Alfred Russel Wallace 



seems to me very beautifully worked out under the influence 

 of gravitation and a resisting medium of cosmical dust — 

 which explains the origin and motions of the moon as well 

 as that of all the planets and satellites far better than Sir 

 G. Darwin's expulsion theory. 



I note however that he is quite ignorant that Proctor, 

 forty years ago, gave full reasons for this " capture " 

 theory in his " Expanse of Heaven," and also that the 

 same writer showed that the Milky Way could not have 

 the enormous lateral extension he gives to it, but that it 

 cannot really be much flattened. He does not even men- 

 tion the proofs given of this both by Proctor and, I think, 

 by Herbert Spencer, while in Mr. Webb's volume (oppo- 

 site p. 212) is a diagram showing the " Coal Sack " as a 

 " vacant lane " running quite through and across the 

 successive spiral extensions laterally of the galaxy, with- 

 out any reference or a word of explanation that such 

 features, of which there are many, really demonstrate the 

 untenability of such extension. 



An even more original and extremely interesting part 

 of Mr. See's work is his very satisfactory solution of the 

 hitherto unsolved geological problem of the origin of all 

 the great mountain ranges of the world, in Chapters X., 

 XI., and XII. of Mr. Webb's volume. It seems quite 

 complete except for the beginnings, but I suppose it is a 

 result of the formation of the earth by accretion and not 

 by expulsion, by heating and not by cooling. . . . — Yours 

 very truly, Alfred R. Wallace. 



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