BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF 1891 A^iMiJr.r J/U/Mff.. Cornell University Library arV18533 Electricity as a motive power. 3 1924 031 230 448 olin,anx The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031230448 ELECTEICITY MOTIVE POWEE BY COUNT TH. pU MONCEL, MEUBBE DB l'iNSTITUT I>B CBANCB; AND FEANK GEEALDY, mG£III£n£ DES FONTS EI CBAUBStsB. TRANSLATED, AND EDITED WITH ADDITIONS, BY C. J. WHAETOE", ASSOC, see. of'tkl. engs, and blec. WITS 113 JENGBAYINGS AND DIAQBAMS. LONDON: E. & F. N, SPON, 16, CHAEING CEOSS. NEW yOEK : 35, MUEEAY STKEET. 1883. PREFACE, Count Dd Monoel's work, ' L'Electricite comme Force Motrice,' has only quite recently been pub- lished in France ; and although I was favoured by him with the rough proofs, in order that the trans- lation should appear as soon as possible after the original, some little time necessarily elapsed; and although that time has been very short, it was necessary, before this present book went to press, that considerable modifications and additions should be made, in order that it should bring down to the present moment the history of all that has been done in the employment of electricity as a motive power, and the almost daily developments and im- provements that are taking place. If further proof were required, this would show how important and pressing a subject at the present moment is the transmission and distribution of power. Owing to the recent wonderful develop- ments in the various applications of electricity, the question of utilizing for the benefit of mankind the vast powers of nature at present wasted has assumed a practical shape, and the number of recent experi- iv Preface. ments, books, papers, lectures, &c., by eminent and learned scientists, shows what a great future is looked for by those who have made a study of the subject. But at the same time very little of the diflSculties or the possibilities of that subject are appreciated by the general public, and it is to them that I trust the present work may be useful and instructive. C. J. Whaeton. 8 and 9, holboen vlabuct, London : August 1883. CONTENTS. INTEODUCTOET CHAPTEE. FAGS INTBODUCTION 1 Principles on whioli tlie construction of Electromotors is founded 6 Electro-magnets and their construction 8 Laws of Electro-magnets 17 Means employed to diminish, the detrimental effects pro- duced in Electromotors .. .. 29 PAET I. FIRST PBASE OF ELECTROMOTORS. CHAPTEE I. HISTOEIOAL SUMMARY 43 CHAPTEE II. HIBTOEICAL MOTORS 51 vi Contents. CHAPTEE III. PAGE EARLY ELECTROMOTORS 82 I. Electromotors founded on the D^fnainio properties of Currents 82 II. Electromotors founded on the attraction of Iron to Electro-magnets 91 III. Electromotors into which Gravity is introduced as a source of power 125 CHAPTEE IV. SPECIAL APPLICATIONS OF BLECTROMOTOES 134 CHAPTEE V. ELECTRO-CHEMICAL MOTORS.. 145 PAET II. SECOND PHASE OF ELECTROMOTORS. CHAPTEE I. BEVERSIBLB MACHINES 151 CHAPTEE II, GENERAL REMARKS ON MODERN MOTORS 166 Contents. Tii CHAPTEE III. FAGE MODBBN SMALL MOTOES 177 CHAPTEE IV, APPLICATIONS OF BMALL MOTOES 194 CHAPTEE V. riEBT APPLICATIONS OF TEANSPOET OF FOECB ,. ., 210 CHAPTEE VI. FIBST APPLICATIONS FOB THE LOCOMOTION OF CAEKIAGES 219 CHAPTEE Vn. TEANSPOET OF FOECE AT THE ELECTEIOAL EXHIBITION OF 1881 234 CHAPTEE VIII. EBOBNT APPLICATIONS AND BXPEEIMENTS 244 CHAPTEE IX, THE DISTEIBUTION OF ELECTEICITT 269 NOTES 292 ELECTEICITY A MOTIVE POWER. INTKODUCTION. Motive Power is the basis of most great industries ; and from the earliest ages of the world, man has been endeavouring to discover its best and most economical source. For a long time this power was obtained from the muscular energy of man and beast, but it was understood that this might be better utilised, and it was thought that it might be more economically and more powerfully obtained from the elements of nature. The effects of gravity, of running water, and of the winds, were first enlisted, and machines were made, capable of transforming these natural actions into a circular movement, sus- ceptible in its turn of being applied in a thousand different ways to the various requirements of arts and manufactures. But there is not always running water at command, the winds are very uncertain and changeable, and the attraction of gravity can only produce a profitable action when it can be in- B 2 Electricity as a Motive Power. definitely continued, which can only be obtained from water falling from a height. The progress of human industry, besides, necessitated motors capable of being placed where their want was felt, and whose power could be deyeloped in any proportion and at any time that might be required; in fact, that they should be entirely subservient to human will. This problem in past ages formed an incentive to inventors, and led to the search for perpetual motion, for which, even in these days, some illusionists still strive; but when it was understood that, in obtaining such a result, one of the great laws of nature (equilibrium) could not exist, healthy minds could only look to physical actions for the solution of the problem ; and it was Denis Papin who opened the way by discovering the expansive power of steam, and himself constructed a motor founded on this principle. The history of this magnificent discovery is well known, and the immense resources which steam-engines have given us. To recount them would be to give the history of all modern in- dustries. However, this source of motive power has not remained the only one to be employed ; and now-a-days we see that engines founded on the ex- pansive power of gas play an important part in small industries ; and every day they tend to multiply : a clear proof that the subdivision of motive power has become the question of the day. From this point of view, however, the problem has been lately solved in a satisfactory manner by a new means, by the help of a physical agent from which it could scarcely have Introduction. 3 been hoped for half a century ago, and which has recently revealed to us effects which one could then hardly have dared to conceive. When we reflect that now we are enabled to transport to almost any distance a force of several horse-power by a wire which could easily be passed through a keyhole without any visible movement or any change in its appearance, imagination itself is stupefied, and we ask ourselves if it is not magic ! This, however, is what electromotors can do to-day. Thanks to them, natural forces, hitherto useless, can perform at. a distance from the source, work which could not have been made use of on the spot. Position now means nothing, and we may demand a supply of power as we demand a supply of water or gas ; the same fluid which gives us power can also give us light. What progress science has thus made in the course of a few years ! Then electricity with great difficulty could develop only a few foot pounds of work ; and now we work ploughs, enormous pumps, cranes, mechanical saws, planing machines, punching machines, drilling machines, and railways even ! The last Exhibition showed these marvels. The first attempts to obtain motive power from electricity were not successful. Many inventors spent large sums of money only to obtain insig- nificant results ; and it was only when the rever- sibility of continuous current induction machines was tiled, that an advantageous solution of the problem could be looked for. Till then we had no electric currents sufficiently powerful to obtain any appre- B 2 4 Electricity as a Motive Power. ciable work. But when it was shown that with two dynamo machines coupled one to the other, we could receive from the one more than half the motive power expended in the other to produce the elec- tricity, we might imagine that not only were we in possession of a system of transmission of power to a distance which could often be utilised very advan- tageously even under these conditions, but that the electromotive machines themselves were capable of furnishing a force much greater than was supposed by supplying them with sufficiently powerful cur- rents. Up till then, in fact, we had never been able to produce in this manner a force reaching one horse- power, and the most perfect motors did not give more than one or two kilogrammetres of force, which was ridiculous when compared with the expense which they necessitated. We were also on a wrong track, for it was sought to increase the power by an exorbitant increase of the size of the electro-magnetic apparatus. Since the question has entered the new phase, it has been studied in a more serious manner, and small motors have been made which can now furnish appreciable and useful work. We will devote a chapter to these little motors, of which the best known types are those of Deprez, Trouve, Griscom, &c. ; but we must explain here that power of any magnitude can only be furnished by con- tinuous-current dynamo-electric machines, such as those of Gramme and Siemens. The causes which led to the failure of the early attempts were principally, that it was only sought Introduction. 5 to utilise the direct attractive force, which is, as all know, extremely limited and almost the same for very large electro-magnets as for small ones ; that the arrangements of the commutators were very favour- .able to the development of induced currents in the coils which acted in a contrary direction to the cur- rent transmitted ; that magnetisation and demagneti' sation took place sluggishly in electro-magnets of any size, and therefore only a small part of their magnetism could be utilised, becoming even hurtful when it was not required ; that the direct attractions between magnet and armature tended to bend the supports, necessitating too great a separation between the parts for the best of the work to be obtained ; and finally, that the commutators were damaged by sparking, especially of the extra currents. We shall have occasion presently to study the various means proposed to modify these different defects, but they were evidently insufScient, since good results were never obtained, and it was only when the new appli- cation was discovered that these obstacles were sufficiently surmounted to enable the machines to work smoothly. These considerations have pointed out to us the order that should be followed in this work, which we will divide into two parts, the one treating of the early phase of electromotors since their origin till the time when the action of induction was discovered, and the other treating of this second phase of the question, with everything relating to the researches and applications of practical motors, in- cluding the transmission of force and its distribution. 6 Electricity as a Motive Power. It has, however, seemed necessary, to enable the reader thoroughly to grasp the technical parts of the question, to give some preliminary ideas as to the electric means employed in such motors, and these ideas -will be found in the next chapter. Principles on which the Construction of Electromotors is founded. All the effects of the electric fluid capable of giving an impulse to a body, or of deyeloping an attractive or repelling force, may be mechanically combined so as to form an electric motor. Thus, the reciprocal effects of electric currents on each other, the action of currents on magnets, of magnets on currents, and of temporary magnets on non-magnetised bodies, may, if the electric force and the size of the parts subjected to the action be sufSciently increased, be utilised as electro-dynamic motors. It may be understood that, possessing in electricity a force which may be cut off at a moment's notice by simply disconnecting the current, very simple mechanism suffices to transform the impulse given by it into a continuous rotary movement. Of all these properties, however, electro-magnetic attractions and repulsions, and those of parallel currents in the same direction, as in solenoids, have been the most utilised, setting aside the reversibility of continuous current dynamo- electric machines, the theory of which has not yet been fully elucidated. To obtain a rotary movement by electro-magnetic attractions it is sufficient, as is easily understood, to Introduction. 7 cause a succession of impulses resulting from these attractions to act upon a movable axis, and to provide this axis with a commutator, which before each electro-magnetic action closes the circuit, and opens it after the effect is produced. This problem may be directly solved by attaching to an axis a series of armatures, arranged like the blades of a paddle-wheel round a non-magnetic circumference, and moving before a like number of electro-magnets fixed round this circumference ; or, indirectly, by fitting to this axis a crank and connecting-rod capable of trans- forming into rotary movement the to-and-fro move- ment caused by the momentary attraction of one or more armatures to the poles of electro-magnets fixed before them. The effects may also be combined so that the reciprocal actions of the armatures and electro-magnets may give rise to two movable systems acting simultaneously on the same axis, and as this arrangement may be applied to all the electric or electro-magnetic properties of which we have spoken, we see that electromotors of very dif- ferent patterns may be constructed, which may be classed under various heads ; but before describing them, it will be well to give some details of the best form of the different parts entering into their con- struction, and we will first speak of electro-magnets and solenoids, which are the most important of these parts. Electricity as a Motive Power, ELECTKO-MAGNETS AND THE CONDITIONS FOE THEIB BEST CONSTKTIOTION. Different kinds of Electro-magnets. — An electro- magnet is, properly speaking, only a bar of iron, surrounded by a coil of insulated wire wound in layers and constituting a sort of bobbin, to which has been given the name of magnetising bobbin. This bar being straight, as in Fig. 1, constitutes a bar electro-magnet; when bent, as in Fig. 2, it is called a horse-shoe magnet. But these latter electro-magnets may also be made of two iron bars of equal length connected by an iron cross bar, as shown in Figs. 3 and 4. The bars are then called the arms, and the magnetising bobbin, instead of Fig. 1. Fig. 2. Fig. 3. Fig. 4. covering the whole magnetic system, is divided into two, and only covers the two arms. The parts covered by these bobbins are generally called the magnetic cores. Sometimes only one of the arms is covered with a bobbin, as in Figs. 5 and 6, and the electro-magnet is then called a one-legged electro- magnet. Sometimes several arms are placed on a single base, as in Figs. 7 and 9, thus making what Introduction. g are called multipolar or consequent pole electro- magnets. In this case the poles are alternately of opposite signs. In other arrangements of electro- magnets with two poles the base is made circular, Fig. 5- Fig. 6. Fis. 7. Fig. 8. ^ >^ '"fflti and an iron cylinder fitted round it which envelops the arm on which the magnetising coil is wound, as in Fig. 8 ; this is called a tubular electro-magnet. In these conditions, one of the two poles forms a circular rim, in the centre of which is the other pole, and between them the magnetising coil. These Fig. 9. Fia. 10. Fig. 11. electro-magnets, as well as the others, may be cylin- drical or oblong, as shown in Fig. 10 ; the latter are most used at the present day. Again, as in Fig. 11,'the cylindrical covering is sometimes made 10 Medricity as a Motive Power. to cover only half of the bobbin, and another cylinder exactly similar, being fitted to the other half, forms a sort of cylindrical iron case with the iron core in the centre and containing tlie magnetising coil. This is a circular electro-magnet, and the poles are constituted by the two iron cylinders fixed to the two extremities of the core. 'I'hey must, in conse- quence, be separated by a space of several milli- metres at the middle of the bar. In this case the electro-magnet can revolve on its armature, always acting upon it by its two poles, which is sometimes very useful. This arrangement, first conceived by Nickles, has often been made use of in electrical applications, and even in electromotors, as we shall see later. The preceding electro-magnet, deprived of the cylindrical covering and retaining only the iron rings where they are fastened, is called a circular electro-magnet with iron rings, and is often applied in the same cases as the other, if the arma- ture is broad enough to unite the two rings. Some- FiG. 12. Pig. 13. times instead of two rings there are three, as shown in Fig. 12. This arrangement has also been em- ployed with advantage as a horse-shoe magnet, but then the rings act only as iron pole pieces. Fig. 13 Introduction. 11 is an electro-magnet of this description. There are also many other arrangements of electro-magnets, such as those in Figs. 14 and 15, by means of which circular plates are magnetised, as in Fig, 14, or so Fia. 14. Fis. 15. Fig. 16. as to create north and south poles at different points of their surface, as in Fig. 15 ; but as these electro- magnets are little used, we will say no more about them now ; , we will only explain that , all these electro-magnets may have their poles prolonged or fitted with iron pole pieces. We shall have occasion to speak of the advantages and disadvantages of these different forms, but we will first say a few words on the manner in which their armatures should be arranged. The armature of an electro-magnet may be parallel or at an angle with the line joining the poles. In the first case it is sustained by rods or levers which work it parallel to this line. In the second case it is pivoted at one of its extremities so as to be very near one pole, and at a distance from the other. It may even be worked by a pivot on the nearer pole itself and constitute an expansion of this pole. We shall see directly that the electro-magnetic effects are infinitely stronger when the armature is acted 12 Electricity as a Motive Power. on by both poles than by only one, and this is why horse-shoe magnets are generally preferred ; but the same advantages may be derived from a bar electro- magnet by bending the armature, and so arranging it as to be able to move before the two magnetic poles, as shown in Fig. 17. The same sort of attrac- tion may also be obtained with a straight armature and a bar electro-magnet fitted with iron pole pieces. Fig. 17. Fio. 18. Lastly, an attractive action may be obtained by placing the armature between the two poles of an electro-magnet, so that the line of the poles and the axis of the armature pivoted in the centre form an X, as in Fig. 18. But one of the arrangements most used in electro- motors is that based on the direct force of magnetic axes, which tends to set an armature moving parallel and tangential with the poles of an electro- magnet in a line coinciding with the polar axis, as wiU be seen in Fig. 19. A longer attractive stroke is thus obtained, but the action is not so powerful. This same action may be obtained with a straight armature pivoted between the poles of an electro- magnet, if these are enlarged and hollowed out, as shown in Fig. 20. Polarised armatures are often Introduction. 13 employed; and as they would rapidly become de- magnetised if they were made of steel bars mag- netised, and as the attractiye action is stronger with iron than with steel, they are polarised by putting Fig. 19. Fig. 20. them in contact at one end with a powerful per- manent magnet. Cecchi, Siemens, de Lafollye, d'Arlincourt, etc., have constructed some very ingenious magnets on this principle, which have been very largely employed in instruments of pre- cision ; but we only refer to them here in passing, as they have never been used for electromotors. The same may be said of Hughes's magnets, in which the iron cores, being fixed to the poles of a very power- ful permanent magnet, are always magnetised, and only act when temporarily demagnetised by the action of their bobbins, thus being of very delicate action. Polarised armatures have also been used. by making them of straight electro-magnets; but this means has seldom been applied except in telegraphy. Solenoids. — Of all the properties of electric cur- 14 Electricity as a Motive Power. rents, that which has been most applied is the attraction exercised by a solenoid on a bar of iron fitting loosely inside the coils. Under the influence of the magnetic action developed in this bar by magnetisation, an attraction of parallel currents is produced between it and the coils of the solenoid or bobbin which tends to draw the bar into the bobbin until the two extremities of the bar correspond with those of the bobbin. By this means a considerable stroke is obtained, which may be still further increased by partitioning the bobbin, as Page and Marcel Deprez have done, and getting several suc- cessive actions. We shall notice later an important application of this arrangement. Fig. 21. Fig. 22. Fig. 23. Fig. 24. I'his action may be still further increased by adding iron rings to the two ends of the bobbin, as shown in Fig. 21, because the attraction of these rings is thus added to the action of the parallel currents. By filling half the bobbin with an iron core, as in Fig. 22, it is made an electro-magnet, and its action, Introduction. 15 added to the attraction of the solenoid in the first half of the bobbin, greatly increases the effect. The same principle may also be adopted for two bobbins placed alongside one another, as shown in Fig. 23, when the electro-magnets become horse-shoe magnets, which increases the strength of the action. In J^'ig. 24 is represented an electro-magnet armature which consists of a bar electro-magnet with expanded flat poles capable of being fitted before the poles of an electro-magnet. Bare Wire Electro-magnets. — For a long time it ■ was thought that the coils of electro-magnets must be constructed of copper wire perfectly insulated with cotton or silk; but Carlier proved, in 1863, that those made of perfectly clean copper wire without covering were just as good ; it was only necessary to be careful that the different layers should be well separated by pieces of paper. Good electro-magnets may be thus obtained which are as powerful as others when the current employed is not of very high ten- sion, and they possess the advantage of furnishing no appreciable extra-currents. These electro-magnets are, however, somewhat difScult to construct. At the Electrical Exhibition of 1881, an American inventor, de Dion, exhibited electro-magnets of this description constructed with oxidised copper strips, which were remarkably powerful. We are surprised that con- structors have not employed such electro-magnets to a greater extent. Complex arrangements of Electro-magnets. — Besides the combinations of electro-magnets of which we 16 Electricity as a Motive Power. have just spoken, an attempt has been made to increase their power and rapidity of action by special arrangements of their armatures and magnetic core. Among these arrangements we will mention that in wliich the magnetic core is composed of cylindrical iron tubes one inside the other, each wound with magnetising coils of various thicknesses, the ends of all the coils being connected. These electro-mag- nets are then called multiple cored, and have been used in several different ways by Camacho and Canoe, who have obtained very good results from them. In Camacho's arrangement the cylindrical cores consist of iron tubes riveted to the cross-bar of the electro-magnet, and are four or five in number, besides a central solid iron core. The coils wound on these tubes are not generally very deep, except the outside one, in which there are more turns than in all the rest together. They are generally joined up in series, that is to say, so that the current goes through them all in succession. In Cance's arrangement these cylindrical cores consist of a large number of iron wires laid close together on and across each coil, which are pressed as closely as possible against the cross-bar so as to establish a magnetic contact between that and this iron covering. It will be understood that these electro-magnets are as easy to construct as ordinary ones, since these small rods of iron may be applied to the different layers in propor- tion to the length of wire wound upon them, and for this there is no necessity for the magnetising coil to be broken at each tubular core thus formed. Introduction. 17 The advantage of these arrangements, from a scientific point of view, is that the residual magnetism is considerably diminished by the subdivision of the iron mass into a large number of diminutive indi- vidual magnets, which are much more rapidly mag- netised and demagnetised than a single mass. They also exert a greater force in consequence of the mutual actions of the tubes on each other. For the same reason armatures composed of thin iron plates are advantageous. Camacho and Chutaux have constructed electromotors on this principle, which were very successful in their time. LAWS OP ELECTRO-MAGNETS. The first data, a knowledge of which is necessary in considering electric motors, are the laws of electro-magnets, and they may be summed up as follows : — 1st. The force of an electro-magnet, or its mag- netic moment, is proportional, for a given arrange- ment and circuit resistance, to the intensity of the current, and for a like electric intensity, to the num- ber of turns in the magnetising coil. But when the electric intensity and the number of turns in the coil remain constant, the dimensions only of the electro- magnet being varied, this force is proportional to the square root of the diameter of the iron core and to the fourth root of its length; so that when all these quantities are variable together, the magnetic 18 Electricity as a Motive Power. moment is found when all the Talues are mnltipKed together. 2nd. The attractive force exerted between an electro-magnet and its armature by reason of their mutual action on each other is proportional to the squares o"f all the quantities just mentioned. If the formulae representing these values are examined mathematically, it will easily be seen that they are susceptible of maximum, and the conditions necessary in order to attain this maximum may be established : first, with reference to the resistance to be given to the magnetising coils ; secondly, wiUi regard to the proportion which should exist between the depth of the coils and the diameter of the core ; thirdly, with reference to the length of the iron core : and these conditions of maximum may be stated in the following manner : — 1. For electro-magnets of the same dimensions having bobbins of the same diameter, the best sized wire for the coils is that which will give an equal resistance to that of the exterior circuit, at least when taking into consideration only the metal wire without its insulating covering. 2. If we take into consideration the thickness of this covering, the best coil is that of which the resistance will be to that of the exterior circuit as the diameter of the bare wire is to that of the same wire with its insulating covering. 3. Between several electro - magnetic bobbins wound with the same wire but having a different number of turns, that will furnish the best results Introdwtion. 19 on a given circuit of resistance, of which the resist- ance is to the exterior circuit as the depth of the coils added to the diameter of the iron core is to that of the coils alone ; 4. The best depth of coil for a given number of turns is that which equals the diameter of the magnetic core ; 5. The most advantageous length for the mag- netic core is eleven times its diameter ; which means practically, that each arm of the electro- magnet should be six times the length of its diameter ; 6. If there are branch circuits, the resistance of an electro-magnet introduced on one of these branches should equal the total resistance of the exterior circuit including the other branches taken inversely — that is to say, as if the electro-magnet and the battery had changed places ; 7. The calculations that may be deduced from these various laws and the formulae leading to them, enable us to establish the following principles, which are of great importance in electric applications : — I. — For equal resistances of circuit, the diameter of an electro-magnet in maximum conditions must be proportional to the electromotive force of the battery employed. n. — For equal electromotive forces this diameter must be in inverse proportion to the square root of the resistance of the circuit, including that of the battery. III. — For equal diameters, the electromotive 2 20 Electricity as a Motive Power. forces must be proportional to the square roots of the resistance of the circuit. IV. — For a given magnetic force, and with electro- magnets under maximum conditions, the electro- motive forces of the exciting batteries should be proportional to the square roots of the resistance of the circuit. These laws have been demonstrated and proved in a small book published under the title of ' Deter- mination des Elements de Construction desElectro- aimants,' by M. Th. du Moncel.* They are, however, only true for electro-magnets attaining a suitable magnetic saturation. When this is not possible, either in consequence of their too great size or the shortness of time during which they are acted upon by the current, it is different; and the resistance of the magnetising coils should then always be less than that of the exterior circuit, in proportion to the length of time during which the current acts. To apply these different laws to the construction of an electro-magnet, we first commence by finding out the diameter e of its magnetic core by means of the formula c = -J -0159, in which E represents the E. M. P. in volts of the battery, E the resistance of the exterior circuit in ohms ; the figure obtained is in decimals of a metre. Knowing c, we at once have the length of each arm of the magnet, which is 6 c, or 12 e for the two, and * Translated and edited in English by C. J. Wharton. Introduction. 21 the diameter of the wire of. the helix is obtained by means of the formula 9 = ^/^f! -0000020106, in which / is a coefficient which for electromotors is 1'4. It expresses the ratio existing between the diameter g of the covered wire and the diameter -^ of the wire naked. The length H of this wire will then be given by the formula ^ — , and the total 12 ">( stopped as easily, whi6h makes it extremely useful in small industries. One of the disadvantages of the engine is the development of a great amount of heat in the interior of the chamber, which would entail the nipping and distortion of the movable parts, if it were not cooled from the exterior. This is effected by a layer of cold water, which is made to circulate round the 150 Electricity as a Motive Power. cylinder inside a jacket, and this layer of water flows away and is automatically renewed when it becomes too hot. In the latest patterns of this engine the Bunsen battery was advantageously replaced by a Clamond thermo-electric battery, fed, as also the motor itself, by ordinary lighting gas. END OF FIRST PART. SECOND PART. SECOND PHASE OF ELECTHIO MOTOES. CHAPTER I. EEVEESIBLE MACHINES. As we have seen, the discoveries with respect to electric motors adapted to produce mechanical work by electricity have been, as far as we have gone, almost restricted to the application of a single prin- ciple : the attraction of a soft-iron armature by an electro-magnet or a solenoid. It was natural to begin thus ; the movement thus produced, which is the basis of telegraphy, was till then the only one obtained by electricity, and it was certainly a mechanical work, very feeble, it is true, but still mathematically appreciable. Of course the first idea was to increase this work, to multiply it in such a way as to be able to get appreciable mechanical work, commonly called force. We have seen the reason of non-success in this line. But while clever and persevering, though unfruit- ful, attempts were made in this direction, another 152 Electricity as a Motive Power. principle was gradually developing, and was being applied in more and more ways, and it was this by which success was at length achieved. This property was called induction by Faraday, who discovered it in 1832, and this is how it is shown. Take a magnet, and a conducting wire connected at its two ends with an ordinary galvanometer; this wire thus forms a closed circuit in communication with no electricity whatever, and the galvanometer shows no sign of any electric current in this con- dition ; but take the wire near to one of the poles of the magnet, and the galvanometer shows a current during the time the wire is in motion towards the magnet ; stop the wire, and the current disappears ; move it away, and a new current in the opposite direction takes place, but stops directly the wire is again still. An electric current can therefore always be thus obtained by moving the wire before a magnet. We must, however, come to particulars a little : theoreti- cally, this will take place at any distance ; in reality, the action is much more feeble at a distance, and for induction currents to be sensible the wire should be brought as near as possible to the magnetic pole. The space in which the pole of a magnet shows its influence is called the magnetic field of the pole. A magnetic action is frequently considered without connecting it with any particular source, and we speak of a magnetic field without specifying the magnetising cause. This may vary from another reason : it is known in fact that magnetic action may Induction. 153 be produced by permanent magnets, by electro-mag- nets, or even by currents ; these different causes may form a magnetic field and give rise to inductions which may be utilised. It may be imagined what interest this principle presents : it gives the means of obtaining an electric current by displacing a wire in certain fixed con- ditions — that is to say, by a movement ; it involves, then, the direct transformation of movement, or, in other words, of force, into electricity. It will be interesting to trace how machines have grown out of Faraday's experiment. We have seen how this consisted in obtaining a current of short duration by passing a conducting-wire across the range, or what we have called the magnetic field, of the pole of a magnet. To make a machine from this we must find out the way to make this motion con- tinuous and frequent, and to collect the currents ; we should thus have an almost instantaneous succession of currents, which together might be likened to a continuous electric production, if the movements succeed each other with sufiScient rapidity. Further, it is as well to pass as long a portion of the wire as possible in the magnetic field, Faraday having shown that the longer the wire submitted to the magnetic action the more energetic this action will be : which is easily understood, the magnetic field acting at once on all parts of the wire. At length Faraday discovered that the effects were considerably augmented if the wires submitted to the magnetic action, called the induced wires, were wound on pieces 154 Electricity as a Motive Power. of soft iron, of which the magnetic reactions served to strengthen those of the inductors. We are thus led to arrange this closed circuit in the form of a bobbin of wire wound on an iron core, and the inductive action will be developed by passing this bobbin as rapidly and as often as possible before the pole of a magnet, which is the inductor. Thus the most simple means, and that which has been adopted from the first, is to mount the bobbin on a rapidly revolving axis, which in its rotation traverses the magnetic field. These principles were applied in the well-known machine of Pixii, invented about 1832, a very short time after Faraday's discoveries. It was simply the application of the idea given above — a magnet turned before two fixed bobbins, this rather incon- venient arrangement doubtless being employed by the inventor because he did not very well know how to collect the current of the bobbins while they were turning. Clarke's machine soon replaced it ; in this two bobbins turned before a magnet, and the current was collected by springs rubbing on metal cylinders. This ingenious, and at that time new arrangement, also served another purpose. We have said that when a wire traversed a magnetic field there were developed in it two currents, the first in one directifm on approaching the magnetic pole, the other in the opposite direction when leaving it. The machines we have just mentioned thus give a series of currents in opposite directions, succeeding each other rapidly and alternately ; therefore machines of this class are Magneto-Electric Machines. 155 called alternating. In Clarke's machine, mentioned aboTe, the movable piece, to which are fastened the rubbing springs which carry off the current, is arranged in such a way as to sort out these contrary currents, and put them right in the exterior circuit. The start being thus given, this type of machine, called magneto-electric, went on developing step by step by accumulating and multiplying similar parts. Instead of putting two bobbins on an axis, several were arranged in a circle ; instead of a single mag- netic pole, there were used as many as there were bobbins. A greater or less number of similar systems to the first were then placed together on the same axis ; and thus was formed, by a series of improve' ments, the first machine furnishing industrial results, that called the Alliance, which is still in use in the lighthouses of La Heve, and which received its present form about 1856. It should be said that by this multiplication of coils it had been necessary to give up the commutator of Clarke ; these machines, therefore, remained alternating. Some time after the invention of these machines an important improvement began to be introduced ; it consisted in replacing the magnets, till then em- ployed as inductors, by electro-magnets. It is known that these can give much more power than the others, only it seems at first sight as if an inevitable compli- cation is thus introduced : for if we wish to make use of electro-magnets, we must have a current to produce them ; we shall then be obliged to have one current already in order to obtain a more powerful one. We 156 Electricity as a Motive Power. shall see directly by what a singular and unexpected turn this difficulty was overcome, which was at first considered insurmountable. Wilde's machine, invented about 1864, consisted of two machines, one on the top of the other : the one had a permanent magnet as inductor, which sent a current into wires wound on iron plates; these became large and powerful magnets, serving as inductors for the second machine, which furnished the useful current. During the time which elapsed before the production of this machine, the induced organ (formerly composed, as we have said, of numerous bobbins placed side by side) had been simplified and reduced to a single long bobbin called by the name of its inventor, Siemens' bobbin. This form is shown further on (Fig. 69). Soon after there appeared at the Exhibition of 1867 a very curious machine, that of Ladd. In this apparatus two induced bobbins were placed between two iron plates, one at each end ; one of the bobbins in turning sent a current into wires wound on these iron plates, as in the first part of Wilde's machine ; these plates became magnetised, and the second bobbin furnished a current for use. Here we are immediately struck with an apparent absurdity. How does it happen that the first bobbin, when it begins to turn, can produce a current? It must have an inductor — a magnet — and it has none, for its duty is to make one j it is its current which has to create the magnet, and this cannot take place if the magnet does not exist. There is a mistake somewhere, it is true, and yet the machine works. Gramme's Machine. 