 
 clay, because the best proportion of chalk or natural lime-stone to the 
 blue clay, by weight, is as 100 to 137 2, and the produce of 100 lbs. 
 of pure carbonate of lime is only about 55 J lbs. of quick-lime, but 
 as 55 is to 137 J, so is 40 to 100 nearly, which last proportion 
 has been chosen as the more simple and easily remembered. Again, 
 as 40 is to 100, so is 30 to 97 J nearly ; the last number being the 
 weight in pounds of one cubic foot of fresh blue clay; or 39 lbs. of lime 
 to one cubic foot of this clay, wiU be the proper proportion. Let there- 
 
158 
 
 ARTIFICIAL CEMENT. 
 
 fore, the lime, fresh from the kiln, be weighed in portions of 39 lbs., 
 and mixed with sufficient water to form lumps of lime-paste, of a 
 thinnish consistency, and in about twenty-four hours afterwards, mix 
 each of these lumps with one cubic foot of the blue clay, and the whole 
 incorporated with a pug mill ; after which, the process of making 
 the mixture into balls, and drying, burning, and grinding will be the 
 same as in working with chalk-paste and clay. 
 
 It will require one measm*e of coals for burning eight measures of 
 the raw cement baUs 
 
 RULES FOR MAKING AN ARTIFICIAL CEMENT EQUAL 
 TO THE BEST NATURAL WATER CEMENTS 
 OF ENGLAND. 
 
 1st. The ingredients : White or upper chalk of the geologists, 
 which is one of the purest carbonates of lime, and which is always in- 
 termixed with a thin strata or nodules of flint. These must be separa- 
 ted, and the chalk either ground dry to an impalpable powder, or, by 
 the aid of water, reduced to an impalpable paste. Marly, or impure 
 chalk, usually found near the surface of the ground, must be re- 
 jected. 
 
 Blue alluvial clay of lakes or rivers, in a state of minute division, 
 and free from sand, procurable from rivers of moderate rapidity; the 
 brown surface with which alluvial clay is usually covered must be re- 
 jected ; and care must be taken that the clay does not become stale 
 by exposure to air, which gradually destroys its color and robs 
 it of its virtue as an ingredient for a water-cement. Where al- 
 luvial clay is not to be had, fine pit clay wiU answer the same 
 purpose. 
 
 The clay, if not required for immediate use, should be preserved 
 in compact iron vessels, of a cubical form, closely pressed in, and 
 covered with a little water, to exclude the air and keep it moist. 
 
ARTIFICIAL CEMENT. 
 
 159 
 
 2d. Proportions of the ingredients : The best proportion is 100 
 lbs. of pure chalk, perfectly dry, mixed with 137 J lbs, of fresh blue 
 alluvial clay, being equivalent to C 4, B 5.5,* which proved the strong- 
 est ot all our experimental artificial cement mixtures ; or if by meas- 
 ure, 1 cubic foot chalk paste, reduced to the consistence of stiff mortar, 
 mixed with 1 i cubic foot of fresh alluvial clay ; the required con- 
 sistency will be obtained by mixing 1 lb. of dry chalk-powder with 7 
 I cubic inches of water, which will produce 18 cubic inches of paste, 
 as required ; so that there will be 96 lbs. of dry chalk to every cubic 
 foot of paste. But these proportions are subject to variation according 
 to the nature or quality of the several materials, and which can only 
 be determined by actual experiment. 
 
 3d. Mode of grinding the chalk : It must first be broken into 
 small pieces, and then ground with water in a wash mill (such as used 
 by whitening-makers), or in a mortar mill (pug mill), both of which 
 being in common use are doubtless well known to our readers. 
 
 4th. Mode of mixing the chalk and clay : The former, when ground 
 with water in one of the mills just described, would probably be in too 
 fluid a state for immediate use. The superfluous water must there- 
 fore be partly drained ofif, and partly evaporated, by allowing it to 
 drain under cover from the weather, until the chalk-paste is brought 
 to a proper consistency ; but if too dry, water must be added as re- 
 quired. It must be then mixed with the blue clay, by means of a 
 couple of small measures, the capacity of which must be as 1 to 1 i, 
 the former for measuring the chalk-paste and the latter, the clay ; the 
 contents of which must be alternately emptied upon each other into 
 the pug mill, until it is quite full ; then set the mill in motion, and 
 pass the contents through, which, if not perfectly incorporated together 
 by the first operation, must be passed through a second time. The 
 measures used should be of a convenient size, neither too small nor 
 too large. 
 
 • Note. C signifies best class chalk-lime, and B the blue liaa clay. 
 
 % 
 
160 
 
 QUALITIES OF CEMENT. 
 
 6th. Mode of preparing the raw cement for the kiln : After pass- 
 ing through the pug mill, the raw cement mixture must be made up 
 into balls of about 2 3 inches diameter, by the hands, which can be 
 performed by women or children. The balls must be allowed to dry, 
 so as not to stick together when in contact, nor to be easily crushed 
 by the superincumbent weight to which they will afterwards be ex- 
 posed in the kiln, for which purpose 48 hours* exposure to the air 
 under cover will probably suffice. 
 
 Balls of a smaller size would be liable to spoil by exposure, and 
 larger ones would not be so convenient for burning. 
 
 VARIOUS RULES FOR TESTING THE QUALITIES OF 
 CEMENTS. 
 
 1st. Rule for judging whether the cement supplied by a manufac- 
 turer is in a proper state for use : — 
 
 Mix up the cement-powder with water and make four or five ex- 
 perimental balls of it, not exceeding an inch in diameter. Allow 
 them to set with warmth, and cool again, which, in good but rather 
 slow-setting cement, will require about half an hour ; after which put 
 two or three of them into a basin of water. If they continue to set 
 m this state, and become very hard in the course of a day or two, 
 the cement is good; but if on the contrary they do not become very 
 hard in this time, both inside and out, whether previously kept in air 
 or water, the cement is not in a fit state to be used, and should Do 
 rejected. 
 
 2ndly. Rule for ascertaining whether cement of improper quality 
 has originally been good, but injured by becoming stale, or whether 
 it may not have been either the produce of bad cement stone, or of 
 good cement stone adulterated after calcination, which two last cases 
 cannot be discriminated in cement prepared for sale: — 
 
QUALITIES OF CEMENT. 
 
 161 
 
 If the experimental balls, made as last described, will not set pro- 
 perly either in air or water, the next point is to ascertain the cause. 
 For this purpose, burn the same balls in a crucible for two or three 
 hours in a common fire-place, exposing them to a full red heat, until 
 they ceased to effervesce with acids ; then pound the calcined cement 
 in a mortar till you reduce it to an impalpable powder, and mix it up 
 once more into experimental balls with water. If the cement, after 
 being thus re-burned, should set well both in air and under water, it 
 is a proof that it was originally good, but had been spoiled by exposure 
 to air and damp. 
 
