on the terrestrial Rays that occasion Heat. 497 



ig$d Experiment. 



Stove. White paper. 



o' 52 52 



This substance stops only 535 invisible rays of scattered 

 heat. 



194^ Experiment. 



Stove. Linen. 



°' 5Si 53i 



3 57i 55i • • • 4i : 2 i = >543 



It stops 457 invisible rays of scattered heat. 



Article vi. — Scattering of Solar Heat. 



We are now come to a branch of our inquiry which, from its 

 novelty, would deserve a fuller investigation than we can at 

 present enter into. The scattering of heat, is a reflection of it 

 on the rough surfaces of bodies : it is therefore a principle of 

 general influence, since all bodies, even the most polished, are 

 sufficiently rough to scatter heat in all directions. In order, there- 

 fore, to compare the effect of rough surfaces on heat with their 

 effect on light, I have made a number of experiments, from 

 which the following are selected, for the purpose of our intended 

 comparative view. 



The apparatus I have used for scattering solar heat, is like 

 that which served for transmissions ; * but here the holes 

 through which the sun's rays enter,-f are very exactly 1^ inch 

 in diameter each ; and are chamferred away on the under side;* 

 * See Plate XXI. Fig. i. f See Plate XXII. Fig. 4. 