157 This is because no iron is absolutely devoid of mag- netisation ; however little it may have, it suffices to give the first bobbin an inductive action, and to create a current. It is at first very feeble, but as it is employed to reinforce the magnetisation it soon augments, and the action increases as far as the limits of the motive force. This curious and fertile principle is not due to Ladd : it was enunciated nearly at the same time by Wheatstone and Siemens ; however, although the official priority has been attri- buted to Siemens, it will be seen from a provisional patent taken out by Hjorth in 1854 that this arrange- ment was very clearly described by him. This patent bears the title, "An Improved Magneto-Electric Battery." * Thus was made the type of machine called dynamo-electric, among which may be classed all the recent patterns and the machines in greatest use, of which the types most worthy of remark till now are those of Gramme and Siemens. The first originally had the form shown in Fig. 66. As may be seen, the inductor is a horseshoe magnet N S. The machine is therefore magneto- electric. The armature has a peculiar form. It is composed of a ring of soft iron, on which is wound the induced wire. This ring is placed on an axis between the two poles of the magnet, which have been fitted with expansions A and B, in order the better to enclose the ring to be induced. The wire * See the ' Journal of the Society of Telegraph Engineers,' vol. Yiii. p. 228. 158 Electricity as a Motive Power. with which the ring is coTered is divided into sections, the ends of which are connected to a cylindrical col- lector M, on which rub two metal springs, or better still, as we have already explained, two metal wire Fig. 66. brushes. These brushes receive the current, and send it into the circuit where it may be utilised. Very soon the improvements we have mentioned were introduced in this apparatus, and it received the form represented in Fig. 67. The bobbin re- mains the same ; it preserves the annular form, which Gramme's Machine. 159 is the essential characteristic of these machines ; the permanent magnet has disappeared, and is replaced by two electro-magnets, which expand round the ring at the poles. The collector and brushes are Fig. 67. not altered; they form part of nearly all recent machines. As we shall see further on, the Gramme machine has undergone alterations, but this is the type most frequently used. Siemens' machine differs from the above in the form of its armature. As may be seen from Fig. 68 this is no longer in the form of a ring ; it is more 160 Electricity as a Motive Power, Siemens^ Machine. 161 like a cylinder, on which the wires are wound length- wise parallel to its axis ; the rotation of this cylinder thus brings them successively into the magnetic fields of two electro-magnets, placed one above the other, below the armature ; they are sometimes^ placed horizontally, one on each side. The coils are, as in Gramme's machine, arranged in sections com- municating with each other, and also with a collector, seen on the right of the figure, on which the brushes rub. We have thought it necessary to give rather a long description of these machines, because they are so often met with in electric applications. Besides, it is desirable that they should be understood by the reader, being, as we shall see, the principal agents for the production and transport of force by elec- tricity. The reader may ask where we are going to wander to? this work professes to be about machines for producing movement, and this chapter has been so far about machines for producing electricity. The two results are not so different as might be believed. On the contrary, they are closely connected by reason of a remarkable property possessed by the machines of which we are speaking. Till now we have sup- posed that we expend force in turning our movable conductor in the magnetic field, and by this means we get electricity. Now let us do the reverse, send electricity into our movable ring, and we shall see it immediately put in motion and rotate rapidly. If we place on the axis of the ring a pulley with belt M 162 Electricity as a Motive Power. or gearing, we shall be able to utilise this rotation, and get frona it force, or more properly speaking, work. So if, in the little Gramme machine (Fig. 66) we turn the handle, we expend some force, but we get an electric current ; if, on the contrary, we send an electric current into the machine by means of any apparatus, a battery for example, we shall expend our electric current, but the ring will be put in movement, the handle will turn, and we shall be able to utilise this rotation and obtain work. Machines of this sort may thus be utilised in two ways, and this striking property has received the well-chosen name of reversibility. The experiment made in 1873 with Gramme's machine at the Vienna Exhibition, is often quoted as the first application of this important principle. One of these machines was set in motion by a steam- engine ; it sent a current into a similar machine at a distance of about 500 metres, which was in turn set in motion, and this rotation was employed to work a pump. This experiment is indeed very interesting, and we may admit that it was the first in which the reversibility of machines was employed to furnish a mechanical work of any importance, but it was not the first exhibition of this fertile principle. It had already been perceived, especially by Messrs. Siemens Brothers in 1867 ; but it had been enunciated still earlier with great clearness and vigour by Pacinotti. This eminent scientist, in advance of his epoch, had, as we have seen earlier in this book, invented about 1861, and published in 1864, a PacinoUi'a Maehine. 163 machine in which were applied and well utilised most of the principles, and even some of the arrangements of detail, which eight or ten years afterwards caused the success of other machines. The attention of the public was not yet attracted in this direction, and Pacinotti's invention was little known till the Electrical Exhibition of 1881 brought it to light, and caused the inventor's merit to be recognised and justly rewarded with a diploma of honour. Pacinotti's machine is given in Fig. 44 ; it may be seen that he had discovered the ring arrangement of the conducting-wire in which the current is developed, and had thus constructed the movable bobbin now called a jing-armature. Two electro-magnets E E' formed the inductor, and we would again refer the reader to the remarkable sentence quoted at page 80, with which he ends his paper describing the apparatus. This is the enunciation of the principle of reversibility, and it is the earliest known ; therefore the honour of having first clearly perceived this scientific fact belongs to the learned Italian. This historical incident is interesting, from the importance of the principle which it involves. It is not indeed peculiar to electric machines, it is a very general property, as was seen at once as soon as attention was drawn in this direction. Nearly all phenomena are theoretically reversible ; in giving out heat we produce movement, as for instance in steam- engines. But everyone knows that by movement we get heat: for example, if we rub two bodies M 2 164 Eleetricity as a Motive Power. together they get hot, and the work used in the movement is represented by the heat produced ; the phenomena are so closely allied, that it is possible to determine what quantity of heat corresponds to a given amount of work, and this is called the mechanical equivalent of heat. By giving out heat certain chemical decompositions may be effected, but if it is possible to reunite the bodies of which the elements have thus been separated, the same amount of heat will be generated in the process of reunion as was necessary to separate them. Eeversibility is thus a very common property ; it cannot always be utilised, but electric phenomena are among those in which it is most easily shown, and where it is generally susceptible of application. It is because induction machines possess it in the highest degree, that they have become the means for the production and transport of mechanical work by electricity. One important remark must be made here; originally electric motors really produced force, they were set in motion by the current of an electric battery, zinc was expended in the battery, labour was gained from the motor. It was real develop- ment of mechanical energy. With induction machines it could doubtless be the same j however, it is not thus we work. The current of the battery being dear, and difficult to produce, we want to get electricity from the machines themselves, and they produce this by expending labour. We thus absorb labour in order to recover it. It may be asked, what is the benefit of such an operation ? It lies in the Transmission of Power, 165 transport. We can imagine many cases in which transport is of the first importance. How many waterfalls, for instance, now useless because of their situation, would be priceless if they could be transported near to a populous centre ! The amount of force thus neglected is immense, and electric transport furnishes the means of adding this to human power. Let us consider too, the enormous number of cases where power might be applied to scattered machinery or tools. Imagine, for instance, the cranes along a quay: in the ordinary way a special engine is necessary for each ; with electricity a single engine might easily be used to work them all. A still more important consideration is that of the sub-division of force. As we shall see further on, the hope is just now established that by means of electricity it will be possible, not only to transport power, but also to divide and distribute it. We will not here dwell upon the importance of this, which must be considered separately ; we only wish to point out to what consequences electric transport of power may lead. Besides, the reader may take note of its importance, seeing in the following chapters the successive development of the applica- tions to which it has already led. 166 Electricity as a Motive Power. CHAPTER IL GENEEAL HEMAKKS ON MODERN MOTOES. Without inquiring further into the working of the machines we are considering, we may see at once why these apparatus have achieved the success till then vainly sought for, and whence comes their superiority to those which have been described in the first part of this book. We have already touched upon this question in the first part, but it will not be amiss to revert to it. In the old machines movement was produced by magnetising one or more masses of iron and making them attract mova- ble armatures, whose displacement produced mecha- nical work; it was of course necessary that the magnetised masses should cease their action as soon as the attraction was complete, in oiAei to recom- mence it again so as to give a fresh impulse. This system has three grave defects : 1st, magnetic actions are rapidly weakened by-distance, so that, the attrac- tions of a magnet only exercising force in a very small radius, the impulses obtained can be strong only in a very small part of the movement ; 2ndly, the motion thus obtained is the result, not of continuous action, but of a succession of jerks, which is always a defective mechanical means of obtaining labour ; General Bemarks. 167 Srdly, and this is the greatest disadvantage, the magnetisation and demagnetisation of masses of iron of any size cannot be effected instantaneously : they require a time, very short indeed, but still apprecia- ble; besides, these alternations do not take place without a considerable loss of force. It will be easy to give one experiment in proof of this. An electro- magnet being rapidly and frequently magnetised and demagnetised, the core is heated perceptibly ; this heat represents so much work, it is the force lost in the successive magnetic movements given to the mass of iron. Yet this expression is erroneous, for force is never lost, only transformed ; only here a part of the force employed, instead of furnishing the magnetisation required, produced heat not required of it, which means a loss of power in the useful work in hand. These three disadvantages are avoided, as may easily be understood, in induction machines. In this sort of apparatus : 1st, the distance of action is reduced to a minimum, the armature turning at a very short distance from the magnetic poles : 2ndly, the action, though not theoretically continuous, is composed of such a rapid succession of impulses that it is practically so ; and Srdly, the magnet pro- ducing the magnetic field which gives rise to the induction remains always in the same state and goes through no alternations, which allows it to be magnet- ised to a far greater degree of intensity than in the old machines. There are also other advantages possessed by these machines. 168 Electricity as a Motive Powei^. Haying recognised this superiority, we must now look a little more closely into tlie manner in which dynamo-electric machines transport force and produce work. Let us first recapitulate some general ideas. When we examine any source of electricity intended to produce a current, the first element to be ascertained is that called the electromotive force, i. e. the force with which this source tends to urge the electricity along. In the same way, if we wish to find the mechanical value of a waterfall, we must first know the height of the fall and the pressure its column of water is capable of exerting ; again, if we wish to value the work to be got from a steam-boiler, we must first know what is the pressure of the steam. These relative elements for such different producers of force are however so similar, that in electricity we use the terms electromotive force, tension, and pressure almost synonymously and indifferently.- In the case of a battery, the E. M. F. once deter- mined depends on the nature of the battery, the number of elements, and their arrangement. In generating machines the E. M. F. depends on the construction of the machine, and also on the speed at which it is driven, increasing with the latter. This force cannot be determined without ascertain- ing at the same time the speed given to the machine. These data are also not sufficient, for the E. M. F. of the machine is influenced besides by exterior con- ditions. The E. M. F. of a generator being known, the Ohm's Law. 169 current that it will furnish depends on the circuit ; in the same way as a fall of water will give a result depending first upon the height, but also upon the diameter and the length of the tubes through which it has to run : so that any electric source gives a cur- rent in proportion to its electromotive force and the resistance of the circuit. It must never be forgotten that in this circuit must be reckoned not only the wires and the apparatus in the exterior circuit, but also the generator itself; for the current flows through that as much as the rest, and the resistance it op- poses to the passage of the electricity is always a necessary element, and sometimes a very important one, to consider. These three elements, then- — the electromotive force E, the intensity of the current I, the total re- sistance of the circuit E — bear a very simple relation E to each other, and it is written I = ™ these quanti- XX ties being reckoned by the units adopted by the recent Congress of Electricians, namely, E in volts, from the name of Volta ; R in ohms, from the name of the scientist who gave the above formula, and I in amperes, from the name of the great French philosopher. Let us return to the machines. Take for example a Gramme machine of the ordinary type represented above. We connect it to a motor, a steam-engine for example, and it is rotated ; we give it a speed, determined and constant, say 1000 revolutions per minute. First, we will put no wires between the ter- 170 Electricity as a Motive Power. minals, the circuit is open ; under these conditions there is no current, but also no work expended to turn the machine. Of course a little is required to overcome the friction, but it is very little, and we may take no notice of it. Let us now join the two bobbins by a long wire of 50 metres for example, and at the same time an instrument to measure the cur- rent. It will show a very weak current, and the steam-engine will begin to do some work ; if we shorten the length of the wire the current will increase, and with it the work expended by the engine, and these two quantities will go on thus increasing as the resistance of the circuit is diminished. It will be asked, what becomes of the work produced by the steam-engine ? We shall very quickly see, if we push the experiment too far. The metal circuit, the machine itself, and the instruments would become dangerously heated, and if we are not careful the whole thing might be burnt up ; the work is turned into heat. Now, instead of this circuit simply closed with a wire, let us couple up with our machine another similar one, leaving in the wires our instrument to measure the current. To begin with, we wiU fix the second machine so that it cannot turn. We shall then find a powerful current, and the steam-engine will expend considerable power ; our second machine in this case only acts as a conductor, and as it has a low resistance, the actions produced are intense. It would even be difficult to try the experiment, or at least to give it any duration, for the two machines Theory of Transmission, 171 would be in great danger of burning, the whole of the work being turned into heat ; we reap no advan- tage, in fact, as the other machine is fixed. Let us now liberate the machine and have it com- pletely free. This is what we shall see : the machine is at once put in movement, and its rotation is very rapidly accelerated ; at the same time the current meter shows that the current decreases very rapidly, and at the end of a moment this current becomes and remains completely nil. If, now, we test the speed of the second machine, we shall find it identi- cally the same as that of the first. The steam-engine then gives no work, things remain as if the first machine had its circuit open ; it must not be for- gotten that under these conditions the second machine also is doing no work. What is happening ? To understand it, it must be remembered that a dynamo-electric machine turning with a closed circuit always produces a current, so that when our second machine began to turn it began to produce a current. If we consider carefully, we shall see that this current will be in an opposite direction to that which it receives. The two machines then tend to send into the same circuit two contrary currents ; they mutually destroy themselves, and the difference between them is all that is apparent ; but when the two machines go at the same speed, the two currents which tend to develop are equal, and they cancel one another completely. In reality, there is no electric current in the circuit: the machines turn as if the circuit were open. 172 Electricity as a Motive Power. Let us now put some work on our second machine, say a weight to lift. The functions of the two ma- chines are now quite distinct. The first machine generates electricity — this will be the generator; the other gives us work — this will be the motor. We see immediately what happens. The motor, having work to perform, goes slower; it cannot maintain a speed equal to that of the generator. Then the coimter current given off will not be equal to the direct current ; this will cease to be counter- balanced, a current resulting from the difference will flow, and will be indicated by the current meter; and it must be well understood that if the work put on the motor is small, it will only be slowed a little. The difference between the speeds of the two machines will be slight, and therefore that of the two currents, so that the actual current will also be small. If, on the other hand, the work is great, the slackening of speed will be considerable, and the great difference in the electromotive forces will give rise to a power- ful current, so that there is a necessary relation between the work put upon the motive machine and the current in the circuit. By increasing this work we slow the motor more and more, the current is constantly increasing, and we come in fact to the point whence we started ; the motor, too heavily laden, will stop, and the current will reach its maximum, as we saw in the first instance. In all this, what work have we obtained? At first, the motor being free, we got none ; at last, the machine being loaded till it stopped, we had none Theory of Transmission. 173 either. It is thus seen that the work obtained de- pends on two things : first, on the work accomplished at each turn ; and secondly, on the number of these turns ; for in increasing the energy and the work in turn the machine is slowed; that is to say, the number of turns is diminished. There must be a maximum. There is one, in fact, which is, when the speed of the motor is equal to half that of the gene- rator ; we then obtain from the second machine the half of the work expended in the first, and we obtain from it the greatest work it can give. This brings us to an important consideration. We see that the work obtained is never equal to that expended ; there is always a loss. The proportion between the two works — in precise terms, the ratio of work obtained to that expended — gives the proportion of loss. This is what is called the return, It cannot be equal to 1, and we have just seen that in the case where we endeavour to obtain the maximum work it is J. This proportion is not necessary ; by not re- quiring the greatest work that can be furnished the amount will be diminished, it is true, but with a better result ; that is to say, with a more advan- tageous return. We shall see how we shall have to work when practical applications of importance are undertaken, which will certainly be very shortly, but we are only beginning at present. Suppose, for ex- ample, that it is desired to transmit and receive electrically work equal to 5 horse-power. We may employ as generator a machine capable of absorbing 10 horse-power ; a similar machine employed at the 174 Eleetrieiiy as a Motive Power. other end under its maximum conditions will give the 5 horse-power required. We should then have a return equal to J ; but we might employ a more powerful generator of higher electromotive force, capable, for instance, of absorbing 15 horse-power. Such a machine employed as a motor would give the five horse-power with a work of say only eight horse- power expended (these figures are not intended to be precise, but are only given to fix the ideas), and that because, not being pushed to its maximum, it is capable of a more advantageous return. It is true that an arrangement of this kind would necessitate a greater original expense, but in exchange it would entail a daily saving of expense. This is not at all an exceptional arrangement ; how are steam-engines used to burn a small amount of coal for a given work ? Expansion engines are used, but it is well known that these engines would give much more power if the full pressure of steam were used. We do hot ask from them all they are capable of doing in order that the result may be obtained under its most favourable conditions; the first outlay is increased in order to reduce the working expense. This will certainly have to be done in the mechanical employ- ment of electric machines, in order to increase the return. We shall return to this point hereafter. Before leaving our two machines, we will try another experiment. Just now, the generator main- taining the same speed, we put on the receiver work constantly increasing, and we saw the current increase from zero to the greatest possible for the resistance Theory of Transmission, X75 of the circuit. We will now try the reverse. The receiying machine will have a constant work to perform — at each turn it will do the same work; whereas the generator we will drive at varying speeds, the galvanometer being left in the circuit. This, then, is what happens. The generator at first going slowly, a feeble current is shown ; the receiver does not stir. As we increase the speed the current increases; for a certain value I of this current,' the motor starts. From this moment, although the speed of the generator increases, the current does not ; only the speed of the motor in- creases at the same time as the other, and in propor- tion to it. As to the work obtained, it naturally increases with the speed of the motor. We see what takes place: as long as the current produced is not enough to overcome the weight put on the motor, it cannot move; it is then only an inert resistance in tlie circuit. When the current becomes just sufficient to overcome this weight, it begins to turn, and at the same time begins to pro- duce a counter electromotive force. If the receiving current increases, it becomes too powerful for the weight to overcome, and the motor moves fast ; but then the counter electromotive force increases also, till the increase of current is exactly counterbalanced, and its value reduced to that which is just sufficient to overcome the weight. This law may be demonstrated otherwise, by giving to the generator a constant speed, and placing a constant weight on the motor, but varying the resist- 176 Electricity as a Motive Power. ances between them ; we may also arrive at a current which cannot be varied, whatever may be the resist- ances, provided that the receiving machine is able to turn ; its speed alone varies. We have already stated this fact, that there is a necessary proportion between the work put on a machine and the current which it receives ; but we may complete it by this important remark, that this proportion is absolutely independent of the speed, and obtains whatever may be the movement of the machine. This law is of fundamental importance, and we shall have to recur to it in the course of these studies. ( 177 ) CHAPTER III. MODERN SMALL MOTORS. Having rapidly examined the nature of the machines which will serve for the transmission of force, and taken account of their mode of action, it will be natural to follow up the chain of experiments by which we have arrived at the results obtained up to the present time, and to see something of the forms of machines in use. This is the method which we will follow; but before going further it is necessary to treat once for all an accessory subject which will embarrass the logical development of this history. At the same time, as machines intended to transmit large forces, we meet with, in fact, a number of apparatus des- tined to produce and transmit small forces ; that is to say, for light work, with a limit of about 10 kilo- grammetres per second. Although their invention was later than that of large machines, we may attach them to the more ancient form. These, as we have seen, were motors susceptible of great precision, but capable only of very small work. The motors of which we will now treat are in a similar position, but with a very much enlarged field. It will therefore be well to study now this group of motors. One N 178 Electricity as a Motive Power. question is immediately met ? How is it that there are special small motors, and why cannot they be made of the ordinary type, but reduced in size ? It is that this construction would be very difficult and costly. Dynamo-electric machines contain parts where very delicate work is required, such, for instance, as the winding of the wires on the revolving bobbins or rings. Below certain dimensions the con- struction of these would be almost impossible, and besides, these machines contain parts which in large ones are already pretty smaU, and they would become microscopic in a machine very much reduced in size. There are also electric reasons ; that is to say, that the proportional reduction of a large machine would Fig. 69. generate in turning, or, on the other hand, would necessitate to turn, currents not in proportion to the larger machine. From all this it will be seen that a small motor must be a different apparatus to a large one. The oldest of these motors, and that which has given the type to nearly all the others, is that of M. Marcel Deprez. Since 1854 a particular bobbin due to Dr. Siemens, of which the above is a representation, has been in existence. It is composed, as may be seen, of a The Siemens Armature. 179 cylinder of soft iron, on which the wires are wound lengthwise. For this purpose two longitudinal grooves are hollowed in the cylinder, in which the wires are laid. When a current flows through these coils, the hobbin becomes a magnet which presents two long polar faces, and the position of these poles changes with the direction of the current. With this bobbin and permanent magnets Siemens had a magneto-electric generator. We have said that this bobbin was employed in a great number of machines, among others those of Wilde and Ladd. Marcel Deprez was the first to show that these machines were reversible, and could be made good electromotors. It is not impossible that this fact had been vaguely seen by some, particularly by the Messrs. Siemens, but they did not see in it anything of im- portance. The reader is well aware that it is hot he who first notices a phenomenon who is the inventor, but he who recognizes the value of it, and draws advantage from it; nearly all scientific facts have been seen and even discussed before they were utilised. He who discovers a thing anew, and makes a machine of it, is the real inventor. However, Ladd's machine, as it was, was only a bad motor. Deprez modified it, took away the metal expansions of the poles, adjusted the position of the brushes, and obtained the form shown in Fig. 70. It will be understood how such a machine works. When an exterior current is sent into it, it magne- tises the soft-iron plates BB and the revolving bobbin A. It is arranged so that each of the poles B N 2 180 Electricity as a Motive Power. repels the pole of the bobbin opposite to it, which then begins to move ; after making half a turn, the brushes C C supplying the current, haying remained stationary whilst the bobbin turned, are now in re- FiG. 70. versed position; the current enters in the opposite direction, and the poles are reversed. The repulsion is thus renewed, and the bobbin continues to revolve. The movement may be utilised either by the wheel G, or by means of K or F, according to the speed required. This form of machine is not M. Marcel Deprea's latest ; he thqught it better to make use of perma- Mared Deprez's Motors. 181 nent magnets, thus approaching the first arrangement adopted by Dr. Siemens, but he gave it a different form by fixing the bobbin between and parallel with the arms of a horse-shoe magnet. All the magnetism of the magnet is thus utilised in a very complete manner. 182 Electricity as a Motive Power. The form of the machine will be seen from Fig. 71. The current enters by two small brushes, seen on the right. In the arrangement shown, the apparatus has a grooved wheel, so that it can be used as a motor, and a handle to use it as a generator. The weight of the machine is not more than 4 or 5 kilogrammes. Eemarking that in Ladd's machine transformed into a motor, the production of the magnetic field entails a loss of energy equal to about one third of that absorbed by that of the whole machine, Deprez considered that, as we have said above, he would gain by doing away with the electro-magnet and replacing it by a permanent one. Dynamometer indications, together with measurements of the zinc consumed, showed in fact that with an electro- magnet as inductor, the work obtained from the consumption of a kilogramme of zinc was from 70,000 to 90,000 kilogrammetres, while it varied from 90,000 to 130,000 kilogrammetres when a permanent magnet was used. The latter also had the advantage of being used as a generator, but, on the other hand, it necessitated a somewhat heavy apparatus compared to the work produced. In practice also a serious obstacle was encountered. The magnet lost its magnetism very rapidly, and to avoid this Deprez had to return to the original arrangement, but in a somewhat altered manner and with very much reduced dimensions. In his new model, in fact, the space occupied is not more than 6 centimetres in width and 7 in length, and the Bejpreis Motors. 183 electro-magnets are doubled. It is composed of two small electro-magnets of 5 centimetres, each with opposite poles presented, and between these poles are the Siemens armatures of 2 centimetres in length and 16 millimetres in diameter. They are arranged on the same horizontal axis, and at right angles one to the other : that is to say, that when one is between the poles of its electro-magnet the other is perpen- dicular to its magnet. As this motor revolves very rapidly, the driving pulley is reduced in speed in the proportion of 1 to 40 by means of a pinion and cogged wheel. The commutator is also so arranged that three distinct currents may be sent into the inductors and bobbins. As it is the base of the electro-magnets which forms the bed of the machine, it will be understood how well devised the arrange- ment is for the production of the greatest force possible with the smallest weight of iron. After the preceding motors comes in chrono- logical order that of Trouve. It resembles the Ladd-Deprez, as will be seen from Fig. 72, and is a dynamo-electric motor. It however contains interest- ing modifications. That to which Trouve attaches the greatest importance, is the alteration in the shape of the bobbin. The Siemens bobbin employed by Deprez is cylindrical, it is therefore always at the same distance from the poles; that of Trouve presents a section representing two half spirals, so that in its rotation the iron approaches the pole, and moves rapidily away from it when the current is reversed. This arrangement we have already 184 MeetricUy as a Motive Power. described at page 115, and Trouve therefore avoids a disadTantage. In the preceding motors it is necessary to start the bobbin or at least to move it a little, as without that the poles would be exactly opposite one another and would not start, being at the " dead point " as it is called. Trouve's arrangement enables this defect to be lessened. The spiral form Fio. 72. is besides very slightly marked, and an increase of one millimetre is sufficient to obtain the effect sought. It may be remarked also that the winding of the electro-magnet has a particular form ; instead of winding the wire on the two arms, as in the Ladd- Deprez machine, there is only one coil on the soft Cbris Baudet's Motor. 185 iron forming the base which joins the two arms. The size of the apparatus is thus reduced. From the experiments of d'Arsonval, it appears that the useful return of this machine is inferior to that of Deprez : that is to say, that the kilogrammetre of force is obtained at a greater expenditure. On the other hand, it must be admitted that for the same weight this motor gives a better result than the former. We may mention in connection with the preceding. Fig. 73. a motor which differs very little from them, namely, that of Cloris Baudot. It is composed of two Fig. 74. Siemens bobbins so fixed that the iron bars are at right angles to one another, so as to avoid the dead- 186 Electricity as a Motive Power. point; two straight electro-magnets embrace this pair of bobbins and give them movement. The form is shown in Figs. 73 and 74. It may be likened to two Ladd-Deprez or Trouvd motors placed end to end. It only differs as regards the bobbin, of which the core, instead of being formed of a single bar, is composed of a series of small cores, each having a separate coil. So that, instead of being a simple armature, it may be considered as a series of small electro-magnets placed close together, and of which the poles are joined by a single bar, as seen in Fig. 75. Figs. 73 and 74 show the arrange- ment of the whole, and, as will be seen, the electro- magnets are straight, and have their bobbins Fig. 75. about the middle of their length ; the arma- tures revolve between the prolonged poles. This little motor has however nothing very original, and has not been much used. As will be seen, in these little motors inventors have taken into consideration one of the conditions we have mentioned above ; the large mass of iron has a constant mag- netism, while the alternating magnetisation only takes place in the bobbin, which is of very small mass. Join to that the very high speed of these motors (about 3000 revolutions per minute), which seems a necessary condition of all electric motors, and the advantages will be understood. It will be interesting to mention one form of motor which M. Deprez has suggested as an experiment. Deprez's Suggestion. 