ITS EARLIEST STAGES. 163 



earth, the whole earth had no such tendency ; that 

 the inequalities on the surface were so small as 

 not materially to affect the shape of so vast a 

 mass; that drops of water naturally form them- 

 selves into figures with a convex surface ; that the 

 end of the ocean would fall if it were not rounded 

 off; that we see ships, when they go out to sea, 

 disappearing downwards, which shows the surface 

 to be convex. These are the arguments still em- 

 ployed in impressing the doctrines of astronomy 

 upon the student of our own days ; and thus we 

 find that, even at the early period of which we 

 are now speaking, truths had begun to accumulate 

 which form a part of our present treasures. 



Sect. 10. The Phases of the Moon. 



WHEN men had formed a steady notion of the 

 moon as a solid body, revolving about the earth, 

 they had only further to conceive it spherical, and 

 to suppose the sun to be beyond the region of the 

 moon, and they would find that they had obtained 

 an explanation of the varying forms which the 

 bright part of the moon assumes in the course of 

 a month. For the convex side of the crescent- 

 moon, and her full edge when she is gibbous, are 

 always turned towards the sun. And this expla- 

 nation, once suggested, would be confirmed, the 

 more it was examined. For instance, if there be 

 near us a spherical stone, on which the sun is 



M2 



