MEMOIR II.] SPECTKUM ANALYSIS OF FLAMES. 55 



introduced an incombustible element into the flame ; for 

 as the carbon burns the incombustible nitrogen is set 

 free. It occurred to me, in selecting the gas for experi- 

 ment, that this condition should impress a physical char- 

 acteristic on the flame. I thought it was not impossible 

 that dark lines in its spectrum might be the result, be- 

 cause there must be a peculiar arrangement of the burn- 

 ing strata which together make up the shell of the flame, 

 every two atoms of carbon setting free one of nitrogen. 

 I did not know, until subsequently, that this flame had 

 already been examined by Faraday. Having therefore 

 confined some cyanogen, made from cyanide of mercury, 

 in a glass gas-holder filled with a saturated solution of 

 common salt, I burned it from the jet-pipe, and found 

 that what I had surmised was actually the fact. There 

 was a spectrum so beautiful that it is impossible to de- 

 scribe it by words, or depict it in colors. It was crossed 

 throughout its extent by black lines, separating it into 

 well-marked divisions. I could plainly count four great 

 red rays of definite refrangibility, followed by one or- 

 ange, one yellow r , and seven green rays ; while in the more 

 refrangible spaces were two extensive groups of black 

 lines, recalling somewhat from their position, but greatly 

 exceeding in extent, Fraunhofer's lines G and H in the 

 sun-rays. I shall return to the consideration of this 

 spectrum and to the relation of fixed lines presently, 

 here only making the remark that the burning of cyan- 

 ogen, both as respects the color of the light and the oc- 

 currence of fixed lines, is a direct consequence of the 

 principle I am establishing. 



The unassisted eye detects two well-marked regions 

 in the cyanogen flame: a greenish-gray stratum on the 

 outside, and a lilac-colored nucleus within. Decomposed 

 by the prism, a horizontal element of this flame shows 

 that the exterior shell contains all the prismatic colors, 



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