19B Mr. PowELL^s experimental inquiry into the nature oj 
(21.) Incandescent iron. 
1 
4 
7 
11 
13 
2 
4 
6 
10 
10 
Mean 
4 
6.5 
10.5 
11.5 
(22.) Lamp. One bulb covered by an opake screen, the other 
exposed at an aperture. Dist. 5 inches. Screen 1.5 
inch from bulb. 
1 
4 
6 
8 
11 
2 
3.5 
6 
9.5 
12 
3 
4 
6 
8 
10.5 
4 
3 
6 
8 
12 
Mean in imin. 3-6 
6 
8.3 
11.3 
) Incandescent iron. 
in 30 sec®. 
3 
4 
12 
9 
(24.) It is perhaps not worth while to make any formal de- 
ductions from these results as to the ratios subsisting in the 
different cases. It will be sufficiently evident upon inspection, 
that when all due allowances are made, the ratio of the effects 
upon the white and black bulbs is considerably greater when 
they were affected only by the transmissible part of the 
heating effect, than when they were exposed to the whole. 
The part then which is added on the removal of the screen, 
is of a nature tending to add to the terms of the former ratio 
quantities in a ratio much nearer equality : quantities in a 