 If on the contrary the cement was in a state unfit for use, should 
 not be improved by the above process, which completely restores the 
 virtue not only of stale cement if originally good, but also of stale 
 lime, it is a proof that it has either been made of inferior cement 
 stone, or that it has been adulterated by mixing earth or sand of the 
 same color, with the cement powder. 
 
 3dly. Kule for judging of the comparative cohesive strength of dif- 
 ferent sorts of cement : — 
 
 Having ascertained that the cements to be compared together are in 
 a serviceable state, by the the foregoing rules, without which further 
 trouble would be useless, two modes present themselves for judging of 
 their comparative strength ; one, the usual mode of setting out 
 bricks from a wall or forming a suspensory arch, and the 
 other, by what is termed the breaking-down apparatus, consisting of 
 a scale-board, planks and weights, and a couple of pairs of nippers to 
 be used with a gyn or triangle, the operation of which we will now 
 describe : Provide two pieces of lay stone, or any other sound hard 
 stone, each exactly 10 inches long, 4 inches broad, and 4 inches deep, 
 more or less, prepared with mortices in the sides, one inch wide and 
 one inch deep, and from J an inch to i high, to receive the nip- 
 pers, which should be so placed as to have at least 2 | inches of 
 solid stone above and below them ; the abutting surfaces of the stone 
 after being properly squared to match, should be jagged or roughed to 
 
162 
 
 QUALITIES OF CEMENT. 
 
 the depth of about §th of an inch, or indented with a mason's pick, 
 Blight or ten pairs of such stones should be prepared for each sort of 
 cement for the purpose of trying several experiments at the same time; 
 these stones must be cemented together in pairs, with the different 
 specimens of cement laid on uniformally, and with a joint not exceed- 
 ing one quarter of an inch in thickness, and then allowed to remain 
 10 or 12 days to properly set and indurate according to the weather 
 or the season of the year. These are to be suspended to a beam, or 
 shears, with a scale or plank attached below to receive the weights, 
 with which it is to be loaded ; then apply the weights equally to each 
 specimen, aud carefully note down each transaction, and register the 
 breaking weight of each sample, the time under trial, and circum- 
 stances and nature of the fracture. The comparisons should be made 
 separately, with the quick or slow setting cements ; otherwise it will 
 be unfair, as some cements are as fully indurated in 10 or 12 days, as 
 others in 3 or 4 months. 
 
 In order to ascertain more precisely the effect which sand produces 
 on the cohesion of cement, I caused three little brick masses to be con- 
 nected by pure cement, and three others to be joined by a mixture of 
 the same cement with clear sharp sand in equal parts, by measure, 
 and in order to compare their relative cohesiveness with that of old 
 chalk lime mortar also, I caused some little masses to be cut out of 
 the best brick walls, built with mortar of this description, which I 
 could find within Chatham lines ; and having prepared these small 
 specimens with proper mortices to receive the nippers, the whole 
 were torn asunder in the usual manner, by successive weights, as stated 
 below. 
 
163 
 
 COMPARATIVE COHESIVE STRENGTH OF PURE CEMENT, OP CEMENT 
 MIXED WITH SAND, AND OF COMMON CHALK LIME MORTAR. 
 
 No. of 
 Expt. 
 
 Whether with cement or 
 chalk lime mortar. 
 
 Age in daijs 
 or years. 
 
 Weight in Ihs. 
 which broke joint 
 
 Average breaking 
 weight in lbs. 
 
 1 
 
 2 
 
 o 
 
 6 
 
 ■ 
 
 ■ Pure cement. 
 
 11 days. 
 pZ days. 
 
 1241 
 1003 
 iUoi 
 
 ; 
 
 • 1092 
 
 1 
 
 2 
 3 
 
 
 • Cement and Sand. 
 
 ) 11 days. 
 J 17 days. 
 
 205 
 257 
 343 
 
 
 . 225 
 
 1 
 
 2 
 
 
 
 
 
 334 
 64 
 
 
 
 3 
 4 
 
 
 - Chalk lime mortar 
 
 
 -30 years. 
 
 75 
 47 
 
 
 ^ 155 
 
 5 
 6 
 
 
 
 
 
 205 
 204 
 
 
 
 Hence it appears that pure cement is more than four times as 
 strong at the same age, as the customary mixture of cement and sand 
 in equal parts, as in common use. Mr. Brunei was therefore quite 
 right in employing only pure cement in the arches of the Thames 
 Tunnel (England), and which method ought to be adopted in all 
 works of risk or importance. Yet in all works of less importance, 
 the addition of an equal volume of sand is not to be reprobated, be- 
 cause this proportion, whilst it renders the cement mortar cheaper, is 
 not sufficient to take away its hydraulic properties, and even when 
 but 17 days old, it appears from these experiments to equal, if not to 
 exceed the strength of the best lime mortar of 30 years of age, and I 
 conceived it probable, that if tried at a greater age, the cement mor- 
 tar would exceed the strength of the chalk lime mortar, in a five-fold 
 rate. 
 
 The author (Col. Pasley) next describes a series of experiments 
 which he made of the comparative adhesiveness of cement to bricks 
 and various sorts of stone, the results of which appear as follows ; tho 
 
164 COMPAEATIVE STRENGTH OF CEMENTS, 
 
 period of the trials extended from the latter end of December, 1836, 
 to the middle of May, 1837. The age of the cement was in general 
 11 days, in two instances only having been extended to 12 days. 
 
 The first 12 experiments were with bricks, the average fracturing 
 weight was 1359 lbs. 
 
 The next 5 experiments were with Bath stone, average fractur- 
 ing weight 1103 lbs. 
 
 Then followed 6 experiments on Cornish granite, which separated 
 with an average weight of 900 lbs. 
 
 The next 5 experiments were with Portland stone, which fractured 
 with an average of 856 lbs. 
 
 Then 5 experiments on Yorkshire landing stones, the average frac- 
 turing weight of which was 823 lbs. 
 
 The next 5 experiments were with Kentish rag-stone, the average 
 breaking weight being 1349 lbs. showing the adhesive power to be 
 nearly equal to that of bricks. 
 
 Then followed 5 experiments with Craigleith stone (Scotch) the 
 average breaking weight being 855 lbs. 
 
 The last 2 experiments were Vvdth Cornish granite polished on 
 the cementing surfaces, the fracturing weight of which averaged 
 928 lbs., which, therefore, nearly equalled in strength to experi- 
 ments Nos. 4 and 5 with Cornish granite (rough) which averaged, 
 1213 lbs. 
 
 The discrepancies which were apparent in the results of some of 
 the foregoing experiments, were considered to be owing to the con- 
 dition of the cement, some of which were, at the time of using, more 
 fluid than others. Upon the whole, these experiments are not fully 
 conclusive, but we safely infer from them that the adhesiveness of 
 cement to the least congenial sort of stone is more than one half, and 
 nearly two-thirds of its adhesiveness to bricks, and that it appears to 
 adhere to hard stones with a greater tenacity than to soft ones, and 
 also that the state of the surfaces operated upon, whether more or 
 less smooth is of very little importance, but these experiments fully 
 
COMPARATIVE STRENGTH OF CEMENTS. 165 
 
 prove that pure cement attaches itself to the most refractory sort 
 of stone with five times as much adhesive force in 11 days, as the 
 best chalk Ume used in brickwork is capable of attaining in 80 
 years. 
 
