Masterpieces of Science 



Saturn, which has been effected by Keeler at 

 Allegheny. That these rings could not be solid 

 has long been a conclusion of the laws of mechan- 

 ics, but Keeler was the first to show that they 

 must consist of separate particles, because the 

 inner portions revolve more rapidly than the 

 outer. The question of the atmosphere of Mars 

 has also received an important advance by the 

 work of Campbell at Mount Hamilton. Although 

 it is not proved that Mars has no atmosphere, 

 for the existence of some atmosphere can scarcely 

 be doubted, yet the Mount Hamilton astronomer 

 seems to have shown, with great conclusiveness, 

 that it is so rare as not to produce any sensible 

 absorption of the solar rays. 



I have left an important subject for the close. 

 It belongs entirely to the older astronomy, and 

 it is one with which I am glad to say this ob- 

 servatory is expected to especially concern 

 itself. I refer to the question of the variation 

 of latitudes, that singular phenomenon scarcely 

 suspected ten years ago, but brought out by ob- 

 servations in Germany during the last eight 

 years, and reduced to law with such brilliant 

 success by our own Chandler. The north pole is 

 not a fixed point on the earth's surface, but 

 moves around in rather an irregular way. True, 

 the motion is small; a circle of sixty feet in dia- 

 meter will include the pole in its widest range. 

 This is a very small matter so far as the interests 

 of daily life are concerned. But it is very im- 

 portant to the astronomer. It is not simply a 

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