CELESTIAL CHEMISTKT. 



SPECTRUM ANALYSIS. 



The Spectroscope and its Revelations. — Within the last few years 

 a new form of chemical analysis has arisen, which ascertains sub- 

 stances by observation upon the color and properties which they 

 impart to flames dui'ing combustion. It has been long known 

 thnt the combustion of certain bodies gave certain colors to 

 flames; strontia, for example, affoi'ding the beautiful ci'imson so 

 well known in pyrotechny. But no sure method existed of using 

 the facts of combustion for chemical investigations, until the in- 

 vention of the sjjectroscope. Si^ectrum analysis enables us to 

 detect the minutest trace of the constituents of substances burnt. 

 It has already discovered several unsuspected new metals ; has 

 given us the power of analyzing bodies whose eomposition we 

 had not the means of ascertaining, and has pi'oved to us that many 

 of the elements of the earth are present in the inaccessible sun, 

 and even in those more remote stars whose distance the most 

 refined researches of astronomy cannot determine. 



The spectroscope is merely a prism to which light can be 

 admitted through a slit one-thirty-second of an inch wide, with 

 apparatus for examining microscoiiically the spectrum or de- 

 composed ray beyond the prism. When this is done, the spec- 

 trum is found to be crossed by an infinite number of lines perpen- 

 dicular to its length. These lines are called, from the name of 

 the distinguished optician who discovered them, Fraunhofer's 

 lines. 



When the light coming from a white-hot mass of metal is 

 examined by the spectroscope, its spectrum is found to be perfectly 

 continuous and unbroken hy any Fraunhofer lines. What is the 

 cause of tlie lines in the solar light, and in what does that 

 luminary differ from the incandescent mass ? 



In order to fathom this question, we must investigate for a few 

 moments the case of artificial lights, such as ordinary flames, and 

 those in which there are purposely introduced various elementaiy 

 or compound bodies. The construction of the spectroscope must 

 also be described. 



The spectroscope is sometimes a very complicated instrument, 

 but, for ordinary analysis, quite a simple form may be used. It 

 consists of a prism, supported on a stand. Two telescopes, of low 

 magnifying jjower are attached by suitable supports. One of 

 these is furnished with an eye-piece like any common spy-glass, 

 but the eye-piece of the other is removed, and in its jjlace is put 

 a vertical slit. Opposite this slit the flame to be examined is 

 placed. The light coming through the slit from the flame falls 

 19* 221 



