272 THE CHEMISTRY OF THE SUN. [CHAP. xix. 



by means of the spectroscope." This result " is accomplished 

 by photographing the absorption spectra of organic compounds 

 in the infra-red part of the spectrum. In these invisible por- 

 tions characteristic and distinct absorption lines and bands occur 

 for each organic radical. The ethyl compounds all show one 

 special ethyl band ; the methyl compounds a special methyl band ; 

 and thus, just as a glance at the luminous portion of the spec- 

 trum satisfies us of the presence of calcium, lithium, and rhu- 

 bidium, so a simple inspection of these infra-red photographs 

 enables us to ascertain the presence of the various organic 

 radicals. This invention is still in its infancy, but one of greater 

 importance to chemists has seldom if ever been communicated 

 to the Society." I have been the more anxious to give these re- 

 sults in Professor Eoscoe's own words, because it will be seen that, 

 mutatis mutandis, these remarks touching the spectra of organic 

 radicals are precisely identical with one statement I have been 

 endeavouring to make with regard to inorganic radicals. It 

 cannot therefore be said that the nature of the principle I bring 

 forward is one with which chemists are not familiar. 



