What We Learn from trie Sun 



chief office in the economy of the planetary 

 scheme. 



Properly speaking, the physical constitution 

 of the sun only requires to be dealt with in such 

 a work as the present, in so far as it is directly 

 associated with the sun's action upon the worlds 

 around him, or as it may bear upon the question 

 of the constitution of those worlds. But the 

 subject is so interesting, and it would indeed be 

 so difficult to draw a line of demarcation between 

 the facts which bear upon the question of other 

 worlds and those which do not, that I may be 

 permitted to enter at some length into a con- 

 sideration of the solar orb, as modern physical 

 discoveries present it to our contemplation. 



The study of solar physics may be said to have 

 commenced with the discovery of the sun-spots, 

 about two hundred and sixty-seven years ago. 

 Ihese spots were presently found to traverse the 

 solar disk in such a way as to indicate that the 

 sun turns upon an axis once in about twenty-six 

 days. Nor will this rotation appear slow when 

 we remember that it implies a motion of the 

 equatorial parts of the sun's surface at a rate 

 exceeding some seventy times the motion of our 

 swiftest express trains. 



Next came the discovery that the solar spots 

 are not surface stains, but deep cavities in the 

 solar substance. The changes of appearance 

 presented by the spots as they traverse the solar 

 disk, led Dr. Wilson to form this theory so far 

 back as 1779; but, strangely enough, it is only 

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