480 THE POPULAR SCIENCE MONTHLY. 



broad plains, which are probably the bottoms of ancient seas that have 

 now dried up, but these cover only about two fifths of the surface 

 visible to us, and most of the remaining three fifths are exceedingly 

 rugged and mountainous. Many of the mountains of the moon are, 

 foot for foot, as lofty as the highest mountains on the earth, while all 

 of them, in proportion to the size of the moon's globe, are much larger 

 than the earth's mountains. It is obvious, then, that the sunshine as 

 it creeps over these Alpine landscapes in the moon, casting the black 

 shadows of the peaks and craters many miles across the plains, and 

 capping the summits of lofty mountains with light, while the lower 

 regions far around them are yet buried in night, must clearly reveal 

 the character of the lunar surface. Mountains that can not be seen at 

 all when the light falls perpendicularly upon them, or, at the most, 

 appear then merely as shining points, picture themselves by their 

 shadows in startling silhouettes when illuminated laterally by the 

 rising sun. 



But at full moon, while the mountains hide themselves in light, the 

 old sea-beds are seen spread out among the shining table-lands with 

 great distinctness. Even the naked eye readily detects these as ill- 

 defined, dark patches upon the face of the moon, and to their presence 

 are due the popular notions that have prevailed in all quarters of the 

 world about the " Man in the Moon," the " Woman in the Moon," 

 " Jacob in the Moon," the " Hare in the Moon," the " Toad in the 

 Moon," and so on. But, however clearly one may imagine that he dis- 

 cerns a man in the moon while recalling the nursery rhymes about 

 him, an opera-glass instantly puts the specter to flight, and shows the 

 round lunar disk diversified and shaded like a map. 



A feature of the full moon's surface that instantly attracts attention 

 is the remarkable brightness of the southern part of the disk, and the 

 brilliant streaks radiating from a bright point near the lower edge. 

 The same simile almost invariably comes to the lips of every person 

 who sees this phenomenon for the first time " It looks like a peeled 

 orange." The bright point, which is the great crater-mountain 

 Tycho, looks exactly like the pip of the orange, and the light streaks 

 radiating from it in all directions bear an equally striking resemblance 

 to the streaks that one sees upon an orange after the outer rind has 

 been removed. I shall have something more to say about these curious 

 streaks farther on ; in the mean time, let us glance at our first illustra- 

 tion, which is a small sketch-map of the moon. 



The so-called seas are marked on the map, for the purpose of refer- 

 ence, by the letters which they ordinarily bear in lunar maps. The 

 numerals indicate craters, or ring-plains, and mountain-ranges. The 

 following key-list will enable the reader to identify all the objects that 

 are lettered or numbered upon the map. I have given English trans- 

 lations of the Latin names which the old astronomers bestowed upon 

 the seas : 



