TEMPERATURE ON THE ELECTRIC CONDUCTING-POWER OF ALLOTS. 
187 
if the constant r t — r’t be determined, then 
r 100 c =r , 100 ° + constant, 
r t =i J t + constant, 
r 0 o =r' a . -f- constant; 
and from these terms a formula for the correction of resistance or conducting-power for 
temperature may be calculated, which in most cases will be found very near the truth. 
Thus, take, for instance, the gold-silver alloy containing 79‘86 volumes per cent, gold 
(hard drawn), and we find 
the first observed conducting-power . . . 2T010 at 11°;7, 
that calculated . 78-866 at ll°-7, 
hence the resistance observed is ... . 475-96 at ll°-7, 
that calculated 126-80 at ll°-7 ; 
therefore 7* f — r' if =349T6. 
But the calculated resistance at 0°=12T36, 
50°=145-75, 
„ „ „ ..... 100°=171-67, 
therefore r, the -true resistance, will be at 
0°=121-36 + 349-16 = 470-52, 
99 99 99 99 
99 99 99 99 
or the conducting-powers will be at . 
99 99 99 99 
50°=145-75 + 349-16=494-91, 
100°=171-67 + 349-16=521-83 ; 
0°=21-253, 
50°=20-206, 
99 99 99 
99 
100°=19-200. 
The formula deduced from these numbers is 
*=21-253-0-021350£+0-000008200f. 
The conducting-power, according to this formula, of the alloy at ll°-45 will be 21-010 ; 
but after having kept the alloys at 100° for three days it altered, and was found at that 
21-031 
temperature to conduct 21-031. If the above formula be multiplied by ^-——=1-001. 
we arrive at 
*=21-274 — 0-0213722 + 0-000008208* 2 ; 
and if the conducting-powers be calculated for the different temperatures in the following 
series, the difference between the observed and calculated values will be found to be 
very small. 
T. 
Conducting-power. 
Difference. 
Observed. 
Calculated. 
11-45 
21-031 
21-031 
0-000 
26 04 
20-698 
20-723 
-0 025 
4004 
20-391 
20-421 
-0 030 
55-26 
20-065 
20118 
-0 053 
6773 
19-806 
19-864 
-0 058 
8413 
19-463 
19-534 
-0-071 
98-45 
19175 
19-250 
-0-075 
