92 TRANSACTIONS OF THE [DEC. 21, 



Englisli horse-power equals 76.04 kilogrammetres per second, 



and, tlierefore. one liorse-power— . Eetnrninofasrain to the 



^ 745.9 == '=' 



ohm, we liave R= -. That is, the resistance is the loss of electro- 

 motive force per second and per unit of intensity which an elec- 

 trical current experiences when passing along a conductor. If 

 this conductor is the standard quick-silver column, R=l ohm. 



In an analogous manner we could say of a horizontal pipe 

 conveying water, that the resistance is the loss of head })er pound, 

 and per second, when passing through the pipe. 



The resistance of the various materials used as conductors for 

 the electrical cui'rent has heen repeatedly and carefully deter- 

 mined. 



I trust I have established a clear and cordial understanding of 

 the terms which I shall need to use. 



By the electro-motive force in volts, I mean something similar 

 to the head of water in feet. 



By the intensity of a current in amperes, I mean something 

 similar to weight of water passing in pounds per second. 



By the resistance in ohms, I mean something similar to the 

 loss of head of water per pound and per second. 



The dynamo-electric machine is the newest, and the most per- 

 fect of machines for the transformation of energy from one form 

 to another. Like the turbine, its efficiency has been proved so 

 great as to preclude all hope of further increase of practical 

 value. Its cost may be reduced by improved processes of the 

 machine shop, we cannot do more. 



One reason for this rapid perfecting lies in the apparent 

 obscurity of electrical phenomena, which lias had the effect of 

 repelling all but subtle and acute minds from their study. The 

 right end of the thread once seized by such minds, they have 

 followed the clue with such rapidity and thoroughness of appre- 

 hension as to leave nothing more for us to accomplish. 



The recent experiments of the Franklin Institute upon the 

 dynamos of Weston and Edison have set the seal of absolute 

 measurement, with as great exactitude as we can hope to reach, 

 upon the ability of these machines to transform mechanical work 

 into electrical work. 



Of the five dynamo-electric machines which successfully with- 

 stood the severe conditions of the code, Weston's mammoth 

 incandescent lamp machine, of a rated capacity of 125 amperes 

 and 160 volts, returned, as an average of four tests, in the form 

 of electrical energy QCij^^\ per cent of the mechanical power used 

 to drive it. SdjW _ 

 able as electrical energy in the external circuit. 



