and on those produced by the Earth's Atmosphere. 529 



period of my own observations, no change has taken place either 

 in the dark lines or luminous bands of the solar spectrum ; a re- 

 sult which seems to indicate, that the apparent body of the sun 

 is not a flame in the ordinary sense of the word, but a solid body 

 or coating raised by intense heat to a state of brilliant incan- 

 descence. 



The atmospheric lines, as they may be called, or those lines 

 and bands which are absorbed by the elements of our atmosphere, 

 have their distinctness a maximum, when the sun sinks beneath 

 the horizon. The study of them, consequently, becomes exceed- 

 ingly difficult in a climate where this luminary, even in a serene day, 

 almost always sets in clouds ; but as I have availed myself of every 

 favourable moment for observation, I have been able to execute a 

 tolerably accurate delineation of the atmospheric spectrum. 



It is a curious circumstance, that the atmosphere acts very 

 powerfully round the line D, and on the space immediately on 

 the least refrangible side of it. It developes a beautiful line in 

 the middle of the double line D, and by enlarging a group of 

 small lines on the red side of D, it creates a band almost as dark 

 as the triple line D itself. It widens generally all the lines, but 

 especially the darkest one which I call m between C and D. It 

 developes a band on the least refrangible side of m, and it acts 

 especially upon several lines, and developes a separate band on 

 the most refrangible side of C. The lines A, B, and C are great- 

 ly widened, and lines and bands are particularly developed be- 

 tween A and B, and generally throughout all the red space. 



Most of the lines thus widened by the atmosphere are faint 

 lines previously existing in the spectrum, and I have no doubt 

 that they would be seen in the spectrum of the Lime Ball light 

 condensed by a polyzonal lens, and acted upon by thirty miles of 

 atmosphere. 



The absorptive action of the atmosphere shews itself in a 

 less precise manner in the production of dark bands, whose limits 



