OIT THE EFFECTIVE TEMPERATURE OF THE SUN. 
379 
column gives the area of aperture, i.e., the quantity of heat falling on the instrument; 
the second gives the deflections (in centims.) on the scale, in the two series ; the third 
gives the mean; and the fourth gives the deflections calculated by a straight line 
formula, y = mx. 
When the observed results are plotted down on curve paper (fig. 7), it will be seen 
at once that they form as nearly as can be a straight line ; and as the extreme 
deflection in these cases was 21^°, the proportionality of radiation and deflection is 
strictly demonstrated, up to the greatest value of the latter used in our experiments. 
Table II. 
Quantity of 
heat. 
Deflection. 
Mean 
observed. 
Calculated from 
y = 3-96a;. 
Observed — calculated. 
0 
00 
0-0 
0-0 
0-0 
1 
LA] 
2-9 J 
?■ 
3-7 
4-0 
- 0-3 
2 
861 
7-2 J 
> 
7-9 
7-9 
0-0 
3 
12 5] 
11-3 J 
11-9 
11-9 
00 
4 
16-81 
15-4 J 
16-1 
15-8 
+ 0-3 
5 
20-71 
19-6 J 
19-9 
19-8 
+ 0-1 
G 
24-4] 
23-9 
24-2 
23-8 
+ 0-4 
7 
27-9] 
27-9 
27-9 
27-7 
+ 0-2 
8 
31-51 
31-8 J 
31-7 
3T7 
0-0 
9 
31-91 
35-3 J 
.35-1 
35-6 
— 0-5 
10 
39-6" 
39-6 
.39-6 
39-6 
00 
Mean 
+ 1-0 — 0 8 _ , .^0 
~ 11 '■ 
It may be noticed here that as the temperature rises, Rosetti’s law becomes 
more nearly a simple third-power law, while ours becomes a simple fourth-power law, 
so that if 
then 
'Rp = radiation from platinum, 
= temperature of platinum, 
Rj = radiation from sun, 
Tj = temperature of sun. 
lb 
or 
which gives when = 6000° and thereabouts, a result differing by less than one 
degree from that obtained by the complete formula R^ = a (T/ — To'^). 
3 c 2 