187 It is represented in Fig. 76. It consists of a very short Siemens bobbin, and, contrary to the foregoing arrangements, this bobbin is fixed. It is surrounded by an iron hoop B B, with two coils of wire. On the current passing, it renders one half of the ring and of the armature magnetic, and these repel one another. If the armature is fixed and the ring movable, it at once revolves, the brushes which communicate the current being so fixed that the current changes direction at each half turn, and the rotation is con- tinued. This is wanting in principle ; it is in the great mass of iron that the magnetic alternations take place. Therefore, this motor is very inferior to those pre- viously described. We have, however, mentioned it 188 Electricity as a Motive Power. on account of the singularity of its form and the analogy which it presents to other machines, par- ticularly to an American motor which was noticed at the Exhibition of 1881, invented by Griscom. This is also a dynamo-electric motor. It consists of a Fig. 77. Siemens bobbin, but, as will be seen in Figs. 77 and 78, this bobbin is surrounded by a sort of hollow cylinder of soft iron, or more correctly, of malleable casting. This cylinder is wound with two coils, diyiding it into two halves, and combined to produce two consequent poles at the two extremities of the same vertical diameter. When the axis of the The Grisoom Motor. 189 bobbin nearly coincides witb the line N S of the consequent poles, the current is reversed, and a repulsion is produced at N and an attraction towards S, which spins the movable electro-magnet from one Fig. 78. side to the other as the reversal takes place to the left of N S. As will be seen, this motor somewhat resembles the defective arrangement of Deprez mentioned above, only that here it is the bobbin which turns while the ring is fixed. It is therefore 190 Electricity as a Motive Power. theoretically correct, and this motor lias giveri very satisfactory results. It is very small and light, and its speed very great. We have no precise details of its effective return, but this motor has perhaps been more used than any other. It has been very exten- sively exhibited, and is very largely used for sewing machines, ventilators, grindstones, knife-cleaning machines, dentists' drills, small lathes, &c. Another little motor which has been a good deal used is that of Messrs. Cuttriss and Co., of Leeds, which has given satisfactory results. It consists of a Siemens armature revolving between the polar extensions of a flat electro-magnet, the magnet and armature being in series. As will be noticed, all these motors are based on the Siemens armature ; they are therefore not induction motors, but magnetic, and in consequence resemble those which have been described in the first part of this work. Another type of motors must still be considered. We know that if we place a magnetised needle in a frame surrounded by wire, when a current is sent through this wire the needle will turn till it sets itself at right angles with the wire. If we now reverse the current, the needle will return to its original position, continuing the turn — at least, if the reversal of the current were carefully arranged. We may thus obtain a continuous rotation, and, in conse- quence, work. It is not necessary either that the needle should be a permanent magnet ; it may be an electro-magnet. Bv/rgin's Motor. 191 It is on this principle that the little spherical motor of Burgin is devised. It will be seen from Fig. 79 that he has taken a sphere covered with wire wound round it approximately following the horizontal parallels. Inside is an iron core movable on a horizontal axis, and also covered with wire, Fig. 79. forming parallel layers. When the current is turned on, these two sets of coils tend to set themselves parallel ; and if the current is reversed just as this position is attained, the movement continues. It will be seen that there is here no variable magnetisation ; the part where the currents are reversed is in the 192 Electricity as a Motive Power. exterior wire. This, then, is a curious principle, and different from the others ; but at the same time, the very powerful action of soft iron, when magnetised, is lost. The spherical form adopted by Burgin is also peculiar; it must render the winding of the Fio. 80. wire difficult, and it gives to the machine a yery strange appearance ; the only thing seen is a closed sphere, with an axis protruding, which by a hidden power is rapidly revolved. This motor is a little heavier than the last mentioned, and we have also no information as to its effective return. Jablochkoff has recently designed a little motor JcAlocMoff's Motor. 193 of ecliptic form, as will be seen by reference to Fig. 80. The movable part is formed by a flat bobbin b, placed obliquely on the rotating axis. This bobbin is of iron, and forms also a short electro- magnet. The part fixed is the larger bobbin, B, with framework of copper, fixed, pbliquely as in the case of the other, but inclined in the opposite direc- tion. The arrangement of the commutator is such that the current traverses the movable bobbin always in the same direction, and that the changes of direc- tion for each half-revolution only take place in the fixed solenoid. The result of the crossing currents in this and the movable bobbin is the revolution of the latter. This motor, as well as the former, has a very original form, and shows that now-a-days every- thing is done to utilise every kind of dynamic property of electric currents. It has the same objections as the rest ; the loss due to residual mag- netism is certainly avoided, but the powerful agency thereof is not utilised. It seems to be acknowledged that it is difficult to obtain powerful action without the help of soft iron. These two small motors are feeble, and rather theoretically curious than really useful. 194 Electricity as a Motive Power. CHAPTER IV. APPLICATIONS OF SMALL MOTORS. The small motors which we have just described have been applied in ways which it wiU be interesting to mention. The first which presents itself, and which has already been applied for some time, as wiU have been seen in the first part of this book, is the work- ing of sewing-machines. It is certain that consider- able efforts have been made to practically realise this ; for the working of these machines for a length of time by manual power cannot but have regrettable results for women. The various small motors that we have described are very readily adapted to this work ; some have been expressly devised for this purpose, notably the Griscom. If this application has not been wide- spread, it is not the fault of the motor, but rather of the supply of electricity. Powerful batteries are not numerous ; they are difficult to handle, and some are dangerous and give off disagreeable fumes. In fact, there is only one which has been effectually employed, and that is the bichromate of potash, but it is difficult to use this for long together. If some day we should have a battery, easily handled, power- Uses of Small Motors. 195 ful, constant, and not wasteful, without doubt this application will be very largely adopted. At the central telegraph oflSce in Paris the small Deprez motors were for a long time employed to work the distributing apparatus of the Baudot mul- tiple telegraph. This mechanism requires a rapid and constant rotation, with very little work hut great regularity; electromotbrs are readily adapted to this, and among them the magneto-electric motor of Deprez has, besides other advantages, a minimum of tendency to variation. At present this work is done by Hum blot's small water turbines; this kind of motor is employed throughout the central Post Office to work the continuous rotary telegraphs. A very interesting application of electromotors was suggested and tried by Messrs. Deprez and Bontemps in 1880. It was proposed to work by their means the carriage of telegrams instead of by the pneumatic tubes now in use. This system, which has great advantages, has also a great drawback ; it will be understood in what it consists. In a cylindrical tube is a little carrier, which is the projectile, and in which are the telegrams; an air-pump produces a vacuum in front of the projectile at the same time that it compresses the air behind it ; thus driven by the difference of pressure, the little carrier flies along the tube and arrives at its destination. In this opera- tion, at the same time that the projectile is driven along, the whole column of air in the tube is also driven through it, and this produces considerable fric- tion. The pneumatic transmission of telegrams in 2 196 Electricity as a Motive Power. Paris at the present moment absorbs no less than 120 horse-power. The idea of Messrs. Deprez and Bon- temps consisted in making a small railway of which the rails would be conductors, a little motor would be arranged as a locomotive as in Fig. 81, of the pattern we have called Ladd-Deprez, that is to say, Pig. 81 with an electro-magnet, but instead of one bobbin it has two, E G, E^ G^ one at each end. These bobbins are directly attached to the wheels, and the current entering from one of the rails through one wheel leaves by the other, in its course rotating the bobbin and thereby the wheels, and thus the macldne goes Synchronous Motion. 197 along. The idea was to build on this locomotive a little box, in which the telegrams or even small parcels might be put. The tube was abandoned and replaced by a small railway, in order to avoid the friction of the air. The trial at the Central Tele- graph Office succeeded very well, and, as will be seen further on, a similar experiment was tried in Germany almost at the same time. It was calculated that the despatch of telegrams in this way for Paris would only require 12 horse-power instead of 120, a very important saving. It has however not been adopted. It would have been necessary to change the entire existing plant, and a further powerful reason was that the proposed railway would require a larger passage than the tubes, and what with water- pipes, telegraph and telephone cables, pneumatic tubes, &c., the room taken up by these modern inven- tions in those subways of Paris, originally destined solely for other purposes, is jealously watched. M. Marcel Deprez has made another very curious application of his motor. It might be necessary to reproduce at a distance some motion, so that the two were synchronous. You might for instance put up at a departure station a needle on a dial, and at the arrival station a similar one to reproduce the move- ment of the first, whatever it was, always turning as quickly as it and stopping at the same point. This problem has been solved by means of the Deprez motor. It is slightly modified ; instead of one bobbin the motor has two, put end to end ; the iron bars of these two bobbins are at right angles, as will be seen 198 Electricity as a Motive Power. at A* B*, Pig. 82. (This arrangement was shown by Deprez before Baudet adopted it for his motor, as will have been already seen.) At the departure station Fig. 82. is a sort of commutator A B, sending along the line a series of currents alternately reversed. Theory shows and experiment proves that the motor then Electric Boats. 199 reproduces with perfect exactitude the movements of the commutator, even for the highest speeds. Trouve principally endeavoured to apply his motor to locomotion. He constructed before the Exhibition of 1881 an electric velocipede with favourable results ; it was less interesting than the boat he put on the Seine, and which was worked on the little lake at the Exhibition. For this he made use of a small double motor, that is to say, two bobbins put close together, fixed on the rudder-head. The movement was communicated by means of an endless chain to a small screw fitted in the rudder itself, which was very handy for steering. The electricity was pro- duced by a bichromate of potash battery in the middle of the boat, and brought to the motor by two flexible cables, which served at the same time for yoke lines. The whole was light and worked well. The general appearance is represented in Fig. 85, and it was possible by this means to go at the rate of 1^ metre per second (about 3^ miles an hour). In the battery used the plates were attached to a small winch, so that they could be raised or lowered into the liquid as desired. The battery therefore was only at work when wanted, and Fig. 84 shows its general arrangement. Trouve has also constructed other arrangements of this motor, as applied to navigation, and where the boat requires considerable motive power he places the motor in the boat itself, so that it acts directly on the screw shaft. Another application of this same motor was shown at the Exhibition of 1881. It was employed 200 EUdricity as a Motive Power. to work a pjanista. A pianista is a sort 'of meclian- ical key:-board, worked by compressed air, and fixed Fig. 83. to an ordinary piano. . By feeding the instrument with sheets of card-board pierced with holes, and Mechanical Pianos: 201 passing tKem tliroiigh by means of a handle, the apparatus worts levers which drop on the notes and perform a tune. The electric motor was employed to turn the handle, which it is rather tedious to work by hand. That which was applied to the pianista in FiQ. 84. the Exhibition, which we give in Fig. 86, was of such small dimensions that it was able to be fitted to the side of the apparatus without causing any incon- venience, and was very well adapted by Journaux, who has also applied Trouve's motor to his sewing- machines. The pianista was worked by six Faure 202 Electricity as a Motive Power. Mechanical Pianos. 203 accumulators with a small extra battery for grand effects. We need not further enlarge upon this application; it will easily be seen how, in every Fid. 86. csase in which a regular rotation is required without much force, these little electromotors come in very conveniently. We can imagine many instances of 204' Electricity as a Motive Power. this description, which there would be no interest in enumerating. Trouve has applied his little motor in another curious way. In agricultural countries, particularly those cultivated as pasturage, running water is much used for irrigation. These waters are, of course, very carefully used and divided. Each little stream has, for instance, its day set apart in which it supplies water for use. To bring it to the land requiring irrigation it is necessary to make trenches and dams to raise the level of the water to that of the land. These works are expensive, both to establish and to maintain. Trouve has employed his little motor to work a chain of buckets which raise the water and replace the dams. Everything being taken into consideration, it does not appear that this means would be less costly than the system of dams, owing chiefly to the heavy expense of the battery ; it is, however, original enough to be worth mentioning. Besides, it might be employed in new works, or in urgent cases when the works already established might be out of order. Usually these little motors have been applied where regular . rotation without much force is re- quired, as was the case with the earlier machines, as we have seen in the first part. They have, as we have said, succeeded their predecessors by extending the field of application. It is sufficient to mention chronographs, gyroscopes, Foucault's mirrors, &c., which are advantageously worked by these motors. D'Arsonval has made an interesting application of Siemens' Postal Railway. :205 the TrouTe motor. In certain physiological obseiTa- ,tions it is necessary to maintain artificial respiration in the animal under experiment ; for this a little ^bellows moved by water was employed. D'Arsonval found it advantageous to employ electric motors; ithey are simply connected with the bellows, and give it a regular movement, thus accomplishing th^ work in complete security. Before quitting the subject of small motors, we must notice some particular types. We have said that usually large machines do not answer if reduced to very small dimensions ; this is true, but not infal- libly so. Thus, about 1880, an experiment was made by Siemens and Halske to make a small postal rail- way, worked by Siemens' ordinary machine, of small dimensions. They made a little locomotive, worked like that described above (p. 196), this last being rather later. The complete apparatus consisted of a model train, with a locomotive and little box-carriages to carry dispatches, as shown in Fig. 87. It was even pro- posed to convey parcels in this way, which would have been a great convenience. DifSculties similaj to those we have already mentioned have put a stop to the final execution of this scheme. The small machine employed differed only in size from Siemens' . large machines. Since the Exhibition two types of motor have been produced, which are taken from the large machines, and hold an intermediate position between, the. large and small motors, .One is- due to Meritens, 206 Electricity as a Motive Power. the other to Gramme. The former has again adopted the Pacinotti ring : that is to say, as seen in Fig. 88, a movable ring formed of coils in distinct sections, separated by small pieces of soft iron. He has made his inductor in the form of a circle, or rather rings of Iron wound round, and made so as to constitute two semicircular magnets, as in the Griscom motor described above. He has thus made a simple machine which can be cheaply produced ; he also constructed Fig. 87. several others, giving from 15 to 50 or 100 kilogram- metres per second. These machines will certainly be much used. One type of these little machines has been provided with gearing, so that it can be set in motion by means of handles turned by four men. It thus furnishes powerful currents for some minutes, and will be most useful in laboratories, giving the means of proving electric experiments without the necessity of maintaining a battery of many elements. It is the same with the little Gramme motor Gramme Motor. 207 shown at the Exhibition, but this has only been in the market since its close. In Fig. 89 is given a section of a slightly modified type of Gramme machine. The ring remains the FiQ. 88. same, but the inducing electro-magnets are placed on one side only, forming at the same time the frame- work of the machine. The return of this machine appears to be favourable. It is very compact and elegant in form. The apparatus is very similar to 208 Electricity as a Motive Power. Pacinotti's machine, and if the reader will refer td that he will see that if the Gramme machine were set on end (as it is figured) it would greatly resemble FiQ. 89. the early, apparatus. Professors Ayrton and Perry have recently designed a new form of motor. They have discovered that for dynamo -machines the Ayrton and Perry's Motor. 209 armature should, for good results to be obtained, be small relatively to the field magnets, whereas for motors the reverse should be the case. They there- fore make the armature large, in the form of a Gramme ring, and inside it revolve a small field magnet, the axis of which carries the revolving brushes. They also adopt a compound winding of the field magnet, consisting of partly shunt and partly series coils, so that the motor automatically regulates itself. When loaded and when light it runs at about the same speed, this being a great advantage. The motor appears to be very good, and its return high. We must expect to see other new patterns of these motors produced as soon as we are able to command a convenient source of electricity. As we have said, the electric battery, as it now is, is impracticable when continuous work of any importance is required ; it is at the same time expensive, inconstant, and very inconvenient. It will, in all probability, be perfected in time, but it is to be supposed that before that elec- tricity will be made in great quantities by large machines, and given out at difiierent places in small quantities ; in a word, we may hope that in the course of the next few years we shall have learnt to distri- bute electricity. We will refer again to this question hereafter. When this problem shall be completely and practically solved, the small and medium-sized motors we have just described will at once be widely circulated, and we shall doubtless see a great many other patterns appear, to the great advantage of individual labour. 210 Eketricity as a Motive Power. CHAPTEE V. FIRST APPLICATIONS OP TRANSPOET OF FOECE. We have already mentioned how, at the Vienna Exhibition of 1873, Fontaine and G-ramme submitted to the public the first real application of the prin- ciple of the reversibility of electric machines, and at the same time the first real example of electric transport of force, by working a pump at the distance of 1 kilometre by means of a gas engine. This process was but slowly applied : for this there were many reasons. At first the machines generating electricity were few and weak ; the rapid growth of this industry, the number of types now in the market, deceive us ; but we must not forget that, in 1873, of those now in use, the Gramme machine was the only one then existing, and that was made for special applications, chiefly for electro -plating. Electric lighting was quite in its infancy ; the arrangements of machines for this sort of work were not at all suit- able for the transport of force, as we shall explain further on. There was, however, one attempt made in 1877, at the Arsenal of St. Thomas d'Aquin. The officers worked a dividing machine 60 metres away from the motor. This is a transmission which greatly re- Ploughing ly Electricity. 211 sembles the preceding examples, owing to the small- ness of the power transmitted. About 1878 Cadiat, at the Val d'Osne and the Lyons Kailway Company, made some attempts of the same sort to work tools ; but the most striking application, and the first which was really practical, was made in 1879 by Felix and Chretien at the sugar-plantation at Sermaize. Ex- tensive public experiments were made, and caused great excitement in the electric world. The work performed by electricity was ploughing. It is well known that mechanical cultivation, and particularly tillage, is very advantageous ; it is at once economical and productive, but presents pecu- liar difficulties; up to the present traction-engines have been used, carrying cylinders round which is wound a steel chain, which draws a plough with several shares. The result is satisfactory ; but these machines are very ponderous, they cannot go every- where, they necessitate a considerable provision of fuel, and use a great quantity of water — all great disadvantages, and costly to convey to the scene of work. With electricity these requirements disap- pear.. In the experiment at Sermaize, two carts were employed, each weighing 2 tons, instead of 18, like the portable engines; these carts each carried a drum provided with a cable to wind and unwind, and two ordinary Gramme dynamo-electric machines. On an electric current being sent into these machines they were set in motion, and this rotation could be utilised either to turn the wheels of the conveyance, which then began to move along p 2 212 Electricity as a Motive Power. Ploughing hy Electricity. 213 like a traction-engine, or to turn the drum which shortened in the cable, and brought towards it an agricultural apparatus which made furrows like a plough. The electricity produced at the works is conveyed by conducting cables to the machines. Fig. 90 gives a general idea of the work. Of course this system would hardly be applied to such a small piece of ground as that represented in the plate. We Pig. 91. have, reduced it to show at a glance the different essential points of the experiment, viz. the works where the electricity is produced, which are seen at the back, and the receptive machines at work at the front of the picture. We give here drawings of the carts which were used for this operation. Fig. 91 is a front view, in 214 Meetricity as a Motive Power. which the two Gramme machines, which are the motors, are easily distinguishable ; they are suspended in some way in a common frame-work, of which the upper piece is a bar with screws, which allows of their pressing on a large pulley between them. We must not, howeyer, forget that these machines rotate very rapidly, making as many as 600 revolutions in a minute ; therefore a considerable change must be effected in the movement before we can obtain the powerful effort necessary to move the cable and slowly draw the plough. Fig. 92 is a side view, in Fig. 92. which one of the Gramme machines is seen. Beneath the frame-work of the cart is seen part of the drum which carries the cable, and the cog-wheels by means of which it is worked. To the left is seen the arrange- Advantage of High Tension. 215 ment by which the movement is transmitted to the wheels of the cart, and makes of it, when required, an electric locomotive. It remains to speak of the generating machines which furnish the electricity to these motors. At first ordinary Gramme machines, originally intended for lighting purposes, were used, but it soon became necessary to construct special machines. There were several reasons for this. In the first place, the generators constructed for other purposes were not competent to absorb and transmit a great electric force ; it was therefore necessary to have them more powerful. In the second place, these generators furnish force in a very inconvenient way, and we must lay a stress on this point. If we wish to estimate how much work a waterfall will furnish, we must take two things into account : we will call the quantity of water furnished per second Q, and the height from which it falls H ; the quantity of work the fall is capable of producing is thus represented by Q H. In the same way, in cal- culating the work furnished by a current, we must take two things into account : the quantity of elec- tricity flowing through it, which is called the inten- sity I, and the force which propels it or the electro- motive force E; the work of which the current is capable is therefore represented by the product E I. Looking at the sum total of the work, it is imma- terial whether this product be obtained in one way or another ; whether E be less and I greater, or the contrary; provided the product remains the same, 216 Electricity as a Motive Power. as it would not affect the total work. This, how- ever, does affect it considerably if the force have to be transmitted through a long conducting wire and made use of at a distance, as we shall see. We have said that in the electric transport of force there is always a loss of some of the work ex- pended ; what becomes of this lost energy ? If we search for it we shall find it transformed into heat in the conducting wires, and in the machines them- selves. The laws of Joule enable us to determine the quantity thus dissipated. If we take E to re- present the total resistance of all the wires of the circuit, machines, and conductors, the heat which will be developed in them by the passing of a cur- rent with the intensity I wiU be represented by R P. In the application we are considering all this heat is useless, and is a loss which we want to reduce to a minimum, which leads us to diminish to the smallest possible quantity the intensity I; but then, to preserve the product EI, which represents the total work, at the same value, we must increase the factor E : we are thus led to employ electricity of high pressure. Although these laws were not elucidated and fixed in 1879, as they have been since, as we shall see, there was already some idea of them ; and endea- vours were made to produce a type of machine of higher tension than those then in use. There are two ways of doing this. We know that currents are obtained by moving a wire in a magnetic field. Ex- perience proves that the quicker this movement the 217 higher the tension obtained. The machine should therefore be made to turn as rapidly as possible. On the other hand, the more numerous the passages of the wire across the magnetic field, the more numerous will be the electric impulses which will accumulate for pressure. We are thus led to multiply the number Fig. 93. of magnetic fields through which the wire must pass in turning. On these principles Gramme recon- structed his apparatus in the manner represented in Fig. 93. The ring is larger; at first sight there appear to be eight electro-magnets, but we soon see 218 Electricity as a Motive Power. that they are joined two and two at their extremities, so as to form four magnetic fields. A collector which is not seen in the figure receives the impulses thus produced, and gives higher tension. The potential of the first lighting machines was about 60 to 70 volts ; that of these octagonal machines was as high as 250 or 300 volts. We shall soon see that this was only a first step, and that it was necessary to go much further. However, these machines were serviceable, and we shall see more of them in speaking of the Electric Exhibition and the applications which followed it. ( 219 ) CHAPTER VI. FIRST APPLICATIONS FOE THE LOCOMOTION OF CAEEIAGES. The application which should best pay, perhaps that in which electricity approaches the nearest to per- fection, is the locomotion of vehicles. In all the systems in use up to the present the motive agent itself moves with the conveyance it has to draw : the horse goes before the carriage, the locomotive with the train ; and then there is not only the motor itself to move — ^that is to say, properly speaking, the steam-engine — but the boiler to produce the steam, and the coal to furnish the heat, besides the water ; all this causes considerable expenditure of force. Certainly, in contemplating some steam-engines, the wonder is, not that they can draw carriages, but that these enormous engines can be made to move them- selves. By making use of electricity, the whole motive power is reduced to the electric motor fitted to the carriage, and which may be very light j the production of the force will take place at a distance, at a fixed centre, where the engines can be arranged as desired without inconvenience. The connection between the fixed generator and the moving motor 220 Electricity as a Motive Power. may be made to act in several ways, but in no case does it interfere with the locomotion. The first attempts in this line were, however, quite recent ; almost all, as we shall see, being due to the German firm of Siemens and Halske. The combination to be applied had nothing com- plicated ; it is the electric transport of force in its most simple form. What is there to do after all ? To set the wheels of a carriage in motion. The dynamo-electric machine is eminently fitted for this purpose; for, applied to produce force, it is in the form of an axis endued with the power of turning by itself. It will suffice, then, to set up at the starting- point a dynamo-electric machine driven by a suitable motor which will send a current to a similar machine carried by the vehicle to be moved. The system in itself cannot properly be called an invention, there not being many variations in the execution, at least in the principal parts ; there are, however, as we shall see, some difficulties in the carrying out, which have required, after all, no small amount of work and ingenuity. The first application of this kind we meet with was effected by the firm of Siemens and Halske, at the Berlin Exhibition, during the summer of 1879. It was a small model railway, laid down on a very small scale. The length of the line was about 500 metres ; it was in the form of an oval, so that the passengers returned to the starting-point. The train was composed of a small electric locomotive and carriages for the passengers. The latter were small Electric Locomotives. 221 platforms mounted on low wheels, with two rows of seats facing outwards parallel with the lines. The general appearance of the train was that given in the ■ accompanying Fig. 95. The locomotive was simply composed of one of Siemeris's dynamo-electric machines like that repre- sented in Fig. 68. This was laid horizontally on a framework with wheels; the bobbin was placed parallel to the line, the field electro-magnets being perpendicular thereto. Fig. 94 is a cross-section, Fig. 94. and Fig. 96 a longitudinal section of this apparatus. The latter shows a section of the cog-wheels % t, v, and X, by which the rotary movement of the bobbin 222 Electricity as a Motive Power. Electric Locomotives. 223 was transformed and transmitted to the driving- wheels of the little locomotives ; Fig. 94 shows the bevelled wheel k, which completed the commimica- tion of the movement. It remains to be seen how the electric current passes from the generating machine. To introduce the current a bar of iron N (Pig. 94) was laid between the two rails, and encased in wood Fig. 96. to insulate it electrically from the soil. On this bar, which ran the whole length of the way, rested two spring rubbers of the locomotive. The current was transmitted by these rubbers into the machine ; after having done its work it passed through the wheels of the locomotive and back to the generator by the iron rails. It was not necessary for the rails to be com- 224 Electricity as a Motive Power. pletely insulated, for if some of the current escaped into the earth it still returned to the generating machine, that being equally connected with the ground. A lever d o served to connect or to interrupt the current, and thus to set the train in motion or to stop it. This beautiful experiment was a great success, and the little railway was set up successively in other towns, Brussels, Dusseldorf, and Frankfort. In the last-mentioned town it ran from the Exhibition to the railway station, a distance of 250 metres ; three miniature tunnels had been erected on its route to make it more picturesque. More important attempts were to follow this first trial. On the 12th of May, 1881, an electric tram- way for real use was inaugurated near Berlin, between Lichterfelde and the Cadet's College, under the superintendence of the same firm, Siemens and Halske. This was not the first project ; there was an idea first of establishing an electric tramway in Berlin itself. For many reasons this work was postponed ; while waiting for the greater, the lesser work was accomplished. The length of the line thus laid down is 2450 metres ; it is laid on the level except for the slight inequalities necessitated by the declivities of the route. The electric generator was at first composed of two Siemens machines. Of course, this arrange- ment was only provisional, these machines being Eleeirie Trams. 225 replaced by a single powerful one connected direct to a rotary steam-engine. The vehicles are, of course, very different from those used in the first experiment ; in this case there is no locomotive drawing other carriages. Each vehicle carries its own motor, the carriage being in the form of the trams in use in many large cities, as Paris, Brussels, &c. These carriages are capable of Fig. 97. {O iL-l.-#)ir;osl]r containing twenty-six persons. A representation of them will be found in Figs. 97 and 98. In the first figure may be seen, under the body of the carriage between the wheels, the electromotor, which is, of course, one of Siemens's ; the bobbin is placed at right angles to the road. Its movement is trans- mitted to the wheels by means of a belt working on cylinders outside the wheels; as seen in Fig. 98. The transmission of force is effected here in a much Q 226 Eleetridty as a Motive Power. Fig. 98. more simple way than in the preceding arrangement. The carriages are provided with brakes, which may be put on at either end, so that the carriage will run in either direction without being turned round, as with ordinary trams. There is also imder the control of the conductor a means of introducing an artificial resistance, so as to be able to regulate the speed ; nevertheless, this is not of very much use, as by a happy property of dynamo-electric ma- chines, the speed, so to speak, regulates itself, and this is rather an im- portant point. In Chapter II. of this second part, which treats of the conditions under which mechanical work is transmitted by means of electricity, we said that when the receptive machihe which does the work has to make a great effort, it goes very slowly ; it follows that the current from the generating machine, being but sL'ghtly resisted, grows in in- tensity, and furnishes to the motor the means of exercising the necessary effort. If this effort diminishes, the receptive machine goes faster and faster, so as to offer more and more resistance to the passage of the current generated ; this grows weaker, Automatic Regulation. 227 and with it the effort exercised, but the total work effected, nevertheless, increases in proportion to the increase of speed up to a certain maximum. It is thus with the application of electric force to the locomotion of vehicles. Let us suppose our vehicle stationary on a level road. At the moment of first sending the electric current to set it in motion, we have that special resistance to overcome which is always felt at starting; therefore, the electric machine, having a great resistance to over- come, will turn slowly; the current will then be very strong, and the effort exercised sufficient to sur- mount the obstacle. The carriage once started, the resistance diminishes ; the machine, and with it the vehicle, is accelerated ; at the same time the current diminishes : and this continues till the carriage has assumed a uniform speed and the current has obtained the value necessary just to overcome the friction, which always tends to retard the motion. If an ascent occurs, the carriage will go more slowly and the current increase again, so that the motor, in proportion to its slackened movement, will receive the increase of force necessary to mount the incline. If, on the contrary, we come to a descending incline, it will itself accelerate its machine, and augment the counter-current in such a way as to diminish the propelling force. It may happen that the motor will turn as quickly as the generator, which will completely annul the current ; and it may even be that the motor, being hurried along by Q 2 228 Electricity as a Motive Power. the vehicle, will turn faster than the other ; then the direction of the current being reTersed, the motor, instead of receiving work, will have to produce it, which will tend to slacken the speed of the carriage, and thus constitute an electric brake. Dynamos may also be made powerful brakes by short-circuiting the machine fixed to the vehicle. The machine, being driven at great speed by the momentum of the vehicle, produces through the short circuit a very powerful current, which pulls the machine up, and thus puts a powerful brake on the wheels. This means must only be employed with great care, for the whole of the electricity thus generated is turned into heat in the machine and in the short circuit, and may, if too strong, burn up the machine and its connections. However, carefully applied, this means may be very useful ; it may be of extreme importance in a moment of danger, where it may be necessary to stop the vehicle on the spot, whatever it may cost, and where it might be impor- tant to sacrifice the machine for the sake of the passengers. The electricity was conveyed to the motor from the generating machine by a simpler arrangement than in the first case ; it was led up by one of the rails, and the other formed the return. It was necessary for the rails to be insulated from the ground, which was managed by taking care that they only touched the sleepers on which they were fixed. The current was then brought up to the Difficulties with the Conduetors. 