$14 LENZ ON THE VARIOUS CONDUCTING POWERS 
bility of wires, and we shall find that Ohm and Fechner ealculated 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. Davy, for instance, connected the 
poles of a voltaic pile in two ways at the same time; the one was by asim- 
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 
Jengths 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 wire 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 no 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 Jaid 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 eléctricity 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 himself. It was only after having ascertained by: other 
experiments that the conductors are in an inverse ratio to the lengths, 
