462 LETTERS TO DARWIN AND OTHERS. [1863, 



Again, in your last sentence. When you unscien- 

 tific people take up a scientific principle you are apt to 

 make too much of it, to push it to conclusions beyond 

 what is warranted by the facts. But, because a par- 

 ticular race has persisted in Egypt, how do you know 

 that it is the only race capable of perpetuating itself ? 



If there had been a large infusion of different peo- 

 ple in Egypt, and if they had exterminated the old 

 race, do you not suppose this would have established 

 itself, perpetuated itself, and that its particular adap- 

 tations to the climate would have been different from 

 that of the present race ? 



If you cut off aU future immigration into North 

 America, would the Indians resume possession of the 

 country ? or else our descendants become a copper- 

 colored race ? 



Enough for the present. When you have cracked 

 these nuts, send me, if you please, another sheet. 



Ever yours cordially, AsA Gkay. 



Cambridge, July 6, 1863. 



Deae Brace, — Yours of 20th ult. came just as J. 

 was off for New Haven and I getting ready to go to 

 her aid. 



We came back only on Thursday, or rather Eriday 

 morning. My hands so full that I could not write to 

 Darwin, to whom I owe a long letter, tiU to-night. I 

 will now inclose your note. 



It would be very like a chemist to think that exter- 

 nal influences will explain everything. But I pre- 

 sume he believes that peculiarities are heritable. If 

 he does, then he thinks he can explain, or will be able 

 to explain, the origination of variations. I cannot, 

 that is, to any extent, and do not expect to. When 