ADDENDA. 
 
 AMERICAN RESOURCES. 
 
 The United States furnish excellent limestone, principally of 
 primary formation. One range which passes unbroken through seve- 
 ral of the States is perhaps one of the most extensive and valuable 
 primary limestones in the world. 
 
 (Extract from Mahan's Engineering.) Limestone is so extensively 
 diffused throughout the United States, and is quarried, either for 
 building stone or to furnish lime, in so many localities, that it would 
 be impracticable to enumerate all within any moderate compass. One 
 of the most remarkable formations of this stone extends, in an unin- 
 terrupted bed, from Canada, through the States of Vermont, Massa- 
 chussets, Connecticut, New York, New Jersey and Virginia, and in 
 all probability, much further south. 
 
 Limestone is burned in almost every locality where deposits of the 
 stone occur. Thomaston, in Maine, has supplied, for some years, most 
 of the markets on the seaboard with a material which is considered as 
 a superior article for ordinary building purposes. One of the greatest 
 additions to the building resources of our country was made in the 
 discovery of the hydraulic or water limestone of New York. The pre- 
 paration of this material, so indispensable for all hydraulic works and 
 heavy structures of stone, is carried on extensively at Rondout, on the 
 Delaware and Hudson canal in Madison county, and is sent to every 
 part of the United States, being in great demand for all the public 
 works carried on under the superintendence of our civil and military 
 engineers. 
 
 A not less valuable addition to our building materials has been 
 
AMERICAN RESOURCES. 
 
 167 
 
 made by Prof. W. B. Rogers, who, a few years since directed the at- 
 tention of engineers to the dolomites, for their good hydraulic proper- 
 ties. From experiments made by Vicat, in France, who first there 
 observed the same properties in the dolomite, and from those in our 
 own country, it appears highly probable that the magnesian lime- 
 stones, containing a certain proportion of magnesia, will be found 
 fully equal to the argillaceous, from which hydraulic lime has hitherto 
 been solely obtained. 
 
 (Extract from Prof. Daniel's Lecture, before the Chicago Academy 
 of Natural Science.) A magnesian limestone which forms the heights 
 of the Upper Mississippi, extends south-west across the Wisconsin 
 River, and westward into Minnesota. At Lasalle, Illinois, it fur- 
 nishes an excellent hydraulic cement. 
 
 The Trenton limestone, 70 feet thick, is a hard, thin-bedded blue 
 limestone, often wholly made up of shells and corals, above this is the 
 Galena limestone, 250 feet thick. Then comes the Hudson River rocks, 
 in whose lower portion are found shell beds as rich as those of the 
 Trenton limestone, bnt of different species. They form the base of 
 the mounds around Galena and through the lead region. 
 
 Joliet, the city of stone quarries, lies in the old river bed of the once 
 mighty Des Plaines, now reduced to a small stream. East and west 
 are rocky bluffs. The valuable and inexhaustable quarries extend 
 more than 20 miles north and south, and near the upper end is the 
 little town of Athens, which gives its name to the celebrated store 
 used in Chicago. Five miles from Joliet is Lockport, underlaid by 
 quarries, for who has not heard of the Lockport stone ? Athens comes 
 next, and here Joliet has a competitor. The stone is of better quality, 
 and more easily obtained. Athens is simply a vast stone quarry, and 
 wiU never be anything else. 
 
 (Extract from Mahan's Engineering.) Lime considered as a 
 building material, is now usually divided into three principal classes, 
 common or air lime, hydraulic lime, and hydraulic or water ce- 
 ment. 
 
168 
 
 ANALYSIS OF CEMENTS. 
 
 The Kmestones which yield hydraulic limes and cements are either 
 argillaceous, or magnesian, or argilo-magnesian. The products of 
 their calcination vary considerably in their hydraulic properties. 
 Some of the hydraulic limes harden, or set very slowly under water, 
 while others set rapidly. The hydraulic cements set in a very short 
 time. This diversity in the hydraulic energy of the argillaceous lime- 
 stones arises from the variable proportions in which the lime and clay 
 enter into their composition. 
 
 M. Petot, in an able work entitled, "Kecherches sur la ChaufFour- 
 nerie," gives the following table, exhibiting those combinations, and 
 the results obtained from their calcination : — 
 
 Idme 
 
 Clay, 
 
 RemUing products. 
 
 100 
 
 0 
 
 Very fat lime. 
 
 90 
 
 10 
 
 Lime, a little hydraulic. 
 
 80 
 
 20 
 
 Do. quite hvdraulic. 
 
 70 
 
 30 
 
 Do. 'do. 
 
 60 
 
 40 
 
 Plastic or hydraulic ce- 
 
 
 
 ment. 
 
 50 
 
 50 
 
 Do. do. 
 
 40 
 
 60 
 
 Do. do. 
 
 30 
 
 70 
 
 Calcareous puzzolana, 
 
 
 
 (brick). 
 
 20 
 
 80 
 
 Do. do. do. 
 
 10 
 
 90 
 
 Do. do. do. 
 
 0 
 
 100 
 
 Puzzolana of pure clay do. 
 
 Distinctive cha/racters of the products. 
 
 Incapable of hardening in water. 
 ) Slakes like pure lime, when pro- 
 
 V perly calcined, and hardens 
 ) under water. 
 
 ) Does not slake under any cir- 
 >. cumstances, and hardens nn- 
 ) der water with rapidity. 
 
 ) Does not slake nor harden un- 
 
 V der water, unless mixed with 
 ) a fat or a hydraulic lime. 
 Same as the preceding. 
 
 The most celebrated European hydraulic cements are obtained from 
 argillaceous limestones, which vary but slightly in their constituent 
 elements and properties. The following table gives the results of 
 analysis to determine the relative proportions of lime and clay in these 
 cements : — 
 
 LOCALITY. LIME. CLAY. 
 
 English (commonly known as Parker's, or Roman ce- 
 ment), 5540 44-60 
 
 French (made from Bologne pebbles), 54-00 46*00 
 
 Do. (Pouilly), 42-86 57-14 
 
 Do. do 36-37 63-63 
 
ANALYSIS OF CEME^JTS. 
 
 169 
 
 LOCALITY. 
 
 LIMB. CLAY. 
 
 French (Baye), 
 Russian, 
 
 21-62 78-38 
 
 62^00 38-00 
 
 The best known hydraulic cements of the United States are manu- 
 factured in the State of New York ; the following analyses of some of 
 the hydraulic limestones, from the most noted localities, published in 
 the Geological Report of the State of New York, 1839, are given by 
 Dr. Beck. 
 
