'314 LENZ ON THE VARIOUS CONDUCTING POWERS 



bility of wires, and we shall find that Ohm and Fechner calculated the 

 results of their experiments according to this principle ; whilst Davy and 

 Becquerel conducted their experiments in such a manner as to avoid the 

 errors which otherwise would have been the consequence of disregard- 

 ing it. This explains why the results of their experiments agree with 

 those of the German philosophers. Davj-, for instance, connected the 

 poles of a voltaic pile in two ways at the same time ; the one was by a sim- 

 ple wire, the other by an apparatus for decomposing water : the current 

 therefore was divided between these two paths, and the conducting power 

 of the current passing through the metal conductor was so far increased, 

 by shortening the length and increasing the thickness of the conductor, 

 that the current passing through the water became so weak that no de- 

 composition took place. Davy endeavoured to obtain the same limit 

 by means of wires of different thicknesses, and in this manner found that 

 two wires of different thicknesses attained the same limit when their 

 lengths were proportional to their sections. Both connecting wires at- 

 taining thus the same strength of current, it would be necessary to bring 

 the conductibility of one w ire to be exactly equal to that of the other, 

 independent of every theory of the dependence of the intensity of the 

 current on the parts of the voltaic arrangement, in order to ascertain the 

 proportion of the length to the thickness. Such experiments would 

 certainly produce results containing nb decisive errors ; they will, how- 

 ever, admit but little accuracy of determination. 



Becquerel coiled two wires of the same substance, but of different 

 length and thickness, round the frame of a multiplier, so that the coils 

 of the one laid between those of the other ; when therefore a current of 

 the same strength was passed through them in opposite directions the 

 needle of the multiplier remained at rest. He joined the ends of each 

 wire with the same voltaic pile, but in opposite directions with respect 

 to its poles. The wires having different sections, the current was, for 

 equal lengths, stronger in the thicker than in the thinner wire, and he 

 therefore found a deviation of the needle of the multiplier. He then 

 diminished the length of the thinner wire till the current became equal 

 in both, — that is to say, till the index returned to its place of rest. He 

 thus obtained two wires of different length and thickness, which both 

 conducted the electricity equally well ; and concluded, from comparing 

 their dimensions, that in equally good conducting wires of the same 

 substance the lengths are proportional to the masses, that is to say, to 

 the sections. It is this proposition alone which the experiments of Davy 

 also demonstrate, and Ritchie is perfectly right in objecting to experi- 

 ments of this kind ; but he unjustly charges Becquerel with not having 

 well observed it h'mself. It was only after having ascertained by other 

 f xperiments that the conductors are in an inverse ratio to the lengths, 



