186 



These lines are of so fixed a character in relation to the 

 colored bands of the spectrum, that if it be desired to in- 

 dicate with great precision any special ray of the spectrum 

 we refer to them by their letters or numbers. 



The origin of these dark lines, spaces in which there is no 

 light, can scarcely be said to be yet resolved. 



Fraunhofer, and others following him, thought that the 

 light emitted from the photosphere, was from the first defi- 

 cient in these rays, or that they were lost either by absorp- 

 tion in passing through the solar atmosphere, or possibly in 

 passing through that of the earth. The investigations of 

 Bunsen and Kirchoff, remarkable alike for the delicacy and 

 caution observed in the inquiry, and for the refined nature 

 of their deductions, lead us probably up to the true expla- 

 nation of these phenomena. 



These investigations of Bunsen and Kirchoff, from their 

 exceeding interest, have lately been attracting great at- 

 tention. 



Angstrom discovered many bright lines in the spectra, 

 from artificial light. He and others have proved that spec- 

 tra obtained from the light emitted from incandescent 

 mineral bodies, dilfer from that obtained from the sun; that 

 the lines from artificial sources of light are in many cases 

 peculiar, and that in the majority of instances, bright lines 

 appear to take their place. So rigidly exact were the posi- 

 tions and characters of the lines obtained from differently 

 colored flames, that spectral or prismatic analysis has been 

 adopted as a means of determining the presence of exceed- 

 ingly minute quantities of any substance. 



These lines, dark and bright, have not only been employ- 

 ed in the analysis of the solid mass of the sun, but also in 

 ordinary analysis, and the extreme delicacy of the indica- 

 tions, is proved from the discovery by Bunsen of two new 

 metalic bodies, one called Ccesium, meaning bluish gray, and 

 the other Rubidium, from the Latin Rubidus, used to 

 express the darkest red color whioh exists in infinite- 



