206 
MEASUREMENT OF HIGH TEMPERATURES 
Table 53.— T and e 2 o- 
[bull. 54: 
I. 
II. 
III. 
T 
^20 
T 
e 2 o 
T 
e?o 
250 
2630 
350 
4050 
960 
1138 
300 
3050 
400 
4490 
995 
1176 
375 
3790 
450 
4860 
1080 
1340 
525 
5800 
470 
5100 
1100 
1373 
670 
7860 
550 
6560 
1130 
1445 
860 
10400 
600 
7050 
1180 
1520 
1016 
12850 
630 
7350 
1240 
1610 
1080 
13800 
702 
730 
820 
847 
1000 
1050 
1100 
1150 
1200 
1250 
8240 
8860 
10000 
10360 
13000 
13420 
14540 
15060 
15640 
15900 
1260 
1628 
The values of temperature are small relative to the electro- mo tivd 
forces. This would result if the stem error applied is too small by aj 
amount quite within the range of possible error, but it is more likely thai 
the thermo-couple is here at a temperature above that of the air ther 
mometer; in other words, that the environments are not identical. A 
reverse of this takes place on cooling; hence the use of a pimple non-rej 
entrant bulb for comparison is not at once permissible. It is necessarj 
if the results are to be uniform and comparable, that both bulb and ther, 
mo-electric junction be not only contiguous, but be enveloped in somi 
thick non-conducting substance. Such additional appliance is object 
tionable, since it interferes with quick and facile manipulation, and aj 
high temperatures is fused into the glaze of the bulb in a way that en 
dangers it. Mere contiguity of the junction and the bulb, even in casj 
of a revolving muffle, is not a sufficient guaranty for the accuracy d 
the calibration results obtained. 
Digression. — Before resolving to change the form of the bulb, I madjl 
another series of experiments, which have an ulterior interest, inasmuci 
as they are made with the soldered bulbs, glazed both within and wital 
out, which are described above, p. 175. It was also expedient, if not necfi 
essary, to change the method of measurement, and in the following 
results, Table 51, the constant-volume method is replaced by the coal 
stant-pressure method. The data are given in a way that will be fuUil 
explained in the next paragraph (p. 217), and it is here only necessary 
to refer to the time series of T, the temperature of the bulb, and of e^ 
the corresponding electromotive force. Corresponding values of e 2() an i 
(860) 
