TEMPERATURE ON THE ELECTRIC CONDUCTING-POWER OF ALLOYS. 183 
made respecting some of the values given in this Table, namely, on those of the annealed 
wires. Elsewhere it has been shown that the conducting-power of hard-drawn wires of 
some metals is greatly altered by annealing them ; with the alloys this does not seem to 
be the case, for the differences here are very small. On account of their smallness we 
have not thought it worth while to investigate this matter any further at present ; for 
to arrive at such results as might show the connexion between the effect of annealing 
on the conducting-power of alloys and on that of the metals composing them, would 
require a long series of experiments. Although the percentage decrements in the con- 
ducting-power of these annealed wires are all somewhat higher than those of the hard 
drawn, yet they may be considered the same, as the percentage decrements in the 
conducting-power of hard-drawn and annealed wires of the pure metals vary also in a 
small degree, but not always in the same direction. Thus those found for silver were — 
Hard drawn. Annealed. 
28-67 28-82 
28-44 28-67 
27-82 ..... 28-21 
We have calculated, as will be seen in the Table, the percentage decrements in two 
ways : — 1st (a), using for the calculations the conducting-powers of the hard-drawn, and 
2ndly (b), those of the annealed metals. The values so obtained for the percentage 
decrement do not differ very much from one another. 
In calculating the results for the iron alloys, Pc has not been taken equal to 29-307, 
but for each alloy Pc has had to be calculated. Thus for the 1st, iron-gold, which 
contains 27'93 volumes per cent, iron, 
The conducting-power of 1 volume of iron may be said to lose between 0° and 
100° 38-260 per cent. ; therefore 0-2793 volume will lose 10-686 
That of 1 volume of gold may be said to lose between 0° and 100° 29-307 per 
cent. ; therefore 0-7207 volume will lose 21-122 
1 volume of iron-gold alloy, containing 27*93 per cent, iron, will therefore lose 31-808 
On comparing the values obtained for the conducting-powers, &c. of the iron-gold 
alloys, the following facts are worth mentioning, — their very low and almost identical 
conducting-powers, and the high percentage decrements found for the first two and the 
low one for the third. That there was no error in this value we convinced ourselves by 
remaking the alloy, which contained, according to analysis, the same percentage amount 
of iron as that given in the Table, and the percentage decrement in its conducting-power 
was found equal to 4 -04. Again, an alloy, made by a well-known firm*, which gave on 
analysis 11*94 volumes per cent, iron, conducted at 0° 2-097, and lost between 0° and 
100° 4-30 per cent, of conducting-power. Unfortunately experiments with alloys richer 
* We are indebted to Messrs. Johnson, Matthey and Co., of Hatton Garden, for many of tbe alloys experi- 
mented with. These were the first two, iron-gold, the platinum-silver, palladium-silver, and aluminium-nickel. 
MDCCCLXIV. 2 C 
