ft dm TefrMrial Sources. 51 



method is probably sufficient. In mentioning a few results which 

 I have in this tvay obtained, I do not therefore conceive it neces- 

 sary to go into numerical details. 



5, It is well known that the general inferences made by 

 De La Roche, with respect to the increasing transmissibiliiy of 

 heat in proportion to the degree of luminosity, have been con- 

 firmed by results of other experimenters on different principles, 

 and in some instances the connexion between increase of light, 

 and the peculiar chemical conditions of the case^ have been esta- 

 blished. By comparing such results, and viewing them on th^ 

 principles now established, we get the connexion between those 

 chemical conditions, and the increase in the heating power of light. 



Thus with respect to an increased intensity of combustion. 

 Count Rumford shewed (Phil. Essays, i, 304,) that in proportion 

 to this increase the illuminating power increased. i)e La Roche 

 has shewn that in the same proportion the transmissibility of heat 

 IS increased. Viewing this according to my principle, there is a 



corresponding increase in the ratio of the two radiations 6r ^- * 



h 



I have also confirmed this by applying the method above de- 

 scribed (4) to the radiations from an Argand lamp, when its 

 flame was in different stages of brightness ; when a regular 

 increase in the ratio was observable. 



6. In the further investigation of this, point, we may make some 

 inferences from a consideration of Mr. Brande's experiments, (on 

 gases, ^c. Phil. Trans. 1820, Part 1.) He has there compared 

 the heating effect by conduction of the flames of several species of 

 gas ; and has also estimated their relative illuminating effects. 

 From the results given of the quantities of each gas requisite to 

 produce equal lights and equal heats, we may deduce the propor- 

 tions of the effects of heat and of light to be nearly as below, on 

 the assumption that the heating is proportional to the illuminating 

 power of light, and the radiant heat to the temperature in the dif- 

 ferent frames. Of the ratio in the same flame we can infer 

 nothing. 



E 2 



