56 EVOLUTION [CHAP. II 



Letter 22 junction with London Clay and Greensand ? If so our house 

 would be a good central place, and my horse would be at 

 your disposal. Could you not spin a long week out of this 

 examination ? it would in truth delight us, and you could 

 bring your papers (like Lyell) and work at odd times. Forbes 

 has been writing to me about his subsidence doctrines ; I wish 

 I had heard his full details, but I have expressed to him in 

 my ignorance my objections, which rest merely on its too 

 great hypothetical basis ; I shall be curious, when I meet 

 him, to hear what he says. He is also speculating on the 

 gulf-weed. I confess I cannot appreciate his reasoning about 

 his Miocene continent, but I daresay it is from want of 

 knowledge. 



You allude to the Sicily flora not being peculiar, and this 

 being caused by its recent elevation (well established) in the 

 main part : you will find Lyell has put forward this very 

 clearly and well. The Apennines (which I was somewhere 

 lately reading about) seems a very curious case. 



I think Forbes ought to allude a little to Lyell's : work on 

 nearly the same subject as his speculations ; not that I mean 

 that Forbes wishes to take the smallest credit from him or 

 any man alive ; no man, as far as I see, likes so much to give 

 credit to others, or more soars above the petty craving for 

 self-celebrity. 



If you come to any more conclusions about polymor- 

 phism, I should be very glad to hear the result : it is 

 delightful to have many points fermenting in one's brain, and 

 your letters and conclusions always give one plenty of this 

 same fermentation. I wish I could even make any return for 

 all your facts, views, and suggestions. 



Letter 23 To J. D. Hooker. 



The following extract gives the germ of what developed into an 

 interesting discussion in the Origin (Ed. I., p. 147). Darwin wrote, "I 

 suspect also that some cases of compensation which have been advanced 

 and likewise some other facts, may be merged under a more general 

 principle: namely, that natural selection is continually trying to economise 

 in every part of the organism." He speaks of the general belief 

 of botanists in compensation, but does not quote any instances. 



1 See Letter 19. 



