THE MOON 399 



when snow was falling it was still possible to see the sun. The 

 fine dusty snow appears to be precipitated directly from the lower 

 layers of the atmosphere without the preliminary formation of 

 clouds. It is what is known as frost snow in some parts of Nor- 

 way. 



When I use the word "pool", the reader is not to 

 presume that I necessarily mean a circular or sub-circu- 

 lar shape. Its shape may indeed be such, but if so, it 

 would be purely accidental. It all depends on the con- 

 figuration of the natural water courses, and these, as 

 everyone knows, may be forked and connected up in any 

 sort of way imaginable. Let a deep lake, for instance, be 

 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 ba- 

 sins. 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 



