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Mr. Powell on Light and Heat 



Hence it would be obvious, that the heating power of light in- 

 creases in a greater ratio than the radiation of simple heat in this 

 series of flames. 



If we compare these results with the remarks of Sir H. Davy, 

 that the increase of light depends on the increase of solid pro- 

 duct, it will be evident, from the chemical nature of the flames 

 employed in this comparison, that not only the increase of light, 

 but also the increase of ratio between the light and heat, takes 

 place, in accordance with Sir H. Davy's doctrine. (See Phil, 

 Trans. 1817. Part i. p. 75.) 



7. But these inferences are grounded entirely on the assumption, 

 that the heat radiating from different flames, is in a proportion not 

 greater than that of the elevation of their temperature. This, 

 perhaps, may not be much questioned. But the other part of the 

 assumption, viz., that the heating is proportional to the illumin- 

 ating power of light from different flames, may admit of doubt. 

 Thus, it would become very desirable to extend the examination, 

 on the principle here suggested, to the flames of different gases. 

 This part of the inquiry I have not the means of attempting ; but 

 there are other phenomena of a description closely analogous to 

 these, and which, coming within the reach of familiar exami- 

 nation, I have made the subject of experiment, so, as in some de- 

 gree, to supply the deficiency. 



8. 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 effect being increased by, at the same time, 

 diluting the spirits with water. (See Dr. Brewster's paper. Edinb. 



