134 
MEASUREMENT OF HIGH TEMPERATURES. 
[BULL. 54 
ferent from the above. In two respects, however, must the following 
results*for specific resistance vary essentially from the former results 
During the process of drawing the wires down from the larger sectior 
(10 6 x q= 12,000 D cm ) to the smaller section (10 6 x # = 1,200 o cm ), break 
ages are not always avoidable nor even unfrequent; hence, it is neces 
sary to refuse and to work the metal over thoroughly. Thus it happens 
that certain metallic constituents are partially volatilized. Again, the 
thin and thick wires can not be identical in homogeneity in the way 
called for by the present measurement unless the thick wires were 
themselves thoroughly homogeneous at the outset, a condition not to 
be premised. Hence the data of Table 31, the symbols of which have 
the same signification as in Table 30, will not be rigorously identical. 
The present data of resistance of thin wires are to be compared in the 
sequel with the thermo-electric and other data of the same wires. It is 
thus manifestly necessary to evaluate the respective constants of small 
lengths or parts of each of the wires. Inasmuch as all the data may be 
obtained accurately from less than 10 cm of wire, and since for thermo- 
electric comparison only a mere point of this same partial length is nec- 
essary, it is obvious that the galvanic and thermo-electric constants may 
be obtained from a length of wire, the homogeneity of which may be 
assumed with impunity. For the total length being from 100 cm to 200 cm 
the efficient length is in every case less than one-tenth the length of the 
whole wire. It will be seen below that the stress I place on these re- 
sults is by no means superfluous. 
These remarks lead directly to Table 31. 
Table 31. — Electrical resistance of platinum alloys (thin wires). 
No. 
Alloy. 
n 
t 
#xl0 6 
12370 
19 
1257 
13300 
19 
1439 
15620 
19 
1452 
17380 
19 
1452 
13490 
22 
1466 
15450 
22 
1486 
22360 
22 
1548 
13170 
22 
1493 
14170 
22 
1520 
16490 
22 
1486 
13110 
22 
1534 
13740 
22 
1534 
15960 
22 
1520 
20660 
21 
1562 
22000 
21 
1548 
40330 
20 
1576 
15160 
23 
1713 
31520 
23 
1706 
14170 
22 
1583 
17*70 
22 
1576 
Platinum . 
..-.do 
Gold 
....do 
....do 
Silver 
....do 
....do 
Palladium 
....do 
....do 
Iridium... 
....do 
....do 
Copper . . . 
....do 
....do 
... do ..... 
....do 
Nickel 
....do 
15.55 
19.13 
22.68 
25.23 
19.78 
22.96 
34.61 
19.67 
21.54 
24.50 
20.11 
21.07 
24.26 
32.27 
34.06 
63.56 
25.98 
53.78 
22.44 
27.54 
(788) 
