234 



KNOBLAUCH ON RADIANT HEAT. 



layer of carmine, post paper and Ivory were in fact diathermanous 

 under the conditions pointed out. 



Thus the great differences which occurred on transmission 

 through red and blue glass, alum, rock salt, calcareous spar and 

 sulphate of lime (see Table XVII.), when these substances were 

 exposed to the rays of the Argand lamp, arose merely from the 

 heat be'mg transmitted by them, and not from the circumstance 

 that that emitted by them would be transmitted by the above 

 media in a different proportion. 



3. From the following numbers it is evident that also the heat 

 evolved by the vital process, e.g. that radiated from the hand, is 

 transmitted by diathermanous media in the same manner as 

 those previously examined*: — • 



Table XXL 



If we connect with this the fact, that the radiant heat of dif- 

 ferent bodies (with the same intensity) also heats one and the 

 same substance to the same extent as it passes through one and 

 the same diathermanous one in the same way, the final result of 

 these observations is, That the heat emitted by the most different 

 solid bodies of unequal thickness and dissimilar structure of their 

 surface, which have as yet been examined, as far as our present 

 means allow, has been proved to be of the same kind, in whatever 

 way, within the limits of these eorjyeriments (i. e. between 88° and 

 234° F.), it may be excited in them. 



Taking into consideration this fact, according to which a body 

 always emits heat of the same kind, be the rays which heat it ever 

 so different (see especially p. 225 to 227), the remark made in 

 the first section appears explicable, that its radiating property, 

 which is the cause of the quantity of this heat, is one and the 

 same under these altered circumstances (p. 217 to 221). 



* This also disproves the opinion of Forbes, that the heat emitted hy boiling 

 water and the iiand must be considered as difFerent. 



