﻿M. H. St.-Claire Deville on the Temperature of Flames. Ill 



the different modes of electric excitation (that of the galvanic 

 current included). The secret of the intimate relations between 

 electricity and heat and light is obvious in view of what has 

 been stated. 



The sethereal atmospheres of molecules, besides playing the 

 part already signalized, are the chief determining cause of the 

 diverse phenomena that attend the transmission of light through 

 transparent media. Thus refraction is chiefly due to the retar- 

 dation attending the propagation of the ray around from one 

 side to the other of the molecular atmospheres • dispersion of 

 the rays in the spectrum to the fact that the rays of the greatest 

 intensity and slowest rate of vibration penetrate to the greatest 

 depth in the molecular atmospheres, pass around in smaller 

 circles, and thus suffer the least retardation ; and double refrac- 

 tion to the fact that the atmospheres have a spheroidal form, 

 owing to unequal molecular compression on different sides. 



XV. On the Temperature of Flames, and its relations with the 

 Pressure. By M. H. St.-Claire Deville*. 



IT is impossible not to be greatly struck by the numerous 

 consequences which may be deduced from the experiments 

 recently published by Professor Frankland, and of which he has 

 given an account in an article in the Comptes Rendus of the 12th 

 of last Octoberf. I will ask leave from the Academy to develope 

 here some ideas which this magnificent research has suggested 

 to me, and to describe a plan of investigation commenced some 

 time ago in my laboratory, the direction of which has been a 

 little changed by the new facts discovered by the illustrious 

 English chemist. 



Professor Frankland (to sum up in brief his principal experi- 

 ments) proves that the higher the pressure of an oxyhydrogen jet 

 burning in a compressed atmosphere, the more brilliant and lu- 

 minousj does its flame become, which under the ordinary pres- 

 sure is scarcely visible. At a high pressure a flame is obtained 

 whose intensity may be compared to that of a wax candle. This 

 single fact is sufficient to show the importance of such results, 

 which may be said to have been as unforeseen as they are clearly 

 and definitely established. 



Professor Frankland finds the best explanation of this great 



* From the Comptes Rendus, November 30, 1868. 



t [See also Phil. Mag. for October, 1868, p. 309.] 



% To make a flame brilliant, it is sufficient that its rays, if they are 

 simple and belonging to a monochromatic light, possess great intensity. 

 That a flame shall be luminous in the ordinary acceptation of this word, it 

 must possess almost all the rays of the solar spectrum ; it must be white, 

 or as nearly so as possible by approximating to sunlight. 



