Engineering Wonders of the World
Volume I

220 ENGINEERING WONDERS OF THE WORLD. Fig. 4.—AN ITALIAN ELECTRIC LOCOMOTIVE, WITH OVERHEAD CURRENT COLLECTORS. As examples of tunnel operation may be mentioned the use of electric locomotives for hauling steam trains, including the locomotive, through a long tunnel under the river at Balti- more ; through the St. Clair tunnel, by which the Grand Trunk Railway passes from Canada into the United States ; and the recently- opened Simplon Tunnel. In this article only the electric locomotive proper, and not the electric motor train, will be dealt with. On the Metropolitan and many other electric railways the current is collected from a conductor rail laid alongside the run- ning rails. In some cases there is a fourth rail for the return ; in others, only the con- ductor rail is provided, and the ordinary rails are bonded for return. Where traffic is heavy and frequent, and direct currents of moderate voltage are used, it is generally preferable to employ a con- ductor rail, to avoid the strain that would be imposed upon an overhead conductor wire, and also because a rail must be of large size (and expensive) to carry the high amperage (equivalent to volume) of current. Abroad, there is a tendency to employ high tension currents which can be conveyed by a com- paratively small overhead wire, and picked up by a trolley pole, or corresponding mechanism, placed on top of the locomotive. Similar sys- tems are being experimented with somewhat largely in this country, and two installations of this character are now in use—one on the Midland Railway between Lancaster and Morecambe and Heysham, the other on the London, Brighton, and South Coast Railway between Victoria and London Bridge. On the New York Central and Hudson River Railroad the trains are now operated for some distance at the New York end by large electric locomotives (Fig. 1). A series of compara- tive trials between steam and. th.es© electric locomotives were carried out when the latter were first introduced. Fig. 5 shows an elec- tric locomotive and train racing a steam in- spection engine. In this case the steam en