229 machine through the tyre of one wheel, and returned by that of the other. This simple and inexpensive arrangement de- veloped grave faults in practice : in the first place, the insulation is very difficult to preserve, and, not- withstanding every care, great loss of current often arose ; and, in the second place, where the rails are crossed by a road, it might happen that a man or a horse should touch both rails, which would then afford a derivation for the current, and might occa- sion a violent and dangerous shock. This system is retained in Lichterfelde, but for other applications it is proposed to give the current a special conductor. For this is arranged along the route a line of posts supporting a wire, and on this wire runs a metal carriage drawn by the conveyance to which the cur- rent is furnished. This arrangement, shown in Fig. 99, has in fact been applied in several cases, especially to the tramway shown at the Exhibition of 1881, as to which we shall have something to say presently. At Lichterfelde, for the first time, a difSculty inherent to this means of transmitting power was made evident ; we refer to the continued variation in the resistance interposed between the two machines. At starting, the motor is quite close to the generator, but the further it goes the greater is the distance between the two, so that the power transmitted becomes weaker and weaker. In a very short run, this fault is not of importance, and in the Lichter- felde railway it was slight, owing to the large size of 230 Mectrieity as a Motive Power. the rails employed as conductors, and their slight electrical resistance, but it was perceptible. It became very marked with the overhead conductors which have just been mentioned, and which were necessarily restricted in size, and the resistance relatively great. We shall presently see that the way to overcome this difficulty is in an appropriate Fis. 99. employment of the electricity and the use of high- tension currents. If the applications of electricity to railways by Siemens and Halske are by far the most numerous and important, they are not the only ones. We must mention the experiment of Edison in his laboratory at Menlo Park. There are however no particular adaptations to record in this case ; they were very much the same arrangements as those of the Berlin experiment described in this chapter. Similar trials have been made in France by Messrs. Chretien and F41ix, who use Gramme Electric Cranes. 231 macliiiies ; they were shown at the Electrical Exhibition, and we shall presently describe them. Before, however, referring to this Exhibition, we must mention sundry other applications. Siemens and Halske put up a lift at Mannheim, and we mention it here to show the date, for we shall meet with a similar more complete and perfect application at the Exhibition ; the arrangements at Paris being essentially the same, it will be more convenient to describe them. At the sugar factory of Sermaize Messrs. F61ix and Chretien made use of electric transmission for several purposes, particularly for the discharging cranes. In factories of this description active work only takes place at one season of the year ; during the other months of the year the central engine has almost nothing to do. Here there was an opportunity to make use of its power at other points than in the factory itself — for example, on the discharging quays. The apparatus is also very simple, as will be seen on reference to Fig. 100. It is a crane formed of a long arm or rocking lever carrying a chain with brackets or trays. A Gramme machine is placed on the movable erection support- ing this lever. The upper end of the lever is furnished with a counter weight, and attached by a rope or chain to the barrel, which is worked by the electric machine. The whole thing is brought alongside the vessel to be discharged ; the barrel is started, and the lever is lowered till its lower end is in the boat. The lever is then made fast, and the 232 Electricity as a Motive Power. Siemens's Installation, 233 electric machine connected to the bucket-chain which brings up the beetroots to be landed, and empties them into the trucks arranged for their reception. Several such apparatus are placed along the quay, and can be set in motion by the workman by the simple means of a switch. A similar though more complete installation has been put up by Dr. (now Sir) William Siemens in his English farm. In this case a portable engine in the central building sets in motion a Siemens dynamo. The different points where work is to be carried out are connected with the central works by conducting- wires, some stationary, others movable and fixed at will. Dynamos are arranged where the work is required to be done, whether in the field, in the barns, or elsewhere; it is only necessary simply to connect the conducting wires with the machines. Thus, in every part of the farm, the current being produced in the central building by means of a steam engine may at any moment instantly be switched on for use. We may add that the electric current thus generated is employed at night for lighting purposes,' and has been used for very interesting experiments as to the development of vegetation under the influence of electric light. 234 Electricity as a Motive Power. CHAPTER VIL TBANSPOET OF FORCE AT THE ELECTBIOAL EXHIBITIOK OF 1881. The Electrical Exhibition which took place at Paris in 1881, and which was so brilliant, contained numerous examples of the electric transport of mechanical work. We cannot say, however, that there was any very new revelation made on this point, except in the exhibits of Marcel Deprez, of which we will speak by themselves. As to the rest, we find currents transmitted in a similar way to those of which we have been speaking : that is to say, worked at a short distance by means of machines of known patterns. Even from this point of view there was very little appearance of innova- tion ; all the transports acted, with the above-named exception, by means of the two types of machines spoken of in the preceding chapters, the ordinary Gramme machine and that of Siemens. Among the numerous new forms of machines produced at this Exhibition, none were applied to this purpose. The study of the transport of force by electricity as shown at the Exhibition would be reduced to a very brief and dry enumeration, were it not for a few not uninteresting peculiarities of some of the exhibits. The Exhibition of 1881. 235 To dispose of the least important first. Several firms exhibited whole work-rooms of sewing machines, all driven by electric motors. All were arranged in the same way; whether they were exhibited by the firms of La Menagere, or Bade, by Bariquand or by Hurtu and Hautin, all consisted of a certain number of sewing machines connected mechanically with a common driving-shaft; a dynamo set this shaft in motion, and the machines worked. In all the exhibits just mentioned, the Gramme machine was employed. It was the same with the machinery of Donnay Hure, Mouchere; the instruments worked varied, planes, lathes, etc., being shown in motion, but were always driven by a Gramme machine, receiving the current from a similar one placed at some distance in the Palais de I'lndustrie. Among the exhibits of this sort, the first to be mentioned is that of Heilmann, Ducommun, and Steinlin of Mulhouse. They set up on one side a regular battery of Gramme machines driven by steam-engines, and on the other a practical engineer's workshop, worked by a shaft driven by the other Gramme machines receiving the current of the first. The distance of transport was of course, as in the above-mentioned cases, very short ; not more than 100 metres. We must also mention Geneste and Herscher's installation ; here a single generating machine served to set in motion three receiving machines. It was a sort of vague attempt at distribution of electricity, 236 Electricity as a Motive Power. of course yery incomplete, but nevertheless interest- ing, and to be noticed as having some originality. We now come to the exhibits in which the elec- tric transport of force was the special object of demonstration. We wiU speak first of that of Chretien and Felix. They reproduced at the Exhi- bition the electric plough executed by them at Sermaize, of which we have already spoken : there is no need to say any more about it, as the whole machinery was exactly as we have already described it ; to this was added .a new apparatus constituting a sort of railway. Strictly speaking, it was a truck' something like the tender of a locomotive engine, the wheels of which were connected by an endless chain to a Gramme machine inside the truck; the current, brought by one rail, returned by the other, as in the Lichterfelde tramway described above. The firm of Chretien and Fdlix also exhibited a number of tools : for instance, a timber saw-mill in which the saws were set in motion by a Gramme machine ; a rotary pump whose axis was connected direct to that of an octagonal Gramme machine. Last, but not least, was an atmospheric rock-borer, for cutting and detaching blocks of stone in a quarry ; for this purpose it had a sort of solid scissor-blade, which moved with a rapid alternating motion, striking the stone, where it is required to be cut, a succession of rapid blows. This operation is accom- plished by means of compressed air to make the blow more elastic. The electric machine was used to Electro deposition. 237 give the rapid alternating movement to the piston working the apparatus. There was also to be seen a hammer, striking very rapidly and worked directly by a Gramme machine. This exhibit, as we may see, was important for its extent and the number of objects exhibited, but it added nothing on the whole to what had already been seen in France. The distance of transport was not more than the width of the Palais de I'lndustrie. Messrs. Siemens and Halske's exhibition was more original — indeed we ought to say exhibitions, for this noted firm exhibited in the German section as a firm, in the French section by right of their branch in Paris ; in the English section in the name of Dr. (now Sir) William Siemens, brother to Dr. Werner Siemens, head of the German firm. A fairly inter- esting installation of a collection of tools was made by them in the French section ; among them were much the same as the others — lathes, planes, rotary pumps, and besides an electro-plating bath. On this point an important remark must be made. We have already said that, to transmit force most econo- mically and conveniently, electricity of high tension must be employeid in order to use a smaller quantity ; the contrary is the case for electro-plating. Experi- ence shows that to obtain a metal deposit, the lower the pressure of the electricity the better. It follows from this, that the electricity used to transmit force is not fitted to deposit copper or gold. This defect is obviated by an ingenious contrivance : the electricity produced by the central engine is employed not to 238 Eledrieity as a Motive Power. deposit the metal, but to turn a motor, which in its turn sets in motion by means of a belt another dynamo ; it is this last which furnishes the elec- tricity for the galvanic bath, and it is so arranged that the electricity coming from this is suitable for the purpose. It is true that by these various trans- formations of electricity into force, and force into electricity, a considerable loss is sustained ; but the object is attained, which could not be the case if the electricity employed for the transport of force were applied direct. The Siemens firm also exhibited two very interest- ing applications : the first, which was not completed till nearly the end of the Exhibition, was a lift repre- sented in Fig. 101. The apparatus consisted of a toothed upright, or more precisely a narrow ladder with the rungs very close together ; two cog-wheels C, C^ fitted their teeth in between these bars. These wheels by means of an endless screw were connected vrith a dynamo-electric machine A. When the latter received the current it began to rotate, setting the wheels in motion, and these fitting into the ladder caused the whole contrivance to ascend. A platform was fixed to this arrangement and moved with it, thus carrying the persons on it up or down. The necessary current was furnished by an engine at a distance of several hundred metres in the Palais. A lift of the same sort had been exhibited the previous year at the Mannheim Exhibition. This application of electricity was curious and interesting, but on a closer inspection it might have Electricity as a Motive Power. Fig. 101. 239 240 Electricity as a Motive Power. been much criticised, especially as regards the mechanism, which absorbed much force. A less novel, but in many respects more interesting application, was the electric tramway installed by the Siemens firm and run between the Palais de I'lndus- trie and the Place de la Concorde. The general arrangement was very like that of the railway at Lichterfelde ; the vehicle was much the same, as may be seen from the accompanying Fig. 102, but differed in certain important details. It will be remembered that at Lichterfelde the current was brought by one rail and returned by the other ; for this the rails were slightly raised from the ground, being sustained and electrically insulated by blocks of wood. A similar arrangement was at first intended to be employed in Paris, the railway being raised to a certain height on a framework of wood and iron. The permission to carry this out arrived, they say, too late. It may be doubted whether it was ever given, the nature of the place being such that a tramway of this nature would have greatly interfered with the traffic, even ordin- ary raised rails not being permitted. They were therefore obliged to use grooved rails like the ordin- ary tramways of Paris, that no projection should disturb the level of the road. The conditions were thus completely altered, and there could no longer be any question of communicating the current by means of the rails, these not being capable of insula- tion. It was resolved to provide a special conductor for the current, which could then descend through the wheels and return by the rails and the earth. Electricity as a Motive Power. 241 242 Electricity as a Motive Power. In trying this, a new difficulty presented itself: the rails being on a level with the ground were covered with mud and dust ; and it will be understood that this would suffice to impede communication between the wheels and the rails in such a way that the return was very badly effected. It was therefore decided to erect a conductor to transmit the current both ways. After much thought and repeated experiments, these conductors were formed of two copper tubes Fig. 103. slit lengthways and laid along a small piece of wood suspended horizontally to posts erected along the road. The movable rubber or jockey, to connect the rubber with these tubes, required very deli- cate adjustment ; the form given in Fig. 103 was finally adopted. The contact was made, as will be seen, by a metal cylinder placed in the tube, one end of which was connected to the other across the longi- tudinal slit ; a roller wheel worked on the tube and The Paris Meetric Tram. 243 was pressed against it by springs, so that the contact took place both at the piece sliding in the tube and by the wheel rolling on the outside ; this was amply sufficient. Each of the two conductors had a runner of this description, which was attached to the tram by insulated conducting wires ; the current was brought by one and returned by the other. This plan worked very well during the time of the Exhibition. The vehicle would have gone at the rate of 70 kilometres an hour, but it never exceeded 20 kilometres, in consequence of the short length of the course and the sharpness of the curves. It has, however, proved to all the practicability of electric railways. Besides these exhibits must be mentioned those of Gravier de Varsovie and Marcel Deprez ; but these will be treated further on, as in them the question of electric transport of force is much complicated with a still more comprehensive and important subject, that of distribution of force. These two exhibitions gave two solutions of this question, of very unequal value, it is true ; that of Gravier being quite elemen- tary, while that of Marcel Deprez is of great im- portance. We shall speak more particularly of these further on. B 2 244 Eleetrieity as a Motive Power. CHAPTEE VIII. RECENT APPLICATIONS AND EXPERIMENTS. Although the Electric Exhibition, with the above exception, did not show any marked progress on what had already been done in the way of electric transport of force, yet it exerted the same good influence as the others — it made publicly known the results obtained, and published the proceedings. Since its close several interesting applications of the transmission of power have been made. At La Eochelle two octagonal Gramme machines were used to bring into the town part of the force of a waterfall situated at a distance of about 3 kilometres. The motor worked a rotary pump which furnished water to part of the town : this installation is in every way similar to those mentioned in the preceding chapter about the Exhibition, but it is no longer only a demonstration but a practical application, which is sometimes very different. This system, which has been in use for more than a year, still works well. At the cannon foundry at Bourges is now being installed a curious transport of force; it works a travelling crane. This apparatus, as is known, moves on rails, and should be able to act at any part of its Locomotive and Elevator at Lisieux. 245 course ; it generally has a steam-engine joined to and moTing with it. At Burgas a very powerful crane was wanted, capable of developing about 12 horse- power. An engine of this power is very heavy, and it was very diflScult and troublesome, if not impossible, to join it to the crane ; besides, there was power to spare in a workshop about 200 or 300 metres from where the crane was wanted. Electricity solved the question, the officers have promptly taken it up, and the apparatus will shortly be completed. According to the scheme, the current brought by a special con- ductor will return by the rails. The machines are of the Gramme type, set up by Chretien and Felix. Along with these examples we will mention one which is very peculiar. At the bleaching establish- ment at Breuil-en-Auge, near Lisieux, owned by Duchesne-Fournet, electricity is employed to gather up the linen. For bleaching and drying purposes the pieces of linen are spread out in the fields, and this has to be repeated many times. Dupuy, engineer to this firm, laid down along the top of the meadow a small railway. The train running on this consists first of two trucks, of which the fore- most contains Faure accumulators. We have not yet had occasion to speak of these accumulators, which have lately been much talked about ; we will only say that the Faure system is a modification of an im- portant invention, due to Grastou Plante; it was the latter who invented an apparatus in which elec- tricity may be stored up and used whenever required. The truck carrying the accumulators is therefore the 246 Electricity as a Motive Power. source of the electricity. Behind this is the second truck containing the motor, which we represent in Fig. 104. Fig. 104. A Gramme machine is employed. It is connected on one side with the wheels of the truck, Lisieux Bleaching Establishment. 247 on the other with a folder. Behind this truck are arranged others carrying baskets to receive the linen. This is collected in the following manner: The current from the accumulators is sent into the machine and the train begins to move ; on arrival at the first piece of linen, a lever, shown in Fig. 105, is worked, which has a double mission, namely, to disconnect the Fia. 105. ..^^^ c current and put a brake on the wheels. The end of the piece of linen is then taken by the folder ; this is connected with the motor and the current is switched on, thus starting the folder which takes hold of the long piece of linen, raising it to the baskets in the trucks behind. When one piece is gathered up 248 Electricity as a Motive Power. the motor is reconnected with the wheels, and the contrivance moves to the next piece. This arrangement is evidently only moderately advantageous; the accumulators are very heavy^ about 800 kilogrammes being required, which make a considerable dead weight. In working it in this way the principal advantage of electricity is lost, which is to bring force from a distance, as we have said ; in the arrangement of which we are speaking, it is only the aptitude of the electric agent to produce work that is turned to account, not its facility of transmission ; but in this case the arrangement adopted was ruled by various circumstances. In the first place, electricity was necessary. The steam engines were obliged to be far away from the meadows, as their smoke was disastrous to the linen; on the other hand, the meadows are very damp, and and it was impossible to insulate the rails so as to serve as conductors for the current ; it would there- fore have been necessary to set up a special con- ductor, as for the tramway at the Exhibition. The accumulators were preferred, as being less expensive, and as the train never had to go quickly, the weight was no great inconvenience. A new application of the same thing has just been made in a bleaching establishment at Berlin. In Fig. 106 is represented an electric locomotive, said to have been constructed by Murchisson, in which the motive force is produced by a simple alternating electromotor, acted upon by a Plante accumulator, which in the sketch is in the act of Murcinson's Locomotive. 249 being charged at the place of departure. De Graffigny, in his book entitled ' Les Moteurs Anciens et Modemes,' speaks of it as superior to that of Siemens tried at the Berlin Exhibition ; but we can- not agree at all with this opinion, nor with that he expresses about accumulators, the principle of which he evidently does not understand. According to this writer the speed of the locomotive may be Fig. 106. ;' III' modified by varying the intensity of the current, and might even be stopped almost simultaneously by applying the current to the wheels which should be made capable of magnetisation, and thus by their strong attraction to the rails their speed would be slackened; Further, the trucks were even to be held together in this system by magnetised buffers, which would allow of instantaneous separation ; the 250 ElectrieUy as a Motive Power. surplus power of the generator might be used to light an electric lamp at midnight to illuminate the road. These very complicated and useless arrange- ments are altogether improbable, and require serious proof; no use has ever been made of them, which compels us to leave them altogether out of the question. Lately, induction machines have also been applied to navigation, and the October papers of 1882 were full of experiments made on September 8th on the Thames, by means of a boat constructed by the Electrical Power Storage Company, and worked by Siemens machines. This boat, called the Electricity, was 7 • 62 metres in length, 1 • 52 metre wide, drawing "52 metre forward and "75 metre aft; it was there- fore nearly as large as that of Jacobi. We give a section of it in Fig. 107. The motor, composed of two machines, M, W, D^ type, was placed under shelter nearly amidships. The belts of the two machines worked on the same pulley P, which set in motion another pulley R, placed on the screw-shaft. This last made 350 revolutions per minute, and the machines 950. The current was supplied to the motors by forty- five Sellon-Volkmar accumulators, A A, with forty plates weighing 816 kilogrammes, and with an E.M.F. of 96 volts. It was said that this electric generator could furnish a current of 30 amperes, which would give four horse-power for six hours. The apparatus was completed by a commutator by which the number of accumulators might be varied. The Eledrie Launch. 251 There was besides a mechanical arrangement made by which either of the motors could be shut off at will; these were also made so that the machines could be reversed. There was thus every facility for stopping the boat quickly, and for going astern. The person in the cabin who attended to the com- mutator also steered. The whistle found in ordinary steamboats was replaced by a large bell also worked by the accumulators. The Electricity would carry twelve persons, but in the experiments made on the Thames between London Bridge and Millwall, only four went in her. The mean speed they went at was nine miles an hour against the current, according to information furnished by the experimenters. 252 Electricity as a Motive Power. Several smaller installations may be mentioned; we will first refer to that of La Belle Jardiniere. In this large outfitting establishment there is on the top storey a workroom full of sewing-machines; it was wished to work these machines by means of a motor, but the engines being in the basement, the mechanical transmission was very difficult. The problem was solved by electricity: a Gramme machine below, another above, two conductors, and the transmission was effected. The women were thus saved the working of the sewing-machines, which is arduous and often seriously injurious to the health if prolonged. There are also applications of this sort in the Grands Magasins du Louvre ; one of which at least was started perhaps even earlier than that of La Belle Jardiniere ; it is used for the transport of force between the Magasins and a workshop in the Eue de Valois ; the wire crosses the Eue St. Honore, and the current sets in motion a collection of cutting-out and sewing-machines. The same method is em- ployed in the workrooms in the Avenue Eapp; a number of sewing-machines are electrically driven by an engine situated at some distance from them. A very interesting application has just been effected in the goods station of the Chemin de fer du Nord. In speaking of the Electric Exhibition we did not mention a small electric windlass exhibited in the English section. It was very simple: a Siemens machine, according to the direction of the current transmitted to it, wound or unwound an endless Cranes at the Gare du Nord. 25t3 chain, and packages could thus be raised or lowered. The apparatus set up in the Gare du Nord by the French branch of the Siemens firm is similar, only- it is also provided with the means of moving from place to place, thus constituting really a travelling crane. To the beams of the goods station, grooved iron rails are attached and suspended. On these rails works a sort of truck, containing a Siemens machine connected with a windlass. Above this arrangement run copper tubes as conductors; they are exactly similar to those described in speaking of the Exhibition tramway enclosing sliding contacts. By means of a chain, the current is sent into the machine, and this is connected, sometimes with the windlass which is then used to raise burdens, some- times with the wheels of the truck which then carry it along from the loading to the unloading place, and vice versa. The electricity is supplied by two Gramme machines about 350 metres away, and the working of this plan is completely satisfactory- We may expect shortly to see many similar appli- cations. Besides the foregoing, numerous important pro- jects have been worked out and proposed ; we can- not yet say how they will turn out, but it will be interesting to say a few words about them. We have already mentioned the projected tramway at Berlin; its arrangements are very similar to those which have been worked out by Messrs. Chretien and Felix for a tramway to be erected on the Boule- vards in Paris, between the Madeleine and the 254 Electricity as a Motive Power. Bastille. We will give a few details of this last project, which is very complete. The double line of rails runs on a viaduct built the whole length of the way, which consists of an iron structure resting on a single row of large pillars; the space occupied is reduced as much as possible, and the height is from 5 to 7 metres above Fig. 108. the level of the ground ; there are no crossings nor changes of line. The stations, branch lines, etc., are designed with great care and thought, and the general appearance is shown in Fig. 108. The motive power is furnished by fixed steam engines, specially de- signed, working Gramme dynamos by which the Projected Overhead Tramway, 255 electricity is furnished. This is conducted along the route by copper wires. Each tram carries a machine which receives the electricity, transforming it into power in a similar manner to those already described. The authors of the project proposed to have two generating centres for the length of the line between the Madeleine and the Bastille. The carriages, similar to the tramcars we have already represented, were to be 8 metres in length and contain fifty passengers; they would not be made up into trains, but each carriage would run singly and frequently like omnibuses. As we may see, all the details of the project have been well thought out, and the question of finance has not been neglected ; an application was even made for a concession, but it is very doubtful if this project will ever be executed, at least in Paris, for the general opinion there seems to be in favour of an underground railway. It is, however, well to take note of this proposal, for similar tramways will certainly be built some day. The recent Electric Exhibition at Munich has shown that this is still one of the questions of the day : some very interesting experiments were made there. Some confined themselves to arrangements already known, and developed no new peculiarities. Thus Edison set up a sort of dairy where the imple- ments were connected to a driving-shaft worked by an Edison machine, which received the current from a similar machine at a distance, which however was in this case not more than a few metres. Schuckert exhibited some agricultural implements running 256 ElectricUy as a Motive Power, light, worked by an electric machine, but in this case the generator was situated at a distance of 5 kilometres, and was set in motion by the Falls of Hirschau. The distance of transport was therefore considerable, though not exceeding the limit of that already attained. We should say that the con- ducting wires connecting the two machines were of copper, 4 ■ 5 millimetres in diameter. This fact should be remembered, for it is not the distance between the machines where the difficulty is found ; this, as we have said, lies in the resistance encountered by the electricity in the conducting wire, through which it must pass from one station to the other. This re- sistance increases with the length of the wire, which is the reason of the increased distance being an obstacle, but it diminishes when the wire is increased in size ; it is also less when the metal of the wire is better adapted to the passage of the current, and possesses what is called a higher conductiyity. Now everyone knows that copper is a better conductor than iron, and it is the latter which is used for telegraph wires ; if we compare the conductivity of the two metals we find that in Schuckert's experi- ment the copper conductor of 5 kilometres was equivalent to 770 metres of telegraph wire : that is to say, if he had employed iron wire, it would have been necessary to place the machines only 770 metres apart in order to get the same effective return. This consideration is very important, for it is the difficulty of laying down the conductor which is the great trouble in the transmission of power. If it were Deprez's Mimich Experiment. 257 possible to place between two stations, however remote, a thick rod of pure copper, there would be little or no diflSculty in the electricity passing, and the distance would be of no account ; but this sort of installation would be an immense expense, out of all proportion to the useful results arising from such a transport. It is this question of expense which is definitely conclusive. When we propose to transmit force by electricity it is in order to turn it to good account, and this becomes impracticable if the installation is too costly. In these installations it is the conducting wire between the two stations that is the great expense, and it is therefore of primary importance to have this as thin as possible and of the least costly metal. From this point of view, as also from others to which we will refer, the experiments made by Marcel Deprez at Munich are of the highest importance. He transmitted a force of about a half cheval-vapeur from the little town of Miesbach to Munich, 57 kilo- metres distant, making use for this purpose of the ordinary iron telegraph wires 4 ■ 5 millimetres in dia- meter. These wires were besides set up and insiilated in the same way as for ordinary telegraph purposes, without taking any special precautions. This trial arose from what had already been done, and which we have described above: this marfes a very important step, and we will explain it more par- ticularly. In electric transmission of work nothing is creatpd any more than in any other case; we only apply s 258 Electricity as a Motive Power. work performed by some special action : therefore we can reap no more force in any particular instance than is generated by that action. This quantity is defined, and is capable of being measured : this is in fact what we can do for electric currents. If, as we have already said, we take E to represent the electromotive force which propels the current, and call the intensity I, the total force generated by this current will be represented by the product E I. We wish to turn it into mechanical work, the value of which we represent by T ; if our transformation were perfect we ought to obtain the whole of the force of the current in work, when we could make EI = T. Unhappily, this equation cannot be realised. There is, besides, an element of which we have taken no account. To have an electric current we must have a conductor to convey it, and this more especially when transmission is required, for it serves to conduct it to a distance ; and we know that any conducting body offers resistance to electricity. It is precisely this resistance to the flow of elec- tricity which we have ignored, but we know that this resistance always manifests itself by generating a certain amount of heat in the passage of the current. We learn how to measure this heat by a law dis- covered by Joule. If we take E as the resistance the electricity has to overcome, and I, as we said above, for the intensity of the current, the total heat generated is expressed by the product E P (I^ being of course the square of I, or I multiplied by itseK). Joule's Law, 259 This heat is produced at the expense of the force generated by the current, and our equation, to be correct, must stand thus : E I = E I^ + T. We see at once that the quantity E I^ is to the detriment of T ; it means a loss, and as we cannot entirely suppress it, we must endeavour to reduce it to the smallest possible dimensions. The first means is to reduce E. Looking at the whole question, we see that E is composed of three parts; the first, which strikes us immediately, is the conductor which unites the generating station with the receiving ma- chine. We have just referred to the difficulty found in reducing the resistance of this conductor, which becomes a question of expense and necessitates the consideration of economic requirements. The two other parts of E are not so striking at first, but will be found in the machines themselves. We must not forget that they are formed of wire coils, which the current has to traverse, and where it also meets with resistance ; other things being equal, it is of value to reduce this as much as possible. After diminishing E, we have yet another means of reducing E I'^ ; it is to lessen I. We may do this, no doubt, but on one condition : admitting that it is advantageous to reduce E I^, which is the loss, we must not reduce the product E I, which is the energy at our disposal ; we can then only reduce I by increasing E, so that EI may not be less. From which we see that to obtain an economical transmis- sion we are obliged to employ currents of low intensity but high tension. s 2 260 ElectrkUy as a Motive Power. We may even go further : we have already seen (Chapter V.) how the machines act in the transmis- sion of force. A generating machine turning at a certain speed sends its current to another machine, which we will suppose similar to the first. The second starts, and if doing no work, goes at the same speed as the first ; in this case, as we have seen, the current generated in the circuit is nil. Why ? The explanation is simple. The second machine in re- volving generates electricity, as does the other, and tends to produce a current in the opposite direction to that of the first machine, and neutralises it to a certain extent. If the two machines are going at equal speeds, the currents are equal ; they cancel one another entirely, and no current is apparent in the circuit. If, however, one of the machines goes slower than the other, the contrary currents are unequal ; there is a difference, which is shown in the form of a current of more or less intensity. That is what happens when the second machine is at work ; it is retarded by this work, and the current shows itself with an intensity great in proportion to the reduction of the speed. We may then consider the receiving machine as an electric generator working in the same circuit as the other, but in the opposite direction ; it is then, like the generator, the seat of an electromotive force, and as we have called the first E, we will call the second e. In the system of two machines which we will consider, there is only one current flowing through the two ; there is then only one intensity. Electrical Beturn. 