3G 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[34J 



rent continues to flow. Fig. 12 shows a lamp screwed into its 

 socket. 

 By varying the length, and also the sectional area of the carbon 



thread, keeping the electromotive force constant, Edison has varied 

 the caudle-power of his lamps. In our circuit we have a few 1G candle- 

 power lamps, though most of them are of 8 candle-power only. The cop- 



Fig. 9. 



Fig. 10. 



per wires, being of high conductivity, and of ample size, 

 rent with but little warming, notwithstanding the 

 white heat of the carbons in the circuit ; by varying 

 the size of the wires it will be found they follow the 

 same law as to resistance and heating as the carbous. 

 Let E = the resistance of a conductor; S = its sec- 

 tional area; L = its length; a = a constant depend- 

 ing on material of which the conductor is made; then 

 S R = a L, and from this simple equation the relative 

 sizes of the wires and carbons have been determined. 



carry the cur- 



Fig 



