ELECTRICAL ENGINEERING PROBLEMS 621 



the only permissible method of conveying electrical energy from the 

 central station to the train. At any rate, this is the meaning con- 

 veyed to my mind by the fact that the New York, New Haven and 

 Hartford Railroad Company has asked permission of the legislature 

 to abolish the third rail and substitute in its place the overhead 

 trolley. But if the overhead trolley method is to be adopted, then 

 the smaller the number of wires employed to convey the elec- 

 trical energy to the train, the better. This seems to me to be the 

 real meaning of the extreme anxiety on the part of the electrical 

 engineer to design an asynchronous single-phase alternating-current 

 motor capable of developing large power. The results obtained 

 in this direction during the last few years are encouraging, and 

 they seem to have brought us very near to the solution of the heavy 

 electrical traction problem. Summing up the considerations dis- 

 cussed above, it seems that the composite judgment of the best 

 technical opinions can be stated somewhat as follows: Convey the 

 electrical energy from the station to the electrical locomotive by 

 means of a single-phase alternating current at high tension, say, 

 20,000 volts, employing, of course, a single trolley-wire. Let the 

 locomotive serve as a sub-station in which the high-tension current 

 is transformed down to a suitably low tension, and employ either 

 induction motors or direct-current motors to convert the low-ten- 

 sion electrical power into mechanical propulsion. 



The possibility of employing single-phase alternating currents 

 contributes very materially to the possibility of securing continuity 

 of service in heavy electrical traction by reducing the multiplicity 

 of contacts to a minimum; theoretically, one contact for each 

 locomotive. But that single contact must be rendered as secure 

 as mechanical art can make it. The trolley-wire hanging with a 

 convex curvature toward the track and supported on wooden poles 

 such as we see on ordinary trolley-roads would never do. In place 

 of the flimsy structures we must have well-anchored steel towers 

 supporting messenger-wires of steel hanging in catenary suspen- 

 sion, and to these the conducting trolley-wires are neatly and se- 

 curely attached so as to be at all of their points parallel to the track. 

 The whole structure when finished looks like an endless suspen- 

 sion bridge, the steel towers being the piers of the bridge. The 

 messenger-wire represents the gracefully curved span between the 

 piers, and the trolley-wire is the platform over which the traffic 

 of the bridge is maintained. Such trolley-lines have actually been 

 constructed and operated not only out West and in some parts 

 of Europe, as for instance on the famous Berlin-Zossen section, 

 but also on the Long Island Railroad, where electrical traction 

 on a somewhat larger scale is contemplated in the very near future. 

 Structures of this kind are extremely solid and quite capable 



