of March, 1881, to which, however, some improvements have been since introduced. The apparatus for compressing the air was placed in the shed. The air was compressed to 63 atmospheres by a pump worked by a steam-engine, and stored in cylindrical reservoirs of wrought iron without rivets. A pipe led the air from the reservoirs to the head of the tramway, where the cylinder placed on the motor for storing the air during the journey could be conveniently charged. The air was compressed by means of four pumps, placed two and two in a water-box, and worked by the direct action of a compound engine with cylinders placed in juxtaposition, of 8 in. and 14 in. diameter respectively, with an equal length of stroke of 13 in. The air, after being forced through the first pump cylinder, passed successively through the other three, the diameters of which were of proportionately decreasing sizes, viz.: 8.2 in., 5 in., 3.5 in., and 2 in., and the air, on leaving each cylinder, passed on its way to the next cylinder through a coiled pipe immersed in flowing water to remove the heat generated. This cooling surface amounted to nearly 54 sq. ft. The cooling of the air was very efficient. In an experiment made on this question, the temperature of the compressor did not vary to the extent of 9° Fahr. in charging the reservoir from 40 to 63 atmospheres, occupying an hour and a-half, the consumption of water during the time being about 1,400 gallons. The fixed reservoirs were of about 240 cu. ft. capacity. The motor formed part of a compound vehicle, which may be said to have consisted of two parts joined together by an articulated corridor, the whole being covered by a roof which was approached from the platform behind by an easy staircase. On this roof were seats for outside passengers. The front part of the compound vehicle contained the motor, as well as a compartment for six inside passengers, with roof space for twenty passengers, and weighed about 15,400 pounds when empty; the hind part contained accom modation inside for twelve passengers, and outside for fourteen passengers, and weighed 6,600 lbs. The combined vehicle was entered from the platform in the rear, which could hold four passengers, and from thence, as already mentioned, the staircase led on to the roof. The total number of passengers this vehicle could accommodate was thus-eighteen inside, thirty-four on the roof, four on the platform, or, fiftysix in all. The total length of the carriage was 29 ft. 7 in., width 7 ft. The distance between the axes of the bogies was 16 ft. 9 in. The distances apart of the centers of the wheels were, in the case of the hind bogie, 3 ft. 9 in., and in the case of the front bogie, 4 ft. 4.6 in. The motor is a compound engine, the diameters of the cylinders being 4.9 in., and 1.9 in., with 12 in. stroke. The diameter of the wheels was 2 ft. 4 in. A small boiler is placed on one side, in front, for creating steam, which passes into a steam-jacket, enclosing the pipe of communication from the reservoir to the cylinders, as well as the cylinders themselves, so that the air was warmed before it escaped. The reservoirs on the motor contained 71 cu. ft. In an experiment made on charging the reservoir in the motor, the pressure in the fixed reservoirs, at the time of charging the reservoirs on the motor, was 63.8 atmospheres, at a temperature of 68° Fahr. One atmosphere was lost by letting the air into the pipe laid between the shed and the tramway where the motor stood; when the reservoir on the motor was charged, the pressure fell to 42.6 atmospheres in the fixed reservoirs, at a temperature of 55° Fahr. The pressure in the reservoir on the motor, when ready to start, was 42.6 atmospheres, at a temperature of 84° Fahr. On its return at the end of forty-six minutes, after a journey, as above mentioned, of about 3 miles, including the triangle, the pressure had fallen to 20.9 atmospheres, and the temperature to 71° Fahr. The weight of air used during the journey was thus about 110 lbs., or, say, 34 lbs. per mile. The coal consumed by the stationary engine to compress the air amounted to 39 lbs. per mile, in addition to 3 lbs. of coke per mile for warming the exhaust. Whilst the motor was performing its journey, the stationary steam-engine was employed in raising the pressure in the fixed cylinders to 63 atmospheres, and worked, on an average, during fifty minutes in each hour; during the rest of the journey it remained idle. It was thus always employed in doing work in excess of the pressure which could be utilized on the car, and the work was, under the circumstances of the case, necessarily intermittent. This was a very unfavorable condition of working. In the electric tram-car the haulage was effected by means of accumulators. The car was of the ordinary type, with two platforms. It was said to have been running as an ordinary tramcar since 1876. It had been altered in 1884 by raising the body about six inches, so as to lift it clear of the wheels, in order to allow the space under the seats to be available for receiving the accumulators, which consisted of Faure batteries of a modified construction. The accumulators employed were of an improved kind, devised by M. Julien, the under manager of the Compagnie l'Electrique, which undertook the work. The principal modification consists in the substitution, for the lead core of the plates, of one composed of a new unalterable metal. By this change the resistance is considerably diminished, the electromotive force rises to 2.40 volts, the return is greater, the output more constant, and the weight is considerably reduced. The plates being no longer subject to deformation, have the prospect of lasting indefinitely. The accumulators used were constructed in August, 1884. The car, as altered, had been running as an electric tramcar on the Brussels tramways since October, 1884, till it was transferred to the experimental tramway at Antwerp. The accumulators had been in use upon the car during the whole of this period, and they were in good order at the end of the experiments, that is to say, when the Exhibition closed at the end of October, 1885. The accumulator had forty elements, divided into four series, each series communicating by means of wires