SO THE UNFINISHED BOOK. [1856. 



change her species and adapt them to the wondrous and ex- 

 quisitely beautiful contingencies to which every living being 

 is exposed. . . . 



C. Darwin to J. D. Hooker, 



Down, July soth, 1856. 



MY DEAR HOOKER, Your letter is of much value to me. 

 I was not able to get a definite answer from Lyell,* as you will 

 see in the enclosed letters, though I inferred that he thought 

 nothing of my arguments. Had it not been for this corre- 

 spondence, I should have written sadly too strongly. You 

 may rely on it I shall put my doubts moderately. There 

 never was such a predicament as mine : here you continental 

 extensionists would remove enormous difficulties opposed to 

 me, and yet I cannot honestly admit the doctrine, and must 

 therefore say so. I cannot get over the fact that not a frag- 

 ment of secondary or palaeozoic rock has been found on any 

 island above 500 or 600 miles from a mainland. You rather 

 misunderstand me when you think I doubt the possibility of 

 subsidence of 20,000 or 30,000 feet ; it is only probability, con- 

 sidering such evidence as we have independently of distribution. 

 I have not yet worked out in full detail the distribution of 

 mammalia, both identical and allied, with respect to the one 

 element of depth of the sea ; but as far as I have gone, the 

 results are to me surprisingly accordant with my very most 

 troublesome belief in not such great geographical changes as 

 you believe ; and in mammalia we certainly know more of 

 means of distribution than in any other class. Nothing is so 

 vexatious to me, as so constantly finding myself drawing 

 different conclusions from better judges than myself, from 

 the same facts. 



I fancy I have lately removed many (not geographical) 

 great difficulties opposed to my notions, but God knows it 

 may be all hallucination. 



* On the continental extensions of Forbes and others. 



