82 THE SUN. 



below them, first, a layer of what we may consider real 

 clouds, which appear comparatively dark, as if they were 

 not self-luminous, but were seen only by the reflected 

 light of the upper layer of bright ones ; secondly, through 

 other openings in this first layer, a second still darker 

 layer, independent of the first, and probably still thou- 

 sands of miles below that, and reached by some but 

 very little light from above ; and thirdly, through 

 again other openings, what at present we must consider 

 to be the body of the sun itself at some vast and im- 

 measurable depth still lower and emitting so little 

 light in comparison as to appear quite black, though that 

 does not prevent its being in as vivid a state of fiery 

 glare as a white-hot iron ; when we remember what has 

 been said of the lime light appearing black against the 

 light of the sun's surface. And it is a fact, that when 

 Venus, and Mercury pass across the sun, and are seen 

 as round spots on it, they do really appear sensibly 

 blacker than the blackest parts of the spots. 



(40.) The sun then has an atmosphere, and in that 

 atmosphere float at least three layers of something, that, 

 for want of a better word, we must call clouds. The 

 two nearest the body are not luminous. They cannot 

 possibly be clouds of watery vapour, such as we have in 

 our air, for water in a non-transparent state could not 

 exist at that heat; but they may be what perhaps we 

 might call smokes, that is to say, clouds in which the 

 metals or their oxides and the earths exist in the same 

 intermediate form that water does in our clouds. The 

 third or upper layer of luminous clouds, or, as it is called, 



