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THE PAST HISTORY OF OUR MOON. 



THE moon, commonly regarded as a mere satellite of the 

 earth, is in truth a planet, the least member of that family 

 of five bodies circling within the asteroidal zone, to which 

 astronomers have given the name of the terrestrial planets. 

 There can be no question that this is the true position of 

 the moon in the solar system. In fact, the fashion of re- 

 garding her as a mere attendant of our earth may be looked 

 upon as the last relic of the old astronomy in which our 

 earth figured as the fixed centre of the universe, and the 

 body for whose sake all the celestial orbs were fashioned. 

 In this aspect, also, the moon is a far more interesting 

 object of research than when viewed as belonging to another 

 and an inferior order. We are able to recognise, in her, ap- 

 pearances probably resulting from the relative smallness of 

 her dimensions, and hence to derive probable information 

 as to the condition of other orbs in the solar system which 

 fall below the earth in point of size. Precisely as the study 

 of the giant planets, Jupiter and Saturn, has led astronomers 

 to infer that certain peculiarities must result from vastness 

 of dimensions, so the study of the dwarf planets, Mars, our 

 moon, and Mercury, may indicate the relations we are to 

 associate with inferiority of size. 



This thought immediately introduces us to another con- 

 ception, which causes us to regard with even greater interest 

 the evidence afforded by the moon's present condition. It 

 can scarcely be questioned that the size of any member of 

 the solar system, or rather the quantity of matter in its 



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