132 
MEASUREMENT OF HIGH TEMPERATURES. 
[BULL. 54. 
by a suitable spring. One of these riders (Fig. 25) is detached, and 
shown at r. In using Matthiessen and Hockin's method, it is merely 
necessary to connect a, b, e, d, successively with the galvanometer. 
Figs. 24 and 25. Resistometer with detached rider. Scale J. 
Table 30 contains the numerical results investigated by aid of this* 
apparatus. r t is the resistance (ohms) at. the temperature t for the sec 
tion q cm , and s t the corresponding specific resistance (microhms). The 
length of rider indicates the efficient length of platinum rod for whichi 
any datum applies. The value of 6 t in parenthesis refers to thin wire 
as containued in Table 31. 
Table 30. — Electrical resistance of platinum alloys (thick ivires). 
[rider — length = 10.04 cm . j 
No. 
Alloy. 
Platinum 
..do 
Gold 
...do 
...do 
Silver 
...do 
.. do 
Palladium 
--do 
--do 
Iridium 
...do 
... do 
(78C) 
rt 
t 
9 
St 
(st) 
1245 
20 
0. 01233 
15.35 
15.5 
1285 
18 
0. 01187 
15.26 
15. 5 
1424 
20 
0. 01333 
18. 98 
19.2 
1678 
21 
1343 
22.44 
22. 7;' 
3441 
21 
0743 
25.58 
25.9 
1516 
22 
0.01285 
19.48 
19.7 
1802 
22 
1265 
22. 79 
23. 
4586 
22 
0759 
34.80 
35.2 
1560 
21 
0. 01252 
19.53 
19.7! 
1628 
20 
1314 
21.40 
21.6 
1864 
20 
1280 
23.86 
24.1 
1571 
17 
0.01265 
19.87 
20.1 
1642 
17 
1289 
21.17 
21. 4 i 
1909 
17 
1280 
24.43 
24.7. 
