Astronomers have occasionally extended their speculations beyond the im- 

 mediate and rigorous limits of observation, and had endeavored by analogy to 

 afford us some idea of the actual condition of lunar surface. I annex here a 

 drawing of a lunar crater, from the design of a French observer. 



THE ORBIT OF THE MOON. 



Although in its general form and character the path of the moon round the 

 earth is, like that of the orbits of the planets and satellites in general, circular, 

 yet, when it is submitted, to accurate observation we find that it is strictly 

 an ellipse or oval, the centre of the earth occupying one of its foci. This 

 fact can be ascertained by immediate observation upon the apparent magnitude 

 of the moon. It will be easily comprehended that any change which the apparent 

 magnitude of the moon as seen from the earth undergoes, must arise from 

 corresponding changes in the moon's distance from us. Thus, if at one time 

 the disk of the moon appears larger than at another time, as it cannot be sup- 

 posed that the actual size of the moon itself could be changed, we can only 

 ascribe the increase of the apparent magnitude to the diminution of its dis 



