78 THE UNFINISHED BOOK. [1856. 



tremely ignorant of means of dispersal, I cannot avoid think- 

 ing that Forbes' ' Atlantis ' was an ill-service to science, as 

 checking a close study of means of dissemination. I shall be 

 really grateful to hear, as briefly as you like, whether these 

 arguments have any weight with you, putting yourself in the 

 position of an honest judge. I told Hooker I was going to 

 write to you on this subject ; and I should like him to read 

 this ; but whether he or you will think it worth time and 

 postage remains to be proved. 



Yours most truly, 



CHARLES DARWIN. 



[On July 8th he wrote to Sir Charles Lyell. 



" I am sorry you cannot give any verdict on Continental 

 extensions ; and I infer that you think my argument of not 

 much weight against such extensions. I know I wish I could 

 believe so."] 



C. Darwin to Asa Gray. 



Down, July 2oth [1856]. 



... It is not a little egotistical, but I should like to tell 

 you (and I do not think I have) how I view my work. 

 Nineteen years (!) ago it occurred to me that whilst otherwise 

 employed on Nat. Hist., I might perhaps do good if I noted 

 any sort of facts bearing on the question of the origin of 

 species, and this I have since been doing. Either species 

 have been independently created, or they have descended 

 from other species, like varieties from one species. I think it 

 can be shown to be probable that man gets his most distinct 

 varieties by preserving such as arise best worth keeping and 

 destroying the others, but I should fill a quire if I were to go 

 on. To be brief, I assume that species arise like our domestic 

 varieties with much extinction ; and then test this hypothesis 

 by comparison with as many general and pretty well-esta- 

 blished propositions as I can find made out, in geographical 



