160 
MEASUREMENT OF HIGH TEMPERATURES. 
[hull. 34. 
simply varying temper. It is obvious therefore that data derived from 
the steel series alone, will be more trustworthy than any others. From 
x= 15.9, 
y= 0.00423, 
28.9, 
0.00244, 
45.7, 
0.00161, 
as directly found for the steel series, there follows 
1=0 JS, m= -0.0001435, n = 0.0682. 
Here the constant I is much smaller, being about 5 per cent, of the 
smallest steel value of x admitted. A similarly favorable result is 
obtained by adding cast-iron to the steel series, and I have therefore 
ventured to assume the equation x(y-{-m)=n, conformably with the 
method of discussion adopted in treating the platinum series. 
Applying the method of least squares to data for steel and cast-iron, 
the results in Table 406 are obtained. /(0) (a+m)=n. 
Table 40/;. — Computation of m and n for iron- carburets. 
No. 
Temper. 
/(0) 
a a 
observed, calculated. 
Diff. 
Steel 
13 to 15.... 
Soft 
15.9 
18.4 
20.5 
26.3 
28.9 
45. 7 
78.5 
0.00423 0.00417 
+ 6 
- 6 
- 3 
+11 
- 5 
-12 
+ 10 
Annealed light blue 
0. 00360 
0. 00330 
0. 00280 
0. 00244 
0. 00161 
0. 00129 
0. 00366 
0. 00333 
0. 00269 
0. 00249 
0. 00173 
0. 00119 
Annealed light yellow 
m = — 0. 000438 ± 0. 000097. 
n = + 0. 05930 ± 0. 00151. 
Applied to steel alone the same method furnishes the constants 
m= -0.000303± 0.000079 
n= +0.0620 ±0.0017; 
applied to Matthiessen's data for pure iron (a?=9.4, y=0.0052), in addi- 
tion to the present data for steel and cast-iron 
m=0.001242± 0.000186 
rc=0.0383 ±0.0034; 
In the latter instance, as in the case above, the computed curve does 
not coincide well with the curve graphically obtained. It is curious to 
note, however, that the constant ??, where iron, steel, and cast-iron are 
selected, is near the same constant for platinum alloys. The values are 
w=0.0383 for iron-carburets and w=0.0378 for steel. Whether this is 
more than a coincidence I am not now prepared to say, and I have ad- 
hered to the values in Table 41, because these are most trustworthy sq 
(814) 