fixed to the floor of the car, with commutators which connected them with the dynamo used as a motor. There were two sets of these batteries, ordinary service of the car, and during or accumulators, one of which was being nine hours for the accelerated service. charged in the shed whilst the other was The accumulators on the car actuated in use. The exchange required ten min. a Siemens dynamo, acting as a motor, utes, including the time for the car to go such as is used for lighting, having a off the tramway into the shed and re- normal speed of 1,000 revolutions, fixed turn to the tramway. This exchange on the frame of the carriage. The motion took place after every seven journeys. was conveyed from the pulley on the dy-' Therefore, the two batteries would have namo by means of a belt passing round a sufficed for working the car over a dis- shaft fixed on movable bearings to regutance of about 42 miles during 16 hours. late its tension, and thence to the axles It may be observed that the first ser- by means of a flat chain of phosphorvice in the morning would be performed bronze. The chain was adopted as the by means of the accumulators charged means of moving the axle, on account of during the afternoon and evening of the its simplicity and facility of repair by unprevious day. skilled labor. Each element of a battery was com- The speed was fixed at 4 meters per posed of 19 plates, of which 9 were posi- second (which corresponds with a speed tive, 4 millimeters thick, and 10 negative, of nearly 9 miles per hour), for 1,000 3 millimeters thick. Each positive plate revolutions of the dynamo, and it was weighed 1.44 lbs., of which about 25 per regulated by cutting a certain number of cent. consisted of active material. Each the accumulators out of circuit, instead negative plate weighed nearly 1 lb., of which one-third consisted of active mat ter. The weight of the metallic part of the battery amounted, therefore, to 1,846 lbs. ; and the whole battery, including the case and the liquid, amounted to 2,464 lbs., which contained 499 lbs. of active matter, or 20.25 per cent. The four cases in which the battery was contained were so arranged as to divide the weight equally between the wheels. Two commutators enclosed in a box were placed on the platforms at the two ends of the carriage, so as to be available for moving in either direction. The accumulators were divided into four series of ten double elements, which, by means of the commutators, could be united under four combinations, viz. : 1st. 4 series in quantity-1 in tension. 2d. 2 66 3d. 4th. 64 2 ..3 4 66 of by the device of inserting resistances which cause a waste of energy. By breaking the circuit entirely the motive power ceased, and the vehicle might either bə stopped by the brakes or allowed to run forward by gravity, if the road were sufficiently inclined. The reversal of the motor was effected by means of a lever which reversed the position of the brushes of the dynamo. The dynamo could be set in motion, and the carriage worked from either end, as desired. The handle to effect this was movable, and as there was only one handle and this one was in charge of the conductor, he used it at either end as required. It should be mentioned that the car was lighted at night by two incandescent lamps, which absorbed 1.5 amperes each; and the brakes also were worked by the accumulators. The weight of the tramcar was 5,654 lbs.; the weight of the accumulators was 2,460 lbs.; the weight of the machinery, including dynamo, 1,232 lbs. The car contained room for fourteen persons inside and twenty outside. Under the conditions of the competition the car was required to draw a second car occasionally. Finally, a fifth movement united the four series in quantity, coupling them on each other, and putting the dynamo out of circuit, thus restoring equilibrium. When in a state of repose the handle was so arranged as to keep this latter switch turned on. The accumulators were arranged for charging in two series united in quantity, each containing twenty The jury made special observations double elements. The charge was effected upon the work required to move the car by a Gramme machine, worked by a port- between the 20th September and 15th able engine. Each of these series received October, 1885. Seals were attached to its charge during seven hours for the the accumulators. Moreover, from the 27th of September, after each charge, seals were placed on the belts from the steam-engine to prevent any movement of the Gramme machine, so that there could be no charges put into the accumulators beyond those measured by the jury. tricity, for producing the energy required to draw the carriage on the level. The electric tramcar was quite equal in speed to those driven by steam or compressed air, and was characterized by its noiselessness and by the care with which it was manipulated. (10d. per pound). To these must be added the cost of erection, and of switches for manipulating the current; as well as the proportion of the cost of a fixed engine to create the electricity. The instruments used for measuring Assuming the car, by itself, cost the were Ayrton's ampere meter and Deprez's same as an ordinary tramcar, the extra volt meter, which had been tested in the cost relatively to other systems was Exhibition by the Commission for Experi- stated as being, according to the followments on Electrical Instruments, under ing figures, viz.: The Gramme machine the presidency of Professor Rousseau. cost £48, the motor £208, and the accuBesides this, Siemens electro-dynamom-mulators 2.25 francs per kilogramme eter and Ayrton's voltmeter were used to check the results; but there was no practical difference discovered. During the period of charging the accumulators, the intensity of the current and the electromotive force was measured every quarter of an hour, and thence the energy stored up in the battery was deduced. It may be mentioned that the charge in the accumulators, when the experiments were commenced, was equal in amount to that at their termination. An experiment was made on 21st October to ascertain, as a practical question, what was the work absorbed by the Gramme machine in charging the accumulators. The work transmitted from the