

What We Learn from the Sun 



clouds, the outer self-luminous and constituting 

 the true solar photosphere, the inner reflecting 

 the light received from the outer layer, and so 

 shielding the real surface of the sun from the 

 intense light and heat which it would otherwise 

 receive. 



But while recent discoveries have confirmed 

 Sir William Herschel's theory about the solar 

 cloud-envelopes, they have by no means given 

 countenance to his view that the body of the sun 

 may possibly be cool. The darkness of the 

 nucleus of a spot is found, on the contrary, to 

 give proof that in that neighborhood the sun is 

 hotter, because it parts less readily with its heat. 

 We shall see presently how this is. Meantime 

 let it be noticed in passing that a close scrutiny 

 of large solar spots has revealed the existence of 

 an intensely dark spot in the midst of the umbra. 

 This spot must be regarded as the true nucleus. 



The circumstance that the spots appear only 

 on two bands of the sun's globe, corresponding 

 to the subtropical zones on our own earth, led 

 the younger Herschel to conclusions as important 

 as those which his father had formed. He 

 reasoned, like his father, from terrestrial analogies. 

 On our own earth the subtropical zones are the 

 regions where the great cyclonic storms have 

 their birth, and rage with their chief fury. Here, 

 therefore, we have the analogue of the solar spots 

 if only we can show reason for believing that 

 any causes resembling those which generate 

 the terrestrial cyclone operate upon those regions 

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