216 THE BORDERLAND OF SCIENCE. 



moon travels round the earth. But in reality this is 

 erroneous, or is at least suggestive of error. The moon 

 ought to be regarded as a companion planet, travelling 

 with the earth around the sun. The^ distinction is not 

 at all a fanciful one. The earth is not the body whose 

 force the moon chiefly obeys. On the contrary, she is 

 attracted more than twice as strongly by the sun. If 

 the motions of the earth and moon could be watched 

 from some far-distant standpoint, the observed move- 

 ments would by no means suggest the idea that the 

 moon was circling round the earth ; and in fact, if the 

 earth were concealed from view while her satellite was 

 thus watched, the moon would appear to circuit round 

 the sun in an orbit which could not be distinguished 

 from that which the earth herself pursues. It is only 

 from our earth as a standpoint that the moon seems to 

 have the earth as the centre round which she travels ; 

 and to show how readily we may be deceived when so 

 viewing any celestial body, we need only remember 

 that, as seen from the earth, even the sun seems to 

 have her as the centre of his motion. It is well to 

 know the true nature of the moon in this respect; 

 because when, instead of regarding her as merely a 

 satellite or attendant upon the earth, we regard her as 

 a companion planet the least of the sun's inner 

 family of planets we perceive that in studying her we 

 are making a first step towards the knowledge of other 

 worlds than ours. 



The most striking feature in the moon's telescopic 

 aspect is the wonderfully disturbed condition of her 



