THE MOON. 



M 



forms its revolution round the earth. The light of the sun 

 illuminates one half of its surface, and leaves the other in 

 darkness. Of this illumination we perceive different de- 

 grees, according to the various positions of the moon, with 

 respect to the sun and the earth. We see one half of its 

 body enlightened, or a fall moon, wheh it is placed in oppo- 

 sition to the sun, or when the sun is in one part of the hea- 

 vens, as west, and the moon in the opposite part, as east. 

 When the moon is in conjunction with the sun, or in that 

 part of its orbit which is between the earth and the sun, its 

 enlightened surface is turned from us, which renders it in- 

 visible ; this is the time of the new moon. When the moon 

 appears in the intermediate part of its orbit, between the 

 conjunction and opposition, it is in its quadratures, and about 

 half of its illuminated surface is turned towards us. 



As the moon illuminates the earth by light reflected from 

 the sun, so she is reciprocally illuminated by the earth which 

 reflects the sun's rays to the surface of the moon. As the 

 surface of the earth is more than thirteen times greater than 

 that of the moon, the earth must appear to the inhabitants 

 of the moon thirteen times larger than the moon does to us, 

 and it will exhibit the same pliases, but in an opposite order. 

 As the rotation of the moon on her axis is performed in the 

 same time that she goes once round the earth, — which is 

 evident from her always presenting the same face to us dur- 

 ing the whole of her monthly revolution, — it is plain, that 

 the inhabitants of one half of the lunar world are totally de- 

 prived of a sight of the earth, unless they travel to the oppo- 

 site hemisphere. 



The face of the moon appears to have shades of different 

 colours. If viewed through an ordinary telescope, her sur- 

 face will appear diversified with long tracts of mountains 

 and cavities. It has been ascertained that these are moun- 

 tains from the shadows which they cast, and some of them 

 are supposed to be volcanic. 



The difference between the rising of the moon on one day 

 and the preceding is generally about fifty minutes. But in 

 places of considerable latitude, there is a remarkable differ- 

 ence about the time of harvest, when at the season of full 

 moon she rises for several nights together only about twenty 

 minutes later on the one day than on that immediately pre- 

 ceding. By thus succeeding the sun before ihe twilight i& 



