RADIATION IN ABSOLUTE MEASURE AT VERY LOW TEMPERATURES. 
377 
Group I.—Sooted and Silvered Globes Cooling in Vacuum (continued). 
V. 
May 31, 1905. 
Copper globe sooted. 
Vacuum pressure = 60 M.* 
Temperature of enclosure = 81° absolute. 
VI. 
September 18, 1906. 
Copper globe finely sooted. 
Increasing in temperature. 
Vacuum pressure immeasurable on M‘Leod gauge. 
Temperature of enclosure = 291°-8 absolute. 
Difference 
Absolute 
Difference 
Absolute 
No 
of tern- 
Emissivity. 
temperature 
No 
of tem- 
Emissivity. 
temperature 
peratures. 
e. 
of globe. 
peratures. 
e. 
of globe. 
(t-ty c. 
9. 
(t - ty C. 
6. 
°c. 
° c. 
1 
209-6 
8-914 x10- 5 
290-6 
1 
60-6 
3-742 x 10~ 5 
231-2 
2 
165-4 
8-559 ,, 
246-4 
2 
56-2 
3-947 „ 
235-6 
3 
133-0 
8-029 „ 
214-0 
3 
52-1 
4-153 „ 
239-7 
4 
118-6 
7-675 „ 
199-6 
4 
47-9 
4-358 ,, 
243-9 
4 
107-0 
7-322 „ 
188-0 
5 
44-1 
4-564 „ 
247-7 
6 
97-8 
6-968 „ 
178 - 8 
6 
40-4 
4-769 „ 
251-4 
7 
86-3 
6-438 „ 
167-3 
7 
36-8 
4-975 
255-0 
8 
76-5 
5-908 „ 
157-5 
8 
33-4 
5-181 „ 
258-4 
9 
68-1 
5 "378 ,, 
149-1 
9 
30-3 
5•386 „ 
261-7 
10 
63-3 
5-023 „ 
144-3 
10 
25-7 
5-728 „ 
266-1 
XL 
XII. 
July 5, 1904. 
July 21, 1905. 
Copper globe sooted. 
Silvered globe highly polished. 
Increasing in temperature. 
Increasing in temperature. 
Vacuum 
pressure = 1-8 M. 
Vacuum 
pressure = 0 • 1 M . 
Temperature of enclosure = 287° absolute. 
Temperature of enclosure = 294° 
absolute. 
Difference 
Absolute 
Difference 
Absolute 
No 
of tern- 
Emissivity. 
temperature 
No 
of tem- 
Emissivity. 
temperature 
peratures. 
e. 
of globe. 
peratures. 
e. 
of globe. 
(t - ty C. 
e. 
(t - ty c. 
9. 
0 C. 
0 c. 
1 
75-8 
6-092 x 10- r ’ 
211-2 
1 
16-9 
9-206 x 10~ (! 
277-1 
2 
70-2 
6-261 
216-8 
2 
16-7 
9-296 „ 
277-3 
3 
64-7 
6-430 „ 
222 • 3 
3 
16-5 
9-382 „ 
277-5 
4 
59-6 
6-597 „ 
227-4 
4 
16-3 
9-470 „ 
277-7 
5 
54-8 
6-766 „ 
232-2 
5 
16-1 
9-556 „ 
277-9 
6 
50-0 
6-934 „ 
237-0 
6 
15-95 
9-645 „ 
278-05 
7 
45-7 
7-103 „ 
241-3 
7 
15-75 
| 9-734 „ 
278-25 
8 
41-7 
7-271 „ 
245 • 3 
8 
15-38 
9-908 „ 
278-62 
9 
37-7 
7-440 „ 
249-3 
9 
15-0 
10-083 „ 
279-0 
10 
31-0 
7-778 „ 
256-0 
10 
14-61 
10-258 „ 
279-39 
* The copper enclosure was leaking slightly and consequently the vacuum pressure was variable. The 
average pressure was 60 M. 
VOL. CCVITT.—A. 3 C 
