SfK WILLIAM SIEMENS, F.R.S 329 



the phenomena of lateral induction, and of faults in the insulating 

 (MM i ing, matters which had to be understood before submarine 

 telegraphy could be attempted with any reasonable prospect of 

 success. 



Regarding the transmission of power to a distance the electric 

 current has now entered the lists in competition with compressed 

 air, the hydraulic accumulator, and the quick running rope as 

 used at Schaffhausen to utilise the power of the Rhine fall. The 

 transformation of electrical into mechanical energy can be accom- 

 plished with no further loss than is due to such incidental causes 

 as friction and the heating of wires ; these in a properly designed 

 dynamo-electric machine do not exceed 10 per cent., as shown by 

 Dr. John Hopkinson, and, judging from recent experiments of 

 my own, a still nearer approach to ultimate perfection is attain- 

 able. Adhering, however, to Dr. Hopkinson's determination for 

 safety's sake, and assuming the same percentage in reconverting 

 the current into mechanical effect, a total loss of 19 per cent, 

 results. To this loss must be added that through electrical re- 

 sistance in the connecting line wires, which depends upon their 

 length and conductivity, and that due to heating by friction of the 

 working parts of the machine. Taking these as being equal to 

 the internal losses incurred in the double process of conversion, 

 there remains a useful effect of 100 - 38 = 62 per cent., attainable 

 at a distance, which agrees with experimental results, although in 

 actual practice it would not be safe at present to expect more 

 than 50 per cent, of ultimate useful effect, to allow for all inci- 

 dental losses. 



In using compressed air or water for the transmission of power, 

 the loss cannot be taken at less than 50 per cent., and, as it 

 depends upon fluid resistance, it increases with distance more 

 rapidly than in the case of electricity. Taking the loss of effect 

 in all cases as 50 per cent., electric transmission presents the 

 advantage that an insulated wire does the work of a pipe capable 

 of withstanding high internal pressure, which latter must be more 

 costly to put down and to maintain. A second metallic conductor 

 is required, however, to complete the' electrical circuit, as the con- 

 ducting power of the earth alone is found unreliable for passing 

 quantity currents, owing to the effects of polarization ; but as this 

 second conductor need not be insulated, water or gas pipes, 



