Kinetic Theory of Gas. 379 



In chemical reactions, if the product is gaseous, and if the 

 electrons which are set swinging are associated with B« 

 events, the most obvious effect is a sudden increase of tem- 

 perature and pressure ; if associated with Bfr 2 events the 

 most obvious effect is a flash of light ; and if associated with 

 B^i events both effects will be conspicuous : and this, in ac- 

 cordance with what we learn through the phosphoroscope, 

 would seem to be what most frequently happens. 



It seems probable that it is when excited by chemical reac- 

 tions that electrons produce their most conspicuous luminous 

 effects, whether in flames or in so-called incandescent spectra. 

 It should be remembered that as electrons are for the most 

 part associated with Bfr motions within the molecule, it may 

 happen that they but slowly influence the temperature of the 

 gas as indicated by the thermometer, and that accordingly 

 the luminous effects may be greatly in excess of what a mere 

 incandescent body at the same moderate temperature could 

 produce. Hence the phrase incandescent spectrum is not 

 always appropriate, since the supposition that the temperature 

 inside a PI ticker tube must be high is erroneous. 



These inferences are entirely borne out by the recently 

 published observations of Professor Lewes upon gas-flames 

 (see Proceedings of the Royal Society for March 7 and 

 March 21, 1895). He finds that the first group of chemical 

 changes which the issuing gas undergoes are brought about 

 by radiant heat ; in other words, by electromagnetic waves 

 in the aether acting on those electrons which are concerned 

 in the chemical changes, and which, from their not being 

 affected by convected heat, must be associated with B6, and 

 not with Ba events. In this way 



H-CiOH g!cf^ and H'H 



Acetylene. Methane. Hydrogen. 



are produced. Of these, acetylene is the one that, on decom- 

 position, emits almost all the light. Professor Lewes finds 

 that, on attaining a situation where the temperature is suf- 

 ficient, the acetylene resolves into carbon and hydrogen, 

 which subsequently combine with oxy r gen ; and that in the 

 brief interval one or both of them emit more light than belongs 

 to the temperature of that situation; in other words, that one 

 or more electrons associated with B6 motions have been 

 roused into great activity by the decomposition, and have 

 time to radiate abundantly, probably a long time from the 

 molecular standpoint, before either they have expended their 