 ANALYSIS OF THE MANLIUS HYDRAULIC LIMESTONE 
 
 Carbonic acid, .....o.. ,..39-80 
 
 Lime, 2624 
 
 Magnesia, 18-80 
 
 Silica and alumina, 13 -50 
 
 Oxide of iron, 1 -25 
 
 Moisture and loss, 1-41 
 
 This stone belongs to the same bed which yields the hydraulic ce- 
 ment obtained near Kingston, in Upper Canada. 
 
 ANALYSIS OF THE CHITTENANGO HYDRAULIC LIMESTONE BEFORE 
 AND AFTER CALCINATION. 
 
 100-00 
 
 TTNBUENT. 
 
 Carbonic acid, 
 
 39-33 Carbonic acid and moisture 10-90 
 
 Lime, 
 
 25-00 Lime, 
 
 39-50 
 
 Magnesia, 
 Silica, 
 
 17-83 Magnesia, 22-27 
 
 11-76 Silica, 16.56 
 
 2*73 Alumina and oxide of iron, 10*77 
 
 1-50 
 
 Alumina, 
 
 Peroxide of iron, 
 Moisture, 
 
 1-85 
 
 10000 
 
 100-00 
 
 8 
 
170 
 
 ANALYSIS OF CEMENTS. 
 
 ANALYSIS OF THE HYDRAULIC LIMESTONE FEOM ULSTEB COUNTT, 
 ALONG THE LINE OP THE DELAWABB AND HUDSON CANAL, 
 BEFOEE AND AFTER BURNING. 
 
 XTNBUENT. BUENT, 
 
 Carbonic acid, 34-20 5-00 
 
 Lime, 25*50 37-60 
 
 Magnesia, 12-35 16-65 
 
 Silica, 15-37 22 75 
 
 Alumina, 9-13 13-40 
 
 Oxide of iron, 2-25 3-30 
 
 Bituminous matter, moisture and loss, 1-20 1-30 
 
 100-00 100-00 
 
 The hydraulic properties of the magnesian limestones of the United 
 States were noticed by Prof. W. B. Rogers, who, in his Report of the 
 Geological Survey of Virginia, 1838, has given the following analysis 
 of some of the stones from different localities : — 
 
 
 No. 1. 
 
 No. 2. 
 
 No. 3. 
 
 No. 4. 
 
 
 55-80 
 
 53-23 
 
 48-20 
 
 55 03 
 
 
 
 41-00 
 
 35-76 
 
 24-16 
 
 
 ... 1-50 
 
 0-80 
 
 1-30 
 
 2-60 
 
 
 2-50 
 
 2-80 
 
 12-10 
 
 15-30 
 
 
 
 0-40 
 
 2-73 
 
 1-20 
 
 
 0-60 
 
 1-77 
 
 0-01 
 
 1-71 
 
 
 100-00 
 
 100 00 
 
 100-00 
 
 100-00 
 
 The limestone No. 1 of the above table is from Sheppardstown on the 
 Potomac, in Virginia, it is extensively manufactured for hydraulic 
 cement. No. 2 is from the Natural Bridge, and banks of Cedar 
 Creek, Virginia ; it makes a good hydraulic cement. No. 3 is from 
 New York, and is extensively burned for cement. No. 4 is from 
 Louisville, Kentucky, said to make a good cement. 
 
 M. Vicat states that a magnesian limestone of France containing 
 the following constituents, lime 40 parts, magnesia 21, and silica 21, 
 
ANALYSIS OF CEMENTS. 
 
 171 
 
 yields a good hydraulic cement, and he gives the following analysis of 
 a stone which gives a good hydraulic lime : — 
 
 Carbonate of lime, 50*60 
 
 Carbonate of magnesia, 42*00 
 
 Silica, 5*00 
 
 Alumina, , 2*00 
 
 Oxide of iron, 0*40 
 
 10000 
 
 Experiments by several eminent chemists have extended the list of 
 natural substances which, when properly burnt and reduced to powder, 
 have the same properties as Puzzolana. They mostly belong to the 
 feldspathic and schistoze rocks, and are either fine sand or clays more 
 or less indurated. 
 
 The following table gives the results of analyses of Puzzolana, trass, 
 a basalt, and a schistus, which, when burnt and powdered, were found 
 
 to possess the properties of Puzzolana : — 
 
 
 
 
 
 PUZZOLANA, 
 
 TRASS. 
 
 BASALT. 
 
 BOHISTTTS. 
 
 
 
 0-570 
 
 44*50 
 
 46-00 
 
 
 
 0*120 
 
 16*75 
 
 26*00 
 
 
 
 0-026 
 
 9-50 
 
 4*00 
 
 
 0*047 
 
 0-010 
 
 
 
 
 0*120 
 
 0*050 
 
 20-00 
 
 14*00 
 
 
 
 
 2 37 
 
 8*00 
 
 
 0*014 
 
 0-070 
 
 
 
 
 0*030 
 
 0*010 
 
 2*60 
 
 
 
 0*106 
 
 0-144 
 
 4*28 
 
 2*00 
 
 
 1*000 
 
 1-000 
 
 100*00 
 
 100*00 
 
 All of these substances, when prepared artificially, are now general- 
 ly known by the name of artificial Puzzolanas, in contradistinction to 
 those which occur naturally. 
 
 (Extracts from Mr. Kirwan.) Puzzolana, reddish or reddish-brown, 
 gray, or grayish-black : — That of Naples is generally gray, that of 
 Civita Vecchia more generally reddish, or reddish-brown. 
 
172 
 
 ANALYSIS OF CEMENTS. 
 
 Its surface, rongh, uneven, and of a baked appearance. It comes 
 to us in pieces of from the size of a nut to that of an egg. 
 Its internal lustre, 0. Its transparency, 0. 
 
 Its fracture uneven, or earthy, and porous, commonly filled with 
 particles of pumice, quartz, scorise, &c. 
 
 Hardness, 3 ; very brittle ; specific gravity, from 2.570, which is 
 that of the black, to 2.785, rarely 2.8 ; has an earthy smell. 
 
 It is not diffusible in cold water, but in boiling water it gradually 
 deposits a fine earth. It does not effervesce with acids. 
 
 Heated, it assumes a darker color, and easily melts into a bla-ck 
 slag, or with borax into a yellowish green glass. 
 
 It is magnetic before it is heated, but not after ; this is the most re- 
 markable of its properties. 
 
 By Mr. Bergman's analysis, it contains from 55 to 60 per cent, of 
 silex, 19 to 20 of argill, and from 15 to 20 of iron. 
 
