Different success of this pioneer railway stimulated the ingenuity of inventors on both sides of the Atlantic, and the progress made in the development of this mode of transmission has been most surprising. At the present time the plans in use may be divided into (T) the overhead system, in which the current, generated at a central station, is conveyed to the motor-truck by a contact-trolley communicating- with an overhead conductor carried on a line of posts (pl. 37, fig. 1); (2) the third-rail sys tem, in which a suppletnentary rail conveys the current from the station, the motor attached to the car-truck taking the current from this and returning- it through the ordinary rails; (3) the underground conduit, in which an insulated conductor is placed, and from which the current is caused to actuate the motor on the truck through the intervention of vari ous forms of contact devices passing- throng-1i a suitable slot provided in the conduit for that purpose; and (4) the storage-battery system, in which the railwav-car carries its own supply of electric power in the form of second ary batteries (accumulators) that have been previously charged. These are placed in a recess provided for their reception iu the sides of the car, and are placed electrically in connection with the motor-truck.
The storage-battery system would appear to be the ideal system. It dispenses with the necessity of a continuous conductor, the electrical gen erator and motive-power are all contained within the car, and there is apparently an entire absence of any possibility of danger to passengers. The Julien storage-battery system at the present time appears to be the representative one of its kind, and has lately been introduced with satisfac tory results on the Fourth Avenue surface-road in New York City. The system, however, is open to the objection that the amount of weight required to be carried to furnish the necessary power is considerable, and it does not return so high a percentage of useful effect as could be wished. These deficiencies, however, bid fair to be remedied in time. The system of Sprague, employing the overhead conductor, appears to have taken the lead in popular favor in American cities, as the table opposite will exhibit. A view of the latest form of electric motor-truck employed in the Sprague system is shown in Figure 6 (pt. 36).
Electric Railzcavs in may be stated, as a fact of general interest, that in the matter of applying electricity as the motive-power this country is far in advance of Europe, where little has been practically accomplished in this direction. Many thousands of electric motors are in regular service in all parts of the United States, and the application of the electfic system to street railways in cities and towns is rapidly extending-. As a matter of historic interest, there is appended a list of the railways in Europe and America which employ electricity as the propelling power.
This list, so far as reliable data can be obtained, is complete up to January 1, 1889: The foregoing includes only the electric railways that are actually in operation. The major portion of those in the United States has been con structed within the past two years. The number of such roads now in course of construction or projected in various cities and towns in the United States will greatly exceed those already open for traffic, from which a fair idea may be had of the rapid growth of the innovation on this side of the Atlantic.
Gravity-railway.—An ingenious gravity-railway adapted for use in cities is the system devised by an American inventor (Thompson) and shown on Plate 36 (fig. 7). ln this the locomotive is dispensed with. The track is undulating-, the inclines being- so disposed with relation to the stations that the car, when started from one station, shall be carried by gravity and at a good rate of speed to the next station. As the car approaches the station a gripping mechanism operating automatically engag-es with a moving cable (actuated by a fixed engine at the stations), bv which it is drawn up over the incline, and also, when it is desired to start from the station, over the incline beyond, when it proceeds on its wa:,,• to the next station by gravity, as before. The plan is an ingenious modifica tion of the so-called " coasting railways " in common use at seaside resorts and the like. Figure 8 exhibits one of these coasting-roads erected at Boulogne-sur-Mer.
Elevatea' Roads in city of Berlin possesses an elevated railway about seven and one-half miles in length. The structure is in the form of an elevated masonry arcade. In Philadelphia the central station of the Pennsylvania Railroad is situated in the heart of the city, which the road enters and traverses on an elevated masonry structure, io8 feet wide and with nine tracks, extending from the Schuylkill River to Broad street. In .New York City the Fourth Avenue improvement of the Harlem Railroad Co/. 37, fig. 4), extending from Forty-second street to One Hun dred and Thirty-third street—a distance of four and a half miles—provides for four tracks, to accommodate express and way traffic. Of the entire distance, one section of 69373', feet is open cut, one of 4562Y3 feet is via duct, and the remainder ao,662 feet) is tunnel or covered way. New York City is provided with the most extensive system of elevated railways in the world, traversing nearly the entire length of Manhattan Island; and the neighboring- city of l3rooklyn has also elevated railways. These structures are supported upon iron columns, permitting unimpeded traffic on the sur face beneath them. Plate 35 (fig. 5) is a view of a portion of the Metro politan Elevated Railway, in New York.