steam-engine was measured every quarter of an hour by a Siemens dynamometer, at the same time the intensity of the electromotive force given out by the machine, as well as the number of the revolutions it was making, was noted. It resulted that for a mean development of 4 mechanical horse-power, the dynamometer gave into the accumulators to be stored up 2.28 electrical horse-power, or 57 per cent. The intensity varied between 25.03 and 23.51 amperes during the whole time of charging. Of this amount stored up in the accumulators a further loss took place in working the motor; so that from 30 to 40 per cent. of the work originally given out by the steam-engine must be taken as the utmost useful effect on the rail. It was estimated that to draw the carriage on the level .714 horse power was required, or, if a second carriage was attached, .848 horse-power would draw the two together. This would mean that, say, 2 horse-power on the fixed engine would be employed to create the elec Having thus given a general description of the various motors which were presented for competition, I will now give a brief summary of some of the principal particulars obtained during the competition. In the first place, it may be mentioned that the Jury consisted of the following: Chef, Inspecteur de Direction à l'admin- istration des chemins de fer de l'Etat des Arts et Manufactures, délégué par le Vice-President.-M. Beliard, Ingénieur Gouvernement Francais. taine du Génie, délégué par le GouvMembers. MM. Douglas Dalton, Capiernement Anglais; Gunther, Ingénieur Commissaire Général de la Section AlleIngénieur à l'administration des chemins mande à l'Exposition d'Anvers; Hubert, Université de Bruxelles; Dery, Ingénieur de fer de l'Etat Belge, Professeur à la Chef de service a l'administration des chemins de fer de l'Etat Belge. Chef du service du matérial et de la tracSecretary.-M. Dupuich. Ingénieur tion à la Société Générale des chemins de fer économiques. Reporter.-M. Belleroche, Ingénieur en Chef, a la traction et au matérial des chemins de fer du Grand Central. Members added by the Jury.-MM. Vinçotte, Ingénieur, Directeur de l' Association pour la surveillance des machines a vapeur; Laurent, Ingénieur des mines et de l'Institut électro-technique de l'Universite de Liége. The original programme of the condi tions which were laid down in the invitation to competitors, as those upon which the adjudication of merit would be awarded, contained twenty heads, to each of which a certain value was to be attached; and, in addition to these special heads, there were also to be weighed the following general considerations, viz: a. The defects or inconveniences established in the course of the trials. b. The necessity or otherwise of turning the motor, or the carriage with motor, at the termini. C. Whether one or two men would be required for the management of the engine. As regards these preliminary special points, the compressed-air motor, as well as the Rowan engine, required to be turned for the return journey, whereas the other motors could run in either direction. In regard to this, the electric car was peculiarly manageable, as it moved in either direction, and the handle by which it was managed was always in front, close to the brake. This carriage was the only one which was entirely free from the necessity of attending to the fire during the progress of the journey, for even the compressed-air engine had its small furnace and boiler for heating the air. 6. Capacity of the brake for acting upon the greatest possible number of wheels of the vehicle or vehicles. 7. The degree to which the outside covering of the motor conceals the machinery from the public, whilst allowing it to be visible and accessible in all parts to the engineer. 8. The facility of communication between the engineer and the conductor of the train. In deciding upon the relative merits of the several motors, so far as the eight points included under this heading are concerned, it is clear that, except possibly as regards absence of noise, the electrical car surpassed all the others. The compressed-air car followed, in its superiority in respect of the first three points, viz., absence of steam, absence of smoke, and absence of noise; but the Rowan was considered superior in respect of the other points included in this class. Under the letter B have been classed considerations of maintenance and construction. 9. Protection, more or less complete, of the machinery against the action of dust and mud. 10. Regularity and smoothness of motion. 11. Capacity for passing over curves of Each of the motors under trial was small radius. managed by one man. The several conditions of the programme may be conveniently classified in three groups, under the letters A, B, C. Under the letter A have been classed accessory considerations, such as those of safety and of police. These are of special importance in towns. But their relative importance varies somewhat with the habits of the people as well as with the requirements of the authorities; for instance, in one locality or country conditions are not objected to, which in another locality are considered entirely prohibitory. The conditions under this head are: 1. Absence of steam. 2. Absence of smoke and cinders. 12. The simplest and most rational construction. 13. Facility for inspecting and cleaning the interior of the boilers. 14. Dead weight of the train compared with the number of places. 15. Effective power of traction when the carriages are completely full. 16. Rapidity with which the motor can be taken out of the shed and made ready for running. 17. The longest daily service without stops other than those compatible with the requirements of the service. 18. Cost of maintenance per kilometer, (It was assumed, for the purposes of this sub-heading, that the motor or carriage which gave the best results under the 3. Absence, more or less complete, of conditions relating to paragraphs 9, 10, noise. 4. Elegance of aspect. 5. The facility with which the motor 12, and 13, would be least costly for repairs.) As regards the first of these, viz., procan be separated from the carriage it-tection of the machinery against dirt, the self. machinery of the electrical car had no VOL. XXXIV.—No. 3—15 |