56 SPECTRUM ANALYSIS OF FLAMES. [MEMOIR II. 



This observation liolds good for those flames reputed 

 to be monochromatic ; for example, alcohol burned from 

 a wick imbued with common salt. It is not only a 

 yellow light which is evolved ; the other colors plainly, 

 though more faintly, appear. 



All flames, no matter what their special colors may 

 be, evolve all the prismatic rays. Their special tints 

 arise from the preponderance of one class of rays over 

 another; thus in cyanogen the red predominates, and 

 in sulphur the blue. 



(Later experiments have proved that the spectrum 

 thus containing all the prismatic colors, and acting as a 

 background to the bright fixed lines, is not due, except 

 indirectly, to the flame under examination, but to other 

 causes, not here taken into account, especially the acci- 

 dental presence of daylight, combustion of dust in the 

 air, etc. The statements here given are, however, in 

 accordance with observations actually made. These are 

 the eifects that will be seen in a partially illuminated 

 room such as the laboratory in which these experiments 

 were made. In a dark room the spectrum background 

 disappears.) 



The production of light in the case of flames is thus 

 proved to be a very complex phenomenon. The chem- 

 ical conditions under which the burning takes place are 

 likewise very complex. The combustible vapor is sur- 

 rounded on all sides by atmospheric air; diffusion oc- 

 curs, and rapid currents are established by the high 

 temperature. Such circumstances complicate the result; 

 and it is only by observing the burning of an elementary 

 solid, in which most of these disturbances are cut off, 

 that we can hope to effect a proper resolution of the 

 problem. 



II. Prismatic analysis of the light of an elementary 



