390 FROM NEBULA TO NEBULA 



erosion, and if not why not, to account for their ruined condition, 

 but have failed. The opinion seems to prevail that they have been 

 submerged, inundated by molten matter welling up from the in- 

 terior burying them. As this would require material enough to 

 spread over between two and three millions of square miles, and 

 to a depth of more than a mile, and as we find no trace of such 

 a lava outflow except in the seas, if there, I find it difficult to 

 accept the theory, even with my great respect for the above named 

 masters of selenography. 



CRATERS. The flatness of Mars, a larger body, indi- 

 cates that the moon should be essentially fully as flat, if 

 not more so. Such a land surface, we know from daily 

 observation, is ordinarily exceedingly cut up by channels 

 into all sorts of irregular islands and peninsulas, diver- 

 sified by equally miscellaneous small expanses of water of 

 varying depth. Let us pick out, to begin with, a large 

 lake of considerable depth and possessing a smooth floor, 

 and question ourselves what sort of a snow structure 

 would be likely to result were the water to be set to boil- 

 ing on the coldest day of an Arctic winter. The rising 

 vapor would, as a matter of course, meeting the icy air, 

 transform itself into snow, and, unless driven far by 

 winds, descend and settle on the nearest land, namely, the 

 margins of the lake, where they would continue to build 

 themselves up as long as there was neighboring water 

 being evaporated. Of course, a good deal of the snow 

 would fall back upon the water, but there it could not lie, 

 unless, indeed, the lake froze over, which, in turn, would 

 mean the cessation of the chain. But let the process con- 

 tinue until the lake went dry, what shall we then have? 

 Surely nothing else but a simple lunar crater a cavity 

 hollowed out of the earth surrounded loy a solid wall of 

 white. 



If instead of a single lake, you will imagine another 

 one adjoining it, and much deeper, you will find at the 

 end of the operation one complete wall encircling the sec- 

 ond or deeper lake encroaching upon and "ruining" the 

 wall of the first. Let there be an island or islands in the 

 lakes, and you will have examples of a peak or peaks, 

 whose thickness and height will depend in large measure 



