400 



KNOBLAUCH ON RADIANT HEAT. 



By these results it is therefore placed beyond all doubt, that 

 heat, on diffuse reflexion, is very differently modified, by some 

 bodies to a great extent, by others it is unchanged. 



It is evident, from the following observations, that these 

 changes, when unpolished bodies are used, are independent 

 of their degree of roughness ; for, e. g. a deflection of 7°'63 to 

 7°"75 is constantly found on the insertion of the red glass, 

 vi'hether the heat of the Argand lamp is reflected by a more 

 or less rough surface of wood, to cause a deviation of 13° in 



Table XXXI. 



As was to be expected, the alteration of the transmission of 

 the heat after reflexion in one diathermanous substance, bears 

 no relation to its passage through any other. 



Rays of the same direct intensity reflected by carmine (see p. 

 389), white velvet (Table XXIV.), and many other surfaces, are 

 transmitted by all the six diathermanous bodies with which we are 

 acquainted in a greater degree than the unreflected, and those I'e- 

 flected by black paper (see p. 394, Table XXV.) and wood-char- 

 coal (p. 397) are transmitted by all in a less degree than the un- 



Table XXXII. 