261 which we have called I. We have seen above that the total energy produced by the generator was E I, so experiment and theory show that the energy developed by the receiver is shown by the formula el; it is the total work which it can develop, and is the value of the quantity we have hitherto called T, and our equation therefore takes the complete form, E I = R P + e I. It is very important to know what is the propor- tion of the work obtained, viz. the ratio between the energy recovered and the whole energy expended. This is the return, and we may ascertain it without difficulty electrically ; the real mechanical return is of course less, owing to friction, etc. The work generated is E I, the work recovered is e I, and the el return will then be -rrr-^ ; or cancelling I common to the two terms of the fraction, when the circuit does not present excessive loss, the return is equal to =^. It will be seen that the resistance is not taken into account in this formula, and as the resistance repre- sents the distance of the transmission, we are led to conclude that the return does not depend upon the distance. It must be observed that if the amount of work recovered and the loss suffered are fixed, that is to say, the return, the figures may be, as we have said, chosen without reference to the distance ; but this can only be the case if the electromotive forces fulfil certain precise conditions, and reach certain ascertained values. 262 Electricity as a Motive Power. These laws were guessed at in the years preceding the Exhibition, and, as we have said, a tendency had been shown to employ electricity of high tension for the transmission of power, but this progress was more instinctive than reasoning. It is to M. Marcel Deprez that we owe the entire theory as we have given it J he was the first to show, in the years 1880-81, that it was possible to obtain at any distance any required force with a return fixed beforehand, provided only that certain requisite electromotive forces were given to the machines. He did more: he showed how to obtain these electromotive forces with certainty. Till then dynamo machines had been treated in a somewhat empirical manner ; certain laws which governed them were well known, viz. the laws of electric induction formulated by Ampere and Faraday, but certain points remained in an obscurity which is not even yet entirely dissipated. Among these little-known points, the magnetisation of iron by electric currents must be placed at the head. The machines, as we have shown, produced electricity by rapidly passing wires before the poles of an electro-magnet; this forms part of the machine itself, and its variation depends upon that of the machine, and unfortunately the laws of this varia- tion are unknown; every time a machine was modified or a new one was made, there remained perforce an unknown element which influenced the result. By a very happy conception M. Marcel Deprez showed that the machines might be varied De^prez's Paris Experiments. 263 without modifying this mysterious magnetic field, and that the known laws were sufficient without taking the rebellious element into account, which remained invariable. From that time it became possible to determine beforehand the results that would be obtained from any machine, and to construct it with a degree of certainty till then impossible. After very complete laboratory studies in this sense, the principles which he enunciated were very minutely verified, and he obtained the remarkable result of which we have spoken, and which was the first example of the electric transmission of force to a great distance under practical conditions. Since the Exhibition much has been done in the way of experimenting, and M. Marcel Deprez has recently surpassed himself in his experiments at the Chemin de fer du Nord in Paris, where, with two machines specially constructed by him, he succeeded in transmitting two horse-power through an ordinary telegraph wire 4 millimetres in diameter, nearly 10 miles long, this being done with an expenditure in the motor of about 6 horse-power. At another similar experiment about 10 horse-power was put into the generator, and about 3 J horse-power received at the motor. In these experiments, however, the machines were placed side by side, two of the poles being joined by the long wire and the other two poles by a short thick wire. To this arrangement some objection may be taken on the ground that it would not correspond with actaal conditions of 264 Electricity as a Motive Power. working, supposing the machines to be 5 miles apart and joined by two telegraph wires, and these experi- ments have, in consequence, been very much criti- cised. In the notes at the end of this work will be found a translation of the report of M. Tresca, pre- sented to the " Academie des Sciences " with all the electrical and mechanical data of the various ex- periments. Many important projects are now also in hand for the practical application on a large scale of the transmission of power by electricity, chiefly for the purposes of locomotion. Among these we may mention the subterranean railway at the mines of Zankerode in Saxony, the Portrush railway in Ireland, the proposed railways in Switzerland and in Cornwall, both of which are to be worked by the natural forces abounding in the districts; also the underground railway from Charing Cross to Waterloo Stations, which is to run underneath the Thames through a tunnel, and the whole of the traffic is to be worked by electricity, Messrs. Siemens Brothers being the contractors. The necessary Bill is now before Parliament, and without doubt the works will very shortly be begun. The two first-mentioned railways, those at Zanke- rode and Portrush, have actually been accomplished, and merit description. In the former case, as the railway was subject to rough usage in the mines, and the rails could be but imperfectly insulated, recourse was had to another method of supplying the locomotive with the current. Two T iron rails The Porirush Bailway, 265 inverted are fixed to the roof running the whole length of the line, and on these work two carriages connected by insulated flexible conductors to the terminals of the motor, which is fixed with its axis lengthwise on the car and works one pair of driying- wheels by means of bevel gearing. The engine is reversible, and the starting or stopping gear, etc., ca.n be worked from either end. The weight of the locomotive is about a ton and a half, and it can develop power sufficient to draw a load of 8 tons at the rate of 7 or 8 miles an hour. The work was designed and carried out by Messrs. Siemens and Halske. The Portrush railway is another example of the successful application of electricity to locomotion. This line is single and is six miles long, uniting the towns of Portrush and Bushmills. The power is at present supplied by a steam-engine, but it is intended to replace this by water power obtained from the Falls of the River Bush in the neighbourhood. The iron conductor consists of a well-insulated iron T rail running alongside the line, two steel rubbing springs making contact to the dynamo, after passing which the current goes to the wheels and thence by the uninsulated rails to the generator. ; The line is in reality a tram-line, and parts of it run through the towns and the remainder alongside the existing road. There are, therefore, several places where the T iron conducting the current has to be broken ; in some the opening is not equal to the length of the car, therefore the two brushes are used so that 266 Electricity as a Motive Power. contact is made with the next conductor before it is broken on the one before, but in other cases, where the openings are wider, the car has to run by its own impetus over the break. This is easily managed in practice. Where the breaks occur the current is conveyed by copper conductors well insulated and buried underground. Comparisons have been made as to the expense of working the line by electricity and by ordinary steam tram locomotives, and from practical experience the electric method is shown to be extremely favourable, even when steam power is used to generate the current ; but when the water power can be made use of the economy will be very marked, and the wear and tear of the permanent way will be very much less than with steam loco- motives, owing to the very much lighter rolling stock required. We must here notice a proposal of Professors Ayrton and Perry for the supply of current to a train in motion. The earliest experiments in electric railways showed the difficulty of supplying the cur- rent through the rails, owing to the impossibility of obtaining perfect insulation thereof. For a short distance this could be managed, but on a long line the leakage became too great for this plan to be eco- nomically used; these inventors therefore propose that a long line should be divided into small sections, each moderately but not perfectly insulated. The current would be supplied to each section by means of well-insulated copper conductors running along the line, and each train as it arrived at a section Uiilisation of Natural Forces. 267 would automatically close the circuit by acting on a lever ; as long as it was on that section it would be be supplied with current, and as it left it, it would shut off the current from the one it had just left, and turn it on to the new one. By this means the rails might be used to convey the current to the motor, and at the same time very efficient insu- lation obtained. This would also provide a very perfect system of blocking, for it might easily be ar- ranged that no current could be supplied to a section immediately behind one on which a train was at the time, so that a train behind, on coming to that sec- tion, would stop of its own accord until the train in front was out of danger. This invention has not yet been applied, but it appears a very good arrange- ment. We have already said that the electrical transmis- sion of energy will no doubt be first applied in the utilisation of natural forces, hitherto useless on account of their situation, and at the head of these are waterfalls. It may be that at first sight one is not struck with the importance of these forces, but let the reader reflect a moment, and he will be able to call to mind some forces in his neighbourhood which have hitherto remained unemployed. Rivers have nearly always falls which might be utilised ; for example, the weirs in the Seine, in the vicinity of Paris, might be made to yield 2000 horse-power each, and there are three within a radius of 10 kilometres. There are few places near which there are not numberless instances of enormous natural 268 Electricity as a Motive Power. powers at present wasted : for instance, the numerous falls of the Thames, near London, and the vast power of the tide in the lower parts of the river would suflSce, not only to light up the whole of London, but also to supply it with all the motive power required ; and it is not necessary to mention the often quoted Falls of Niagara to show that there are around us innumerable sources of energy, the sum of which would add immensely to human power. This is only one instance of the transport of force, which is the most striking and will undoubtedly be the first utilised, but there are others : the enormous power of the tides may be utilised ; the irregular, but at the same time very great power of the winds may be accumulated and transported, and there are many others. From a general point of view it is a valuable property, that we are able to give to power a sort of privilege of ubiquity; its advantages are thus multiplied in an immense proportion, more especially if to it may be joined the property of sub-division, of which we will now treat. ( 269 ) CHAPTEE IX. THE DISTRIBUTION OF ELECTEICITT, It will have been seen from the preceding chapter how useful it is to be able to transport a power, and how this property has already received and will yet re- ceive numerous applications. The question appears most promising, for in this way we shall be able to bring to the work to be executed the very great natural powers, such as those of waterfalls, hitherto useless. But the problem is not thus completely solved. Suppose in fact — and the case will certainly happen — that a force of 1000 horse-power has been reclaimed and transported ; advantage must be ta*ken of it. But there are comparatively few establishments which have need of such an amount of motive power, and it must be divided among several factories j this is possible, within certain limits, by mechanical means, but the distance is very restricted, and it can only be done at great expense and with great loss of power. The true solution is evidently to divide the electricity itself, and only to transform it into mechanical energy after it has been distributed among the consumers. The distribution may in this manner be more easily managed, electricity being 270 Electricity as a Motive Power. easily diyided and distributed by means of simple conducting wires. A mucb larger subdivision may therefore at once be imagined, almost unlimited: not only will a greater power be distributed among several manufactories, but in each one the motive power will be again sub-divided to supply each individual machine or tool ; further, the total current will be sub-divided into numberless separate currents, each supplying separate places, whether factories, works, or private houses, thus distributing everywhere the numerous advantages of electricity. All that is, no doubt, possible, but on the condition that this subdivision of the current is carried out with regularity and certainty. It is necessary that every individual apparatus and consumer shall receive the allotted portion without influencing the others ; in a word, electricity must be distributed in the same way as water. The problem is not without difficulties, for although it is easy to subdivide electricity by simply presenting to it an open passage, it is not so easy to do so in a precise manner. First let us recall Ohm's fundamental law. We know that if we call I the intensity of the current, E the electromotive force of the generator, and E the resistance of the circuit, the proportion between.these E two quantities is expressed by the equation 1 = 5- Suppose then that we dispose of a source of elec- tricity and distribute the current equally among several machines (which may be lamps, depositing Theory of Distribution. 271 baths, motors, etc.), whicli for simplification we will suppose all similar. We connect the first apparatus, and a certain order of things is the result ; a current of intensity I resulting from the electromotive source E and the resistance E is established, and the instal- lation is adjusted : we have now to put on a second apparatus ; how is this to be done ? We will first put it following the other, and on the same circuit, but then its resistance will be added to that already existing and the intensity cannot be the same — it will be diminished ; consequently, if the installation was before properly adjusted, such can no longer be the case, and both the first and second machines will be insufficiently supplied. To re-establish the previous state of things and maintain the original intensity of current, we must, in proportion as we introduce in the circuit any apparatus increasing the resistance, increase the electromotive force of the generator, i. e. give it a suitable regulation. Before adopting this means, let us try another way. In the first case, having one machine in the circuit, we put the second in the same circuit ; instead of doing this, we might make another circuit for the second apparatus, thus affording the current another path. Let us see the result : with the first apparatus E the current had an intensity, I = =, and everything went well; we introduce a second apparatus on a second circuit, the current thus finds two paths open instead of one, the resistance is therefore half as great as at first; E is diminished by half, and 272 Mectricity as a Motive Power. "R becomes equal to j;-; it follows, then, that the in- tensity I will be doubled ; thus doubled it will divide itself between the two similar paths open to it ; the first apparatus will maintain its intensity I, and the new one will receive another similar intensity. From this it would seem that the problem was solved ; but unfortunately the reasoning that we have given is not exact, and we have neglected a necessary element. We have admitted that in offering to the current two circuits instead of one, the resistance which it would have to overcome would be halved, which is not correct ;. in fact, the resistance through which the current has to flow does not consist solely of the two circuits on which are the machines, it includes also the individual resistance of the generator. Whether this be a machine, a battery, or whatever we may suppose, the current must always traverse it, and it always meets with a resistance therein; it follows therefrom that by doubling the exterior circuit pre- sented to the current we have halved the exterior resistance, but we have not touched the resistance of , the generator, which is called the interior resistance. The total resistance has therefore been ditninished, but not by half; therefore, although the intensity has been increased, it has not been doubled, as we supposed just now, and our installation is still defec- tive : it could only be exact by doing away with the resistance of the generator, which is impossible. In default of this means, we must vary the electro- Bequirements for Perfect Regulation. 273 motive force of the generator, or in other words, effect a regulation. In whatever way we may work, we are therefore obliged to regulate the electric generator according to the demand of energy caused by introducing other apparatus successively into its circuit. In looking a little more closely into the question, we see that to be satisfactory this regulation must comply with three conditions : — 1st. The several apparatus placed under distri- bution must be separately supplied ; that is to say, each must receive its necessary share of electricity at any moment and in any place, without affecting the others placed in the same circuit. 2nd. The generator must therefore continuously furnish all the force required, but not more, or there will be loss. 3rd. The movement of electricity being very rapid, it is of importance that the regulation necessary to fulfil these conditions should be automatic. Such are the necessary exterior conditions for any distribution to be complete. Before enumerating the attempts made in this direction, we will glance at the conditions which they ought to fulfil. As we have said, there are two ways of supplying several electric apparatus from the same source. The first consists in putting them one after the other in the same circuit, or in series ; the second is when each has a separate circuit, or rather a separate T 274 Electricity as a Motive Power. brancli off the main circuit. This arrangement is variously called in parallel, in multiple arc, or in derivation. In both cases, if it is required that the various machines should receive their proper supply of current continuously, and that the addition of one should not affect the others, a regulation of the electromotive force or the current must be effected, the nature of such regulation depending on the system adopted, whether the series or parallel. For example, suppose we wish to utilise a waterfall which, we will say, is of great height but of small volume, and we arrange a set of water-wheels one under the other, so that each receives the whole of the water escaping from the one above it. Each wheel then utilises the whole of the volume of the fall, but only a portion of the head. If with this arrangement we wish to add another wheel, we must put it above the others, and consequently the height and not the volume of the fall must be altered. If, on the other hand, we have a broad fall but of moderate height, we may take off a certain number of channels of suitable width, and in each place a wheel. Then each wheel will utilise the whole of the height of the fall, but only a portion of the volume. If we want to add another, we must take off another channel for the current, when the total volume of water must be increased, the height of the fall remaining unchanged. The two above-mentioned arrangements for electric Regulation of Potential, 275 macliines are somewhat similar ; if they are placed one after the other in the same circuit, when one is added we have only to increase the tension which corresponds to the height of the waterfall without increasing the amount of the current. If, however, they are in parallel, and the number is altered, the current must be modified, the tension remaining the same. We have thus two modes of regulation. The series arrangement has many defects, for in the first place each machine is dependent on all the rest. If one of them meets with an accident, all the others are at once stopped ; and further, very great varia- tion in the electromotive force is pre-supposed, and extremely high tensions would often be necessary. This arrangement is theoretically possible, but it is doubtful if it could be practically employed. The parallel system appears more possible and certain in its action, and is the only one which has been at all used hitherto. The problem is, therefore, to maintain a constant pressure or tension, whatever may be the number of machines, etc, in the parallels ; and it will be seen that the tension which it is required to maintain constant is that at the terminals of the generating machine ; it is from these points that the derived circuits feeding the various motors, etc., are supposed to take their origin, and it is the tension at these points which determines the exterior current; this tension, then (scientifically termed, difference of poten- tial), must be so regulated that at any moment it T 2 276 Electricity as a Motive Power. may be constant, ■whatever may be the exterior circuit, or whatever variations it may undergo. The solution of this question has recently become of such urgent importance that a considerable number of plans have been put forward from different quar- ters, all of which have more or less helped to solve the difficulty. We will therefore refer to some of these, but we must at once state that the period in which they have all been brought out is really so short, that it is next to impossible to give them in chronological order, or to award the various priorities of conception. The legal points of the question, based on authenti- cated dates, are of course easily solved, but, as a matter of science, to decide the priority of invention is difficult, owing to the number of claims put forward. Besides, now-a-days scientific researches are, so to speak, democracised. Formerly, inventors were a small and select aristocracy, but now the results seem to arise from a number of small indi- vidual researches, rendering them neither less bril- liant nor less useful, but somewhat hiding the origin in mystery. We will therefore, instead of following the chronological order, go through them in such a way as to see the successive development of the means eniployed. One of the earliest was that of Edison, in which he sought to obtain regularity by modifying the production of the current. There are, of course, three ways of varying the current produced by a machine : the first is to vary the speed, which is ex- Edison's Begulator. 277 tremely difficult mechanically, and not very prac- tical; the second way is to vary the action of the field magnets by moving them further away from the armature, and it will be seen that this is out of the question; the third way is to vary the current through the field magnets ; this is evidently the most convenient method, and the one which has been most generally adopted. For this there is an essential condition, namely, that the magnets are not excited solely by the useful current of the machine ; in fact, it would then be im- possible to vary the excitation of the magnets without equally varying the exterior circuit. In the Edison system the field magnets are excited by a shunt from the main circuit. In this accessory cir- cuit is placed a box, and by means of a handle worked by an attendant variable resistances may be thrown in, as may be shown necessary by an indi- cator, thus always maintaining the proper current according to the demand. The necessary presence of this attendant is the weak point in this arrangement ; it is not automatic, and for an extended service, supplying various and unforeseen wants, this kind of regulation would be insufiScient. Mr. Edison has, however, applied his system to a large lighting installation in New York, which is said to work well ; but in any case it must be observed that this description of distribution is one of the simplest, including only apparatus all identical, namely, lamps, and has only to supply wants which may in a great measure be foretold. 278 Electricity as a Motive Power. At the Exhibition was also shown Mr. Maxim's regulator, represented in Fig. 109. This is a mechanical regulator, and consists essentially of a lever continually worked by the machine. This Pia. 109. meujs. lever, having two cams on it, h suspended between two cog-wheels ; if it rises, it touches the upper one, and by means of the cam turns one tooth at each Maxim's Begulator. 279 oscillation ; if it falls, the lower wheel is turned. The lever is fixed to the armature of an electro-mag- net, through the coils of which passes the current to be regulated ; it follows that if the current is too great the armature is attracted and falls, carrying the lever, which then acts on the lower wheel ; if the current is too weak the armature, acted on by a spring, is drawn up, thus putting in motion the upper wheel ; but for a normal current there is no movement. The cogged wheels thus put in play are not employed to put in resistances as in the Edison arrangement, but they act on the brushes of the machine and alter their position. It will be remem- bered that in dynamo-electric machines the current is collected by two springs or brushes rubbing on the revolving cylindrical commutator. According to the position of these brushes the current may be collected either at the maximum point or at any other, when there will be less; it will thus be seen that by varying the position of the brushes the current may be varied. This arrangement is very defective, as will be easily understood. From what has been said about dynamo-electric machines, it will have been under- stood that the position of the brushes was deter- mined; but if these brushes must be capable of being shifted either way, it follows that their mean position which they occupy normally is not their most advantageous position, and it will be understood how grave a fault this is. This system has also the great disadvantage of 280 Electricity as a Motive Power. slowness : theoretically, it ought to act ; practically, it did not do so at the Ethibition, and it is very doubtful if it has ever really been used. For a large distribution it would be quite insufficient. The Lane Fox regulator somewhat resembled the foregoing. Like it, it relied on the action of an electro-magnet, but instead of acting on the brushes as in the Maxim system, it served to introduce or take out artificial resistances in the exciting circuit. These modifications being occasioned by the attrac- tion of a magnet, take place very slowly, and alto- gether it is not likely to be much used, on account of its being so very slow working. The Brush system of lighting was very much noticed at the Exhibition, and for some things very rightly so. Without being actually more perfect than others as regards the lamp and the results ob- tained, it must share with the Jamin candles the honour of having first employed high tensions in the application of electricity to lighting. It has been already stated that M. Gramme had made machines reaching tensions of 300 volts ; those of Mr. Brush reached 1000 and even 2000 volts. We have re- marked that M. Marcel Deprez, in his experiments on the transmission of force, has also attained and surpassed these tensions. It is interesting to note that an inventor who was not, like Jamin and Deprez, guided by well-thought-out theory, should also have so well understood the necessity for high tensions as to adopt them with boldness. Our readers will excuse this digression. This was Gravier's System. 281 not the only point of notice in the Brush system, which included also a regulating arrangement, which was, however, very elementary. To vary the exciting current, a shunt was arranged which was opened more or less according to the energy required. It will be seen that by this arrangement any excess was lost, the production remaining uniform. The system also consists of a double regulating arrangement, the one automatic, the other worked by hand, both of which may be criticised from several points. Simi- larly with those already mentioned, it has not acted well, and is not capable of being extensively used. Interesting theoretical studies were being at the same time carried on, and to M. Hospitalier is due a complete projected system, apparently satisfying the required conditions. To M. G. Cabanella is also due a special system of distribution. Instead of arrang- ing all the apparatus ia parallel as others had done, he put them in series : this has, as we have stated, the objection of necessitating the use of very high tensions, which we think can never be really applied. One of the most elementary systems of regulation is that of M. Gravier. He reduces the problem to its most simple terms. We have said that the difficulty consisted in the fact of the generating machines having an internal resistance, and that the problem would disappear if this resistance could be done away with. This not being possible, M. Gravier set himself to reduce it. For this he took a number of 282 Electricity as a Motive Power. machines, and joined them up for quantity, so that they offered the least resistance possible to the current. To reduce it still further, he took care to excite the field magnets separately. This done, he places the machines in circuits as equal as possible, in which he employs very thick leads. It therefore happens that if one circuit is taken out, the re- mainder, being equal, continue to be supplied as before, and the interior resistance being also very slight, the electric production remains approximately proportional to the exterior resistance. M. Gravier had at the Electric Exhibition an installation on this system ; he fed lamps and machines on six different circuits, his generating apparatus being five machines coupled together. This, however, is not a solution — it is an arrange- ment which may be useful, a good application of a known principle ; but it will be seen that the diffi- culty is not got over, it is only lessened. It also possesses a great disadvantage, namely, that machines with slight internal resistance necessarily produce electricity of very low tension, and it will therefore be seen that they would in consequence not be adapted to the transport of electricity to a distance. But to distribute usefully, transmission is necessary ; this system is then only useful within certain very narrow limits. We now come to the solution proposed by M. Marcel Deprez, which is certainly the most im- portant of those which we have yet enumerated, and it has' this advantage, that it has been tried. This Deprez's Oompound Machines. 283 took place at the Palais de I'lndustrie during the Electrical Exhibition of 1881. The circuit from the generator almost made the round of the building, formiug a total lead of about 2 kilometres ; at various points chosen without distinction, and only taking into consideration the requirements, parallels were taken off each, feeding various kinds of apparatus working machines for sewing, folding, cutting out, sawing, turning, &c. At one point a number were placed together and formed a small workshop, a branch being taken off for the production of light as well. At the end of the circuit was installed a printing-press driven by a motor also supplied by a branch off the main circuit. All these were started or stopped at will, and each one quite independently of any other, thus forming an example of distribu- tion. The system merely consisted of two generating machines, one large and one small, working together, and presenting the appearance shown in Fig. 110. That was all ; in fact, its great simplicity was its great advantage. No mechanical apparatus was necessary ; it was solely dependent on the action of physical forces. M. Deprez discovered that the re- quired result could be arrived at by combining two exciting circuits on the field magnets. For this purpose, on the magnets of the large machine he winds two separate wires; the one being traversed by the current from the small machine, thus giving to the generator a constant magnetisation entirely unconnected with the exterior circuit, and the second 284 Electricity as a Motive Power. •wire, being in the main exterior circuit, is traversed by a variable current, thus adding to the constant magnetisation one varying with the requirements of the exterior circuit. He showed that by proper adjustment this variable magnetisation would be just sufficient to give the necessary increase of electro- PlG. 110. motive force as the demand increased. He thus obtained an automatic regulation without the inter- vention of any exterior apparatus, and satisfying in the most complete manner the required conditions. The Palais de I'lndustrie experiment was on a small scale ; prudence demands that, before giving a final The Grompton-Kapp Compound Machine. 285 opinion, a larger or more practical realisation should be waited for; however, it must be acknowledged that we have here the greatest guarantee for ultimate success. Closely connected with the above system of com- pound winding of the field magnets is the Crompton- Kapp principle. These inventors only use one machine, the Biirgin, and on the field magnets they wind two wires, the one being included in the main circuit as in an ordinary series dynamo, and the other being a shunt off that circuit ; by this means, with a varying resistance in the exterior circuit, very perfect automatic regulation is obtained. This arrangement was designed for lighting incandescent lamps in multiple arc, and is very largely and suc- cessfully used for this purpose ; but at Messrs. Crompton's works, at Chelmsford, this machine is also used for the distribution of electric energy of every description. Wires are laid throughout the building having a convenient number of terminals, switches, and safety fuses, placed in the different shops, oflSces, and the laboratory. To some of these terminals are attached branch circuits (all in parallel arc), which feed Swan lamps for lighting the different parts of the works ; other terminals have no perma- nent connection with branch circuits, but can at any time be coupled up to such branches for the purpose of using the current for some special experimental work. The main circuit is kept charged to a diffe- rence of potential of 80 volts by one of these com- pound wound machines, the combination of main and 286 Electricity as a Motive Power. shunt wires being so chosen that, no matter what current is taken out of the machine, that current is always delivered at a predetermined and fixed diffe- rence of potential. In the present instance, the current taken from the machine varies largely throughout the day, because from the main circuit the following operations are carried on independently of each other, viz, lighting by means of Swan lamps in parallel, testing arc lamps, testing and classifying Swan lamps, charging secondary battery, and trans- mission of motive power. This last is done in the following manner : each dynamo, after it is finished, and before being sent out, is carefully tested. But before driving it by steam power it is found con- venient to run it for some time as a motor, but doing no work, so as to get the journals and the brushes to a proper bearing. The current is also used for polar- ising dynamos, for the purpose of making sure that the different coils on the field magnets are properly connected up ; calibrating volt- and am-meters, testing the fusing point of safety fuses, testing the magnetic properties of different mixtures of cast iron, and a number of other laboratory experiments, which of necessity are constantly going on in a large electric light works. As most of these operations are carried on independently of each other, it often happens that current is required at the same time for many diffe- rent purposes. Yet there is no difiBculty whatever in this, the machine always proving equal to the demand. Another system of distribution is that proposed by Professors Ayrton and Perry, who advocate the use Ayrton and Perry's Scheme. 