322 LENZ ON THE VARIOUS CONDUCTING POWERS 
that thick conductors conduct electricity better than thin ones. How 
far the conductibility of metals is altered by even a very slight mixture 
of foreign substances, is proved by the experiments of Pouillet with 
wires made of different alloys of silver with copper, and gold with silver. 
These prove that their conductibility is far below that of pure unalloyed 
metals. Thus, for instance, the conductibility of fine gold = 84°41, 
that of the 18-carat gold = 14°77, whilst the silver with which the gold 
is alloyed is a much better conductor than fine gold itself. 
In order to avoid the inequality of the purity of the copper, I pro- 
cured the wires myself by cutting a thick piece of copper into smaller 
pieces, and drawing it afterwards to different thicknesses: but the thinner 
wires become thus by drawing somewhat more dense than the thicker 
ones, which produces always a difference in the substance. I endea- 
voured to remedy this evil by making the wires red hot before covering 
them with silk ; but the greater or less degree of heat may perhaps have 
some influence. 
From these observation it follows, that so close an agreement cannot 
be expected from the following experiments as from those made for 
the purpose of ascertaining the influence of the length of wires on their 
conductibility ; this agreement will, however, be sufficiently close to 
remove every doubt with respect to the correctness of the law to be 
established. 
The wires employed were, as has already been said, wrought all 
out of the same piece of thick wire, and drawn through the holes 
1, 6, 11, 18, 24, 30, with which numbers they are also marked in the 
table ; they were all heated to redness and overspun with silk, and were 
successively inserted between the electromotive spiral and the wire of 
the multiplier, and the deviation determined in the same manner as in 
the previous experiments. In order to obtain the proportion of the 
sections of the wires, I took 2 feet of each and weighed them before 
they were covered with silk. The weight is proportional to the section, 
and is as follows: 
Weight of 2 feet of wire No. 1 ...... 7°7370 grammes. 
NOs 62.000. 5°0250 
No. 11 ...... 3°2408 
No. 18 ...... 1-4783 
Ne! 24 ...... 0°7750 
It is not of much importance to know the absolute thickness of the 
wires, but it may be easily deduced from this, that the diameter of the 
wire No. 1 was nearly 0°046 Engl. line. 
The experiments were thus performed: I observed first the deviation 
without any wire being interposed, then with the interposition of No.1, 2, 