 When mixed with a small proportion of lime it quickly hardens, 
 and this induration takes place even under water. This singular prop- 
 erty appears to me to proceed from the magnetic state of the iron it 
 contains, for this iron being unoxygenated, subtilely divided, and dis- 
 persed through the whole mass, and thus offering a large surface, 
 quickly decomposes the water with which it is mixed, when made into 
 mortar, and forms a hard substance analogous to the specular iron 
 ore as it does in the iron tubes in which water is decomposed in Mr, 
 Lavoiser's and Dr. Priestley's experiments; for in these the iron 
 swells and increases in bulk, and so does Puzzolana when formed into 
 mortar. One principal use of lime seems to be to heat the water, as 
 while cold it cannot readily pervade the caked argill that invests the 
 ferruginous particles, yet in time even cold water may pervade it, and 
 produce hardness, and hence lavas become harder when moistened, as 
 Mr. Dolomieu has observed. If the mortar be long exposed to the 
 atmosphere, fixed air, as well as pure air, will unite to the iron, rust 
 will be produced, and the mortar will not then harden, as Dr. Hig- 
 gins has also noticed. Clay over which lava has flowed is frequently 
 
ANALYSIS OF CEMENTS. 173 
 
 converted into Puzzolana. But volcanic scoriae never afford it, either 
 because they are much calcined, or retain sulphur, or its acid. 
 
 Trass or terras. I couple this with Puzzolana on account of their 
 similarity to each other, and not because I look upon it as constantly 
 and necessarily, a volcanic production. On the contrary, I believe it 
 to be generally the product of pseudo-volcanoes or external fires. It 
 is found in many places, but principally near Andernach, in the vi- 
 cinity of the Khine, also near Frankfort, Cologne, Pleith, &c., and 
 there called tuff stein. It is found in valleys some feet under the sur- 
 face, to which no stream of water has had access ; sometimes in 
 columnar masses of a gray or Isabella yellow color, some round and 
 some quadrangular, standing close to each other, and forming inter- 
 nally one common mass. According to Mr. Bergman, it consists of 
 nearly the same principles as Puzzolana, only the calcareous seems 
 more plentiful in this. Artificial terras or Puzzolana is made by 
 burning clays or slates that abound in iron, and then grinding them 
 to a fine powder. 
 
 Tufas. These seem to be a Puzzolana formed by nature into a 
 mortar. 
 
 Piperino. This also seems a concretion of volcanic ashes, and is 
 said to be the substance that covers Pompeia. It seems to differ from 
 tufas, in containing more heterogenities, being in fact a kind of por- 
 phyiy, or breccia, and being more easily decomposed by exposure to 
 moisture and the open air, but if preserved from moisture, it hardens 
 when exposed to the air. 
 
 Cement. In 1770 M. Loriet pretended to have discovered the se- 
 cret of the cement of the ancient Romans, which, according to him, 
 was only a mixture of powdered quick-lime with lime which had been 
 long slaked and kept under water. The slaked lime was first to be 
 made up with sand, earth, brick-dust &c., into mortar, and then about 
 one-third of quick-lime in powder added to the mixture. This pro- 
 duced an almost instantaneous petrifaction, something like what is 
 called the setting of alabaster. But the invention of this cement has 
 
174 
 
 STRENGTH OF MORTAR. 
 
 not succeeded to the degree the inventor expected, owing to the pre- 
 cision necessary in its preparation. Dr. Black informs us that a ce- 
 ment of this kind is certainly practicable. It is done, he says, by 
 powdering the lime while hot from the kiln, and throwing it into a 
 thin paste of sand and water, which, not slaking immediately, absorbs 
 the water from the mortar by degrees, and forms a very hard mass. 
 It is plain, he adds, that the strength of this mortar depends on using 
 the lime hot or fresh from the kiln. 
 
 STRENGTH OP MORTABS, 
 
 A very wide range of experiments has beeii tnade, by engineers 
 both at home and abroad, upon the resistance offered by mortars to 
 a transversal strain, with a view to compare their qualities. As 
 might naturally have been anticipated, these experiments have pre- 
 sented very diversified, and, in many instances, contradictory results. 
 
 M. Vicat gives the following as the average resistance on the 
 square inch offered by mortars to a force of tractioo, the deductions 
 being drawn from experiments on the resistance to a transversal 
 
 strain : — 
 
 Mortars of very strong hydraulic lime, 170 pounds. 
 
 ordinary " 140 
 
 medium " 100 
 
 common lime, , 40 " 
 
 " " (bad quality) 10 " 
 
 These experiments were made upon prisms a year old, which had 
 been exposed to the ordinary changes of weather. 
 
 General Treussart, in his work on hydraulic and common mortars, 
 has given in detail, a large number of experiments on the transversal 
 strength of artificial hydraulic mortars, made by submitting rectan- 
 gular parallelopipeds of mortar, 6 inches in length and 2 inches 
 square, to a transversal strain applied at the centre point between 
 bearings 4 inches apart. From these he deduces the following prac 
 tical conclusions : — 
 
STRENGTH OF CONCRETE 
 
 175 
 
 That when the parallelepipeds sustain a transversal strain varying 
 between 220 and 330 lbs. the corresponding mortar will be suitable 
 for common gross masonry, but that for important hydraulic works 
 the parallelopipeds should sustain before yielding, from 330 to 440 lbs. 
 
 The only published experiments on this subject made in this country 
 are those of Colonel Totter, appended to his translation of General 
 Treussart's work. 
 
 From experiments, Colonel Totten deduces the following general 
 results : — 
 
 1st. That mortar of hydraulic cement and sand is the stronger and 
 harder as the quantity of sand is less. 
 
 2d. That common mortar is the stronger and harder as the quan- 
 tity of sand is less. 
 
 3d. That any addition of common lime to a mortar of hydraulic 
 cement and sand weakens the mortar, but that a little lime may be 
 added without any considerable diminution of the strength of the 
 mortar, and with a saving of expense. 
 
 4th. The strength of common mortars is considerably improved by 
 the addition of an artificial Puzzolana, but more so by the addition of 
 an hydraulic cement. 
 
 5th. Fine sand generally gives a stronger mortar than coarse sand. 
 
 6th. Lime slaked by sprinkling gave better results than lime slaked 
 by drowning. A few experiments made on air-slaked lime were un- 
 favorable to that mode of slaking. 
 
 7th. Both hydraulic and common mortar yielded better results 
 when made with a small quantity of water than when made thin. 
 
 8th. Mortar made in the mortar-mill was found to be superior to 
 that mixed in the usual way with a hoe. 
 
 9th. Fresh water gave better results than salt water. 
 
 STRENGTH OF CONCRETE AND BETON. 
 
 From experiments made on concrete, prepared according to tho 
 most approved process in England, by Colonel Pasley, it appears that 
 
176 STRENGTH OF CONCKETE. 
 
 that this material is very inferior in strength to good brick and the 
 
 weaker kinds of natural stones. 
 
 Concrete. — This term is applied by English architects and en- 
 gineers, to a mortar of finely pulverized quick-lime, sand and gravel. 
 
 Beton. — The term beton is applied by French engineers to any 
 mixture of hydraulic mortar with fragments of brick, stone, or gravel, 
 and it is now also used by English engineers in the same sense. 
 
 From experiments made by Colonel Totten on beton, the following 
 conclusions are drawn : — 
 
 That beton made of a mortar composed of hydraulic cement, com- 
 mon lime, and sand, or of a mortar of hydraulic cement and sand, 
 without lime, was the stronger as the quantity of sand was the smaller, 
 But there may be 0*50 of sand, 0-25 of common lime, without sensi- 
 ble deterioration, and as much as 1*00 of sand, and 0*25 of lime. 
 ^7ithout great loss of strength. 
 
