The experiments of M. Marcel Deprez have entered on a decisive phase. The dynamos are completed, and were put in place on the 20th October, when M. Deprez carried out some preliminary tests in the presence of a commission consisting of MM. Collignon, Inspector-General des Ponts et Chaussées; Delebecque, Ingenieur en Chef du Materiel et de la Traction of the Northern Railway of France; Contanini, engineer in the same company; and Sartaux. The generating dynamos made by MM. Breguet, and the receiving dynamos constructed by MM. Mignon and Rouart, were during a preliminary trial placed side by side, one portion of the circuit being very short, and the other twice the distance between La Chapelle and Creil, or seventy miles. In future experiments the two dynamos will be placed in their normal positions at each end of the line. The generating machine is driven by a locomotive engine; the resistance of its field magnets is 5.68 ohms, and of the two armatures 33 ohms. The resistance of the two armatures of the receiving machine is 36.8 ohms, and the resistance of the line is 97 ohms; the generator and receiver field magnets are excited each by a separate machine.
Five different trials were made at varying speeds of the driving shaft; the initial work on this shaft was measured by a dynamometer, and the available energy of the shaft of the receiving machine was ascertained by a Prony brake; the other results of the experiments were deduced from the constants of the machines and from galvanometric measurements. For the first trials the different elements were as follows:
1. Generating dynamos: Velocity of shaft 123 revolutions. Electromotive force at terminals, 3370.25 volts. " " total 3624.7 " Available work at driving shaft. 43 h. p. Electrical work of generator 37.38 " Difference absorbed 5.62 " 2. Line: Work absorbed by the line. 7.59 h. p. 3. Receiving dynamos: Velocity of shaft 154 revolutions. Electromotive force at terminals, 2616.25 volts. " " total 2336.94 " Electrical work of receiver 24.10 h. p. Available work on shaft 22.10 " Difference absorbed 2 "
The duty obtained would thus be 22.10/43 = 51.3 per cent., if the work absorbed by the exciting machines be not considered. Taking this into account, it would be reduced to 40 per cent.
In subsequent experiments the speed of the generator was increased gradually. In the last trial the following were the elements:
1. Generating dynamos: Speed of shaft 190 revolutions. Electromotive force at terminals 5231.25 volts. " " total 5469.75 " Available work on driving shaft, 62 h. p. Electrical work on generator 53.59 " Difference absorbed 8.51 " Work absorbed by armature 2.33 " 2. Line: Work absorbed by conductors 7.21 h. p. 3. Receiving dynamos: Speed of shaft 248 revolutions. Electromotive force at terminals 4508 volts. Electromotive force total 4242.67 " Electrical work of receiver 41.44 h. p. Work measured on receiver shaft 35.8 " Difference absorbed 5.64 " Duty obtained, not including exciting machine 57 per cent. Duty obtained, including exciting machine 48 "
During the various experiments the current traversing the line varied from 7.59 amperes to 7.21 amperes. No heating of any kind was observed.
M.J. Bertrand, who communicated a paper to the Academy of Sciences on the subject, commented on the relatively low speeds. It corresponds to a linear displacement of the surface armatures, in no case exceeding the speed of a locomotive wheel. The tension reached 5,500 volts., under very satisfactory mechanical conditions, and with a current that in no way endangered the line. This first experiment is certainly encouraging, and it will be followed by others of a more complete and exhaustive character. MM. De Rothschild are now embodying a powerful commission of French and foreign scientists who will follow the subject carefully, and report upon it. It may be safely predicted that one result of this action will be the development of a new series of observations of the highest technical interest and value. - Engineering.