TEMPERATURE AND STRUCTURE OF THE SUN. 83 
nr = 4.03 X 10 33 cm. 
c 
5.42 X 10 — 5 <//•- 
1.34 x 10 ~ 43 sec. 
3.63 x 10 32 °C. 
1 hcse natural units depend only on the radiation of the 
black body, the force of gravitation, and the velocity of light. 
According to the measurements of Lummer and Prings- 
iieim, the radiation laws of the black body are exact up to 
2o00 C., and can be considered to be true laws of nature. 
A e are therefore justified in basing upon these laws our 
scale of temperature. Each of these laws can serve as a 
loundation upon which to establish a method of measuring 
temperatures. 
Let me tell you in a few words about the experimental 
verification of the first law, 
o 
S k d\ = aT\ 
In the following table our results are reproduced : 
No. 
I. 
Type of 
black body. 
II. 
Abs. temp, 
observed. 
III. 
Reduced 
deflection . 
IV. 
C X 10 10 . 
V. 
Abs. temp, 
calculated. 
VI. 
T. obs. — 
T. calc. 
1 
Steam boiler. . . . 
373,1 
156 
127 
374,6 
— 1,5° 
2 
Fused salt bath. 
492,5 
638 
124 
492,0 
+ 0, 5 
3 
1 ( 
723,0 
3 320 
124,8 
724,3 
— 1,3 
4 
i c 
745 
3 810 
126,6 
749,1 
- 4d 
.5 
Fire clay furnace 
810 
5 150 
121,6 
806,5 
-(- 3,5 
6 
< < 
868 
6 910 
123,3 
867,1 
4- 0,9 
7 
< < 
1378 
44 700 
124,2 
1379 
— 1 
8 
< C 
1470 
57 400 
123,1 
1468 
4- 2 
9 
l c 
1497 
60 600 
120,9 
1488 
+ 9 
10 
< c 
1535 
67 800 
122,3 
1531 
4- 4 
Mean 
123,8 
13— Bull. Phil. Soc., Wash., Vol. 15. 
