132 LIGHT SCIENCE FOR LEISURE HOURS. 



known lines, and to note differences of brightness. 

 Thus, near B, one of the nine strong lines to which 

 Fraunhofer assigned the first nine letters of the 

 alphabet (and called large B in the telegram to 

 distinguish it from a certain triple line called little b) r 

 several very bright lines were seen. Dark lines 

 belonging to the oxygen and nitrogen of our own air 

 have been observed in this part of the sun's spectrum r 

 and it may be that we here have evidence corroborating 

 Dr. H. Draper's recognition of bright oxygen lines in 

 the solar spectrum. ' Bright line F was seen,' but that 

 being one of the hydrogen lines, its being seen was 

 nothing new ; it would have been surprising, indeed, 

 if it had not been seen. The line 1474 Kirchhoff is 

 one of the most interesting of all. It is the chief 

 bright line of the corona's spectrum. It was once 

 thought to be a line of iron, but Professor Young 

 showed that this could not be the case. The presence 

 of this line among the bright reversed lines, and its 

 absence from the dark lines of the solar spectrum, as 

 ordinarily seen, is an interesting discovery, if it has 

 been certainly established. It would imply that the 

 substance to which the line is due a substance 

 present in large quantities in the corona of 1869, 1870, 

 and 1871 exists ordinarily at a temperature higher 

 than that of the vapours in the sun's atmosphere ; for 

 these absorb more light than they emit, which indicates 

 that they are cooler than the sun's surface beneath 

 them, whereas the matter producing the line 1474 

 Kirchhoff must be as hot as the surface of the sun, 



