200 
MEASUREMENT OF HIGH TEMPERATURES. 
[BULL. 54.: 
These results are such an enormous improvement on the discrepancies 
of Table 48 that it seemed expedient to endeavor to further investigate 
the behavior of these instruments at high temperatures. If under these] 
conditions the bulbs show no greater variations than is in accordance 
with the above data, the further improvement of the bulb presents it-] 
self emphatically. Values of high temperatures sufficiently approximate 
for the present purposes are obtainable by the method investigated iifl 
Chapter II, where apparatus for calibrating thermoelements witli 
known boiling points are described. It seemed especially desirable toj 
make this high-temperature comparison in order that some definite pre-] 
liminary notion of the degree of accuracy of high-temperature dutaj 
in general might be independently obtained. Examples of these re- 
sults are given in the following tables, 50 and 51. The first of these] 
(Table 50) contains a comparison of the calibrated therm o-element 
and air thermometer made in the large gas-muffle furnace described on 
page 181. The junction of the thermo-couple having been tied wita 
asbestus wicking to the equatorial parts of the air thermometer, th 
whole bulb was thereupon surrounded with a non-conducting jacket o 
carded asbestus, from one to two inches thick, inclosed in a cylindrical 
asbestus box. Both the thermo-electric and the air thermometer meas- 
urements were made in time series, with one observer at each instruJ 
ment. 1 In this way the rate of heating or cooling of the furnace appears] 
among the results. As usual h is the (calculated) zero reading of the 
air thermometer, H the corresponding reading at the high temperature 
T, and at the time given in the same horizontal row. Again, t is the 
temperature of the cold junction of the thermoelement, e the corre- 
sponding electro-motive force, in microvolts T hg and T zn the calculated 
(thermoelectric) temperature when in the first case the calibration is 
carried only as far as the boiling point of mercury, in the second case 
when carried as far as the boiling point of zinc. T hg and T zn are the 
results of graphic interpolation, as explained in Chapter II, page 114. 
Table 50. — Comparison of air thermometer and thermo-element. 
Bulb No. 3 ; ft„= 
26. 6™> 
Thermo- 
couple IS! 
o. 36. 
H 
T 
Time. 
t 
«20 
Thg 
Tzn 
Time. 
cm. 
o(7. 
hours. 
°0. 
microvolts. 
*C. 
°<7. 
hours. 
330. 1 
60 
12.46 
24.7 
650 
97 
97 
12.52 
464.3 
207 
.53 
.8 
1530 
196 
196 
.55 
637.9 
389 
.57 
.8 
2220 
264 
268 
.56 
705.7 
462 
.60 
.9 
4270 
443 
460 
' .61 
759. 4 
519 
.63 
25.0 
6400 
596 
636 
.71 
817.1 
581 
.66 
.3 
7260 
655 
705 
.79 
Dr. Hallock kindly assisted me in this series of measurements. 
(854) 
