24 CONSTITUENT MATERIALS OF THE EARTH, 



equal in height to nearly the highest of our Andes. They 

 are generally of extreme steepness, and sharp of outline, 

 a peculiarity which might be looked for in a planet defi- 

 cient in water and atmosphere, seeing that these are the 

 agents which wear down ruggedness on the surface of our 

 earth. The volcanic operations are on a stupendous scale. 

 They are the cause of the bright spots of the moon, while 

 the want of them is what distinguishes the duller portions, 

 usually but erroneously called seas. In some parts, bright 

 volcanic matter, besides covering one large patch, radiates 

 out in long streams, which appear studded with subordi- 

 nate foci of the same kind of energy. Other objects of a 

 most remarkable character are ring-mountains, mounts 

 like those of the craters of earthly volcanoes, surrounded 

 immediately by vast and profound circular pits, hollowed 

 under the general surface, these again being surrounded 

 by a circular wall of mountain, rising far above the cen- 

 tral one, and in the inside of which are terraces about the 

 same height as the inner eminence. The well-known 

 bright spot in the south-east quarter, called by astrono- 

 mers, Tycho, and which can be readily distinguished by 

 the naked eye, is one of these ring-mountains. There is 

 one of 200 miles in diameter, with a pit 22,000 feet deep ; 

 that is, twice the height of Etna. It is remarkable, that 

 the maps given by Humboldt of a volcanic district in 

 South America, and one illustrative of the formerly vol- 

 canic district of Auvergne, in France, present features 

 strikingly like many parts of the moon's surface, as seen 

 through a good glass. 



These characteristics of the moon forbid the idea that 

 it can be at present a theatre of life like the earth, and 

 almost seem to declare that it never can become so. But 

 we must not rashly draw any such conclusions. The 

 moon may be only in an earlier stage of the progress 

 through which the earth has already gone. The elements 

 which seem wanting may be only in combinations diffe- 

 rent in those which exist here, and may yet be deve- 

 loped as we here find them. Seas may yet fill the profound 

 hollows of the surface ; an atmosphere may spread over 

 the whole. Should these events take place, meteorological 

 phenomena, and all the phenomena of organic life will 

 commence, and the moon, like the earth, will become a 

 green and inhabited world. 



It is unavoidably held as a strong proof in favor of any 



