34G THE CANADIAN NATURALIST. [Vol. X. 



shown by Dr. John Hopkinson, and, judging- from recent experi- 

 ments of my own, a still nearer approach to ultimate success is 

 attainable. Adhering, however, to Dr. Hopkinson's determina- 

 tion, for safety's sake, and assuming the same percentage in 

 re-converting the current into mechanical effect, a total loss of 

 19 per cent results. To this loss must be added that through 

 electrical resistance in the connecting line wires, which depends 

 upon their length and conductivity, and that due to heating by 

 friction of the working parts of tlie machine. Taking these as 

 being equal to the internal losses incurred in the double process 

 of conversion, there remaios 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 pres- 

 ent to expect more than 50 per cent of ultimate useful effect, 

 to allow for all mechanical 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 at 50 per cent, electric transmission presents the ad- 

 vantage 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 conducting power of the earth alone is found unreliable 

 for passing quantity currents, owing to the effect of polarisation ; 

 but as this second conductor need not be insulated, water or gas 

 pipes, railway metal or fencing wire, may be called into requisi- 

 tion for the purpose. The small space occupied by the electro- 

 motor, its high working speed, and the absence of waste products, 

 render it specially available for the general distribution of power 

 to cranes and light machinery of every description. A loss of 

 effect of 50 per cent does not stand in the way of such applica- 

 tions, for it must be remembered that a powerful central engine 

 of best construction produces motive power with a consumption 

 of two pounds of coal per horse-power per hour, whereas small en- 

 gines distributed over a district would consume not less than 

 five ; we thus see that there is an advantage in favor of electric 

 transmission as regards fuel, independently of the saving of labor 

 and other collateral benefits. 



To agriculture electric transmission of power seems adapted 



