The familiar overhead trolley cars, and the far superior conduit trolley system, represent perhaps the largest use made of electric motors. The motors are arranged under the cars in varying forms adapted to the structure of the car. In the overhead trolley, shown in Fig. 34, the current is taken from the overhead wire by a flexible trolley pole, and in the conduit system a trolley known as a plow extends from the bottom of the car through a narrow slot in the top of the conduit and makes a traveling contact with the conductor rails within the conduit, which carry the electric current. Fig. 35 is an end view of a street car of the latter type, with the conduit and conductor rails in cross section. The current goes from one rail to one bearing surface of the plow, thence to the motor on the car and back to the other bearing surface of the plow and the other conductor rail in the conduit. [Illustration: FIG. 36.--THIRD RAIL SYSTEM ON THE N. Y., N. H. & H. RAILROAD--FRONT END OF MOTOR CAR.] A third system, which has supplanted to some extent the use of steam on short line railways, is the so-called third rail system, of which an example is seen in Fig. 36. A third conductor rail is placed between the usual track rails, and from this conductor the current is taken by a sliding shoe on the car, and carried to the motor and thence through the car wheels to the track rails. To reduce danger from the live rail, the third rail in some systems is made in sections, and, by an automatic switching process as the car moves along, only the sections of the rail beneath the car are brought into circuit, all other portions being cut out. The use of electric motors has greatly extended, cheapened, and expedited the street car service. All the principal thoroughfares of cities and even towns are now so equipped, and radiating suburban lines extend for miles from the city, affording for five cents a pleasant and cheap excursion for the poor to the green fields and fresh air of the country. [Illustration: FIG. 37.--ELECTRIC RAILWAY MOTOR, CLOSED.] [Illustration: FIG. 38.--ELECTRIC RAILWAY MOTOR, OPENED.] Figs. 37 and 38 show an electric motor used on street cars, as made by the General Electric Company. Externally it presents the appearance of some curious, uncouth, cast iron box, which, to the uninitiated, piques the curiosity, and when opened adds no explanation of its real character. In it, however, the electrician finds a most interesting combination of metal and magnetism. [Illustration: FIG. 39.--ELECTRIC LOCOMOTIVE OF B. & O. TUNNEL IN BALTIMORE.]