PHYSICAL CHARACTER OP THE SURFACE. 



ends and the dark hemisphere begins, we shall find that it is not 

 an even and regular curve, which it undoubtedly would be if the 

 surface of the globe of the moon were smooth and regular, or 

 nearly so. If, for example, the lunar surface resembled in its 

 general characteristics that of our globe ; granting the total 

 absence of water, and that the entire surface is land, but that land 

 had the general characteristics of the continents of the globe of 

 the earth ; then I say, that the inner boundary of the lunar cres- 

 cent would still be a regular curve, broken or interrupted only at 

 particular points. Where great mountain ranges, like those of 

 the Alps, the Andes, or the Himalaya, might chance to cross it, 

 these lofty peaks would project vastly-elongated shadows along 

 the adjacent plain ; for it will be remembered that, being situated 

 at the moment in question at the boundary of the enlightened and 

 darkened hemispheres, the shadows would be those of evening 

 and morning; which are prodigiously longer than the objects 

 themselves. The effects of these would be to cause gaps or 

 irregularities in the general outline of the inner boundary of the 

 crescent ; with these rare exceptions, the inner boundary of the 

 crescent produced by a globe like the earth would be an even and 

 regular curve. 



Such, however, is not the case with the inner boundary of the 

 lunar crescent, even when viewed 



by the naked eye, and still less ^ 



so when magnified by a telescope. 

 It is found, on the contrary, 

 rugged and serrated, and bril- 

 liantly illuminated points are seen 

 in the dark parts at some distance 

 from it, while dark shadows of 

 considerable length appear to 

 break into the illuminated sur- 

 face. The inequalities thus ap- 

 parent indicate singular cha- 

 racteristics of the surface. The 

 bright points seen within the dark 

 hemisphere are the peaks of lofty 

 mountains tinged with the sun's 

 light. They are in the condition 

 with which all travellers in Alpine 

 countries are familiar ; after the 

 sun has set, and darkness has set in over the valleys at the foot of 

 the chain, the sun still continues to illuminate the peaks above. 

 The sketch (fig. 6), of the lunar crescent, will illustrate these 

 observations. 



45 



