1882.] on Electric Eailivays. 69 



work done by the steam-engine on the generator, quite y^^ of a foot- 

 pound of work can be done by the distant motor. 



One reason why electric transmission of power can be effected with 

 so little waste is because electricity has aj^parently no mass, and con- 

 sequently no inertia ; there is, therefore, no waste of power in making 

 it go round a corner, as there is with water or with any kind of 

 material fluid. Another reason why electro-motors are so valuable for 

 travelling machinery is on account of the light weight of the motor. 

 Experiment shows, that one horse-power can be developed per 50 lbs. 

 of dead weight of electro-motor ; a result immensely more favourable 

 than can be obtained with steam, gas, or compressed-air engines. 



In addition to the loss of power arising from the heating of the 

 wires by the passage of the current, there is another kind of loss that 

 may be most serious in the case of a long electric railway, viz. that 

 arising from actual leakage of the electricity due to defective insulation. 

 To send an electric current through a distant motor, two wires, a " going " 

 and " return " wire must be employed, insulated from one another by 

 silk, guttapercha, or some insulating substance ; and if the motor be 

 on a moving train, there must be some means of keeping up continuous 

 connection between the two ends of the moving electro-motor and the 

 going and return wire. The simjilest plan is to use the two rails as 

 the two wires, and make connection with the motor through the 

 wheels of the train ; those on one side being well insulated from 

 those of the other, otherwise the current would pass through the 

 axles of the wheels, instead of through the motor. It is this simple 

 plan that is employed in Siemens' Lichterfelde Electric Railway, now 

 running at Berlin ; the insulation arising from the rails being merely 

 laid on wooden sleepers having been found sufficient for the short 

 length, li mile. The car is similar to an ordinary tram-car, and 

 holds twenty passengers. [Photographs were then projected on the 

 screen of this and of the original electric railway laid by Siemens in 

 the grounds of the Berlin Exhibition of 1879, and exhibited in 1881 

 at the Crystal Palace, Sydenham.] It was explained, that on this 

 latter railway, which was 900 yards long, both the ordinary rails were 

 used as the return wire, and that the going wire was a third insulated 

 rail rubbed by the passing train. [Photographs were then projected 

 on the screen of Siemens' electric tram-car at Paris, used to carry fifty 

 passengers backwards and forwards last year to the Electrical 

 Exhibition.] In this the going and return wires were overhead 

 and insulated, connection being maintained between them and 

 the moving car by two light wires attached to the car, and which 

 pulled along two little carriages running on the overhead in- 

 sulated wires, and making electric contact with them. [Experi- 

 ments followed, proving that although two bare wires lying 

 on the ground could be quite efficiently employed as the going and 

 return wire, if the wires were short and the ground dry, the leakage 

 that occurred if the wires were long and the ground moist was so 

 great, as to more than compensate for the absence of the locomotive.] 



