THE MOON, PLANETS, AND COMETS 247 



253. Erosion and craters. In consequence of the fact that 

 the surface of the moon has neither atmosphere nor water, 

 it has suffered no erosion. It is not known that rains and 

 snows have ever dissolved the rocks or that winds have ever 

 scattered their 

 disintegrated re- 

 mains in the 

 valleys. How 

 different it has 

 been upon the 

 earth! On its 

 surface rocks 

 have crumbled 

 away, and moun- 

 tains have actu- 

 ally disappeared 

 in the course of 

 geological time 

 as a result of the 

 disintegrating 

 effects of water 

 and the atmos- 

 phere. The rec- 

 ords of the early 

 condition of the 

 earth's surface 

 have been de- 

 Stroyed by the FlG " 124 ' The moon at six days 



Wasting effects Photograph by the Yerkes Observatory 



of air and water. On the other hand, on the surface of the 

 moon there are preserved for our inspection through the great 

 telescopes of modern times the records of the forces which 

 broke up and scattered about in wild disorder materials of the 

 surfaces of worlds in their early stages. Its surface is covered 

 with great circular pits called craters (fig. 124), some of which 



