352 FROM NEBULA TO NEBULA 



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 by 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 

 upon whether they were originally submerged, and if so 

 to what depth. 



Just as there may be peaks within craters so there 

 may be craters within craters. The difference consists in 

 this, that whereas the peaks are solid columns mounted 

 on islands from snow supplied by the vapors risen from 

 surrounding pools, the craters are hollow chimneys 

 grounded upon the margins of enclosed wells sunken into 

 the floor of the main basin. That is to say, some pools, 

 both large and small, when baled out, -exhibit not only 

 protuberances on their floors, but also pit holes that still 

 remain filled with water, and these sub-pools by going 

 through the same modus operandi as did the original one 

 give birth to sub-craters. In fine, every dent in the 

 moon's surface that normally would be filled with water 



