ASTRONOMY. 437 



than the rest. It has been conjectured that the 

 part which reflects the least light is water, and that 

 the brightest part is land. This, however, is un- 

 certain ; and some are of opinion that the moon 

 contains no water. 



It has been doubted whether the moon has an 

 atmosphere like ours ; and notwithstanding great 

 pains have been taken on this subject, no proofs of 

 an atmosphere have been established. 



The moon is seen by means of the light which 

 comes to it from the sun being reflected from it. 

 Its changes or phases depend upon its situation 

 relatively to the earth and the sun. When the 

 moon is in opposition to the sun, the enlightened 

 side is turned towards the earth, and it appears 

 full. When the moon is in conjunction with the 

 sun, its dark side is turned towards us, and it is in- 

 visible. As it proceeds in its orbit, a small part of 

 the enlightened side is seen, and then we have a 

 new moon; and we continue to see more and more 

 of the enlightened side, as the moon approaches to 

 the state of opposition or full moon. The waning 

 or decreasing of the moon takes place in the same 

 manner, but in a contrary order. 



The earth must perform the same office to the 

 moon, that the moon does to us; and it will appear 

 to the inhabitants of the moon, (if there be any,) 

 like a very magnificent moon, being to them about 

 fifteen times as big as the moon to us, and it will 

 also have the same changes or phases. 



The moon's motion is subject to many irregu- 

 larities, on account of the inclination of its orbit 

 to the plane of the ecliptic, and the attraction of 

 the sun and the other planets. 



Mars is not so bright as Venus, nor even as 

 Jupiter, though nearer to the sun. Its colour is a 



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