May 1, 1886.] 



♦ KNOWLEDGE ♦ 



211 



reader may ask, a very different result from the former 1 

 On the contrary, it is precisely the same re.-iiilt ! For, by our 

 present assumption, the rate at which either planet ages is 

 only one-hundredtli of the rate we liad before assumed. 

 Hence the tliree thousand millions of years in our result 

 indicate an amount of aging ctiuivalent only to that 

 i-esulting in thii-ty millions of years according to our former 

 assumption. 



Since, then, we are quite certain of this, that the time 

 when earth and moon were equally advanced in planetary 

 life must bs set millions of years ago, we ai-e at least certain 

 also of this, that our earth will not be so old as the moon 

 now is. she will not be so wi-etchodly decrepit (if not so 

 utterly dead) a world until many millions of years have 

 passed. 



So far as this reasoning is concerned, the moon might 

 have passed through a life much like that of our earth. She 

 might well have had a life-bearing period akin to that 

 through which the earth is passing at present. True, the 

 various stages of her life would be very much shorter, and 

 we can very well believe that, therefore, the various forms of 

 animal life which have been developed on the earth would 

 not have bad the same chance of being properly developed 

 on the moon. Or, considering the progre.ss of a single race 

 — our own — we can very well imagine that a being like 

 man on the moon would not have had sufficient time to pa's 

 through all the stages by which man has passed from the 

 arboreal, hairy, pointed-eared, and four-legged ancestry 

 now assigned liim, to the civilised man of to-day, inventing 

 every year more perfect instruments for destroying his 

 fellows. The Lunai-ian, thus understood, may have been 

 no better fighter than the man of the caves, or even than 

 the more advanced fighters among the anthropoid apes, our 

 cousins. In other words, he may have been a perfectly 

 contemptible creature, instead of a being of murderously 

 imperial instincts. 



But now a consideration comas in which suggests the idea 

 that at no time could the forms of animal and vegetable life 

 on the moon have resembled those on the earth. We must 

 apportion to the moon no more than her fair allowance of 

 water, no more than her fair allowance of air. And when we 

 have done this, we find strong reason for thinking that, though 

 that allowance of water and of air may have done very 

 well for the Lunarians, it would not have done at all for us. 

 Let us begin with the water. The moon would have had 

 one eighty-first part of the quantity of water which foi'med 

 our earth's share. So far, good, That seems altogether 

 fair. But observe. Our earth, with eighty-one times as 

 much water, had a surface only thirteen and a half times as 

 large over which to distribute that water in seas. It needs 

 not even the ghost of Cocker to show that the e:irth had six 

 times as much water per square mile. That of itself must 

 have sufiiced to make a very marked difference between the 

 moon's condition tlif-n and our earth's condition now. Nor 

 does it seem at all likely that at any stage, either earlier or 

 liter, the moon would have had a better chance of doing 

 well in the universe than she had then — that is, at the time 

 when she had reached the same sfcige of cooling which the 

 earth has reached now. 



But the want, or the short allowance, of water was as 

 nothing compared with the thin air the Lunarians, if there 

 ever were any, had to bre;ithe. 



Of course, as regards quantity of aii-, the reasoning is the 

 same precisely as for water. Only one sixth part of the 

 quantity of air which we have on this earth per square mile 

 was (on the average) above each square mile of the moon. 

 On the earth this would be a most serious matter. For the 

 density of au- depends on the weight of the total quantity 

 above the surface ; so that the density of the air would be 



reduced to one sixth part if the quantity of air above aich 

 square mile were no greater here than it probably was on 

 the moon, in the corresponding part of her planetary life. 

 Now in the highest ascent above the sea-level which men 

 have yet made — the celebrated balloon ascent by Messrs. 

 Coxwell and Glaisher — the height attained was within a 

 very few feet of the height of Mount Everest, the highest 

 known peak of the Himalayas. At that height the air was 

 reduced to little more than one-fourth its density at the sea- 

 level. Mr. Glaisher faiuted, and, if he had been alone, it 

 would have been all up with him, even though the balloon 

 might eventually have come down. Mr. Coxwell remained 

 conscious, however. Nay, with creditable zeal for science, 

 he even urged the fainting meteorologist to " make one 

 other little observation, now — do," to which, however, Mr. 

 Glaisher only responded by fainting dead away. Mr. Cox- 

 well began, he tells us, to feel rather blue. Looking at his 

 hands, he perceived that they were quite blue. They were 

 also powerless, which was an even more serious matter ; for 

 it was neces,sary that the valve-strings should be pulled, if 

 the conscious and the unconscious aeronauts were to be 

 saved. !Mr. Coxwell was equal to the occasion. Seizing 

 hold of the valve-string with his teeth, he drew it — feebly 

 indeed, but still so that it worked — and the balloon began 

 to descend. He had saved himself and his companion, but 

 only as by the skin of his teeth. Certainly this proved 

 that no man could live, even for a few minutes, in air of 

 only one-sixth of the density of the air at our sea-level — 

 for that would be but two-thirds as dense as the air whose 

 rarity so nearly killed our aeronauts. 



Even this, however, wovdd be as nothing compared with 

 the tenuity of the lunar air, if we are right in supposing that, 

 at the coiTespondtng stage of her planetary life, the moon had 

 the same allowance of air as compared with her mass that our 

 eiirth has now. For, the smaller quantity of air would be 

 drawn down with smaller force, gravity at the moon's sur- 

 face being only one sixth part of gravity at the suifaee of 

 our earth. Instead of the lunar air having one-sixth, it 

 would only have one thirty-sixth, of the density of our air at 

 the sea-level. Air so thin would not only be unbreathable 

 by creatures like ourselves ; it would not suppoi t any kind 

 of life known to us on earth, except such life as there is (if 

 life it Kin be called) in rotifers and other such creatures, 

 which can not only live with the smallest possible allowance 

 of air, but resist with apparently unimpaired cheerfulness 

 the action of a roasting heat and a much more than freezing 

 cold, and can neither be boiled nor baked, nor drowned nor 

 desiccated, to death. 



Consider, agiiin, some of the unpleas<int results of such 

 extreme rarity or tenuity of the air. It may seem rathei- a 

 convenience than otherwise that the mercurial barometer 

 would be only five-sixths of an inch in height. But the 

 water barometer, instead of being, as with us, about thirty- 

 three feet in height, would have a height of less than one foot. 

 Now this in itself would not signify, but it would me;in 

 (and this would signify) that one foot would be the extreme 

 height to which a suction pump would raise water. "What 

 a nuisance that would be 1 especially, too, where, as we have 

 seen, water would not be very plentiful, and wells would 

 have to be dug deeper than on the earth to reach it. Then 

 drinking would be much more diflicult — which might, how- 

 ever, be as well, where water would be so hard to get at — 

 for in drinking we exhaust the air on one side of the water 

 in our drinking- vessel (the air inside the mouth), and the 

 air on the other side (outside the mouth) obligingly presses 

 the water into the mouth, where we want it to go. But 

 the air outside would not do this with sufficient energy if 

 its density were reduced to one-sixteenth ; so that, in order 

 to drink, one would have to tip the drinking- vessel up till 



