OF WIRES FOR ELECTRICITY. 313 



the term conductibility. The latter is inversely proportional to the con- 

 ductibility, so that when L signifies conducting resistance, 



L= U_. 



conductibility 



If therefore the conducting resistance of a galvanic arrangement be ex- 

 pressed by L, and its electromotive power by A (which we may here 

 suppose to be produced either by contact or chemical affinity), then 

 Ohm's formula for the power of the current will be 



But L expresses not only the conducting resistance of the connecting 

 wire, but that of the entire voltaic arrangement; that is to say, the sum 

 of all the conducting resistances of the fluid and of the fixed parts of the 

 circuit. If we take for unity of conducting resistance the length and 

 thickness of a wire of a given substance, we may in this unity express 

 by I the resistance of the battery itself (both plates and acid taken to- 

 gether); and by \ the resistance of the connecting wire, the conducti- 

 bility of which is to be ascertained ; and the formula will then stand 

 thus: 



F- A 



which will give for the conducting resistance of the connecting wire 



We may take the electromotive power itself for unity, should it re- 

 main unaltered, which is almost always the case in experiments on the 

 conductibility of wires ; the formula will then stand thus : 



By closing now the battery with wires of diflTerent conducting re- 

 sistances, \/jy X/,y X/gy &C., and denoting the corresponding currents 



• by F/jy F/gy F^gy we shall have the following proportion : 



The conducting resistances therefore are not in an inverse ratio to 

 the intensities of the observed currents, or in a direct ratio to the con- 

 ductibilities ; but we must deduct from the latter the constant quantity 

 / before such proportion can obtain. 



After having established this simple principle, let us now return to the 

 above-mentioned experiments of various philosophers on the conduct!- 