287 of accumulators in the town or centre where the electricity is required, the charging current being supplied from a distance wherever the motive power may be available. They propose the use of elec- tricity of very high tension but of low intensity ; by this means, as we have already shown, increasing the economy of working, and not necessitating the use of heavy and expensive conductors. To transform this current into useful proportions, it is to be used to charge a great number of accumulators in series; these are then to be broken up by commutator switches into a number of batteries, each giving a proportionately large current of moderate tension, such as can be made use of for arc or incandescent lamps, motors, etc. This system has never been worked on a large scale, but it has, in common with so many others, the objection of necessitating the use of currents of extremely high tension, which, although necessary for the economical transmission of power to a distance, would in this case be more than usually dangerous to life, as the circuit through the accumu- lators would of necessity be exposed ; and any two persons standing on the ground and simultaneously touching the two extreme accumulators during the charging would be instantaneously killed, owing to the immense difference of potential, which might often amount to many thousands of volts. Of course, when broken up into batteries for use this danger would not exist, as the only current then would be that from the battery itself, being perhaps only 100 to 200 volts. 288 Electricity as a Motive Power. Another solution of the problem is that put for- ward recently by Messrs. Goulard and Gibbs. They have shown a small installation on their system at the Westminster Koyal Aquarium Electrical Ex- hibition, where the results obtained certainly appear very satisfactory. The principle employed is that of the induction coil, and consists of a cardboard or wooden cylinder about 50 centimetres high, on which is wound in parallel spirals, and in rows one above the other, a cable, composed of a central copper wire of 4 millimetres diameter, highly insulated. Parallel to this, and completely surrounding it, are six strands of twelve small wires each, individually insulated. The large wire forming the inductor is traversed by the current from an alternating current machine, and the six strands of twelve wires each in which the induced currents are generated have their ends attached to a commutator, so that they may be joined up at will in quantity or in tension. Inside this hollow column is placed a soft-iron cylinder, which can be raised or lowered, by which the current induced in the small wires may be regulated. The instruments shown at the Aquarium consist each of four of these columns arranged in a square, and the ends of all the wires are brought up to the commutator in the middle, so that the whole of the wires may be grouped in ten- sion or in quantity, or some in quantity and some in tension. The practicability of this is shown : one of the instruments has all its wires grouped for quan- tity, and the current lights twenty-six incandescent lamps. The other generator has two columns Ooulard and Gibhs's Distributor.. 289 grouped in tension, and lights a Jablochkoff candle, and at the same time one of the remaining columns lights five Swan lamps in multiple arc, and the other drives a small motor. The intensity of the current induced is proportional to that of the primary current, and the tension may be varied according to the way in which the induced wires are coupled up. The inducing wire forms a closed circuit, and of course may traverse any number of these instruments, pro- vided the electromotive force is sufficient to over- come the resistance of the circuit and of the electromotive force generated by the secondary current. The inventors therefore propose to use for the transmission and distribution of power, alternating currents of very high tension, traversing as many of these secondary generators as may be required, they being all arranged in series. From this arrangement they say there can be no danger, since the primary current only traverses a closed metallic circuit, and contact with the body at any part of the circuit would offer too great a resistance to allow the slightest derivation of the current. This system has at present only been shown on this small scale, and tlierefore it is impossible to speak with certainty as to its action in a practical shape, but the objection to it appears to be in the necessary use of alternating currents of high tension ; whether such currents can advantageously be employed on long circuits, where the effects of static charge and induction will have to be taken into account, yet remains to be seen. u 290 Eleetricity as a Motive Power. This, then, is the present position of the all-im- portant question of the day — the transport and distribution of power by means of electricity. Much, very much has beea done, but much yet remains to be accomplished before that almost Utopian state of things arrives, when all the vast powers of nature at present wasted shall be reclaimed and made subser- vient to human will by being transported through a wire to the centres of civilisation, and there dis- tributed to every one according to each individual requirement. But in the immediate future we may safely prophesy that great progress will be made, and that before many years have elapsed electricity will be almost universally distributed. That will, then, certainly be one of the greatest events of our century, and will constitute a veritable social revo- lution. This progress may be summed up in one word : to bring electricity to the home. And electricity is at the same time light, chemical work, and motive power ; and that in the smallest quantities that may be desired at the disposal of the consumer, by the simple turning of a key. What advancements may we not look for, then, when many who have now no opportunity of making the experiments necessary to useful discoveries have this wonderful power readily obtainable, when every one has in his own hands, power in its most varied forms, and that at his own home, at his own time, and without being compelled to go to a stuffy workshop for it. The workshop ! This word opens to our view other points, for if the Prospects for the Future. 291 distribution of electricity has for men an immense advantage, it has much more for women. It is for them that the workshop is in the highest degree baneful : all know the dangers of this life in common, so profoundly destructive to health and morals. We have already mentioned that the first practical appli- cation of the transmission of power was to a factory of sewing machines, thus saving women from a hurtful labour. How much greater will be the ad- vantage when the woman can work her machine, no longer in the workshop, but at home by the hearth of her husband, by the cradle of her infant ! It is thus that will be found the true equality of the sexes ; it is thus that must be sought the solution of this burning question, the support and the indepen- dence of woman. This distribution will prove an efficient remedy for these social difficulties, and if we do not now actually possess it, we may consider it as certain that we soon shall do so. u 2 ( ,292 ) NOTES. Note A. — Jaoobi's opinions on the futueb of Electric MOTOES. EXTEAOT FEOM THE PaPEB PRESENTED BY HIM TO THE PaEIS AoADEMIK DES SCIENCES, IN DeOEM- BBE, 1834. In the history that we have given on pages 44 and 51 of the researches of Jacobi on the subject of Electro- Motors we have not given the theoretical part of this paper, for it would have appeared too scientific to the readers to whom our volume is addressed. Nevertheless, as, in view of the progress lately accomplished, this question has excited considerable interest, we have thought it right to give it in the form of a note, in order that those not frightened by formulae may see that this eminent Eussian had from the first made a very profound study of the question, and that his hopes were not as vain as might have been thought a little while ago, and as he himself thought a short time after his last attempts. At the time Jacobi presented his paper to the Acad6mie des Sciences, this Institution did not publish an account of its doings, for it was only in 1835, on the proposal of Arago, that was started that most useful publication which, under the title of ' Comptes rendus des Seances de I'Academie des Sciences,' is to-day so appreciated throughout the whole world. Jacobi's paper could not therefore be published by the Academic, but there was in existence a journal Notes. 293 founded by Arnoult, under the title of ' L'Institut,' which took its place, and a resum6 of Jacobi's paper is there published in No. 82 (December 3rd, 1834). It is from this that we have borrowed the description given in page 42. Here then are the conclusions with which this resume ends : " 1. The mechanism of this motor is very simple, compared with that of steam-engines. There are neither cylinder, piston nor valves, &c., the construction of which necessitates great exactitude, and therefore expense, and none of that friction which consumes in pure loss more than half the total work ; here there is almost no useless work beyond the friction of the axles in the bearings. Further, this machine gives direct a continuous rotary motion which may be changed into other movements much more easily than when the prime motion is a rectilinear back- wards and forwards one. Here also there is no risk of an explosion. " 2. All the motors hitherto employed for the working of machinery are hopelessly subject to the law, that their power is directly proportional to the economical effect or to the cost of production. Here, the intensity of the magnetic force may be increased in three ways : by in- creasing the voltaic apparatus ; by increasing the size of the wires which surround the bars ; or by increasing the dimensions of these bars, principally their diameter. The increase of the battery has a limit beyond which the magnetic effect only increases insensibly. The increase of the wire has also a limit, but it is not so restricted. But as for the gain in increasing the dimensions of the iron subjected to the magnetising power of the current, no limit is known. Thus, the new motor does not belong to the category of the motive forces hitherto employed, by the non-proportion between the cost and the effect. If it could still be doubted that even its minimum expense of 294 Notes. working did not in any way correspond with that principle of economy which is always the sine qua non of any mechanical or iadustrial system, these doubts would be removed when we reflect that magnetism is a force, and and that the electro-magnetic excitation is instantaneously effected. In fact, when the voltaic circuit is closed, the wire, and in consequence the bar on which it is wound, acquires its maximum force in an instant. If some ex- periments seem to contradict this instantaneousness, there must be some fault in the experiment : either a little oxide on the wire may have retarded the metallic contact, or there must be some other similar disturbing cause foreign to the actual properties of the magnetic force. " In the same way, if two magnetic systems move one towards the other, their mutual action is always in terms of their distance, so that the total action may be expressed /Mds. In this integral formula the time or speed only enters into the formula of the universal attraction ; it is not affected in any way by the speed with which the two magnetic systems move one towards the other. There- fore, we may get the work iMcJg done in any time whatever, changing nothing of the nature of the active systems, and without increasing the source of the force. That being settled, and the changing of the poles being made instantaneously, we are able to dispose of a force J 'Mds may be compared to the known quantity g." " The movement of the system will then be an acceler- ated motion, and cannot become uniform unless some force or resistance is met with which wUl be expressed in terms of the time or speed. It is with this movement as with that of a body falling from a great height, which Notes. 295 only becomes uniform by the resistance of the air. But we think that such an element, being entirely outside the force, may be reduced at will. " We shall see that it is not the same with other motors. In fact, if we establish an integral of the same form I P d s, for the work we can get from it, we may easily suppose that the point where the force P is applied has no other movement than that which is given to it by the motive force, which properly speaking is not a force, but, like muscular power, water, wind and vapour, a system of material points animated by forces. As soon as the point of application takes a normal movement, its speed must enter into the formula I P d s, and combines in it with the time which must elapse to produce the in- tensity which the maintaining of this new speed demands. Prom this often result very complicated phenomena, as for instance in locomotive steam-engines. " To establish a precise difference between ordinary motors and the new magnetic agent, we may say that with the former the accelerated movement becomes uniform, not by the increase of the resistance, but because the action of the force on the point of application is weak- ened ; whilst with the latter, if the movement can be made uniform, it is in consequence of some extraneous cause altogether independent of the principle of the force. Magnetic force may then be compared to gravity by sup- posing that we have at our disposal an infinite height ; it acts in all directions without meeting a fixed obstacle, whilst gravity does so at the surface of the earth. " In short, to enunciate in one word the technical im- portance of the new agent, we may say — in electric ma- chines speed costs nothing." 296 Notes. Note B. — Some Details of Teouv:6's Batteet, as used ni HIS Elbotbio Boat, Each element of this battery is composed of a plate of zinc placed between two carbons. The dimensions are as follows : — Total height -24 metre. Width -16 „ Thickness • 005 to • 008 metre. The immersed surface is about • 16 metre square. The carbons are electro-coppered at the upper part, which considerably diminishes the resistance of the bat- tery, gives a good surface for the contacts, and consoli- dates the carbon, always rather a brittle substance. The zinc plates, heavily amalgamated, have on their upper part a notch, into which is fitted the metal couplings covered with india-rubber, which supports the elements. This allows of ready removal, either for amalgamation qr for any other purpose. The exciting liquid contains much more bichromate of potash than ordinary solutions, and it was also found necessary to increase the quantity of sulphuric acid to as much as a fifth, or even a fourth, of the total weight of water. As much as 250 grammes of bichromate per litre of water have in this manner been dissolved, and the constants of each element are, according to M. d'Arsonval : — Electromotive force E l"9volt. Internal resistance r -08 ohm. Intensity at moment of insertion ., 118 amperes. On joining up a battery of six cells of this description Notes, 297 with a one-bobbin Trouve motor, M. d'Arsonval gives the following as the result : — ■ Work in the brake .. 3'75 kilogrammetres per second. Current 20 ampferee. Zinc expended per hour Hi grammes. ' Whence it appears that each gramme of zinc gives by this means 91 kilogrammetres of force. If we add to this 20 per cent, for the work absorbed in the double trans- mission by gearing and endless chain (the brake not being able to be applied direct on the axis of the motor), we have an effective work of 112 kilogrammetres per gramme of zinc consumed ; and it is said that, with motors having several bobbins, this return has been exceeded. It is also said that this battery, when used in conjunction with a Gramme machine, has been made to furnish for three consecutive hours a force of 14 kilogrammetres per second, and the following is a table of experiments imder- taken by M. Trouve : — Weight of Motor. Work Number Kilogram- Work Motor. Measured of metres per Gramme at Brake. Cells, per Hour. of Zinc. klgmes. klg. kgm. kgm. 1 bobbin 3-300 3-75 6 13-500 93-75 112-75 2 bobbins 5 8 12 28-800 100 120 4 „ 10 20 24 72-000 ,125 150 8 „ 20 56 48 201-600 ,175 206 Note C. — On the Eleotbio Ebtuen. — Count dtj Mon- oel's Eeplt to certain Criticisms on Depebz's expekiments between miesbaoh and munich. The inaccurate manner in which my communication to the Academic with respect to these experiments has been received, compels me to explain myself more fully than I have hitherto done on the subject of what is called the 298 Notes. elecirie return. It is for want of exactly understanding this term that many persons have believed that there was a regrettable contradiction between the figure of the elec- tric return as at first given by M. Deprez and the figure of the mechanical return afterwards obtained by the Electro- technical Commission. The return of an electromotive machine in regard to another which puts it in motion is expressed by the pro- portion of the useful mechanical work developed by the second to the work absorbed by the first. But the work may be estimated in two different ways: either by me- chanically applying a dynamometer to the generating machine, and a Prony brake or some other similar appa- ratus to the second; or by electrically measuring the intensity of the current traversing the two machines, as also the electromotive forces, the one direct and the other inverse, developed by the two machines. In the second case, the mechanical work absorbed by the first machine and that returned by the second may be ascertained by the electric measurements taken, by applying certain fundamental dynamic theorems which I will here briefly recapitulate. But, before going further, it is necessary to observe that the return calculated from this second method is necessarily higher than that obtained by direct mechanical measurement, for it is nothing less than the expression of what the mechanical return would be if the machines were perfect, i.e. exempt from friction, insta- bility, and even certain electric imperfections which can only be completely eliminated if the armature ring were composed of an infinite number of sections infinitely small. These last causes of loss are generally very small, and do not exceed 3 or 4 per cent. Joule's law enables us to calculate easily the mechanical work developed in the form of heat in an inert circuit, that is to say, in which there are neither mechanical nor Notes. 299 chemical actions. This quantity of work has for expres- sion one of the three forms, E P, ^ , or E I. The first is where the resistance E and the intensity of the current I are known, the second when the electromotive force E and the resistance E, and the last when the electromotive force E and the intensity I are respectively known. The two last expressions are easily deduced from the first (which was obtained by experiment by Joule) by com- bining it with Ohm's law. It must be observed that the numbers obtained by these expressions represent kilogrammetres per second when E, I, and K are respectively expressed in volts, amperes, and ohms, and when each is divided by the number g = 9 '81 metres, which represents the acceleration due to gravity. If it is required to know the number of calorics developed in one second by the passage of a current, the number of kilogrammetres found must be divided by the mechanical equivalent of heat, or 425. The quantity of mechanical work (expressed in kilogrammetres per second) liberated in an inert circuit under the form of heat, by the passage of an electric current, is represented indif- . ET E^ EI ferently by one of the expressions — , -^, — ■ • Let us now consider the case where the circuit instead of being inert, as we have supposed, contains a perfect electric motor (i. e. one based on the principle first applied by Pacinotti), free from friction and vibration, and the axis of which is provided with a brake enabling the total work developed to be measured when the motor turns. The total energy developed by the source of electricity then appears in the whole circuit in two different forms : heat and work. Since the intensity of the current being the same at allpointsbf the circuit, whatever may be the nature of the phenomena taking place therein (Ohm's law 300 Notes. verified by Faraday), and the resistance of a metallic circuit being under proper conditions independent of its state of repose or of motion, as also of the electromotive forces of which it may be the seat,* the quantity of heat developed in the whole circuit is always represented by 9 Again, the total quantity of work or energy generated by the source and expended in the total circuit, either in the form of heat or in the form of work, is in every EI case represented in kilogrammetres per second by — • Numerous demonstrations have been given of this funda- mental theory, and it is not necessary to repeat them here, but we will show how it may be directly deduced from the principle of the conservation of energy, and from the law of Faraday. Take a battery of n elements, having each an electromotive force taken as unity and producing a current of intensity I. According to the law of Faraday, the quantity of zinc dissolved in each element in unit time is proportional to I, and the total quantity of zinc dissolved in the n elements will consequently be proportional to n I, that is to say, to E I. But to this quantity of zinc dissolved corresponds a certain number of calorics, i. e. a quantity of energy perfectly determined. We may thus say that the total quantity of energy pro- duced by a source of electricity in unit time is propor- EI tional to E I, and is in reality measured by — ■ , as we * Some have thouglit that certain effects observed in the movable parts of macbmea in motion were caused by a real increase of the resistance of the machine ; but a closer study showed that this was accounted for by secondary effects, the electromotive force of extra currents having nothing to do with the resistance of the circuit. Notes. 301 have said above, when the British Association units are adopted. Let us now call T the mechanical work produced by the motor expressed in kilogrammetres per second : the total energy developed by the source equals the sum of the partial energies developed in the whole circuit, and EI It I^ we shall have the equation — = + T ; whence we 9 9 haveT = I(5jL^. 9 To understand the second term of this equation, let us bring the expression E — E I into its simpler form, and for that let us remark that in the fundamental equation E representing Ohm's law I = =^ , it is expressly understood that E represents the algebraic sum of the positive electro- motive forces and the negative electromotive forces (if there be any) in the circuit, so that if we represent the first by E and the second by e, the equation becomes E — e I = — = — , whence e = E — E I. The expression ix E — E I then always represents a negative electromotive force, and we may conclude that when a motor furnishes work it necessarily generates a contrary electromotive force, which is exactly what is proved by experiment. Using this form for the term E — E I, the equation of el E — e work becomes T = — ■, or remembering that I = — ^ — g a T = -^^ — = — - , so that the total energy developed by the g a ^ EI E ( E - e) ^ ,^ source becomes T = = — ^— ■=: — - and the work lost 9 9^ . ^, . „, EP E/E-e\, (E - ey , in the form oi heat - — or — 1 — =r — I ^ or ^ — 5-^ . g g \ B, J gB 302 Notes. We will tabulate these results as follows : a'o ( fE I B (E - e) " £ . I Spent by the source \ — = = ffl i g I Eecovered in the form of work in f £_! _ e (E — e) S g S \ the motor \ g gE , ^4 xTi. Lost in the circuit in the form of fE V (B — e)' E-i3 ^, heat \ g gB These expressions constitute what may be called the fundamental equations of the theory of the transport of force. They are, however, strictly applicable only to motors electrically perfect, i. e. to those in which the electro- motive force undergoes no variation throughout a complete revolution. This ideal is realised by instruments which serve to demonstrate the rotation of a movable circuit by a magnet acting as the axis of this circuit. Motors founded on the principle of Pacinotti approach the nearer to this perfec- tion the greater the number of sections in the ring ; but, as we said above, they may be considered as being at present so near to absolute perfection, that there is little hope of improving them in this respect. The dynamometric ex- periments which these machines have undergone of late EI years, have proved in fact that the expression represents about • 95 of the mechanical work applied to the pulley after deductions are made for the work ex- pended in overcoming friction ; that is to say, that if the total work applied to the pulley is represented by 100, ■p T and the work absorbed by friction by 10, the product — 95 may reach r-^ of the remaining work (100 — 10) absorbed in work purely electric, or 85 • 5. The difference 90 — 85 ■ 5 Notes. 303 then represents the loss due to electric imperfections, which would exist even in a motor free from all friction, which amounts, as I said at the beginning of this article, to 4 or 5 per cent. The fundamental equations enable us to calculate immediately the value of the economical return, i. e. the proportion of mechanical work recovered in the motor to that absorbed in the generator. For that it suffices to divide the first expression by the second. We therefore have, calling h this economic return, el . EI _ e But this expression is independent of the resistance, and it may therefore be concluded that the economic return only depends upon the proportion between the counter electromotive force of the receiver and the electromotive force of the generator. This is what M. Deprez tersely expressed when he said, " the return is independent of the distance." But if the economic return is independent of the resistance, the absolute work * is not in the same case, and it is this which some who have discussed the 'experi- ments of M. Duprez have affected to call the return, being ignorant of the fact that this term has always had in mechanics a perfectly defined signification long before it was thought of applying it to electromotors. In order to see the influence of resistance in the circuit on the absolute work, we will introduce into the above equations the value of the economic return k which it is desired to obtain. From the equation & = — we have * To maintain constant the work transmitted, whatever may be the resistance, M. Marcel Deprez has shown that the electro- motive force of the source must be increased proportionately to the square root of the resistance. 304 NoUs. e = k'E, and making use of this value of e in the pre- ceding equations, they become : — Work absorbed by the generator . . — ^ ~ ' g E Work recovered in the motor .. • LJZ — I gB Work lost in the form of heat .. '^ ~" — i- But in this form they lend themselves to discussion. The second shows immediately that if we suppose the electromotive force E of the generator as given, the work recovered in the receiver may be obtained by giving the economic return two different values complementary 2 8 3 7 4 one of the other, such as -rj: and tt; > or — and 77; j o"" tk and^. Thus the absolute work of the receiver may be the same in two different experiments, although the economic return has very dissimilar values. We shall see that these differences result from the weight put on the brake applied to the machine. According as the weight on the brake is great or small, so the speed of the receiver is low or high, but the work per second, i. e. the product of the resisting effort of the brake, and the speed at the point of application of this effort, may be the same. This work also may be nil in two cases, when k = 0, and when ^ = 1. The first of these is when the brake is so heavily loaded as to completely prevent the receiver from turning, and the second when it is, on the other hand, completely taken off. There is therefore a value for the economic return, for which the useful work of the receiver is the greatest possible. The sum of the two expressions k and Notes. 305 1 — Jc being constant, this maximum is reached when they are equal : that is to say, when 4 = J. This further gives the result -^ (1 — 2 A) of the second term of the second g a equation. The useful work recovered therefore becomes E^ ' E* J— =■, and the work spent in the generator s— ^ . If the *9 ^ 2gB, receiver is entirely prevented from turning we should have h = 0, and the work absorbed by the generator then E^ become the greatest possible, or ^5 , the identical value gK which would be obtained by Joule's law for an inert circuit. We see that the maximum mechanical work developed by the receiver corresponds to the economic return being equal to J, and that when the economic return is varied between 1 and zero the work spent in the generator constantly increases from zero to — p, although the electromotive force remains constant. These considerations, although very simple, appear somewhat delicate and complicated at first, and it is from not having well comprehended them that many have lately written a vast amount of inaccurate criticisms on the transport of force. To cite only one example, one of the most common errors consists in the belief that the economic return can never exceed 50 per cent., because it reaches this value when the work developed by the receiver is the greatest possible in absolute value. All the functions of generator and receiver become perfectly clear when we take as a starting point the weight on the brake on the receiver, as M. Deprez has done in his latest theoretical studies on the transport of force. He has, in fact, shown that this suigle element is s 306 Notes. sufficient to completely determine the speed, and in con- sequence the absolute work of the receiver, its counter electromotive force, the economic return, and the intensity of the current, provided that certain elements in the construction of the machines and the resistance of the circuit are known. He was thus enabled to obtain formulas remarkable for their simplicity and for the small number of variable elements contained therein, and in which electrical symbols do not appear, but are replaced by a new element to which M. Deprez has given the name of " Cost of the static effort" (Prix de I'effort statique). This depends solely upon the construction of the machine, and has no reference to its internal resistance. I would refer those who wish to go further into this question to ' La Lumiere Electrique ' for November 4tb, 1882 ; but I think it well to describe here the fundamental experiment on which this new theory is based, which experiment M. Deprez very recently repeated in my presence. On the axis of any receiver, Gramme or Hefner- Alteneck, is fixed an automatic regulating dynamometer brake, that is to say, one maintaining strictly constant the tangential effort applied to the pulley of the brake, whatever may be the variation in the fnction. A current is then sent through the receiver, taking care to have an intensity galvanometer or am-meter in the circuit. Another galva- nometer, which must have a very high resistance, is placed in derivation at the terminals of the generator in order to ascertain the difference of potential between these terminals. These arrangements being made, the generator is revolved at a gradually increasing speed, and it will be seen that as long as the receiver does not move, the two galvanometers are progressively deflected proportionately and continuously, showing that the electromotive force of the generator and the intensity of the current generated Notes. 307 are proportionately increased. But from the moment when the receiver begins to move, the needle of the intensity galvanometer remains steadily fixed at the then deflection, whatever may be the speed of the generator, while the needle of the galvanometer in derivation shows that the electromotive force increases more and more with the speed of the generator. The speed of the receiver is in the same case, which in the experiment I witnessed varied between zero and 32 revolutions per second, the intensity of the current not varying more than -^ of its proper value. The same result may be obtained if the experiment is made in another manner, namely, by adding to or decreasing the resistance in the circuit when the intensity of the current remains constant. Wbatever we may do, there- fore, as long as the receiving machine moves at all, it is impossible to vary the current as long as the weight on the brake is not altered. Any increase in the electro- motive force of the generator, or, what comes to the same thing, any decrease in the resistance of the circuit, has only the effect of increasing the speed of the receiver. But on the other hand, if the weight on the brake is changed, the current necessary to keep the receiver iu motion with this weight changes also, at the same time remaining independent of the speed of the receiver. The necessary conclusion with regard to this important experi- ment is, according to M. Deprez, that the effort developed between the fixed and movable parts of a dynamo-electric machine, when it is traversed by a current, is independent of the speed and direction of the ring, and only depends on the intensity of the current. This principle was, moreover, suggested by Mr. Pollard about three years ago. M. Marcel Deprez has, by means of this single law, entirely reconstructed the theory of the transport of force, rendering it so simple that it will not be out of X 2 308 Notes. place to give here an example of its application to a particular case, since it has already been made public. Suppose two precisely similar dynamos, the one being generator and the other receiver, placed on a circuit of any resistance ; the receiver being fitted with a brake with a known weight on it, and the generator being driven at a gradually increasing speed. In virtue of the above law, the current will become constant as soon as the receiver begins to revolve, and the tangential effort developed on the pulley of the generator will be equal to that applied to the pulley of the receiver, by reason of the independence of the mechanical action of the current (which is the same at all points of the circuit), in respect of the speed or direction of the movement of the armature. But the two rings having similar dimensions and being subject to similar tangential efforts, the return is expressed by the proportion between their respective speeds. But it has long been indisputably established that in a magneto-electric machine the electromotive force is pro- portional to the tangential speed of the pulley, and the intensity of the magnetic field, and the two machines being similar and traversed by the same current, their magnetic fields are equal ; therefore the electromotive forces respect- ively developed by the receiver and generator are pro- portional to the speeds of the armatures. Consequently, calling the corresponding electromotive forces and speeds of the two machines e, E, and v, V, respectively, and h the return, we shall have =■ = =r = ifc. E V We thus come back to the value =; , which we have E' already obtained for the economic return by quite a different method. With regard to the experiments of M. Marcel Deprez, when it is remembered that before this experiment the Notes. 309 boldest enterprise in this direction was with a 4 milli- metre copper wire, 6400 metres long, with a resistance of 8 • 4 ohms very carefully insulated throughout its entire length, and that M. Deprez elected to make use of an iron telegraph wire exposed to the rain, 114,000 metres in length and with a resistance of 950 ohms, and that not- withstanding these enormous differences in the conditions of the two experiments, the same indiistrial return was obtained, namely, 60 per cent., it will be conceded that the Miesbaeh-Munich experiment was of the utmost im- portance in the history of the transport of force. The obstinacy with which the adversaries of M. Deprez, no longer being able to raise doubts as to the reality of the experiment which they prophesied beforehand would cover him with ridicule, now do all they can to make light of and detract from the results by disputing the mechanical return, is the completest proof that could be desired. Carried away by their spirit of criticism, they endeavour to destroy every point of the new theory of the transport of force ; and quoting figures entirely without proofs, they triumphantly calculate that theoretically the return should be less than that actually arrived at by means of brake and dynamometer ! When M. Marcel Deprez, in his communication to the " Academie," gave for the value of the return 60 per cent., he took care to say that this return was measured (the two machines being identical) by the proportion between their^ speeds (2000 and 1200 revolutions), deducting all passive resistances, and this showed that it was the theo- retical return =-. His communication was addressed to scientific men, and there was no necessity to explain him- self further, because he knew that the special public to whom it was addressed would not misunderstand it and 310 Notes. would know how to distinguish between the return — or r=r and the industrial return. He could besides not give the direct electrical measure- ments (electromotive force and current), because he had not the instruments necessary to obtain them, nor dynamometrical measurements as to the generator. He was therefore obliged to wait for the Electro-Technical Commission to make their experiments. In 'La Lumiere Electrique' he published a detailed account of the circumstances attending the experiments, and I will only add one particular given to me by M. Deprez himself authorising me to publish it, making a reserve as to the absolute exactitude of the figures, which he was only able to obtain verbally from the members of the Commission, who were themselves unable to obtain the figures for all the experiments. The difference of potential measured direct between the terminals of the Munich machine, revolving at between 720 and 760 a miaute, was about 830 volts, and the current as measured at Miesbach was '4 ampere. But from the experiments of Professor Kittler with a battery of 100 Meidinger cells (having a total E. M. P. of 105 volts), after 14 days' raia and using the earth as return, it appeared that a current having at Munich an intensity of • 0692 ampere was still, on its arrival at Miesbach, equal to • 0674, or • 974 of its original intensity. It may be taken, then, that the current had practically the same intensity at Miesbach as at Munich, namely, • 4 ampere ;* but the resistance of the machine at Munich was 475 * According to the official figures subsequently published, it appears that this intensity was '5 ampfere instead of 4. From this it results that the efficiency above estimated of "46 only reached, according to the report of the committee, • 389. Notes. 