 Beton made with just sufficient mortar to fill the void spaces between 
 the fragments of stone was found to be less strong than that made 
 with double this bulk of mortar. But Colonel Totten remarks, 
 that this result is perhaps attributable to the difficulty of causing so 
 small a quantity of mortar to penetrate the voids, and unite all the 
 fragments perfectly, in experiments made on a small scale. 
 
 The strongest beton was obtained by using quite small fragments 
 of brick, and the weakest from small, rounded, stone gravel. 
 
 A beton formed by pouring grout among fragments of stone or 
 brick, was inferior in strength to that made m the usual way with 
 mortar. 
 
 Comparing the strength of the betons on which the experiments 
 were made, which were eight months old when tried, with that of a 
 sample of sound red sandstone of good quality," it appears that the 
 strongest prisms of beton were only half as strong as the sandstone. 
 
 Previous to giving my experiments and by way of conclusion I will 
 just remark that, in making computations it will be quite safe to esti- 
 mate a cubic foot of mortar at 108 to 110 lbs. Tenacity 50 lbs. to 
 
VARIOUS EXPERIMENTS. 
 
 177 
 
 the square inch, and specific gravity 1*75; sand at 90 to 120 lbs. j 
 unslaked lime 53 to 90 lbs. ; brick-dust and brick-work at 112 lbs., 
 and limestone at 171 to 197 lbs. Mr. Kirwan gives. the weight of a 
 cubic foot of Puzzolana at 169-37 lbs. and specific gravity 2-67. 
 
 THE FOLLOWING ARE THE RESULTS OF VARIOUS 
 EXPERIMENTS. 
 
 No. 1. A. Stearns & Co., Bridgeport Kiln, Prairie Stone. 
 
 Thirty-three cubic inches of unslaked lime weighed 23 ounces, gave, 
 as a result after being slaked by sprinkling, a volume of 82.5 cubic 
 inches and weighed 28.5 ounces, equal to 2.5 of slaked lime to 1 of 
 unslaked. 
 
 No. 1. 
 
 33.0 cubic in. fine sand 27 ozs. C Mixed as mor- 
 
 16.5 Utiea hydraulic cement 8 tar, and when per- 
 
 16.5 slaked lime 5.7 " fectly dried meas- 
 
 ured 48 cubic ins. 
 
 66.0 iO.7 Land weigh'd 45 oz. 
 
 No. 2. 
 
 33.00 cubic in. sand • 
 8.25 Utica cement 
 
 8.25 slaked lime 
 
 49.50 
 
 27.00 ozs. f Mixed as mor- 
 4.00*' tar, and when per- 
 2.85 " 'I fectly dried meas- 
 
 — - — ured 34 cubic ins. 
 
 33.85 Land weigh'd38 oz. 
 
 No. 3. 
 
 16.50 cubic in. slaked lime 
 5.50 *' brick-dust 
 11.00 sand 
 
 33.00 
 
 5.70 ozs. r Mixed as mor- 
 5.59" tar, and when per- 
 9.00 " -{ fectly dried meas- 
 
 ur'd23.20cub'cin. 
 
 20.29 Land weigh'd 20 oz. 
 
VARIOUS EXPERIMENTa 
 
 No. 4. 
 
 16.50 cubic in. Utica cement, 
 
 16.50 cubic 
 16.50 " 
 16.50 " 
 8.25 " 
 
 in. sand 
 
 pounded brick 
 Utica cement 
 slaked lime 
 
 57.75 
 
 8.00 02S. 
 
 No. 5. 
 
 13.50 ozs. 
 16.77 *' 
 
 8.00 
 
 2.85 " 
 
 41.12 
 
 Mixed as above, 
 and when perfect 
 ly dried measured 
 16 cubic ins. and 
 ^weighed 11.50 oz. 
 
 " Mixed as above, 
 and when per- 
 fectly dried meas- 
 ured 45 cubic ins. 
 and weighed 39 
 
 .ozs, 
 
 No. 6. 
 
 16.50 cubic in. slaked lime 
 
 No. 7. 
 
 8.25 cubic 
 8.25 
 
 16.50 
 
 in. slaked lime 
 Utica cement 
 
 5.7 ozs.^ 
 
 2.85 ozs. 
 4.00 
 
 6.85 
 
 Mixed as lime 
 putty, when per- 
 fectly dried, meas- 
 ur'dl2.75cub'cin. 
 ^and weigh'd 7 oz. 
 
 Mixed as above, 
 and when perfect- 
 ly dried measured 
 13.57 cubics ins. 
 ^and weighed 10 oz. 
 
 No. 2. B. Stearns & Co., Bridgeport Kiln, Pbairie Stone. 
 58 cubic inches of unslaked lime weighed 48*50 ozs., gave, as a re- 
 sult after being slaked by sprinkling, a volume of 206*25 cubic inches 
 of slaked lime and weighed 57 ounces, equal to 3*55 of slaked lime to 
 1 of unslaked. 
 
 No. 8. 
 
 203*00 cubic inches of sand, 166*70 ozs. 
 
 103*12 slaked lime, 28*50 ** 
 
 306-12 195*20 
 
 Mixed as mortar 
 as 7 of sand to 1 04 
 unslaked lime, and 
 when thoroughly 
 dried measured 
 201*13 cubic ins, 
 and weighed 208 
 L ounces. 
 
VARIOUS EXPERIMENTS. 
 
 179 
 
 No. 9. 
 
 103-12 cubic ins. slaked lime, 
 
 Mixed as lim 
 putty and pressed 
 into a mould and 
 when thoroughly 
 28*50 ozs. -{ dried measured 54* 
 60 cubic inches and 
 weighed 30 ounces. 
 This contracted in 
 _ dry 'g 4-65 cubic ins. 
 
 'No, 3. C. Sheriman & Co., Lyons Kiln, Prairie Stone. 
 8*90 cubic inches of unslaked lime weighed 7*5 ounces, gave, as a 
 result after being slaked by sprinkling, a volume of 23*29 cubic inches 
 of slaked lime, and weighed 9 ounces, equal to 2*62 of slaked lime to 
 1 of unslaked. 
 
 No. 10. 
 
 Mixed as lime 
 putty and pressed 
 into a mould and 
 when thoroughly 
 9 ozs. -l dried measured 1 5. 
 85 cubic inches and 
 weighed 9 -5 ozs. 
 This contracted in 
 ^dry'g 1*67 cubic in. 
 
 23*29 cubic inches slaked lime, 
 
 No. 4. D. Sturtevant & Co., Kiln near Lyons, Prairie Stone. 
 
 16*80 cubic inches of unslaked lime weighed 14 ounces, gave as a 
 result after being slaked by drowning, a volume of 55 cubic inches oi 
 slaked lime, and weighed 17 ounces, equal to 3*33 of slaked lime to 
 1 of unslaked. 
 
