IS TEE MO OK DEAD? 



279 



the farther or unseen hemisphere of the moon, 

 needs serious refutation. (The other two are 

 Whiston's theory, that a comet carried off the 

 lunar seas and air ; and the theory — whose au- 

 thor is unknown to us — that the lunar seas, and 

 later the lunar atmosphere, have been frozen 

 through the intensity of cold to which, in the 

 long lunar nights, the moon is exposed.) But 

 this theory is no longer entertained by astron- 

 omers, simply because it has been shown that 

 the peculiarity of the moon's shape which had 

 suggested the theory has been found, first, to have 

 no real existence ; and, secondly, to be incapable, 

 if it existed, of exercising the supposed effect." 1 



The theory independently advanced by the 

 four students of science named above is simply 

 this, that seas formerly existing on the surface 

 of the moon have been gradually withdrawn into 

 the moon's interior, and that a similar process, 

 but chemical rather than mechanical, has led to 

 the withdrawal of the greater portion of the air 

 which formerly enveloped the moon's frame. 



It may be well, first, to inquire whether the 

 moon is likely to have had originally an atmos- 

 phere of considerable density and oceans of con- 



1 The idea was that the moon, though nearly spherical, 

 is somewhat egg-shaped, the smaller end of the egg- 

 shaped figure being directed toward our earth. Now, 

 while it is perfectly clear that on this supposition the 

 greater part of the moon's visible half would be of the na- 

 ture of a gigantic elevation sbove the mean level, and 

 would therefore be denuded (or might be denuded) of its 

 6eas and the denser parts of the air formerly covering it, 

 yet it is equally clear that all round the base of this 

 monstrous lunar elevation the seas would be gathered to- 

 gether, and the air would be at its densest. But it is 

 precisely round the base of this part of the moon, or, in 

 other words, round the bolder of the visible lunar hemi- 

 sphere, that we should have the best chance of perceiving 

 the effects of air and seas, if any really existed ; and it is 

 because of the absolute absence of all evidence of the 

 kind that astronomers regard the moon as having no 

 seas and very little air. It is worthy of notice that 

 Hansen's theory was anticipated by the author of that 

 clever little pamphlet called "The Lunar Hoax." who 

 places the human inhabitants (the Bat-men) in the regions 

 near the edge of the lunar disk, on the strength of some 

 such views as Hansen advanced a quarter of a century 

 later. Recently the Chicago Times published several 

 columns of lunar-hoax matter, purporting to be an account 

 of observations made in France with a new and exceed- 

 ingly powerful reflecting telescope. The observations 

 made with this instrument showed a number of lunar 

 folks, whose movements rendered it manifest that they 

 were prisoners undergoing some kind of penal servi- 

 tude, the visible lunar hemisphere being a sort of Botany 

 Bay or Cayenne for lunar offenders, while the other hemi- 

 sphere is a comfortable place of abode for good moon 

 people. But what an unhappy state of things is here 

 suggested ! Conceive a world, one half of whose surface 

 is required as an abode for its malefactors 1 



siderahle extent. Supposing, for the sake of ar- 

 gument, that the materials of the moon's mass 

 (including air and water) were originally propor- 

 tioned as to quantity very much like those of our 

 earth's mass, it is easily seen that the quantity 

 of air above each square mile, of the moon's sur- 

 face, at the time when the moon had reached the 

 stage of planetary development through which 

 our earth is now passing, must have been very 

 much less than the quatitity of air now existing 

 above each square mile of the earth's surface. 

 For, the moon's mass being about an eighty-first 

 part of the earth's, the mass of the lunar air 

 must have been about an eighty-first part of the 

 mass of our present atmosphere. But the moon's 

 surface bears a much greater proportion to the 

 earth's, being about a thirteenth. Whence it fol- 

 lows that, on the assumptions we have made, the 

 quantity of air above each square mile of the 

 moon's surface would be only about one-sixth 

 part of the quantity above each square mile of 

 the earth's surface. And this air being drawn 

 downward only by lunar gravity, which has but 

 about a sixth part of the energy of our terrestrial 

 gravity, would be less compressed in the same 

 degree on this account. One-sixth of the quan- 

 tity of air being thus compressed with one-sixth 

 the amount of force, it is clear that the density 

 of the lunar air in that stage of the moon's exist- 

 ence would onlv be about one thirty-sixth of the 

 density of our air. Similar reasoning applies to 

 the water, except as to the compression under 

 lunar gravity. The average quantity of water to 

 each square mile of the moon's surface would be 

 but about one-sixth part of the quantity there is 

 for each square mile of the earth's surface. The 

 relative extent of the lunar oceans would not be 

 less in precisely the same degree, however. For, 

 speaking generally, the bed of the ocean slopes 

 downward from the shore-line in such a way that 

 more than half, or a third, or a fourth, or so on, 

 would have to be removed to diminish the surface 

 by a half, a third, or a fourth, or so on, respec- 

 tively. We may illustrate our meaning here by 

 considering the relation between the quantity of 

 water in a wineglass (supposed to be cone-shaped) 

 and the surface of the water. Suppose the wine- 

 glass full at first, and the circular surface of the 

 water to be three square inches, then if five- 

 sixths of the water are thrown out, so that only 

 one-sixth remains, the surface will not be reduced 

 to one-sixth its former extent — that is, to one- 

 half of a square inch, but will be about nine- 

 tenths of a square inch. It is clear that in the 

 case of an ocean having a bottom very steeply 



