102 TRANSACTIONS OF THE [DEC. 21, 



It will be a surprise to me should not the direct conversion of 

 heat into electrical power prove to have quite as many difficulties, 

 -and as narrow limits as the conversion of heat into mechanical 

 power by means of the steam engine. 



The Conversion of Electrical Power into Meclianiccd Poiver. 



The problem which just now is demanding of electricians their 

 most earnest effort, is the transmission of work by means of 

 electricity. This effort will be repaid by the utilization of other- 

 wise inaccessible water-powers ; and the problems of locomotion 

 will have their simplest and least objectionable solution when it 

 is an accomplished fact. 



Marcel Deprez has recently transmitted 80 horse-power from 

 Creil to Paris with a mechanical efficiency of 53 per cent. 



The expense attendant upon an experiment of this magnitude 

 has been very great, but the scientific possibility once proved, we 

 can rely upon the progress of manufacturers to reduce this 

 expense, and to define the limits within which power can be 

 economically delivered. 



Seventy-five percent of the indicated power of the engine is not 

 an overestimate of the power required to move the cable alone 

 for our cable cars on a road of two or three miles length, but it 

 would at once condemn an electric railway, which should be 

 made to yield a practical efficiency of over 50 per cent. 



Before discussing the details of the transmission of power, I 

 Avill, with the aid of our previously-used hypothetical fluid and 

 pipe, and with two pumps to represent the dynamo and motor, 

 endeavor to make clear to you the laws controlling the transmis- 

 sion of ])ower by electricity. 



I must again remind you of the fact that I disclaim any knowl- 

 edge of the real nature of electricity, and that I am reasoning 

 from analogy alone. 



Assume two pumps, Fig. 5, A and B, connected by a closed 

 line of pipe so that the fluid must be pumped round a closed 

 circuit. Let the pump A be driven by means of any external 

 power. Let the pump B be reversed and acting as a motor. 

 Let each of these pumps have a vertical stand-pipe projecting 

 from its top, which will show the head E or e resulting from its 

 action. The pump A acts under the law that its head E is pro- 

 portional to the speed at which it is driven. The motor B acts 

 under a similar law that its counterhead e is proportional to the 

 speed at which it is allowed to run. The weight of fluid, per 

 second, passing through the conduit, is directly proportional to 

 the difference of these heads, and, inversely, to the resistance. 



Let I equal the weight of fluid passing along the pipe each 



cond. 



