444; Mr. B. Powell's experimental Inquiry into the Nature 



and that of the exposed effects will be in reality greater than 

 appears. 



The results are comprised in the following table : 



(20.) Lamp. Bulb in the focus of a reflector. Coatings, 

 white silk and Indian ink. 



(22.) Lamp. One bulb covered by an opake screen, the 

 other exposed at an aperture. Distance 5 inches. Screen 

 1-5 inch from bulb. 



(23.) 



Incandescent iron. 



(24.) It is, perhaps, not worth while to make any formal de- 

 ductions from these results as to the ratio subsisting in the dif- 

 ferent 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 na- 

 ture tendmg to add to the terms of the fomier ratio quantities 

 in a ratio much nearer equality: quantities in a ratio very 

 nearly that which the effects of simple radiant heat would give. 



III. (25.) 



