FIG. 31.—NEFF MOTOR.
FIG. 32.—WESTINGHOUSE ELECTRIC MOTOR.
All these motors were operated by voltaic batteries, and on account of the cost of the latter but little practical use of the electric motor was made until the dynamo was invented. In 1873 an accidental discovery led to the rapid practical development of the electric motor. It is said that at the industrial exhibition at Vienna in that year, a number of Gramme dynamos were being placed in position, and a workman in making the electrical connections for one of these machines, inadvertently connected it to another dynamo in active operation, and was surprised to find that the dynamo he was connecting began to revolve in the opposite direction. This was the clue that led to the important recognition of the structural identity of the dynamo and the modern type of electric motor. The dynamo and the electric motor then grew into development together, and the same inventors who brought the dynamo to its present high efficiency, produced electric motors of corresponding principles and value. In the illustration, [Fig. 32], is shown a modern electric motor. It is a Westinghouse two-phase machine, of 300 horse power, of the self starting induction type, designed to operate at a speed of 500 revolutions per minute when supplied with two-phase currents of 3,000 alternations per minute and 2,000 volts pressure.
FIG. 33.—SIEMENS’ FIRST ELECTRIC RAILWAY.
The most important application of the electric motor is for street car operation. The first electric railway was that of Dr. Werner Siemens, at Berlin, in 1879, an illustration of which is given in [Fig. 33]. The first electric railway in America was installed at Baltimore in 1885, and ran to Hampden, a distance of two miles.