362 



Mr. Pou/ell on Terrestrial Light and Heat. [May, 



Number 

 of experi- 

 ments. 



3 



2 



Particulars. 



exposed = I, 



Argand lamp 7 inches 

 from bulb with chimney 



Ditto no chimney . 



Wick increased. 

 Alore increased. 



Rise in 1 min. corrected for adventi- 

 tious light. 



Plain bulb 

 Both bulbs screened = 



15 



18 

 14 

 29 

 30 



I + h. 



28 

 30 

 31 

 40 

 52 



Hence h. 



13 

 12 

 IT 

 11 



22 



1 



0^ 

 1 



6^ 

 1 



ri 

 1 



0^ 



1 



0^ 



It is obvious that there is a limit beyond which increasing the 

 •wick does not produce more complete combustion. 



Of several other experiments tried on flame, one case regards 

 the alteration which takes place in a flame as exhibited in the 

 simple experiment of placing salt in the wick of a spirit-lamp; 

 the eflect being increased also by diluting the spirits with water. 

 (See Dr. Brewster's paper on a Monochromatic Lamp, Edinb. 

 Phil. Journ.'No, 19, p. 123.) This experiment gave the follow- 

 ing results. . The instrument employed in this and all the subse- 

 quent experiments was a small photometer, having its bulbs in 

 the same vertical line. 



(8.) Count Rumford found that, when by employing many 

 flames near each other, the temperature of the flame was 

 increased, the lioht given out increased in a much greater pro- 

 portion. (See Phil. Trans. 1820, Part I. p. 22 ; Davy's Elements 

 of Chem. Phil. p. 224.) If the simple heat radiated increases 

 in a proportion not greater than the temperature of the flame, 

 we shall here observe the same increase of ratio between the 

 radiant heat and the light as in the preceding instances. 



This point I proceeded to examine in the following set of 

 experiments, in which I compared by the same method as before, 

 the effects of light and heat produced from a single flame, and 

 from the juxta-position of flames. 



