1 34 SPECTR UM ANAL YSIS. PART i. 



exhibits one single red ray.' Whence Mr. Fox Talbot 

 observes, ( I hesitate not to say that optical analysis 

 can distinguish the minutest portions of these two 

 substances from each other with as much certainty, 

 if not more, than any other known method.' Thus 

 Sir John Herschel and Mr. Fox Talbot laid the foun- 

 dation of a spectrum analysis of unrivalled delicacy 

 and beauty, since carried to perfection by Messrs. 

 Bunsen, Kirchhoff and other experimenters, presently to 

 be mentioned. 



M. Bunsen detected the characteristic crimson lithium 

 line in the spectra of numerous substances ; in granite, 

 in the earliest geological strata, in meteoric stones, in 

 the ashes of most land plants, in blood and other animal 

 matter; so that instead of being one of the rarest metals, 

 it exists in all the three kingdoms of nature. In the year 

 1857 Mr. Swan gave an instance of the extreme minute- 

 ness of spectrum analysis, by detecting the 2)5 j )|0ou th part 

 of a grain of salt by its yellow light ; but by the same 

 reaction M. Bunsen not only recognised the 180 mil- 

 lionth part of a grain of sodium, but found that there 

 is hardly any substance that does not contain it. It 

 exists in the dust on our clothes and furniture, particles 

 of it float in the air we breathe, so that while examining 

 the spectra of other incandescent substances, flashes of 

 yellow light appear as these atoms are volatilized and 

 instantly burnt up, which shows that common salt is 

 perhaps more universally diffused than any other kind 

 of matter. 



M$ By spectrum analysis, M. Bunsen has discovered the 

 i two new metals, rubidium and csesium. While examining 

 with a prism the spectrum of the hundredth part of a 

 grain of an alkaline substance separated from the resi- 

 duum of the Durckheim mineral water, he saw coloured 

 lines, which he had never seen before on the spectrum 

 of any other alkali, and at once concluded that they 



