ANINALS 



OF 



PHILOSOPHY. 



JUNE, 1825. 



Article I. 



Additional Experii/ievts mid Remarks on Light and Heat. 

 By Baden Powell, MA. FRS, 



(1.) In my last communication I mentioned several experi- 

 ments I had tried, by way of varying' the principal ones, on 

 which my conclusion relative to the existence of two distinct 

 species of heat, in the emanation from luminous hot bodies, 

 depended. I now beg leave to lay before the readers of the 

 Annals one or two other experiments having the same object in 

 view. These were made with a large differential thermometer 

 having the bulbs differently coated, as hereafter expressed. It 

 was placed with the bulbs exactly in a line from the source of 

 heat, each being alternately nearest ; and each being tried with 

 and without the intervention of a glass screen. If the effect 

 were due to one simple radiating agent, the ratio of the effects 

 on the smooth black and the absorptive white with the screen, 

 ought to be the same as without: the following results however, 

 indicate a considerable difference ; the divisions are not Lesliean 

 degrees. The first column describes which bulb was nearest 

 the source of heat. They were nearly three inches asunder, and 

 at about two from the flame, imd six -from the hot iron. 



Flame of a candle. Effect in 1 min. 



Screened. Exposed. 



Indian ink 2 4 



Thin brown silk a 



riv 



Argand lamp. No chimney. 



Indian ink 3 4 



Thin brown silk 1 3 



Incandescent iron. Effect in 30 seconds. 



Indian ink 2 4 



Thin brown silk 1 5 



New Seiie^y vol., ix. 2 d 



