The measurements of speed were made by dividing the track into 19 sections of 500 ft., each section being provided with a circuit-closing plate connected with a chronograph which was carefully tested. The indicator cards were taken at the central station by Mr. Idell and his assistants, and the dynamometer used was of the liquid type made by Mr. Shaw, of Philadelphia. The diagrams prepared from the data obtained were then explained by the speaker, who stated that there was not a marked difference between the 10 ton motor and the 18 ton locomotive in the initial effort on the level, as will be seen by comparing a run observed by a railroad officer on March 9 with a steam motor and a load of about 571/2 tons. The steam motor required 1 min. and 29 sec. to make the distance from 14th to 23d streets, while the electric motor with a train of 70 tons made the same trip in 1 min. and 50 sec.; the absence of power brakes compelled the current to be taken off at 19th street, while it was probable that the throttle of the steam locomotive was not closed until it reached 23d street, this being the usual practice. The data obtained in these experiments shows that 29,940 h.p. is required to operate the Ninth avenue railroad for the 16 hours' service, or an average of 1,871 h.p. per hour, or 2,181 h.p., adding station friction. The varying requirements of the traffic during the day shows that the service could be advantageously divided up between four stationary engines of 800 h.p. each, there being but five hours of the day when all of them would be required. The fuel consumption per day, allowing 22 lb. of coal per h.p. per hour at $2.25 per ton, would make a total of $92.25 per diem for fuel, the coal being a mixture deliverable at the dock for about $1.80 per ton. The weight of coal used for the present locomotives is about the same, viz., 40 tons per day, but practice has shown it to be most economical to use coal of the best quality, costing $5 per ton, making the cost of fuel about double that required for the electric system. Without entering into other economies which the speaker claimed were in favor of electricity, and ignoring the plan suggested by Sir William Siemens of braking the train by converting the motor into a dynamo and thus utilizing the energy of momentum, he believed that the economy in fuel alone was sufficient to prove that the application of power by electricity was preferable to direct steam propulsion for the elevated railroad service. * * * * * MAGNETISM IN ITS RELATION TO INDUCED ELECTROMOTIVE FORCE AND CURRENT.[1] [Footnote 1: A paper read before the American Institute of Electrical Engineers, New York, May 22, 1889.] By ELIHU THOMSON.