26 
DE. A. MATTHIESSEN AND M. VON BOSE ON THE INELIJENCE OE 
Table XX. 
T. 
Couducting power. 
Difference. 
Conducting 
power, 
calculated from 
formula of 
four terms. 
Difference. 
Observed. 
Calculated from 
formula of 
three terms. 
i6-9 
95-169 
95-134 
-1-0-035 
95-166 
-f- 0-003 
30-1 
88-537 
88-588 
— 0-051 
88-534 
-1-0-003 
49-5 
82-610 
82-627 
-0-017 
82-605 
-f 0-005 
69-0 
77-320 
77*297 
-1-0-023 
77-304 
— 0-014 
82’8 
73-976 
73-926 
-f 0-050 
73-966 
-f 0-010 
97-9 
70-579 
70-619 
— 0-040 
70-580 
-0-001 
The formula of three terms, deduced from the observations, was 
X=99-137-0-37675^+0-0008728f, 
and that of four terms 
X = 99-307-0-39301#+0-0012318f-0-000002193f. 
From the above it will be seen how much better the observed values agree with the 
formula of four terms. We have, however, contented ourselves with a formula of three 
terms, as the conducting powers calculated from it agree with those observed to values 
corresponding to 0°T or 0°’2, and as the calculations for a formula of four terms would 
have increased the labour of the research to a very great extent. But it may be asked 
how it happens that the formulae obtained for wires of one and the same metal vary so 
much, in fact, show differences almost equal to the mean of those deduced for the 
different metals ] 
That this is not due to errors of observation we have repeatedly satisfied ourselves ; 
for compare only the formulae of the hard-drawn (or rather partially annealed) and the 
annealed wu'es, and see how well they agree with each other. It appears, however, to 
be probably due to the molecular arrangement of the wires being different in each case. 
Take, for instance, the copper wires experimented with : wire 1 increased in conducting 
power by heating to 100° for several days, almost to the same extent as if it had been 
annealed, wire 2 partially so, and wire 3 hardly at all ; and here it may be mentioned 
that silver and copper wires become softer and lose their elasticity, whereas gold does not 
seem to be annealed at all after having been kept at 100° for several days. Again, take 
cadmium, where we know that the wires become brittle and crystalline at 80°, and we find 
the formulae vary more than those of any other metals ; and, lastly, look at the results 
obtained with bismuth and tellurium, and there can be little doubt that the reason why 
the formulae of the wires and bars of the same metal do not agree together is that the 
molecular arrangement is different in each ; and that this is the cause of the differences 
in the formulae, we may also assume from the fact that, when the wires on being heated 
do not at all or only to a very slight degree permanently alter in their conducting power, 
when cooled again, then the formulae of wires of the same metal agree very closely with 
each other. Compare, for instance, those of lead, tin, mercury, &c. 