 No. 11. 
 
 r 
 
 82*5 cubic inches of fine and coarse 
 
 sand, 67*50 ozs. 
 
 55-0 « " slaked lime, 17*00 
 
 137.5 
 
 S4-50 
 
 Mixed as mortar 
 as 1 1-2 of sand to 
 1 of slaked lime or 
 as 5 of sand to 1 ot 
 '{unslaked lime, 
 
 I nearly, and when 
 P'i.'fesjly drj^fl mea- 
 sured '97'ci',biu ins.; 
 ' ' Lwoi^hsd 100 (M^. ' 
 
180 
 
 COMPARATIVE RESULTS. 
 
 Weight of 
 
 Ko. Names of Materia\3. 1 cubic ft. in Iba, 
 
 1 2 measures of sand, 1 Utica hydraulic cement, 1 slaked 
 
 lime (mortar) * 101.25 
 
 2 2 " sand, ^ Utica hydraulic cement, J slaked lime 
 
 (mortar) 120.70 
 
 3 s *' sand, i brick-dust, 1 slaked lime (mortar) 93.10 
 
 4 1 ** Utica cement (without sand) 75.27 
 
 5 1 sand, 1 brick-dust, 1 cement, J slaked lime 
 
 (mortar) 93.60 
 
 6 1 ** slaked lime as putty (1st experiment) 63.57 
 
 7 J slaked lime, J Utica cement 79.58 
 
 8 7 " sand to 1 of unslaked lime (mortar) 112.22 
 
 9 1 " slaked lime as putty (2d experiment)...- 65.59 
 
 10 1 " " (3d ) 64.08 
 
 11 H sand, 1 of slaked lime (mortar) 111.33 
 
 12 1 " Utica cement exposed to the air 5 months be- 
 
 fore being mixed, and then dried for 3 
 months 96.77 
 
 13 1 " Sandusky cement, fresh from cask (without 
 
 sand) 85.71 
 
 14 1 measure Utica cement 1 1-2 of sand, under water for 117.02 
 
 12 months, and then dried for 3 months 
 
 15 1 " Utica cement, 2 of sand, 121*93 
 
 16 1 " Utica cement, 1 of sand, 114-54 
 
 17 1 sand, 1 slaked lime (mortar) 102-12 
 
 18 Utica hydraulic cement, in a dry state (in cask) 52-36 
 
 19 Unslaked lime, in a dry state (1st experiment,) 75*27 
 
 20 " (2d ) 90*31 
 
 21 (3d ) 91*01 
 
 22 " (4th " ) 90.00 
 
 23 Slaked lime, " (1st " ) 37*30 
 
 24 " (2d ) 29-88 
 
 25 " " (3d u^:.„ 41-72 
 
 2a " (4tlf-' ' '\ . 33*38 
 
 27 !3r^ckdThst,' I' 110*00 
 
181 
 
 COMPARATIVE RESULTS— ContiKued. 
 
 Weight of 1 
 
 No, Names of Materials. cubic ft. in Iba. 
 
 28 Fine sand, in a dry state, (Lake Michigan) 88*36 
 
 29 larger grains, in a dry state, (Lake Michigan) 94 '90 
 
 30 Coarse sand, large grain, in a dry state (pit sand) 124*36 
 
 Note. — M. Berthier says that a late analysis of Parker's Roman 
 cement shows that its constituents are of chalk and common clay 
 and he proposes the manufacture of a similar cement by the mere mis- 
 ture of them in certain proportions. Thus one part of the clay and 
 two and a half parts of the chalk set almost instantly, and may, tliere- 
 iove.. be regarded as Roman cement. 
 
 FINIS. 
 
PLATE I. 
 
 Fig. 3. Fig. 4. 
 
 Fig. 1, plan (or horizontal section). Fig. 2, section on line E — F. 
 Fig. 3, section on shed, and part of exterior. Fig. 4, section from A 
 towards the shed. 
 
 A Hatchway. B Furnace. C Grate-bars. D Ash-pit. E Rough 
 chalk-ashes. F Level of ground beneath shed. G Level of ground 
 at hatchway. 
 
PLATE n. 
 
 CEMENT KILN. 
 
PLATE in. 
 
INDEX. 
 
 PAGE. 
 
 Acidulous gas in the induration of mortar, agency of. 46 
 
 " from lime, necessity of expelling..- 82 
 
 Air in the preparation of lime, agency of. 10 
 
 Analysis of trass and puzzolana 113 
 
 " limestones, and mode of testing their several properties 120 
 
 Beton, description of French 132 
 
 Black rock of Quebec 125 
 
 Bricks, observations on.., 51 
 
 Buildings, cause of speedy ruin of, and precautions necessary to 
 
 ensure safety of. 51 
 
 effect of agitations and percussions upon " 
 
 Caustic or quicklime, on 55 
 
 Cements general remarks upon, and descriptions of varieties of 
 
 experiments upon old 52 
 
 ^' specification of Dr. Higgins' patent 101 
 
 water on... 120 
 
 " Sheppy and Harwich o- 122 
 
 " for incrustations, Dahl's, Hamlin's, Leardels, mastic... 129 
 
 *' Beavan's building mortar 130 
 
 " for floors, terraces, roofs, &c., Venetian " 
 
 " used in construction of Eddystone lighthouse, Smeaton's 131 
 
 ** for mending earthenware, cold and hot 135 
 
 " or a'-tificial puzzolana. Frost's water " 
 
 ** for waterproof purposes, Dobb's " 
 
 " for floors, &c., bituminous limestone 137 
 
 " and iron rust, plumbers' and coppersmiths' diamond... " 
 " for manufacturing purposes, jewellers', carpenters', and 
 
 sundry other 138 
 
 " for mouldings, repairing pipes of aqueducts, air-pumps " 
 
 " for small work, for marble and stone, a delicate 134 
 
 Tartar „ 
 
 Parker's Roman 133 
 
 " for voltaic plates and wooden troughs, chemists' and 
 
 statuaries, steam, electrical, bituminous 139 
 
ii. 
 
 INDEX. 
 
 PAGE. 
 
