118 
MEASUREMENT OF HIGH TEMPERATURES. 
[BULL. 64 
fore to be discontinued. T would have the approximate significatior 
stated. The porcelain tubes again soften. 
In operating upon cadmium, I first tried glass tubes. But after manj 
trials the experiment was abandoned, both because of the decidedly re 
duced viscosity of glass at low red heat, and because the simple rin£ 
burner, even while a powerful pair of bellows is used to intensify the 
blast, is not capable of easily boiling cadmium. Hence the clay cruci 
bles were used and results were obtained as follows. The value of Tit 
here appended, as derived from Table 16, both for the case in which the 
exterpolation is made with zinc, and as made without zinc. The cad 
mium used is of commercial purity only. What I aim at here is a mere 
illustration of method. 
Table 20. — Crucible, Fig. 13, charged with cadmium. 
No. 
t. 
e. 
eto. 
Time. 
Cum zinc 
T. 
Sine zinc 
T. 
° a 
Micro- 
volts. 
Micro- 
volts. 
h. m. 
° a 
° a 
17 
21. 2 
7568 
7577 
12 38 
783 
734 
17 
22.8 
7626 
7648 
1 
790 
740 
17 
23.8 
7558 
7588 
18 
783 
735 
18 
21.6 
7541 
7553 
12 43 
785 
743 
18 
22.9 
7528 
7550 
1 3 
785 
743 
22 
21.9 
7568 
7583 
12 47 
784 
740 
22 
23.1 
7577 
7601 
1 6 
785 
742 
35 
22.2 
8346 
8363 
12 52 
785 
725 
35 
23.2 
8337 
8362 
1 10 
785 
725 
36 
22.5 
8333 
8352 
12 55 
784 
724 
36 
23.5 
8325 
8352 
1 12 
784 
724 
The results are given here chiefly by way of contrast with the above 
tables for bismuth and antimony, since they show an admirable de 
gree of constant temperature maintained for nearly one hour at j j 
relatively low temperature. Inasmuch as the interval between 500<| 
and 1,000°, if the assumed boiling point of zinc be correct, is anomalous 
and not simply quadratic, the interpolation here made for the measure 
ment of T is unsafe. Hence I have given T both as exterpolated fron 
calibrations (0° to 450°) excluding zinc, and as interpolated irom cali 
orations including zinc. If there were no anomaly the constancy of the 
values of T found by operating with divers elements would make these 
results very trustworthy. 
I have macle other similar experiments with selenium and with zinc 
chloride; but respecting all of these the remarks made for cadmiuir 
apply. Further data are therefore omitted here. 
Duration of continuous ebullition, low temperatures. — Returning froun 
this digression, I will next exhibit the constancy of temperature for the 
(772) 
