198 



KNOBLAUCH ON RADIANT HEAT. 



Table II. [continued). 



Thus it is proved that the temperature of one and the same 

 source of heat within the hmits of these experiments, i. e. between 

 88° and 212° F., has not the shghtest influence upon the trans- 

 mission of the heat radiating from it through diathermanous 

 bodies. 



I must here again refer to Melloni's experiment, which has been 

 alluded to above (p. 195), and appeared to show that the property 

 of heat to pass through mica increases with the temperature of 

 the source of heat even between 122° and 212° F. As my ex- 

 periments, just now detailed, did not agree with this statement, 

 I have repeated them so very frequently that I have no doubt 

 of their accuracy. So far as I have repeated Melloni's experi- 

 ments, this is the only case in which my results differ from those 

 of this distinguished philosopher, for whom I entertain the most 

 profound respect and admiration. 



(2.) The next question was, how heat at temperatures above 

 212° F., radiating from one and the same body, would behave 

 as regards transmission through diathermanous bodies. 



For the purpose of investigating this, I placed a cylinder of 

 blackened sheet iron, copper or brass, 17 centim. in height and 

 3 centim, in diameter above the flame of an Argand lamp, by 

 which I was enabled to heat it to different and sufficiently constant 

 degrees of temperature. I certainly had no means of determining 

 these during the experiment in ordinary thermometric degrees, 



