

ON RADIANT UK AT. ] 09 



Vet we know, that the painted glass is more heated than the 

 plai-i, (or the hot flask being- removed, the painted glass 

 skreen occasioned a farther rise as 15 to plain glass as 13. 



The best theory of the radiation of caloric supposes it to Theory of re- 

 alise from the repulsive force, which prevails between the dlUi11 eat * 

 particles of this fluid, from which property it is projected in 

 right lines from every body in which it is accumulated. Now 

 as diaphanous bodies admit some rays oi" caloric to pass Thehigherthe 

 throvigli their substance, and intercept others, it seems a J^fweVrayi 

 probable conjecture, that ail the rays of caloric have not the W ;ll be detain- 



same decree of velocity; and that, the higher the tempera- ed ina di *i ,ha - 

 ° J i ,. ... . . nous medium. 



ture of a body is, the greater number ot rays will it project 



with such a velocity, as (its them for passing through a dense 

 medium. AVe might therefore with much reason suppose, 

 that a certain number of calorific rays projected from a 

 burning caudle, and falling perpendicularly, or nearly so, on 

 the surface of a sheet of glass, would penetrate its substance: 

 that, from the boiling sulphuric acid fewer would have the 

 ite degree of velocity ; and from the boiling water 

 still fewer. On such an hypothesis we can readiiy explain, 

 why with a burning candle the thermometer is brought to a 

 higher temperature than the plain glass screen; why with a 

 Bask of boiling sulphuric acid and water the thermometer 

 and screen are at nearly the same temperature; and why 

 with a flask of boiling water the screen is hotter than the 

 thermometer. 



Mr. Leslie, having convinced himself, that the calorific Mr. Leslie's 

 ray does not pass through a sheet of ice, considers this fact ^Jhfeenot 

 as an additional evidence of the truth of his position. — But conclusive, 

 it sorely cannot be admitted as such. Experiment proves, 

 that water in its fluid state stops a considerable number of 

 the calorific rays emanated from the sun, which we have rea- 

 son to believe travel with greater velocity than those pro- 

 jected from bodies artificially heated. Besides, when water 

 freezes, its particles take on a crystallize.d arrangement ; the 

 8 did mass becomes porous, whence it is less adapted for the 

 transmission of the calorific ray, and will nodonbt be, from 

 the sane cause, less pervious to radiant caloric. But the 

 experiment was made with a single reflector, and it has been 



already 



