ASTRONOMY OF EIGHTEENTH CENTURY. 



275 



FIG. 129. 



the moon's relation to the earth, have been unable to admit that she 

 turns on her axis at all. Now, it is impossible, by all the laws of 

 probability, for us to believe that this perfect equality is a mere acci- 

 dental coincidence, and not the effect of some connecting cause. 

 Attentive observation of the lunar spots shows that certain parts of 

 the surface near the edge of the moon's disc disappear and reappear 

 periodically. These oscillations seeming to indicate a sort of balanc- 



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