311 ohms. These numbers enable us to calculate the electro- motive force and the theoretical value of the work which should be produced by the machine at Munich. We have then e = 830 - (-4 X 475) = 640 volts, — = 25-6 kilo- s' grammetres. 1'5 X 740 But the work indicated by the brake was ^rr = " 60 18 • 5 kilogrammetres ; the efficiency of the receiver was then about ir--^ = ' '^2. Further, the resistance of the is •00 line was 950 ohms, that of the generator at Miesbach 470 ohms ; and these figures easily enable the electromotive force of the Miesbach machine to be shown, namely, 830 + (-4 X 1420) = 1400 volts. * 1400 X "4 The work absorbed was theoretically — — — = 56 y "oi kilogrammetres per second ; and supposing that its effi- ciency was also • 72, it will be found that a mechanical work of about 80 kilogrammetres should have been ab- sorbed. The electric return measured by the proportion between the electromotive forces would therefore be — — = ■ 46, and measuring it by the proportion between the speeds * (the Miesbach machine making 1600 revolu- 730 tions per minute), we have v^ttt, = ' 455. Too great im- portance need not be attached to the remarkable coin- * In the experiment made on the 26th September by M. Saroia, the speed of the generator was 2200 revolutions per minute, that of the receiver 1508, and the vrork on the break reached 37" 5. These numbers were checked by Mr. Tatterer, who was attached to the technical service of the Exhibition. 312 Notes. cidenee of these two figures: they might have largely differed, and still have confirmed the expression of the electric return. It may be added that for a week the receiver worked a centrifugal pump running at 900 revo- lutions per minute (the pulleys being the same size), and fed a'pretty fountain nearly 3 metres in height. After several hours' consecutive running the two machines showed no appreciable rise in temperature, which, considering their enormous internal resistance, shows plainly that the intensity of the current was very slight, as well as the quantity of energy lost in the form of heat. I think I have abundantly shown that the success of the bold experiment undertaken by M. Marcel Deprez has fully confirmed the calculations and the theoretical views of this scientist, and that the incompatibility which his opponents wished to establish between the electric return and the mechanical return does not exist. In concluding, I must express the regret that the experiments of the Commission were not able to be undertaken under the same conditions as the first experiment made by M. Sarcia, when the useful work reached ^ horse-power, and the return would have reached a higher figure. M. Deprez has, with many other details given in his letter of the 11th of November last, stated the causes which pre- vented the Commission from working under similar conditions. Th. du Moncel. Notes. 313 Note D. — On the Chaeaotkbistio Curve op Dtnamo- ELBOTEIO MaOHENBS. Since the application of dynamo machines has become so common, the different effects that they realise, and the characteristics and properties that they possess, have been much studied ; and M. Deprez has found a very simple method of representing by a curve these different cha- racters, and by simple graphic lines the different effects that a machine will give. To^.this curve has been given the name " Characteristic." To obtain it, currents of known intensity are sent from an independent source through the field-magiiet coils, the armature being revolved at speeds also known. For each intensity of current thus sent, through the inducing circuit, the electromotive forces developed in the armature are measured, and are successively plotted off along a ver- tical line forming the ordinates of the required curve, at the same time marking off the intensities as abscissae on the perpendicular line. Then by describing a line through the different intersections of the vertical and perpendicular lines, the characteristic curve of the machine experimented upon is obtained. The form of this curve depends upon the construction of the machine, its dimensions, and the proportion between its various parts; it represents its actions and clearly shows the properties of the apparatus, hence the name which has been given to it. It even enables a graphic solution of the questions which may arise in the use of such machines to be readily obtained, and assists in the explanation of several interesting phenomena. Thus, for example, when the curve for a Gramme machine, as shown in Fig. Ill, is studied, it is seen that the electromotive force developed increases rapidly at first, becoming less 314 Notes. and less rapid, and ends by remaining stationary towards H, the curve tending to become parallel to the horizontal line ; this shows that the magnetization of the soft iron does not increase indefinitely, and that there is a point of saturation which, it is true, is not completely attained, but towards which it more and more tends. As the intensity of a current is proportional at the same time to the electromotive force and the resistance, it will be easily understood that, knowing by the- pre- ceding curve the electromotive force and the intensity of Fig. 1X1. the current at the different points of the curve, the resist- ance of the circuit R corresponding to an intensity and electromotive force given may be readily deduced; for, if their proportion exactly represents this resistance, as is E . E given by Ohm's formula, E = tj, and as ithe proportion y represents the two sides of a right-angled triangle, it then becomes equal to the tangent of the angle formed by the line of absoisssB X with the line G 0, for example, which joins with the point G of the curve. If this angle is 45° the tangent becomes equal to 1, repre- Notes. 315 senting'^the ratio of unit E. M. F. to pait intensity, i.e. the ohm, or unit resistance, and it may be made use of to form a graduated scale of resistances. Let us now examine what happens when we increase or diminish the resistance represented, as we have said, by the tangent of the angle corresponding to the different points of the curve. It will be seen that, for points in the part almost parallel with the line of abscissae as H, the resistance of the circuit becomes less and less, and that on the other hand it becomes greater for points on the opposite side, which consequently shows a pro- gressive increase of the electric intensity in the one case, and a rapid decrease of this intensity in the other; a point will even be reached when there is no longer any current transmitted: this will be when the line D limiting the tangent will itself be tangent to the curve at its origin O. This shows that for dynamo-electric machines there is a resistance for which the excitation is nil, and ceases to act. The characteristic curve of a dynamo is essentially connected with the speed V of the armature and with the number of turns, t, of the coil surrounding it; for the electromotive force developed is, as experiment proves, proportional to these two quantities. Consequently, to obtain the characteristic curve of a machine in which we vary the speed and the number of turns on the ring, the V *' ordinates of the curve must be multiplied by— or , which V * will give the electromotive force ; and we may also ascer- tain the resistance of the circuit as well as the intensity of the current by means of a simple geometrical figure which Marcel Deprez has given, with many others relating to this question in his great work on characteristics, published in " La Lumiere Electrique " for December 3rd, 1881, to which we would refer the reader. 316 Notes. In a series of other articles, published in vols. vi. and vii. of " La Lumiere Electrique," M. Deprez also gives the curves for the principal dynamo-electric machines in use, exemplified in .different manners and with different speeds. These will be foimd very valuable to those who are concerned in the question of electromotors. They wiU be found vol. vi. p. 364; vol. vii. pp. 114, 160, 219, 580, 599. LONDON : PEINTED BY WIIUAM CLOWES & SONS, LIMITED, STAMFOED STEEET AND CHAEING CEOSS. 1892. BOOKS RELATING TO APPLIED SCIENCE, PUBLISHED BY E. & F. N. SPON, LONDON: 125, STRAND. NEW YORK : 12, CORTLANDT STREET. The Engineers^ Sketch-Book of Mechanical Move- ments, Devices, Appliances, Contrivances, Details employed in the Design and Construction of Machinery for every purpose. Collected from numerous Sources and from Actual Work. Classified and Arranged for Reference. Nearly 2CX30 Illustrations. By T. B. Barber, Engineer. Second Edition, 8vo, cloth, 7/. (>d. 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Thieves and Fire. — Precautions against Thieves and Fire ; Methods of Detection Domestic Fire Escapes ; Fireproofing Clothes, etc. The Larder. — Keeping Food fresh for a limited time ; Storing Food without change, such as Fruits, Vegetables, Eggs, Honey, etc. Curing Foods for lenirthened Preservation, as Smoking, Salting, Canning, Potting, Pickling, Bottling Fruits, etc. ; Jams, Jellies, Marmalade, etc. The Dairy.— The Building and Fitting of Dairies in the most approved modern style ; Butter-making ; Cheesemaking and Curing. The Cellar. — Building and Fitting ; Cleaning Casks and Bottles ; Corks and Corking ; ASrated Drinks ; Syrups for Drinks ; Beers ; Bitters ; Cordials and Liqueurs ; Wines ; Miscellaneous Drinks. The Pantry. — Bread-making ; Ovens and Pyrometers ; Yeast ; German Yeast ; Biscuits; Cakes; Fancy Breads; Buns. The Kitchen.— On Fitting Kitchens ; a description of the best Cooking Ranges, close and open ; the Management and Care of'Hot Plates, Baking Ovens, Dampers, Flues, and Chimneys ; Cooking by Gas ; Cooking by Oil; the Arts of Roasting, Grilling, Boiling, Stewing, Braising, Frying. Receipts for Dishes —Soups, Fish, Meat, Game, Poultry, Vegetables, Salads, Puddings, Pastry, Confectionery, Ices, etc., etc. ; Foreign Dishes. The Housewife's Room. — Testing Air, Water, and Foods ; Cleaning and Renovat- ing ; Destroying Vermin, Housekeeping:, Marketing. The Dininir-Rooni. — Dietetics; Laying and Waiting at Table; Carving; Dinners, Breakfasts, Luncheons, Teas, Suppers, etc. The Dra-wingr-Room.— Etiquette; Dancing; Amateur Theatricals; Tricks and Illusions ; Games (indoor). The Bedroom and Dressing-Room ; Sleep ; the Toilet ; Dress ; Buying Clothes ; Outfits; Fancy Dress. The Nursery.— The Room ; Clothing ; Washing ; Exercise ; Sleep ; Feeding ; Teeth- ing ; Illness ; Home Training. The Siok-Room.— The Room; the Nurse; the Bed; Sick Room Accessories ; Feeding Patients ; Invalid Dishes and Drinks ; Administering Physic ; Domestic Remedies ; Accidents and Eniergencies ; Bandaging; Burns; Carrying Injured Persons; Wounds; Drowning; Fits Frost-bites; Poisons and Antidotes; Sunstroke; Common Complaints ; Disinfection, etc. PUBLISHED BY E. & F. N. SPON. The Bath-Eoom.— Bathing in General i Management of Hot- Water System. 1^ The Iiaundry.— Small Domestic Washing Machines, and methods of getting up linen Fittmg up and Working a Steam Laundry. b b v The School-Room.— The Room and its Fittings ; Teaching, etc. The Playground.— Air and Exercise; Training ; Outdoor Games and Sports. The Workroom.— Darning, Patching, and Mending Garments. The Library.— Care of Books. The Q-arden.— Calendar of Operations for Lawn, Flower Garden, and Kitchen liarden. The Farmyard.— Management of the Horse, Cow, Pig, Poultry, Bees, etc., etc. Small motors.- A description of the various small Engines useful for domestic purposes, from i man to i horse power, worked by various methods, such as Electric *.ngines. Gas Engines, Petroleum Engines, Steam Engines, Condensing Engines, Water Jr'ower, Wmd Power, and the various methods of working and managing them. T> ^PJ^,^?'''?!^ Law.— The Law relating to Landlords and Tenants, Lodgers, Servants, I'arocliial Authorities, Juries, Insurance, Nuisance, etc. On Designing Belt Gearing. By E. J. Cowling Welch, Mem. Inst. Mech. Engineers, Author of 'Designing Valve Gearing.' Fcap. 8vo, sewed, 6d. A Handbook of Formulce, Tables, and Memoranda, for Architectural Surveyors and others engaged in Building. By J. T. Hurst, C.E. Fourteenth edition, royal 32mo, roan, Sj. ^**It is no disparagement to the many excellent publications we refer to, to say that in our opinion this little pocket-book of Hurst's is the very best of them all, without any exception. It would be useless to attempt a recapitulation of the contents, for it appears to contain almost everything that anyone connected with building could require, and, best of all, made up in a compact form for carrying in the pocket, measuring only 5 in. by 3 in., and about \ in. thick, m a limp cover. We congratulate the author on the success of his laborious and practically compiled little book, which has received unqualified and deserved praise from every profes- sional person to whom we have shown it.'"— The Dublin Builder. Tabulated Weights of Angle, Tee, Bulb, Round, Square, and Flat Iron and Steel, and other information for the use of Naval Architects and Shipbuilders. By C. H. Jordan, M.I.N.A. Fourth edition, 32mo, cloth, aj. (td. A Complete Set of Contract Documents for a Country Lodge, comprising Drawings, Specifications, Dimensions (for quantities). Abstracts, BiU of Quantities, Form of Tender and Contract, with Notes by J. Leaning, printed in facsimile of the original documents, on single sheets.fcap., in paper case, loj. A Practical Treatise on Heat, as applied to the Useful Arts; for the Use of Engineers, Architects, &c. By Thomas Box. With 11^ plates. Sixth edition, crown 8vo, cloth, I2.f. dd. A Descriptive Treatise on Mathematical Drawing Instruments : their construction, uses, qualities, selection, preservation, and suggestions for improvements, with hints upon Drawing and Colour- ing. By W. F. Stanley, M.R.I, Sixth edition, with numerous illustrations, crown 8vo, cloth, 5^. E 2 CATALOGUE OF SCIENTIFIC BOOKS Schedule of Prices. Form of Schedule of Prices. Analysis of Schedule of Prices. Adjustment of Accounts. Form of a Bill of Variations. Remarks on Specifications. Prices and Valuation of Work, with Examples and Remarks upon each Trade. The Law as it affects Quantity Surveyors, with Law Reports. Taking Off after the Old Method. Northern Practice. The General Statement of the Methods recommended by the Manchester Society of Architects for taking Quantities. Examples of Collections. Examples of *' Taking Off" in each Trade. Remarks on the Past and Present Methods of Estimating. ^ Quantity Surveying. By J. Leaning. With 42 illus- trations. Second edition, revised, crown 8vo, cloth, gj. Contents : A complete Explanation of the London Practice. General Instructions. Order of Taking Off. Modes of Measurement of the various Trades. Use and Waste. Ventilation and Wanning. Credits, with various Examples of Treatment. ' Abbreviations. Squaring the Dimensions. Abstracting, with Examples in illustration of each Trade. Billing. Examples of Preambles to each Trade. Form for a Bill of Quantities. Bo. Bill of Credits. Do. Bill for Alternative Estimate. Restorations and Repairs, and Form of Bill. Variations before Acceptance of Tender, Errors in a Builder's Estimate. Spans' Architects' and Builders' Price Book, with useful Memoranda. Edited by W. Young, Architect. Crown 8vo, cloth, red edges, 3^. (>d. Published annually. Nineteenth edition. Now ready. Long-Span Railway Bridges, comprising Investiga- tions of the Comparative Theoretical and Practical Advantages of the various adopted or proposed Type Systems of Construction, with numerous Formulae and Tables giving the weight of Iron or Steel required in Bridges from 300 feet to the limiting Spans ; to which are added similar Investigations and Tables relating to Short-span Railway Bridges. Second and revised edition. By B. Baker, Assoc. Inst. C.E. Plates, crown 8vo, cloth, 5j. Elementary Theory and Calculation of Iron Bridges and Roofs. By AUGUST Ritter, Ph.D., Professor at the Polytechnic School at Aix-la-Chapelle. Translated from the third German edition, by H. R. Sankey, Capt. R.E. With 500 illustrations, 8vo, cloth, 15^. The Elementary Principles of Carpentry. By Thomas Tredgold. Revised from the original edition, and partly re-written, by John Thomas Hurst. Contained in 517 pages of letter- press, and illustrated with 48 plates and 150 mood engravings. Sixth edition, reprinted from the third, crovm 8vo, cloth, I2j-. di. Section I. On the Equality and Distribution of Forces — Section 17. Resistance of Timber — Section III. Construction of Floors — Section IV. Construction of Roofs — Sec- tion V. Construction of Domes and Cupolas — Section VI. Construction of Partitions — Section VII. Scaffolds, Staging, and Gantries — Section VIII. Construction of Centres for Bridges— Section IX. Coffer-dams, Shoring, and Strutting— Section X. Wooden Bridges and Viaducts— Section XI. Joints, Straps, and other Fastenings — Section XII. Timber. The Builders Clerk : a Guide to the Management of a Builder's Business. By Thomas Bales. Fcap. 8vo, cloth, is. 6d, PUBLISHED BY E. & F. N. SPON. Practical Gold-Mining : a Comprehensive Treatise on the Origin and Occurrence of Gold-bearing Gravels, Rocks and Ores, and the methods by which the Gold is extracted. By C. G. Warnfoko Lock, co- Author of ' Gold : its Occurrence and Extraction.' With 8 plates and 275 engravittgs in the text, royal 8vo, cloth, 2/. 2s, Hot Water Supply : A Practical Treatise upon the Fitting of Circulating Apparatus in connection with Kitchen Range and other Boilers, to supply Hot Water for Domestic and General Purposes. With a Chapter upon Estimating. Futfy illustrated, crown Svo, cloth, 3^. Hot Water Apparatus: An Elementary Guide for the Fitting and Fixing of Boilers and Apparatus for the Circulation of Hot Water for Heating and for Domestic Supply, and containing a Chapter upon Boilers and Fittings for Steam Cooking. 32 illustratioits, fcap. Svo, cloth, IS. dd. The Use and Misuse, and the Proper and Improper Fixing of a Cooking Range. Illustrated, fcap. Svo, sewed, dd. Iron Roofs : Examples of Design, Description. Illus- trated with 64 Working Drawings of Executed Roofs. By Arthur T. Walmisley, Assoc. Mem. Inst. C.fe. Second edition, revised, imp. 4to, half-morocco, 3/. %s. A History of Electric Telegraphy, to the Year 1837. Chiefly compiled from Original Sources, and hitherto Unpublished Docu- ments, by J. J. Fahie, Mem. Soc. of Tel. Engineers, and of the Inter- national Society of Electricians, Paris. Crown Svo, cloth, gj. Spons* Information for Colonial Engineers. Edited by J. T. Hurst. Demy Svo, sewed. No. I, Ceylon. By Abraham Deane, C.E. zs. 6d. Contents : Introductory Remarks — Natural Productions— Architecture and Engineering — Topo- graphy, Trade, and Natural History— Principal Stations— Weights and Measures, etc., etc. No. 2. Southern Africa, fncluding the Cape Colony, Natal, and the Dutch Republics. By Henry Hall, F.R.G.S., r.R.C.I. With Map. 3^. 6d. Contents : General Description of South Africa— Physical Geography with reference to Engineering Operations— Notes on Labour and Material in Cape Colony— Geological Notes on Rock Formation in South Africa— Engineering Instruments for Use in South Africa— Principal Public Works in Cape Colony : Railways, Mountain Roads and Passes, Harbour Works, Bridzes, Gas Works, Irrigation and Water Supply, Lighthouses, Drainage and Sanitary Engineering, Public Buildings, Mines— Table of Woods in South Africa— Animals used for Draught Purposes— Statistical Notes— Table of Distances— Rates of Carnage, etc. No. 3. India. By F. C. Danvers, Assoc. Inst. C.E. With Map. 4J. 6d. Contents ; '■• Physical Geography of India— Building Materials— Roads— Railways— Bridges— Irriga- tion- River Works — Harboiirs- Lighthouse Buildings — Native Labour — The Principal Trees of India— Money— Weights and Measures— Glossary of Indian Terms, esc. CATALOGUE OF SCIENTIFIC BOOKS Our Factories, Workshops, and Warehouses: their Sanitary and Fire-Resisting Arrangements. By B. H. Thwaite, Assoc. Mem. fiist. C.E. With 183 wood engravings, crown 8vo, doth, gj. A Practical Treatise on Coal Mining. By George G. Andr^, F.G.S., Assoc. Inst C.E., Member of the Society of Engineers. With 82 lithographic plates. 2 vols., royal 4to, cloth, 3/. 12s. A Practical Treatise on Casting and Founding, including descriptions of the modem machinery employed in the art. By N. E. Spretson, Engineer. Fifth edition, with 82 plates drawn to scale, 412 pp., demy 8vo, cloth, 18^. A Handbook of Electrical Testing. By H. R. Kempe, M.S.T.E. Fourth edition, revised and enlarged, crown 8vo, cloth, i6j. The Clerk of Works: a Vade-Mecum for all engaged in the Superintendence of Building Operations. By G. G. HOSKINS, F.R.I.B.A. Third edition, fcap. 8vo, cloth, is. td. American Foundry Practice: Treating of Loam, Dry Sand, and Green Sand Moulding, and containing a Practical Treatise upon the Management of Cupolas, and the Melting of Iron. By T. D. West, Practical Iron Moulder and Foundry Foreman. Second edition, with numerous illustrations, crown 8vo, cloth, \0s. bd. The Maintenance of Macadamised Roads. By T. CODRINGTON, M.I.C.E, F.G.S., General Superintendent of County Roads for South Wales. Second edition, 8vo, cloth, "js. 6d. Hydraulic Steam and Hand Power Lifting and Pressing Machinery. By Frederick Colyer, M. Inst. C.E., M. Inst. M.E. With Ti plates, Svo, cloth, i8j. Pumps and Pumping Machinery. By F. Colyer, M.I.C.E., M.I,M.E. With ij, folding plates, 8vo, cloth, laf. (>d. Pumps and Pumping Machinery. By F. Colyer. Second Part. With 11 large plates, 8vo, cloth, \zs. 6d. A Treatise on the Origin, Progress, Prevention, and Cure of Dry Rot in Timber; with Remarks on the Means of Preserving Wood from Destruction by Sea- Worms, Beetles, Ants, etc. By Thomas Allen Britton, late Surveyor to the Metropolitan Board of Works, etc., etc. With 10 plates, crown Svo, cloth, "js. 6d. The Artillery of the Future and the New Powders. By J. A. LoNGRiDGE, Mem. Inst. C.E. Svo, cloth, t^s. PUBLISHED BY E. & F. N. SPON. Gas Works : their Arrangement, Construction, Plant, and Machinery. By F. Colyer, M. Inst. C.E. IViiA y. folding plates, 8vo, cloth, \2s. i)d. The Municipal and Sanitary Engineer s Handbook. By H. Percy Boulnois, Mem. Inst. C.E., Borough Engineer, Ports- mouth. With numerous illustrations. Second edition, demy 8vo, cloth, I5J. Contents : The Appointment and Duties of the Town Surveyor — Traffic — Macadamised Roadways- Steam Rolling— Road Metal and Breaking— Pitched Pavements— Asphalte— Wood Pavements — Footpaths — Kerbs and Gutters — Street Naming and Numbering— Street Lighting — Sewer- age — Ventilation of Sewers — Disposal of Sewage — House Drainaee — Disinfection — Gas and Water Companies, etc., Breaking up Streets — Improvement of Private Streets — Borrowing Powers — Artizans' and Labourers' Dwellings — Public Conveniences — Scavenging, including Street Cleansing— Watering and the Removing of Snow— Planting Street Trees— Deposit of Plans^Dangerous Buildings — Hoardings — Obstructions — Improvmg Street Lines — Cellar Openings — Public Pleasure Grounds — Cemeteries — Mortuaries — Cattle and (Ordinary Markets —Public Slaughter-houseSj etc. — Giving numerous Forms of Notices, Specifications,- and General Information upon these and other subjects of great importance to Municipal Engi- neers and others engaged in Sanitary Work. Metrical Tables. By Sir G. L. Molesworth, M.I.C.E. 32mo, cloth, is. 6d. Contents. General — Linear Measures — Square Measures — Cubic Measures — Measures of Capacity- Weights — Combinations — ^Thermometers. Elements of Construction for Electro-Magnets. By Count Th. Du Moncel, Mem. de I'Institut de France. Translated from the French by C. J. Wharton. Crown 8vo, cloth, /{j. bd. A Treatise on the Use of Belting for the Transmis- sion of Power. By J. H. Cooper, Second edition, illustrated, 8vo, cloth, 1 5 J. A Pocket-Book of Useful Formulcs and Memoranda for Civil and Mechanical Engineers. By Sir GuiLFORD L. Molesworth, Mem. Inst. C.E. With numerous illustrations, 744 pp. Twenty-second edition, 32mo, roan, 6s. Synopsis of Contents; ' Surveying, Levelling, etc. — Strength and Weight of Materials — Earthwork, Brickwork, Masonry, Arches, etc. — Struts, Columns, Beams, and Trusses — Flooring, Roofing, and Roof Trusses— Girders, Bridges, etc. — Railways and Roads — Hydraulic Formulae — Canals, Sewers, Waterworks, Docks — Irrigation and Breakwaters — Gas, Ventilation, and Warming — Heat, Light, Colour, and Sound— Gravity : Centres, Forces, and Powers— Millwork, Teeth of Wheels, Shafting, etc. — Workshop Recipes — Sundry Machinery — Animal Power — Steam and the Steam Engine — Water-power, Water-wheels, Turbines, etc. — ^Wind and Windmills- Steam Navigation, Ship Building, Tonnage, etc. — Gunnery, Projectiles, etc.— Weights, Measures, and Money — ^Trigonometry, Conic Sections, and Curves — ^Telegraphy— Mensura- tion — Tables of Areas and Circumference, and Arcs of Circles — Logarithms, Square and Cube Roots, Powers — Reciprocals, etc. — Useful Numbers — ^Differential and Integral Calcu- lus—Algebraic Signs— Telegraphic Construction and Formulae. 8 CATALOGUE OF SCIENTIFIC BOOKS Hints on Architectural Draughtsmanship. By G. W. TuxFORD Hallatt. Fcap. 8vo, cloth, \s. 6d. Spons' Tables and Memoranda for Engineers; ■ selected and arranged by J. T. Hurst, C.E., Author of 'Architectural Surveyors' Handbook,' ' Hurst's Tredgold's Carpentry,' etc. Eleventh edition, 64010, roan, gilt edges, 11. ; or in cloth case, is. 6d. This work is printed in a pearl type, and is so small, measuring only 2^ in. by 1$ in, by i in. thick, that it may be easily carried in the waistcoat pocket. " It is certainly an extremely rare thing for a reviewer to be called upon to notice a volume measuring but 2^ in. by if in., yet these dimensions faithfully represent the size of the handy little book before us. The volume — which contains 118 printed pag:es, besides a few blank pages for memoranda—^, in fact, a true pocket-book, adapted for being carried in the waist- coat pocket, and containing a far greater amount and variety of information than most people would imagine could be compressed into so small a space The little volume has been compiled with considerable care and judgment, and we can cordially recommend it to our readers as a useful little pocket companion." — Eiigineerins. A Practical Treatise on Natural and Artificial Concrete, its Varieties and Constructive Adaptations. By Henry Reid, Author of the ' Science and Art of the Manufacture of Portland Cement.' New Edition, with 59 woodcuts and t, plates, 8vo, cloth, 15J. Notes on Concrete and Works in Concrete; especially written to assist those engaged upon Public Works. By John Newman, Assoc. Mem. Inst. C.E., crown 8vo, cloth, 4J. dd. Electricity as a Motive Power. By Count Th. Du MONCEL, Membre de I'lnstitut de France, and Frank Geraldy, Ing^- nieur des Ponts et Chaussees. Translated and Edited, with Additions, by C. J. Wharton, Assoc. See. TeL Eng. and Elec. With 113 engravings and diagrams, crown 8vo, cloth, "js. 6d. Treatise on Valve-Gears, with special consideration of the Link-Motions of Locomotive Engines. By Dr. GtJSTAV Zeuner, Professor of Applied Mechanics at the Confederated Polytechnikum of Zurich. Translated from the Fourth German Edition, by Professor J. F. Klein, Lehigh University, Bethlehem, Pa. Illustrated, 8vo, cloth, 12s. id. The French- Polisher s Manual. By a French- Polisher; containing Timber Staining, Washing, Matching, Improving, Painting, Imitations, Directions for Staining, Sizing, Embodying, Smoothing, Spirit Varnishing, French-Polishing, Directions for Re- , polishing. Third edition, royal 32mo, sewed, 6a?. Hops, their Cultivation, Commerce, and Uses in various Countries. By P. L. Simmonds. Crown 8vo, cloth, 4r. 6d. The Principles of Graphic Statics. By George Sydenham Clarke, Major Royal Engineers. With 112 illustrations. Second edition, 4to, cloth, \zs. 6d, PUBLISHED BY E. & F. N. SPON. Dynamo Tenders' Hand-Book. By F. B. Badt, late 1st Lieut. Royal Prussian Artillery. With 10 illustrations. Third edition, l8mo, cloth, 4J. dd. Practical Geometry, Perspective, and Engineering Drawing; a Course of Descriptive Geometry adapted to the Require- ments of the Engineering Draughtsman, including the determination of cast shadows and Isometric Projection, each chapter being followed by numerous examples ; to which are added rules for Shading, Shade-lining, etc., together with practical instructions as to the Lining, Colouring, Printing, and general treatment of Engineering Drawings, with a chapter on drawing Instruments. By George S. Clarke, Capt. R.E. Second edition, with 21 plates. 2 vols., cloth, \os. 6d. The Elements of Graphic Statics. By Professor Karl Von Ott, translated from the German by G. S. Clarke, Capt. R.E., Instructor in Mechanical Drawing, Royal Indian Engineering College. With 93 illustrations, crown 8vo, cloth, 5j. A Practical Treatise on the Manufacture and Distri- bution of Coal Gas. By William Richards. Demy 4to, with numerous wood engravings and 29 plates, cloth, 28j. Synopsis of Contents : Introduction— History of Gas Lighting — Chemistry of Gas Manufacture, by Lewis Thompson, Esq., M.R.C.S. — Coal, with Ajnalyses, by J. Faterson, Lewis Tliompson, and G. R. Hislop, Esqrs. — Retorts, Iron and Clay — Retort Setting — Hydraulic Main — Con- densers — Exhausters — Washers and Scrubbers ^Purifiers — Purification — History of Gas Holder — Tanks, Brick and Stone, Composite, Concrete, Cast-iron, Compound Annular Wrought-iron — Specifications — Gas Holders — Station Meter — Governor — Distribution — Mains — Gas Mathematics, or Formulae for the Distribution of Gas, by Lewis Thompson, Esq.— Services — Consumers* Meters — Regulators — Burners — Fittings — ^Photometer — Carburization of Gas— Air Gas and Water Gas — Composition of Coal Gas, by Lewis Thompson, Esq.— Analyses of Gas — Influence of Atmospheric Pressure and Temperature on Gas — Residual Products— Appendix — Description of Retort Settings, Buildings, etc., etc. The New Formula for Mean Velocity of Discharge of Rivers and Canals. By W. R. Kutter. Translated from articles in the ' Cultur-Ingenieur,' by Lowis D'A. Jackson, Assoc. Inst. C.E. 8vo, cloth, I2s. 6d. The Practical Millwright and Engineers Ready Reckoner; or Tables for finding the diameter and power of cog-wheels, diameter, weight, and power of shafts, diameter and strength of bolts, etc. By Thomas Dixon. Fourth edition, i2mo, cloth, 3/. Tin: Describing the Chief Methods of Mining, Dressing and Smelting it abroad ; virith Notes upon Arsenic, Bismuth and Wolfram. By Arthur G. Charleton, Mem. American Inst, of Mining Engineers. With plates, 8vo, cloth, 12s. 6d. 10 CATALOGUE OF SCIENTIFIC BOOKS Perspective, Explained and Illustrated. By G. S. Clarke, Capt. R.E. With illustrations, 8vo, cloth, y. fid. Practical Hydratdics ; a Series of Rules and Tables for the use of Engineers, etc., etc. By Thomas Box. Ninth edition, numerous plates, post 8vo, cloth, S-f. The Essential Elements of Practical Mechanics; based on the Principle of Work, designed for Engineering Students. By Oliver Byrne, formerly Professor of Mathematics, College for Civil Engineers. Third edition, with 148 wood engravings, post 8vo, cloth, •]s. 6d. Contents : Chap. I. How Work is Measured by a Unit, both with and without reference to a Unit of Time — Chap. 2. The Work of Living Agents, the InSuence of Friction, and introduces one of the most beautiful Laws of Motion — Chap. 3. The principles expounded in the first and second chapters are applied to the Motion of Bodies — Chap. 4. The Transmission of Work by simple Machines — Chap. 5. Useful Propositions and Rules. Breweries and Mailings : their Arrangement, Con- struction, Machinery, and Plant. By G. Scamell, F.R.I.B.A. Second edition, revised, enlarged, and partly rewritten. By F. CoLYER, M.LC.E., M.I.M.E. With 20 plates, 8vo, cloth, 12s. 6d. A Practical Treatise on the Construction of Hori- zontal and Vertical Waterwheels, specially designed for the use of opera- tive mechanics. By William Cullen, Millvirright and Engineer. With II plates. Second edition, revised and enlarged, small 4to, cloth, \2s.(>d. A Practical Treatise on Mill-gearing, Wheels, Shafts, Riggers, etc.; for the use of Engineers. By THOMAS Box. Third edition, with 1 1 plates. Crown 8vo, cloth, 7^- (>d. Mining Machinery: a Descriptive Treatise on the Machinery, Tools, and other Appliances used in Mining. By G. G. Andre, F.G.S., Assoc. Inst. C.E., Mem. of the Society of Engineers. Royal 4to, uniform with the Author's Treatise on Coal Mining, con- taining 182 plates, accurately drawn to scale, with descriptive text, in 2 vols., cloth, 3/. 12s. Contents : Machinery for Prospecting, Excavating, Hauling, and Hoisting— Ventilation— Pumping— Treatment of Mineral Products, including Gold and Silver, Copper, Tin, and Lead, Iron, Coal, Sulphur, China Clay, Brick Earth, etc. Tables for Setting out Curves for Railways, Canals, Roads, etc., varying from a radius of five chains to three miles. By A. Kennedy and R. W, Hackwood. Illustrated 32mo, cloth, 2s. 6d. PUBLISHED BY E. & F. N. SPON. ii Practical Electrical Notes and Definitions for the use of Engineering Students and Practical Men. By W. Perren Maycock, Assoc. M. Inst. E.E., Instructor in Electrical Engineering at the Pitlake Institute, Croydon, together with the Rules and Regulations to be observed in Electrical Installation Work. Second edition. Royal 32mo, roan, gilt edges, 4?. (>d., or cloth, red edges, 3^. The Draughtsman s Handbook of Plan and Map Drawing; including instructions for the preparation of Engineering, Architectural, and Mechanical Drawings. With numerous illustrations in the text, and 33 plates (IJ printed in colours). By G. G. Andre, F.G.S., Assoc. Inst. C.E. 4to, cloth, gj. Contents : The Drawing Office and its Furnishings — Geometrical Problems — Lines, Dots, and their Combinations — Colours, Shading;, Lettering, Bordering, and North Points — Scales — Plotting — Civil Engineers' and Surveyors' Plans — Map Drawing — Mechanical and Architectural Drawing — Copying and Reducing Trigonometrical Formula, etc., etc. The B oiler-maker s andiron Ship-builders Companion, comprising a series of original and carefully calculated tables, of the utmost utility to persons interested in the iron trades. By James Foden, author of ' Mechanical Tables,' etc. . Second edition revised, with illustra- tions, crown 8vo, cloth, 5^. Rock Blasting: a Practical Treatise on the means employed in Blasting Rocks for Industrial Purposes. By G. G. Andre, F.G.S., Assoc. Inst. C.E. With 56 illustrations and \2 plates, 8vo, cloth, \os. 6d. Experimental Science: Elementary, Practical, and Experimental Physics. By Geo. M. Hopkins. Illustrated by 672 engravings. In one large vol., 8vo, cloth, 15^'. A Treatise on Ropemaking as practised in public and private Rope-yards, with a Description of the Manufacture, Rules, Tables of Weights, etc., adapted to the Trade, Shipping, Mining, Railways, Builders, etc. By R. Chapman, formerly foreman to Messrs. Huddart and Co., Limehouse, and late Master Ropemaker to H.M. Dockyard, Deptford. Second edition, l2mo, cloth, 3J-. Laxtons Builders' and Contractors' Tables ; for the use of Engineers, Architects, Surveyors, Builders, Land Agents, and others. Bricklayer, containing 22 tables, with nearly 30,000 calculations. 4to, cloth, 5^. Laxton's Builders and Contractors' Tables. Ex- cavator, Earth, Land, Water, and Gas, containing 53 tables, with nearly 24,000 calculations. 4to, cloth, ^s. B 4 CATALOGUE OF SCIENTIFIC BOOKS Egyptian Irrigation. By W. Willcocks, M.I.C.E., Inaan Public Works Department, Inspector of Irrigation, Egypt. With Introduction by Lieut.-Col. J. C. Ross, R.E., Inspector-General of Irrigation. With numerous lithographs and wood engravings, royal 8vo, cloth, I/. i6j. Screw Cutting Tables for Engineers and Machinists, giving the values of the different trains of Wheels required to produce Screws of any pitch, calculated by Lord Lindsay, M.P., F.R.S., F.R.A.S., etc. Cloth, oblong, 2j. Screw Cutting Tables, for the use of Mechanical Engineers, showing the proper arrangement of Wheels for cutting the Threads of Screws of any required pitch, with a Table for making the Universal Gas-pipe Threads and Taps. By W. A. Martin, Engineer, Second edition, oblong, cloth, is., or sewed, fid. A Treatise on a Practical Method of Designing Slide- Valve Gears by Simple Geometrical Construction, based upon the principles enunciated in Euclid's Elements, and comprising the various forms of Plain Slide- Valve and Expansion Gearing ; together with Stephenson's, Gooch's, and Allan's Link-Motions, as applied either to reversing or to variable expansion combinations. By Edward J. Cowling Welch, Memb. Inst. Mechanical Engineers. Crown 8vo, cloth, 6^. Cleaning and Scouring : a Manual for Dyers, Laun- dresses, and for Domestic Use. By S. Christopher. i8mo, sewed, bd. A Glossary of Terms used in Coal Mining. By William Stukeley Gresley, Assoc. Mem. Inst C.E., F.G.S., Member of the North of England Institute of Mining Engineers. Illustrated with numerous woodcuts and diagrams, crown 8vo, cloth, 5^ . A Pocket-Book for Boiler Makers and Steam Users, comprising a variety of useful information for Employer and Workman, Government Inspectors, Board of Trade Surveyors, Engineers in charge of Works and Slips, Foremen of Manufactories, and the general Steam- using Public. By Maurice John Sexton. Second edition, royal 32mo, roan, gilt edges, 5j. Electrolysis: a Practical Treatise on Nickeling, Coppering, Gilding, Silvering, the Refining of Metals, and the treatment of Ores by means of Electricity. By Hippolyte Fontaine, translated from the French by J, A. Berly, C.E., Assoc. S.T.E. With engravings. 8vo, cloth, plates, in one Volume, half-bound morocco, 2/. 