710 THE UNIVERSE. 



and that its pretended blemishes only existed on the glasses 

 of the telescopes of astronomers. 



But though the existence of these is now an incontestable 

 fact, yet their real nature is as yet very imperfectly ex- 

 plained. Some astronomers maintain that they are only 

 holes in the luminous envelope of the sun, which allow us 

 to see its dark strata. Others think they are clouds of 

 vapor, which wander over the surface of this immense globe 

 of fire. However this may be, it is to the observation of 

 these spots that we owe the discovery of the rotatory move- 

 ment of the sun, a movement which takes place in twenty- 

 five days. 1 



The solar heat is so powerful that we can only form a 

 very imperfect idea of it. The greatest combustion in our 

 blast furnaces, pushed to a white heat, cannot for a moment 

 be compared with it. An attempt, however, has been made 

 to estimate the temperature of this formidable furnace. 



1 It seems probable, from the solar observations recently made by De La Rue, 

 Stewart, and Loewig, on the nature of sun spots, that the spots are colder than 

 either the photosphere or the sun; that this greater cold is not due to the 

 general body of the sun at the bottom of a spot being of a lower temperature than 

 the photosphere, and is not produced by any chemical or molecular process, but 

 by matter coming from a colder region; and that when a spot is formed there is a 

 down-rush and melting of photospheric matter. In a paper by M. Faye, in the 

 Complcs-Rendus, the author deduces from Mr. Carrington's researches the con- 

 clusions that sun spots are depressions beneath the surface of the sun's photo- 

 sphere, from 20,000 to 40,000 miles in depth; that many of the apparent irregu- 

 larities of their motion, attributed to cyclones, are probably explicable by the con- 

 tinued variation in the motion proper to each successive parallel of the photo- 

 sphere; and that the great regularity of their motions seems incompatible with 

 any hypothesis of mere superficial or local movements in the photosphere, and 

 rather points to some more general action arising from the internal mass of the 

 sun. TR. 



