CHAPTER V. 



THE FRAUNHOFER LINES EXPLAINED. 



WHILE the strange dark lines in the solar spectrum were 

 attracting attention, various attempts were made to account for 

 their existence, and many new facts throwing light on the 

 matter were discovered. 



We have seen, for instance, that Brewster and Herschel in 

 their work came across substances which seemed to give, so to 

 speak, an artificial solar spectrum, that is, a spectrum crossed 

 by dark lines, 



I have been favoured by Dr. Gladstone with the following 

 extract from Brewster's note-book, dated St. Andrew's, Oct. 

 28th, 1841 : 



" I have this evening discovered the remarkable fact that in the 

 combustion of nitre upon charcoal there are definite bright rays 

 corresponding to the double lines of A and B, and the group of lines 

 a in the space AB. The coincidence of two yellow rays with the two 

 deficient ones at D, with the existence of definite bright rays in the 

 nitre flame, not only at D, but also at A, , and B, is so extraordinary 

 that it indicates some regular connection between the two classes of 

 phenomena." 



Brewster had already indicated how close the connection 

 might be between absorption phenomena going on here and at 

 the sun. Now he indicates a possible connection between 

 radiation phenomena here and absorption at the sun. 



E 