2s.; or cheaper edition, cloth, 25^. ^This work is not, in any sense, an elementary treatise, or history of the steam engine, but is intended to describe examples of Fixed Steam Engines without entering into the wide domain of locomotive or marine practice. To this end illustrations will be given of the most recent arrangements of Horizontal, Vertical, Beam, Pumping, Winding, Portable, Semi- gtrtable, Corliss, Allen, Compound, and other similar Engines, by the most eminent Firms in reat Britain and America. The laws relating to the action and precautions to be observed in the construction of the various details, such as Cylinders, Pistons, Piston-rods, Connecting- rods, Cross-heads, Motion-bloclcs, Eccentrics, Simple, Expansion, Balanced, aud Equilibrium Slide-valves, and Valve-gearing will be minutely dealt with. In this connection will be found articles upon the Velocity of Reciprocating Parts and the Mode of Ai>plying the Indicator, Heat and Expansion of Steam Governors, and the like. It is the writer's desire to draw illustrations from every possible source, and give only those rules that present practice deems correct. A Practical Treatise on the Science of Land and Engineering Surveying, Levelling, Estimating Quantities, etc., with a general description of the sever^ Instruments required for Surveying, Levelling, Plotting, etc. By H. S. Merrett. Fourth edition, revised by G. W. UsiLL, Assoc. Mem. Inst. C.E. 41 plates, with illustrations and tables, royal 8vo, cloth, 12s. 6d. Principal Contents : Part I. Introduction and the Principles of Geometry. Part 2. Land Surveying; com- prising General Observations — The Cham — Offsets Surveying by the Chain only — Surveying Pilly Ground— To Survey an Estate or Parish by the Chain only— Surveying with the Theodolite — Mining and Town Surveying — Railroad Surveying — Mapping — Division and Laying out of Land — Observations on Enclosures— Plane Trigonometry. Part 3. Levelling— Simple and Compound Levelling— The Level Book — Parliamentary Plan and Section- Levelling with a Theodolite— Gradients— Wooden Curves— To Lay out a Railway Curve- Setting out Widths. Part 4. Calculating Quantities generally for Estimates — Cuttings and Embankments— Tunnels— Brickwork — Ironwork— Timber Measuring. Part 5. Description and Use of Instruments in Surveying and Plotting— The Improved Dumpy Level— Troughton's Level — The Prismatic Compass — Proportional Compass — Box Sextant— Vernier — Panta- graph— Merrett's Improved Quadrant— Improved Computation Scale — ^The Diagonal Scale — Straight Edge and Sector. Part 6. Logarithms of Numbers — Logarithmic Sines and Co-Sines, Tangents and Co-Tangents— Natural Sines and Co-Sines— Tables for Earthwork, for Setting out Curves, and for various Calculations, etc., etc., etc. Mechanical Graphics. A Second Course of Me- chanical Drawing. With Preface by Prof. Perrv, E.Sc, F.R.S. Arranged for use in Technical and Science and Art Institutes, Schools and Colleges, by George Halliday, Whitworth Scholar. 8vo, cloth, f>s. 14 CATALOGUE OF SCIENTIFIC BOOKS The Assayers Manual: an Abridged Treatise on the Docimastic Examination of Ores and Furnace and other Artificial Products. By Bruno Kerl. Translated by W. T. Brannt. With 6$ illustrations, 8vo, cloth, I2J. (>d. Dynamo - Electric Machinery : a Text - Book for Students of Electro-Technology. By Silvanus P. Thompson, B.A., D.Sc, M.S.T.E. [JVew edition in the pras. The Practice of Hand Turning in Wood, Ivory, Shell, etc., with Instructions for Turning such Work in Metal as may be required in the Practice of Turning in Wood, Ivory, etc. ; also an Appendix on Ornamental Turning. (A book for beginners.) By Francis Campin. Third edition, with wood engravings, crown 8vo, cloth, 6j. Contents : On Lathes — ^Turning Tools — ^Turning Wood — ^Drilling — Screw Cutting — Miscellaneous Apparatus and Processes — Turning Particular Forms — Staining — Polishing — Spinning Metals --Materials — Ornamental Turning, etc. Treatise on Watchwork, Past and Present. By the Rev. H. L. Nelthropp; M.A., F.S.A. With 32 illustrations, crown 8vo, cloth, 6^. (id. Contents : Definitions of Words and Terms used in Watchwork — Tools — Time — Historical Sum- mary — On Calculations of the Numbers for Wheels and Pinions; their Proportional Sizes, Trains, etc. — Of Dial Wheels, or Motion Work — Length of Time of Going without Winding up — ^The Verge— The Horizontal — The Duplex — The Lever — The Chronometer — Repeatmg Watches — Keyless Watches — The Pendulum, or Spiral Spring — Compensation — Jewelling of Pivot Holes — Clerkenwell — Fallacies of the Trade — Incapacity of Workmen — How to Choose and Use a Watch, etc. Algebra Self-Taught. By W. P. Higgs, M.A., D.Sc, LL..D., Assoc. Inst. C.E., Author of "A Handbook of the Differ" ential Calculus,' etc. Second edition, crown Svo, cloth, 2J. dd. Contents ; Symbols and the Signs of Operation — ^The Equation and the Unknown Quantity^ Positive and Negative Quantities — Multiplication — Involution — Exponents — Negative Expo- nents — Roots, and the Use of Exponents as Logarithms — Logarithms — Tables of Logarithms and Proportionate Parts — Transformation of System of Logarithms — Common Uses of Common Logarithms — Compound Multiplication and the Binomial Theorem — Division, Fractions, and Ratio — Continued Proportion — ^The Series and the Summation of the Series- Limit of Series — Square and Cube Roots — Equations — List of Formulae, etc. Spons Dictionary of Engineering, Civil, Mechanical, Military, and Naval; with technical terms in French, German, Italian, and Spanish, 3100 pp., and nearly 8000 engravings, in super-royal 8voi in 8 divisions, 5/. %s. Complete in 3 vols., cloth, 5/. 5^. Bound in a superior manner, half-morocco, top edge gilt, 3 vols., 6/. I2x, PUBLISHED BY E. & F. N. SPON. 15 Notes in Mechanical Engineering. Compiled prin- cipally for the use of the Students attending the Classes- on this subject at the City of London College. By Henry Adams, Mem. Inst. M.E., Mem. Inst. C.E., Mem. Soc. of Engineers. Crown 8vo, cloth, 2.s. 6d. Canoe and Boat Building: a complete Manual for Amateurs, containing plain and comprehensive directions for the con- struction of Canoes, Rowing and Sailing Boats, and Hunting Craft. By W. P. Stephens. With numerous illustrations and 24 plates of Working Drawings, Crown 8vo, cloth, gj. Proceedings of the National Conference of Electricians, Philadelphia, October 8th to 13th, 1884. l8mo, cloth, 3J-. Dynamo - Electricity, its Generation, Application, Transmission, Storage, and Measurement. By G. B. Prescott. IViih 545 illustrations, 8vo, cloth, I/. \s. Domestic Electricity for Amateurs. Translated from the French of E. Hospitalier, Editor of "L'Electricien," by C. J. Wharton, Assoc. Soc. Tel. Eng. Numerous illustrations. Demy 8vo, cloth, 6^. Contents : I. Production of the Electric Current^a. Electric Bells — 3. Automatic Alarms— 4. Domestic Telephones — s. Electric Clocks-T6. Electric Lighters— 7. Domestic Electric Lighting — 8. Domestic Application of the Electric Light— 9. Electric Motors— 10. Electrical Locomo- tion — II. Electrotyping, Plating, and Gilding— 12, Electric Recreations — 13. Various appli- cations — ^Workshop of the Electrician. Wrinkles in Electric Lighting. By Vincent Stephen. With illustrations, i8mo, cloth, 2j. dd. Contents : I. The Electric Current and its production by Chemical means— 2. Production "of Electric Currents by Mechanical means— 3. Dynamo-Electric Machines— 4. Electric Lamps— 5. Lead— 6. Ship Lighting. Foundations and Foundation Walls for all classes of Buildings, Pile Driving, Building Stones and Bricks, Pier and Wall construction, Mortars, Limes, Cements, Concretes, Stuccos, &c. 64 illus- trations. By G. T. Powell and F. Bauman. 8vo, cloth, ioj. bd. Manual for Gas Engineering Students. By D. Lee. l8mo, cloth, IJ. 1 6 CATALOGUE OF SCIENTIFIC BOOKS Telephones, their Construction and Management. By F. C. Allsop. Crown 8vo, cloth, Sj. Hydraulic Machinery, Past and Present. A Lecture delivered to the London and Suburban Railway Officials' Association. By H. Adams, Mem. Inst. C.E. Folding plate. 8vo, sewed, ij. Twenty Years with the Indicator. By Thomas Pray, Jun., C.E., M.E., Member of the American Society of Civil Engineers. 2 vols., royal 8vo, cloth, \2s. 6d. Annual Statistical Report of the Secretary to the Members of the Iron and steel Association on the Home and Foreign Iron and Steel Industries in 1889. Issued June 1890. 8vo, sewed, ^s. , Bad Drains, and How to Test them ; with Notes on the Ventilation of Sewers, Drains, and Sanitary Fittings, and the Origin and Transmission of Zymotic Disease. By R. Harris Reeves. Crown 8vo, cloth, y. 6d. Well Sinking. The modern practice of Sinking and Boring Wells, with geological considerations and examples of Wells. By Ernest Spon, Assoc. Mem. Inst. C.E., Mem. Soc. Eng., and of the Franklin Inst., etc. Second edition, revised and enlarged. Crown 8vo, cloth, 10^. 6d. The Voltaic Accumulator : an Elementary Treatise. By iSmile Reynier. Translated by J. A. Berly, Assoc. Inst. E.E. With 62 illustrations, 8vo, cloth, gj. Ten Years Experience in Works of Intermittent Downward Filtration. By J. Bailey Denton, Mem. Inst. C.E. Second edition, with additions. Royal 8vo, cloth, ^s. Land Surveying on the Meridian and Perpendicular System. By William Penman, C.E. 8vo, cloth, %s, 6d. The Electromagnet and Electromagnetic Mechanism. By SiLVANUs p. Thompson, D.Sc., F.R.S. Second edition, 8vo, cloth, I 5 J. PUBLISHED BY E. & F. N. SPON. 17 Incandescent Wiring Hand-Book. By F. B. Badt, late 1st Lieut. Royal Prussian Artillery. With 41 illustrations and S tables. i8mo, cloth, 4^. (td. A Pocket-book for Pharmacists, Medical Prac- titioners, Students, etc., etc. (British, Colonial, and American). By Thomas Bayley, Assoc. R. Coll. of Science, Consulting Chemist, Analyst, and Assayer, Author of a 'Pocket-book for Chemists,' 'The Assay and Analysis of Iron and Steel, Iron Ores, and Fuel,' etc., etc. Royal 32mo, boards, gilt edges, 6j. The Fireman's Guide ; a Handbook on the Care of Boilers. By Teknolog, foreningen T. I. Stockholm. Translated from the third edition, and revised by Karl P. Dahlstrom, M.E. Second edition. Fcap. 8vo, cloth, zs. The Mechanician : A Treatise on the Construction and Manipulation of Tools, for the use and instruction of Young Engineers and Scientific Amateurs, comprising the Arts of Blacksmithing and Forg- ing ; the Construction and Manufacture of Hand Tools, and the various Mediods of Using and Grinding them ; description of Hand and Machine Processes ; Turning and Screw Cutting. By Cameron Knight, Engineer. Containing w^l illustrations, and 397 pages of letter-press. -Fourth edition, 4to, cloth, l&r, A Treatise on Modem Steam Engines and Boilers, including Land Locomotive, and Marine Engines and Boilers, for the use of Students. By Frederick Colyer, M. Inst. C.E., Mem. Inst. M.E, With 2,6 plates. 4to, cloth, 12s. 6d. Contents : I. Introduction— 2. Origmal Engines — 3. Boilers — 4. High-Pressure Beam Engines— s. Cornish Beam Engines— 6. Horizontal Engines— 7. Oscillatmg Engines— 8. Vertical High- Pressure Engines— 9. Special Engines — 10. Portable Engines— n. Locomotive Engines- is. Marine Engines. Steam Engine Management; a Treatise on the Working and Management of Steam Boilers. By F. Colyer, M. Inst. C.E., Mem. Inst. M.E. New edition, i8mo, cloth, 3^. dd. Aid Book to Engineering Enterprise. By Ewing Matheson, M. Inst. C.E. The Inception of Public Works, Parlia- mentary Procedure for Railways, Concessions for Foreign Works, and means of Providing Money, the Points which determine Success or Failure, Contract and Purchase, Commerce in Coal, Iron, and Steelj &c. Second edition, revised and enlarged, 8vo, cloth, 2\s. i8 CATALOGUE OF SCIENTIFIC BOOKS Pumps, Historically, Theoretically, and Practically Considered. By P. R. BjoRLlNG. With 156 illustratioiu. Crown 8vo, cloth, 7^. td. The Marine Transport of Petroleum. A Book for the use of Shipowners, Shipbuilders, Underwriters, Merchants, Captains and OfScers of Petroleum-carrying Vessels. By G. H. Little, Editor of the ' Liverpool Journal of Commerce.' Crown 8vo, cloth, lOf. 6rf. Liquid Fuel for Mechanical and Industrial Purposes. Compiled by E. A. Brayley Hodgetts. With wood engravings. 8vo, cloth. Is. 6d. Tropical Agriculture : A Treatise on the Culture, Preparation, Commerce and Consumption of the principal Products of the Vegetable Kingdom. By P. L. Simmonds, F.L.S., F.R.C.I. New edition, revised and enlarged, Svo, cloth, 21s. Health and Comfort in House Building ; or, Ventila- tion with Warm Air by Self-acting Suction Power. With Review of the Mode of Calculating the Draught in Hot-air Flues, and with some Actual Experiments by J. Drysdale, M.D., and J. W. Hayward, M.D. With, plates and woodcuts. Third edition, with some New Sections, and the whole carefully Revised, Svo, cloth, 7j. (>d. , Losses in Gold Amalgamation. With Notes on the Concentration of Gold and Silver Ores. With six plates. By W. McDermott and P. W. Duffield. Svo, cloth, 5^. A Guide for the Electric Testing of Telegraph Cables. By Col. V. HOSKICER, Royal Danish Engineers. Third edition, crown Svo, cloth, 4J-. 6a?. The Hydraulic Gold Miners Manual. By T. S. G. KiRKPATRiCK, M.A. Oxon. With 6 plates. Crown Svo, cloth, 6j. " We venture to think that this work will become a text-book on the important subject of which it treats. Until comparatively recently hydraulic mines_ were neglected. This was scarcely to be surprised at, seeing that their working in California was brought to an abrupt termination by the action of the farmers on the dibris question, whilst their working in other parts of the world had not been attended with the anticipated success." — The MiTiing World atid En£ineerin£r Record. A Text-Book of Tanning, embracing the Preparation of all kinds of Leather. By Harry R. Proctor, F.C.S., of Low Lights Tanneries. With illustrations. Crown Svo, cloth, 10s. 6d. PUBLISHED BY E. & F. N. SPON. 19 The Arithmetic of Electricity. By T. O'Conor Sloane. Crown 8vo, cloth, 4J. dd. The Turkish Bath : Its Design and Construction for Public and Commercial Purposes. By R.-O. Allsop, Architect. WM plans and sections, 8vo, cloth, 6j. Earthwork Slips and Subsidences upon Public Works : Their Causes, Prevention and Reparation. Especially written to assist those engaged in the Construction or Maintenance of Railways, Docks, Canals, Waterworks, River Banks, Reclamation Embankments, Drainage Works, &c., &c. By John Newman, Assoc. Mem. Inst. C.E., Author of ' Notes on Concrete,' &c. Crown 8vo, cloth, Js. 6d. Gas and Petroleum Engines : A Practical Treatise on the Internal Combustion Engine. By Wm. Robinson, M.E., Senior Demonstrator and Lecturer on Applied Mechanics, Physics, &c.. City and Guilds of London College, Finsbury, Assoc. Mem. Inst. C.E., &c. Numerous illustrations. 8vo, cloth, 14^. Waterways and Water Transport in Different Coun- tries. With a description of the Panama, Suez, Manchester, Nicaraguan, and other Canals. By J. Stephen Jeans, Author of 'England's Supremacy,' ' Railway, Problems,' &c. Numerous illustrations. 8vo, cloth, 14J. A Treatise on the Richards Steam-Engine Indicator and the Development and Application of Force in the Steam-Engine. By Charles T. Porter. Fourth Edition, revised and enlarged, 8vo, cloth, gj. Contents. The Nature and Use of the Indicator : The several lines on the Diagram. Examination of Diagram No. I. Of Truth in the Dia^am. Description of the Richards Indicator. Practical Directionsfor Applying and Taking Care of the Indicator. Introductory Remarks. Units. Expansion. Directions for ascertaining from the Diagram the Power exerted by the Engine. To Measure from the Diagram the Quantity of Steam Consumed. To Measure from the Diagram the Quantity of Heat Expended. Of the Real Diagram.and how to Construct it. Of the Conversion of Heat into Work in the Steam-engine. Observations on the several Lines of the Diagram. Of the Loss attending the Employment of Slow-piston Speed, and the Extent to which this is Shown by the Indicator. Of other Applications of the Indicator. _ Of the use of the Tables of the Properties of Steam in Calculating the Duty of Boilers. Introductory. Of the Pressure on the Crank when the Con- necting-rod is conceived to be of Infinite Length. The Modification of the Acceleration and Retardation that is occasioned _ by the Angular Vibration of the Connecting-rod. Method of representing the actual pressure on the crank at every point of its revolu- tion. The Rotative Effect of the Pressure exerted on the Crank. The Transmitting Parts of an Engine, con- sidered as an Equaliser of Motion. A Ride on a Buffer-beam (Appendix). 20 CATALOGUE OF SCIENTIFIC BOOKS. In demy 4to, handsomely bound in cloth, illustrated with Z^Q full page plates. Price 1 5 J. ARCHITECTURAL EXAMPLES IN BRICK, STONE, WOOD, AND IRON. A COMPLETE WOBK ON THE DETAILS AND ARRANGEMENT OP BUILDING CONSTRXICTION AND DESIGN. By WILLIAM FULLERTON, Architect. Containing 220 Plates, with numerous Drawings selected from the Architecture of Former and Present Times. The Details and Designs are Drawn to Scale, J", \", §", and Full size being chiefly used. The Plates are arranged in Two Parts. The First Part contains Details of Work in the four principal Building materials, the following being a few of the subjects in this Part : — Various forms of Doors and Windows, Wood and Iron Roofs, Half Timber Work, Porches, Towers, Spires, Belfries, Flying Buttresses, Groining, Carving, Church Fittings, Constructive and Ornamental Iron Work, Classic and Gothic Molds and Ornament, Foliation Natural and Conventional, Stained Glass, Coloured Decoration, a Section to Scale of the Great Pyramid, Grecian and Roman Work, Continental and English Gothic, Pile Foundations, Chimney Shafts according to the regulations of the London County Council, Board Schools. The Second Part consists of Drawings of Plans and Elevations of Buildings, arranged under the following heads : — Workmen's Cottages and Dwellings, Cottage Resi- dences and Dwelling Houses, Shops, Factories, Warehouses, Schools, Churches and Chapels, Public Buildings, Hotels and Taverns, and Buildings of a general character. AU the Plates are accompanied with particulars of the Work, with Explanatory Notes and Dimensions of the various parts. uj/aimea l^ugtS, rcancc^ jrs-^% the originals. Archiru/uraf ExamjjlM"— Town Holl^ 2 CATALOGUE OF SCIENTIFIC BOOKS Crown 8vo, cloth, with illustrations, 5s. WORKSHOP RECEIPTS, FIRST SERIES. By ERNEST SPON, Bookbinding. Bronzes and Bronzing. Candles. Cement. Cleaning. Colourwashing. Concretes. Dipping Acids. Drawing Office Details. Drying Oils. Dynamite. Electro - Metallurgy — (Cleaning, Dipping, Scratch-brushing, Bat- teries, Baths, and Deposits of every description). Enamels. Engraving on Wood, Copper, Gold, Silver, Steel, and Stone. Etching and Aqua Tint. Firework Making — (Rockets, Stars, Rains, Gerbes, Jets, Tour- billons, Candles, Fires, Lances,Lights, Wheels, Fire-balloons, and minor Fireworks). Fluxes. Foundry Mixtures. Synopsis of Contents. Freezing. Fulminates. Furniture Creams, Oils, Polishes, Lacquers, and Pastes. Gilding. Glass Cutting, Cleaning, Frosting, Drilling, Darkening, Bending, Staining, and Paint- ing. Glass Making. Glues. Gold. Graining. Gums. Gun Cotton. Gunpowder. Horn Working. Indiarubber. Japans, Japanning, and kindred processes. Lacquers. Lathing. Lubricants. Marble Working. Matches. Mortars. Nitro-Glycerine. Oils. Paper. Paper Hanging. Painting in Oils, in Water Colours, as well as Fresco, House, Trans- parency, Sign, and Carriage Painting. Photography. Plastering. Polishes. Pottery — (Clays, Bodies, Glazes, Colours, Oils, Stains, Fluxes, Ena- mels, and Lustres). Scouring. Silvering. Soap. Solders. Tanning. Taxidermy. Tempering Metals. Treating Horn, Mother- o'-Pearl, and like sub- stances. Varnishes, Manufacture and Use of. Veneering. Washing. Waterproofing. Welding. Besides Receipts relating to the lesser Technological matters and processes, such as the manufacture and use of Stencil Plates, Blacking, Crayons, Paste, Putty, Wax, Size, Alloys, Catgut, Tunbridge Ware, Picture Frame and Architectural Mouldings, Compos, Cameos, and others too numerous to mention. PUBLISHED BY E. & F. N. SPON. 23 Crown 8vo, cloth, 485 pages, with illustrations, Jr. WORKSHOP RECEIPTS, SECOND SERIES. By ROBERT HALDANE. Synopsis of Contents. and Disinfectants. Dyeing, Staining, Colouring. Essences. Extracts. Fireproofing. Gelatine, Glue, and Size, Glycerine. Gut. Hydrogen peroxide. Ink. Iodine. Iodoform. Isinglass. Ivory substitutes. Leather. Luminous bodies. Magnesia. Matches. Paper. Parchment. Perchloric acid. Potassium oxalate. Preserving. Acidimetry and Alkali- metry. Albumen. Alcohol . Alkaloids. Baking-powders. Bitters. Bleaching. Boiler Incrustations. Cements and Lutes. Cleansing. Confectionery. Copying. Figments, Paint, and Fainting : embracing the preparation of Pigments, including alumina lakes, blacks (animal, bone, Frankfort, ivory, lamp, sight, soot), blues (antimony, Antwerp, cobalt, casruleum, Egyptian, manganate, Paris, Peligot, Prussian, smalt, ultramarine), browns (bistre, hinau, sepia, sienna, umber, Vandyke), greens (baryta, Brighton, Brunswickj chrome, cobalt, Douglas, emerald, manganese, mitis, mountain, Prussian, sap, Scheele's, Schweinfurth, titanium, verdigris, zinc), reds (Brazilwood lake, carminated lake, carmine, Cassius purple, cobalt pink, cochineal lake, colco- thar, Indian red, madder lake, red chalk, red lead, vermilion), whites (alum, baryta, Chinese, lead sulphate, -white lead — by American, Dutch, French, German, Kremnitz, and Pattinson processes, precautions in making, and composition of commercial samples — whiting, Wilkinson's white, zinc white), yellows (chrome, gamboge, Naples, orpiment, realgar, yellow lakes) ; Paint (vehicles, testing oils, driers, grinding, storing, applying, priming, drying, filling, coats, brushes, surface, water-colours, removing smell, discoloration ; miscellaneous paints— cement paint for carton-pierre, copper paint, gold paint, iron paint, lime paints, silicated paints, steatite paint, transparent paints, tungsten paints, window paint, zinc paints) ; Painting (general instructions, proportions of ingredients, measuring paint work ; carriage painting— priming paint, best putty, finishing colour, cause of cracking, mixing the paints, oils, driers, and colours, varnishing, importance of washing vehicles, re-vamishing, how to dry paint ; woodwork painting). 24 CATALOGUE OF SCIENTIFIC BOOKS Crown 8vo, cloth, 480 pages, with 183 illustrations, is. WORKSHOP RECEIPTS. THIRD SERIES, By C. G. WARNFORD LOCK, Uniform with the First and Second Series. Synopsis of Coktents. Alloys, Indium. Rubidium. Aluminium. Iridium. Ruthenium. Antimony. Iron and Steel. Selenium. Barium. Lacquers and Lacquering. Silver. Beryllium. Lanthanum, Slag. Bismuth. Lead, Sodium. Cadmium, Lithium. Strontium. Csesium. Lubricants. Tantalum. Calcium. Magnesium, Terbium. Cerium. Manganese. Thallium. Chromium, Mercury. Thorium. Cobalt, Mica, Tin. Copper, Molybdenum, Titanium. Didymium, Nickel. Tungsten. Electrics. Niobium. Uranium, Enamels and Glazes. Osmium. Vanadium. Erbium. Palladium. Yttrium. Gallium. Platinum. Zinc. Glass. Potassium. Zirconium. Gold. Rhodium. PUBLISHED BY E. & F. N. SPON. 25 WORKSHOP RECEIPTS, FOURTH SERIES, DEVOTED MAINLY TO HANDICRAFTS & MECHANICAL SUBJECTS. By C. G. WARNFORD LOCK. 250 niustrations, with Complete Index, and a General Index to the Fonr Series, Ss. Waterproofing — rubber goods, cuprammonium processes, miscellaneous preparations. Packing and Storing articles of delicate odour or colour, of a deliquescent character, liable to ignition, apt to suffer from insects or damp, or easily broken. Embalming and Preserving anatomical specimens. Leather Polishes: Cooling Air and Water, producing low temperatures, making ice, cooling syrups and solutions, and separating salts from liquors by refrigeration. Pumps and Siphons, embracing every useful contrivance for raising and supplying water on a. moderate scale, and moving corrosive, tenaciou.', and other liquids. Desiccating — air- and water-ovens, and other appliances for drying natural and artificial products. Distilling — water, tinctures, extracts, pharmaceutical preparations, essences, perfumes, and alcoholic liquids. Emulsifying as required by pharmacists and photographers. Evaporating — saline and other solutions, and liquids demanding special precautions. Filtering — water, and solutions of various kinds. Percolating and Macerating. Electrotyping. Stereotyping by both plaster and paper processes. Bookbinding in all its details. Stravi^ Plaiting and the fabrication of baskets, matting, etc. Musical Instruments— the preservation, tuning, and repair of pianos, harmoniums, musical boxes, etc. Clock and Watch Mending — adapted for intelligent amateurs. Photography — recent development in rapid processes, handy apparatus, numerous recipes for sensitizing and developing solutions, and applica- tions to modem illustrative purposes. 26 CATALOGUE OF SCIENTIFIC BOOKS Crown 8vo, cloth, with 373 illustrations, price 5^. WORKSHOP RECEIPTS. FIFTH SERIES. By C. G. WARNFORD LOCK, F.L.S. Containing many new Articles, as well as additions to Articles included in the previous Series, as follows, viz. : — Anemometers. Barometers, How to make. Boat Building. Camera Lucida, How to use. Cements and Lutes. Cooling. Copying. Corrosion and Protection of Metal Surfaces. Dendrometer, How to use. Desiccating. Diamond Cutting and Polishing. Elec- trics. New Chemical Batteries, Bells, Commutators, Galvanometers, Cost of Electric Lighting, Microphones, Simple Motors, Phonogram and Graphophone, Registering Appa- ratus, Regulators, Electric Welding and Apparatus, Transformers. Evaporating. Explosives. Filtering. Fireproofing, Buildings, Textile Fa- brics. Fire-extinguishing Compounds and Apparatus. Glass Manipulating. Drilling, Cut- ting, Breaking, Etching, Frosting, Powdering, &c. Glass Manipulations for Laboratory Apparatus. Labels. Lacquers. Illuminating Agents. Inks. Writing, Copying, Invisible, Marking, Stamping. Magic Lanterns, their management and preparation of slides. Metal Work. Casting Ornamental Metal Work, Copper Welding, Enamels for Iron and other Metals, Gold Beating, Smiths' Work. Modelling and Plaster Casting. Netting. Packing and Storing. Acids, &c. Percolation. Preserving Books. Preserving Food, Plants, &c. Pumps and Syphons for various liquids. Repairing Books. Rope Tackle. Stereotyping. Taps, Various. Tobacco Pipe Manufacture. Tying and Splicing Ropes. Velocipedes, Repairing. Walking Sticks. Waterproofing. PUBLISHED BY E. & F. N. SPON, 27 NOW COMPLETE. IVitA nearly 15CX) illustrations, in super-royal 8vo, in 5 Divisions, cloth. Divisions I to 4, 13J. td. each ; Division J, 17J. 6d. ; or 2 vols., cloth, ^3 loj. SPONS' ENCYCLOPiEDIA PP- Explosives, 22 pp. 33 figs. Feathers. Fibrous Substances, 92 pp. 79 figs. Floor-cloth, 16 pp. 21 figs. Food Preservation, 8 pp. Fruit, 8 pp. Fur, S pp.- Gas, Coal, 8 pp. Gems. Glass, 45 pp. 77 figs. Graphite, 7 pp. Hair, 7 pp. Hair Manufactures.. Hats, 26 pp. 26 figs. Honey. Hops. Horn. Ice, 10 pp. 14 figs. Indiarubber Manufac- tures, 23 pp. 17 figs. Ink, 17 pp. Ivory. Jute Manufactures, 1 1 pp., II figs. Knitted Fabrics — Hosiery, 15 pp. 13 figs. Lace, 13 pp. 9 figs. Leather, 28 pp. 31 figs. Linen Manufactures," 16 pp. 6 figs. Manures, 21 pp. 30 figs. Matches, 1 7 pp. 38 figs. Mordants, 13 pp. Narcotics, 47 pp. Nuts, 10 pp. Oils and Fatty Sub- stances, 125 pp. Paint. Paper, 26 pp. 23 figs. Paraffin, 8 pp. 6 figs. Pearl and Coral, 8 pp. Perfumes, 10 pp. Photography, 13 pp. 20 figs. Pigments, 9 pp. 6 figs. Pottery, 46 pp. 57 figs. Printing and Engraving, 20 pp. 8 figs. INDUSTRIAL ARTS, MANUFACTURES, AND COMMERGIAL PRODUCTS. Edited by C. G. WARNFORD LOCK, F.L.S. Among the more important of the subjects treated of, are the following :— Acids, 207 pp. 220 figs. Alcohol, 23 pp. 16 figs. Alcoholic Liquors, 13 pp. Alkalies, 89 pp. 78 figs. Alloys. Alum. Asphalt Assaying. Beverages, 89 pp. 29 figs. Blacks. Bleaching Powder, 15 pp. Bleaching, 51 pp. 48 fi^. Candles, 18 pp. 9 figs. Carbon Bisulphide. Celluloid, 9 pp. Cements. Clay. Coal-tar Products, 44 pp. 14 figs. Cocoa, 8 pp. Coffee, 32 pp. 13 figs. Cork, 8 pp. 17 figs. Cotton Manufactures, 62 pp. 57 figs. Drugs, 38 pp. Dyeing and Calico Printing, 28 pp. 9 figs. Dyestuffs, 16 pp. Electro-Metallurgy, 13 Resinous and Gummy Substances, 75 pp. 16 figs. Rope, 16 pp. 17 figs. Salt, 31 pp. 23 figs. Silk, 8 pp. Silk Manufactures, 9 pp. II figs. Skins, 5 pp. Small Wares, 4 pp. Soap and Glycerine, 39 pp. 45 figs. , Spices, 16 pp. Sponge, 5 pp. Starch, 9 pp. lo figs. Sugar, 15s pp. 134 figs. Sulphur. Tannin, 18 pp. Tea, 12 pp. Timber, 13 pp. Varnish, 15 pp. Vinegar, 5 pp. Wax, 5 pp. Wool, 2 pp. Woollen Manufactures, 58 pp. 39 figs. 28 CATALOGUE OF SCIENTIFIC BOOKS MECHANICAL MANIPULATION. THE MECHANICIAN: A TREATISEON THE CONSTRUCTION AND MANIPUUTION OF TOOLS, FOR THE USE AND INSTRUCTION OF YOUNG ENGINEERS AND SCIENTIFIC AMATEURS; Comprising the Arts of Blacksmithing and Forging ;4the Construction and Manufacture of Hand Tools, and the various Methods of Using and Grinding them ; the Construction of Machine Tools, and how to work them; Turning and Screw-cutting; the various details of setting out work, &c., &c. By CAMERON KNIGHT, Engineer. 96 4to plates, containing 1147 illustrations, and 397 pages of letterpress, second edition, reprinted from the first, 4to, cloth, 18s. Of the six chapters constituting the work, the first is devoted to forging ; in which the fundamental principles to be observed in making forged articles of every class are stated, giving the proper relative positions for the constituent fibres of each article, the mode of selecting proper quantities of material, steam- hammer operations, shaping-moulds, and the manipulations resorted to for shaping the component masses to the intended forms. Engineers' tools and their construction are next treated, because they must be used during all operations described in the remaining chapters, the author thinking that the student should first acquire knowledge of the apparatus which he is supposed to be using in the course of the processes given in Chapters 4, 5, and 6. In the fourth chapter planing and lining are treated, because these are the elements of machine-making in general. The processes described in this chapter are those on which all accuracy of fitting and finishing depend. The next chapter, which treats of shaping and slotting, the author endeavours to render comprehensive by giving the hand-shaping processes in addition to the machine-shaping. In many cases hand-shaping is indispensable, such as sudden breakage, operations abroad, and on board ship, also for constructors having a limited number of machines. Turning and screw-cutting occupy the last chapter. In this, the operations for lining, centering, turning, and screw-forming are detailed and their principles elucidated. The Mechanician is the result of the author's experience in engine making during twenty years ; and he has concluded that, however retentive the memory of a machinist might be, it would be convenient for him to have a book of primary principles and processes to which he could refer with confidence. PUBLISHED BY E. & F. N. SPON. 29 JTTST PUBLISHED. In demy 8vo, cloth, 600 pages, and 1420 Illustrations, 6s. SPONS' MEGHANIGS' OWN BOOK; A MANUAL FOR HANDICRAFTSMEN AND AMATEURS. Contents. Mechanical Drawing — Casting and Founding in Iron, Brass, Bronze, and other Alloys — Forging and Finishing Iron— Sheetmetal Working —Soldering, Brazing, and Burning— Carpentry and Joinery, embracing descriptions of some 400 Woods, over 200 Illustrations of Tools and their uses. Explanations (with Diagrams) of 116 joints and hinges, and Details of Construction of Workshop appliances, rough furniture. Garden and Yard Erections, and House Building— Cabinet-Making and Veneering — Carving and Fretcutting — Upholstery — Painting, Graining, and Marbling — Staining Furniture, Woods, Floors, and Fittings— Gilding, dead and bright, on various grounds— Polishing Marble, Metals, and Wood— Varnishing— Mechanical movements, illustrating contrivances for transmitting motion— Turning in Wood and Metals— Masonry, embracing Stonework, Brickwork, Terracotta and Concrete— Roofing with Thatch, Tiles, Slates, Felt, Zinc, &c.— Glazing with and without putty, and lead glazing— Plastering and Whitewashing— Paper-hanging— Gas-fitting— Bell-hanging, ordinary and electric Systems — Lighting — Warming — Ventilating — Roads, Pavements, and Bridges — Hedges, Ditches, and Drains— Water Supply and Sanitation— Hints on House Construction suited to new countries. E. & P. N. SPON, 1S5, Strand, London. New York : 12, Cortlandt Street. 3° CATALOGUE OF SCIENTIFIC BOOKS 8P0N8' DICTIONARY OF ENGINEERING, CIVIL, MECHANICAL, MILITARY, & NAVAL, WITH Technical Terms in French, German, Italian, and Spanish. In 97 numbers, Super-royal 8vo, containing ^I'^z prinled pages and 7414 engravings. Any number can be had separate : Nos. i to 95 ij. each post free ; Nos. 96, 97, 2s., post free. See also page 112. Complete List of all the Subjects : Abacus Adhesion .. Agricultural Engines Air-Chamber Air- Pump .. Algebraic Signs .. AUoy Aluminium Amalgamating Machine . . Ambulance Anchors Anemometer Angular Motion . . Angle-iron . , . . . , Angle of Friction . . Animal Charcoal Machine Antimony, 4; Anvil Aqueduct, 4 ; Arch Archimedean Screw Arming Press Armour, 5; Arsenic Artesian Well Artillery, 5 and 6 ; Assaying Atomic Weights .. ., : Auger, 7; Axles ., Balance, 7 ; Ballast Bank Note Machinery .. Bam Machinery .. Barker's Mill Barometer, 8; Barracks .. Nos. I I [ and 2 .. 2 .. 2 .. 2 .. 2 .. 2 .. 2 .. 2 .. 2 ! and 3 i and 4 •• 3 •• 3 •• 4 .. 4 .. 4 .. 4 |.ands .. s • • 5 .. 6 i and 7 • ■ 7 •• 7 •• 7 ' and 8 .. 8 .. 8 Barrage . , , , Battery BeU and Bell-hanging Belts and Belting . . Bismuth Blast Furnace Blowing Machine Body Plan.. Boilers Bond Bone Mill.. Boot-making Machinery , Boring and Blasting Brake Bread Machine Brewing Apparatus Brick-making Machines , Bridges . . . . Buffer Cables Cam, 29; Canal ., Candles Cement, 30 ; Chimney Nos. 8 and 9 9 2nd lo .. 10 10 and 1 1 .. II 11 and 12 .. 12 12 and 13 13. 14. IS 15 and 16 .. 16 .. 16 16 to 19 19 and 20 .. 20 20 and 21 .. 21 21 to 28 .. 28 28 and 29 .. 29 29 and 30 30 Coal Cutting and Washing Ma chinery .. Coast Defence Compasses . . Construction Cooler, 34 ; Copper Cork-cutting Machine .. 31 31. 32 .. 32 32 and 33 •• 34 •• 34 PUBLISHED BY E. & F. N. SPON. 31 Nos. Corrosion ., .. 34 and 35 Cotton Machinery ... 35 Damming .. •■ 35 to 37 Details of Engines 37, 38 Displacement .. 38 Distilling Apparatus .. 38 and 39 Diving and Diving Bells . . 39 Docks . . . . . • 39 and 40 Drainage .. .. .,40 and 41 Drawbridge .. .. ..41 Dredging Machine .. .,41 Dynamometer .. .. 41 to 43 Electro-Metallurgy .. 43, 44 Engines, Varieties .. 44, 45 Engines, Agricultural .. i and 2 Engines, Marine .. .. 74, 75 Engines, Screw .. ,. 89, 90 Engines, Stationary .. 91, 92 Escapement .. .. 45, 46 Fan 46 File-cutting Machine . , . . 46 File-arms .. .. .. 46, 47 Flax Machinery . . . . 47, 48 Float Water-wheels . . . . 48 Forging .. ., .. ..48 Founding and Casting . . 48 to 50 Friction, 50 ; Friction, Angle of 3 Fuel, 50; Furnace .. 50, 51 Fuze, SI ; Gas 51 Gearing 51, 52 Gearing Belt .. .. 10, 11 Geodesy 52 and S3 Glass Machinery .. .. •■ S3 Gold, S3, 54 ; Governor . . . . 54 Gravity, S4 ; Grindstone . . 54 Gun-carriage, 54; Gun Metal .. S4 Gunnery 54 to 56 Gunpowder .. .. ..56 Gun Machinery .. .. 5^,57 Hand Tools ., .. 57, 58 Hanger, 58; Harbour .. ..58 Haulage, 58, S9 ; Hinging .. S9 Hydraulics and Hydraulic Ma- chinery 59 to 63 Ice-making Machine . . . . 63 India-rubber .. .. ..63 Indicator 63 and 64 Injector .. .. .. ..64 Iron 641067 Iron Ship Building .. ..67 Irrigation 67 and 68 Nos. Isomoi-phism, 68 ; Joints ,, 68 Keels and Coal Shipping 68 and 69 Kiln, 69 ; Knitting Machine .. 69 Kyanising .. .. ,. ..69 Lamp, Safety .. .. 69, 70 Lead .. .. .. ..70 Lifts, Hoists .. ., 70, 71 Lights, Buoys, Beacons .. 71 and 72 Limes, Mortars, and Cements .. 72 Locks and Lock Gates . . 72, 73 Locomotive .. ., ••73 Machine Tools .. ., 73,74 Manganese .. .. ..74 Marine Engine . , • • 74 and 75 Materials of Construction 75 and 76 Measuring and Folding . . . . 76 Mechanical Movements . , id, 77 Mercury, 77 ; Metallurgy .. 77 Meter 77, 78 Metric System .. .. ,• 78 Mills 78, 79 Molecule, 79 ; Oblique Arch • . , 79 Ores, 79, 80 ; Ovens •. •.80 Over-shot Water-wheel •• 80, 8l Paper Machinery . . .. ..81 Permanent Way •• ., 81,82 Piles and Pile-driving . . 82 and 83 Pipes 83, 84 Planimeter ., .. ... 84 Pumps . . . . . . 84 and 85 Quarrying .. .. .. ..85 Railway Engineering . . 85 and 86 Retaining Walls .. .. ..86 Rivers, 86, 87 ; Rivetted Joint . . 87 Roads 87,88 Roofs 88, 89 Rope^making Machinery . . 89 Scaffolding .. ., ..89 Screw Engines . , . . 89, go Signals, 90; Silver .. 90, 91 Stationary Engine .. 91,92 Stave-making & Cask Machinery 92 Steel, 92 ; Sugar Mill , . 92, 93 Surveying and Surveying Instru- ments 93, 94 Telegraphy .. .. 94, 95 Testing, 9S ; Turbine .. ■• 9S Ventilation .. 95, 96, 97 Waterw.orks .. .. 96,,97 Wood-v?orking Machinery 96, 97 Zinc 96,97 32 CATALOGUE OF SCIENTIFIC BOOKS. In super-royal 8vo, 1168 pp., with 2400 illustraitons, in 3 Divisions, cloth, price 13*. td each ; or i Vol., cloth, s/. ; or half-morocco, s/. Zt. A SUPPLEMENT TO SPONS' DICTIONARY OF ENGINEERING. Edited by ERNEST SPON, Memb. Soc, Engineers. Abacus, Counters, Speed Coal Mining. Lighthouses, Buoys, and Indicators, and Slide Coal Cutting Machines. Beacons. Rule. Coke Ovens. Copper, Machine Tools. Agricultural Implements Docks, Drainage. Materials of Construc- and Machinery, Dredging Machinery. tion. Air Compressors. Dynamo - Electric and Meters. Animal Charcoal Ma- Magneto-Electric Ma- Ores, Machinery and chinery. chines. Processes employed to Antimony. Dynamometers. Dress. Axles and Axle-boxes. Electrical Engineering, Piers. Bam Machinery. Telegraphy, Electric Pile Driving. Belts and Belting, Lighting and its prac- Pneumatic Transmis- Blasting. Boilers. ticaldetails,Telephones sion. Brakes. Engines, Varieties of. Pumps. Brick Machinery. Explosives. Fans. Pyrometers. Bridges. Founding, Moulding and Road Locomotives. Cages for Mines. the practical work of Rock Drills. Calculus, Differential and the Foundry. Rolling Stock. Integral. Gas, Manufacture of. Sanitary Engineering Canals. Hammers, Steam and Shafting. Carpentry. other Power, Steel. Cast Iron. Heat. Horse Power. Steam Navvy, Cement, Concrete, Hydraulics. Stone Machinery. T.imes, and Mortar. Hydro-geology. Tramways. Chimney Shafts. Indicators. Iron. WeU Sinking. Coal Cleansing and Lifts, Hoists, and Eleva- Washing. tors.