754 



Notes and Correspondence. 



[Oct. 



these differences are such as to 

 affect the periods of the moon's 

 development, rather in degree than 

 in kind ; in time, for instance, or in 

 intensity. May we not therefore 

 reasonably suppose, when the mass 

 of the moon had only cooled down to 

 the state in which the earth now is, 

 that at such period of her existence 

 the relative densities of the various 

 component elements, one with 

 another, might resemble those 

 which we now see on the earth ; 

 and that certain of them might 

 then exist in a fluid or gaseous 

 state, and form such watery and 

 atmospheric envelopes as we pos- 

 sess? Owing to the small mass of 

 the moon, this stage would be of 

 much shorter dui'ation than with us, 

 but are we not bound to assume, in 

 default of proof to the contrary, 

 that it has been traversed ? Our 

 paltry experiments can give us but 

 a feeble conception of the results of 

 the intense cold of the now shrunken 

 and burnt-out mass ; but it is quite 

 in analogy with them to suppose 

 that those limits may be passed 

 within which elements can exist 

 as fluids or gases. It is indeed, 

 a priori, unlikely that the moon 

 should now possess such envelopes. 

 We must remember that the fluid 

 and gaseous states are but states of 

 relative densities, and do not inhere 

 in the nature or constitution of any 

 particular element. 



I would now ask permission to 

 pursue these speculations a step 

 farther, to carry them on from the 

 physical to the possible vital en- 

 dowments of the moon. The 

 present want of life upon the moon 

 is even more certain than the want 

 of air and water: but must this 

 have always been so ? To repeat 

 my former suggestions, I may say 

 that the mass of the moon must 

 in cooling have passed through a 

 temperature more or less fitted for 

 certain forms of life. Its constituent 

 elements, moreover, being in all like- 

 lihood similar to our own, we may 

 well conceive that they would de- 

 velop into similar combinations*; 



that is, into combinations fitted for 

 the support of life. 



If such combinations existed, we 

 have no reason to conclude that 

 the gift of life was withh olden 

 from the moon ; or if life be looked 

 upon simply as a product of plane- 

 tary change, we have every reason 

 to suppose that it would find its 

 place in the weaving together of 

 the moon's processes. I cannot 

 then help looking upon the moon, 

 now cold and dead, as having once 

 passed through the bloom of life, 

 that bloom which will one day pass 

 away from this beautiful earth when 

 all we who dwell in it are beyond 

 its gates. On the other hand, I 

 would not have it supposed that I 

 overlook the many difficulties which 

 oppose me, such, for instance, as the 

 peculiar aspects which the moon 

 bears to the sun. 



Nor do I ask that the moon may 

 be regarded with certainty as a 

 depopulated world ; I only ask 

 whether the probabilities from 

 analogy are not strong enough to 

 make us pause before we speak 

 unhesitatingly of the moon as of 

 a body blasted from its birth. It 

 may be urged against me that my 

 speculations are too fanciful, and 

 that mere dreaming of possible 

 pasts is no gain to science. I 

 should reply that I did not initiate 

 the dreaming process. It is not 

 for me now to assert, though it 

 may well be asserted, that any 

 speculation on the past history of 

 heavenly bodies is full of gain to 

 science. All I have now to do is 

 to offer one inference in place of 

 another, to show that in this argu- 

 ment from the known to the un- 

 known, two solutions at least are 

 possible, and to show if I can that 

 one is more probable than the 

 other. With my apology for in- 

 truding so far upon your space, I 

 remain, sir, yours faithfully, 



T. Clifford Allbutt, 



Physician to the Leeds Infirmary. 

 Leeds, Aug. 28, 1865. 