 Cement for uniting stones, floors, &c., and used for ironwork 
 
 at Southwark Bridge, London 140 
 
 " description ot kiln for burning (with illustration) 155 
 
 " rule for making an artifical 157 
 
 " " " equal to the best English 
 
 water cements 158 
 
 " rule for testing the qualities of. 160 
 
 " comparative cohesive strength of. 163 
 
 properties which ought to be fully understood 124 
 
 " Thames tunnel, Lond., fully establishes the character of ** 
 
 " experiments on artificial (water) 126 
 
 " powder, calcined 122 
 
 Composition for mouldings , 134 
 
 " for incrustations 132 and 135 
 
 Experiments showing how quickly lime imbibes acidulous gas 
 
 and is injured by exposure to the air 38 
 
 ** showing the quantity of water imbibed by lime... 40 
 
 ** and observations made to determine whether mor- 
 tar becomes better by being kept long before it is 
 
 used 42 
 
 ** showing the agency of acidulous gas in the in- 
 duration of mortar, and circumstances which im- 
 pede or promote it 45 
 
 showing the effects of finest sand and quartoze 
 powder in mortar; observations on the finest cal- 
 careous cements, &c 67 
 
 " made on a larger scale,with best mixture of sands,&c, 67 
 
 " showing the integrant parts of gravel 70 
 
 " " effects of plaster-powder, alum, vi- 
 
 triolic acid, earth-salts, and alkalies in mortar, &c. 73 
 " showing the eff'ects of skimmed milk, serum of 
 ox-blood, decoction of linseed, mucilage of linseed, 
 linseed-oil and resin in mortar, and the effect of 
 
 painting incrustations 76 
 
 showing the effect ofsulphur introduced into mortar 79 
 " " crude antimony, regulus of 
 antimony, lead matt, potters' ore, white-lead, &c., 
 in mortar 81 
 
INDEX. iii. 
 
 PAGE. 
 
 Experiments showing the effect of iron scales, colcothar, ochres, 
 &c., &c., in mortar, and advice concerning inside 
 
 stucco and damp walls 83 
 
 " showing the effect of common wood-ashes, &c., 
 
 &c., in mortar 89 
 
 ** showing the effect of bone ashes and charred bones, 
 and theory of their agency in the best calcareous 
 
 cements 95 
 
 " conclusions drawn from other 127 
 
 results and inferences obtained from 146 
 
 Experimental comparison of chalk with stone lime ; advice to 
 manufacturers of chalk-lime concerning the art of making 
 
 it equal, if not superior, to stone-lime 108 
 
 Eelspar, ground 132 
 
 Eire-proof floors, on 146 
 
 Elint-powder injurious to mortar 64 
 
 Gravel in mortar, use and properties of. 65 
 
 " a substitute for sand, varieties of. 21 
 
 " remarks on 65 
 
 Gypsum, and other earthy matter in lime, how detected 9 
 
 Hydrate of lime 58 
 
 Hydraulic lime, M. Berthiers 136 
 
 ** mortar, essential constituents of. " 
 
 " limes, M.Vicat's method of preparing 145 
 
 Incrustations or stuccoes, experiments or remarks on 67 
 
 " remark on method of coloring 83 
 
 " description and causes of damp on, and remedies for 86 
 
 Kiln, description of cement (with illustration) 155 
 
 " lime, description of a modern (with illustration) 150 
 
 Lime and limestones, remarks on, and description of varieties of 6 
 " Dr. Higgins' observations and experiments on the different 
 
 modes of burning and results 7 
 
 " the art of making good, and test thereof. 10 
 
 " Dr. Higgins' remarks on the different modes of slaking. . . 23 
 
 " injured by exposure to air 41 
 
 " qualifications and components of good 53 
 
 " effete and slaked 56 
 
 <^ remarks on plasterers' 44 
 
iy. INDEX. 
 
 PAGE. 
 
 Limes, properties of rich, meagre, and purest..**. 58 
 
 " observations from Lieut.-Col. C. Pasley's work on... 118 
 
 " on water or hydraulic... 119 
 
 " expansion of. 125 
 
 " M. Vicat's opinion of the best combinations of. 144 
 
 *' method of preparing artificial hydraulic 145 
 
 " on the measurement of - 148 
 
 " different modes of measuring.............. 149 
 
 Limestone, on the burning of...., 150 
 
 " suited for hydraulic cements, varieties of. 132 
 
 *' in burning, vitrification of. 9 
 
 Lime-water in the composition of mortar, superiority of. 24 
 
 Maltha, on the ancient 133 
 
 Manganese, property of hardening underwater 136 
 
 Mortar, components of. ........^ 6 
 
 *' sundry^ ingredients often introduced into 24 
 
 on the composition of various kinds of ; their application, 
 properties, and relative values, with occasional notes of 
 
 the experiments of Dr. Higgins and. other authorities... 25 
 
 ^ on. the induration of. 30 
 
 " principal cause of the imperfection.of.......« 37 
 
 ** on. the preparation of common 55 
 
 *• proper consistency and induration cf. 57 
 
 " relative proportions of lime and sand in 58 
 
 on various substances sometimes added to 59 
 
 Plaster-of-Paris, on 1 33 
 
 Buzzolana,Col.Pasley's inferences from various experiments upon 1 41 
 " M. Vicat's rules for judging of the quality of natural 
 
 or artificial 142 
 
 M. Baggi, Count Chaptal, Gen. Treussart, &c., ex- 
 perience on e 143 
 
 ** description of. 112 
 
 " analysis of. 113 
 
 " artificial 114 
 
 " Col. Pasley's experiments on artificial 116 
 
 Plasterers* mortar, remarks upon 44 
 
 Phlogisticated air in chalk and limestone, remarks on 37 
 
 ilecipes for coal-ash mortar, Dutch terras mortar, and puzzolana 141 
 
INDEX. 
 
 V. 
 
 PAOB. 
 
 Recipes various, for cements and mortars 129 
 
 " for manufacturing and domestic purposes 137 
 
 Remarks-general 5 
 
 Road-drift, &c., varieties and qualifications, and test of. 11 
 
 Rubbish in mortar, effect of old ground 66 
 
 Rubble, Dr.Higgin's experim'ts on sundry varieties of, and results 12 
 " ** in the composition of mortar..... 17 
 
 " , " . test of best proportion in mortar 20 
 
 Sand 10 
 
 ' * Dr. Higgin's remarks on varieties used for building purposes 1 2 
 
 " objectionable for mortar, sea 10 
 
 " general remarks on • 21 
 
 " remarks on washing and preparing 64 
 
 " and lime, sundry experiments and results 33 
 
 Trass (Dutch), or terras, description of. 131 
 
 " analysis of, and puzzolana 117 
 
 Water, description of varieties and remarks upon.,. 22 
 
 " Dr. Higgin's remarks on the application thereof in mortar 23 
 Water-tight roofs, on the construction of. 146 
 
 ADDENDA. 
 
 AMERICAN RESOURCES OF MATERIAL, &c., 
 
 BY "COSMOrOLlTAN." 
 
 PAGE. 
 
 American local resources 166 
 
 Cement of the Romans, M. Loriet's remarks on the 174 
 
 Concrete and Beton, strength of, and remarks on 176 
 
 Experiments, result of the author's, ...» 178 
 
vi. * INDEX. 
 
 PAGE. 
 
 Hydraulic cement, M. Pctot's notes and analysis of. 168 
 
 " analysis of European " 
 
 limestone, " " the Manlius 170 
 
 " " " " Chittenango " 
 
 Lime, mortar, cement, concrete, beton, &c., sundry opinions on 175 
 
 Limestone, United States varieties of. 166 
 
 " Professor Roger's report of nagnesian 171 
 
 Ulster county hydraulic „ 
 
 Puzzolana, analysis of. 172 
 
 " trass, basalt, and schistus, analysis of. " 
 
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