250 
MEASUREMENT OF HIGH TEMPERATURES. 
[bull. 54. 
may be made to differ over quite a wide range, as is shown by tbe fol- 
lowing table : 
Table 80. — Thermal constants of the oil student lamp. 
d 
Time. e 
6" 
Remarks. 
cm. 
m. 

2 

4168 
414 
] 
^ Very low flame. 
2 
2 
7 
14 
4201 
4255 
416 
421 
2 
21 
4288 
423 
J 
3 
7437 
669 
1 
14 
14 
10 
20 
7593 
7G47 
681 
685 
}> Low flame. 
J 
14 
30 
7784 
695 
9 
,25 
10690 
904 
. 
9 
30 
10690 
904 
3 
3 
40 
60 
9563 
9563 
825 
825 
} High flame. 
14 
63 
11490 
956 
14 
69 
11490 
956 
J 
Incipient fusion of the glass 
1 
chimney surrounding the 
^ Flam* very high. 
flame. Devitrification. 
In Table 80, d denotes the depth of the junction of the thermo-couple 
below the top of the chimney, which top is about 20 cm above the mean 
height of the flame. 6", e, denote the temperature and the correspond- 
ing thermo-electric force of the thermo-couple used for measurement 
at the time given in the* second column. The thermo-couple in this 
instance was. No. 39 (calibrated above), and the junction, after be- 
ing surrounded by a little cushion of carded asbestus, was enveloped 
by a jacket of thin platinum foil fastened to the stem insulator. The 
junction is, of course, placed in the axis of the chimney, since tempera- 
ture decreases towards the walls. The highest temperatures are ob- 
tained by enveloping the chimney in the cylindrical tube of asbestus 
referred to above, in which case the glass is easily fused. Lower tem- 
peratures than those of the table may be obtained by lengthening the 
chimney with the asbestus tube and observing near the top. The aux- 
iliary tubes are suitably wired in position. 
In addition to the large interval of temperature, the Argand lamp has 
the advantage of furnishing an air bath. Since platinum is pervious to 
hydrogen (see below), direct exposure to the Bunsen flame introduces 
an error because of the hydrogen which passes through the metal. But 
this error does not seem to be serious unless the temperatures are very 
high. 
In all these cases the mean temperatures are satisfactorily constant, 
but it does not follow that temperature will be constant throughout the 
(904) 
