54 SPECTRUM ANALYSIS OF FLAMES. [MEMOIR II. 



must necessarily be one of the fundamental theories of 

 chemistry. It must include the nature of all chemical 

 changes whatsoever. The subject is therefore not alone 

 interesting in a popular sense, but of great importance 

 in its scientific connections. 



I. Prismatic analyses of the flames of various vapors 

 and gases ; proving that they yield all the colors of the 

 spectrum. 



I commenced this investigation of the nature of flame 

 and of combustion generally by an optical examination 

 of various bodies in the act of burning. Some authors 

 have asserted that certain flames yield monochromatic 

 light. It is necessary to verify this assertion, if true, or 

 set it aside if false. 



The instrumental arrangement I resorted to for the 

 determination of the structure of a flame may be thus 

 described : The rays of the flame of which the examina- 

 tion was to be made passed through a horizontal slit, 

 one thirtieth of an inch wide and one inch long, in a 

 metallic screen placed near to the flame, and were re- 

 ceived at a distance of six or eight feet on a flint-glass 

 prism, the axis of which was parallel to the slit. After 

 passing the prism, they entered a telescope, which had a 

 divided micrometer and parallel wires in its eye-piece. 

 Through this telescope the resulting spectrum was 

 viewed. In this form of spectroscope no collimating 

 lens was used. 



In Fig. 7, a is the candle, or flame which is to be ex- 

 amined, b the screen with a horizontal slit, c the prism, 

 d d the telescope. 



If it be the flame of a lamp of any kind that is to be 

 examined, by using a movable stand we are able to raise 

 or lower it, and thus analyze different horizontal elements 

 in its lower, its middle, or its upper parts at pleasure. 



