THE MOON 361 



connected with a distant one by means of a channel, then 

 the appearance at noonday would be that of a dumb-bell 

 crater, with a very black handle connecting the two cen- 

 ters. It so happens in the special case of Aristillus, which 

 Prof. Pickering discusses, that the natural configuration 

 of the crateral basin is such as the dark lines and areas 

 he describes indicate. The basins must possess some 

 shape. 



There are, however, it appears, some broader change- 

 ful areas in the midst of level plains, far distant from the 

 crateral regions, and upon these Prof. Pickering seems to 

 rely most securely for his contention that there is "vege- 

 tation on the moon." My own opinion is that these areas, 

 being far remote from the snow producing pools, are 

 covered with horizontal glacial sheets less than a score of 

 feet in thickness, which either become sopped by the mid- 

 day thaws into a dull slush or, in places very far remote 

 from the pools, may even be so thin as to melt away en- 

 tirely and leave considerable spots wholly bare of icy 

 covering. Obviously, under my theory of lunar condi- 

 tions, vegetation and animal life there are alike out of the 

 question, and candor compels me to add that, even under 

 the volcanic hypothesis of the origin of the moon's fea- 

 tures, which Mr. Pickering champions, I cannot see the 

 reasonableness of his view, best qualified of all men 

 though he may be to speak at first hand on this subject. 



Why are there no clouds to be seen on the moon, 

 where so much water exists? My answer is, that vapor 

 cannot arise directly from a crystalline surface, but must 

 first pass through the detached liquid stage. Until a 

 blanket of snow is reduced to at least the condition of a 

 very shallow slush, it will never give off "steam". On 

 the moon there is indeed an immense amount of thawing 

 going on during the day, but the fluid water, where in im- 

 mediate contact with crystallic ice, preserves its liquidity 

 and seeps down into and through the porous, spongy 

 snow underneath. Not only this, but such little vapor as 

 does form obviously becomes quickly frosted by the "air" 

 and settles immediately. Either of these explanations 



