1 859.] RESTING AT ILKLEY. 1 73 



the book produces on you. I know that there will be much 

 in it which you will object to, and I do not doubt many 

 errors. I am very far from expecting to convert you to 

 many of my heresies ; but if, on the whole, you and two or 

 three others think I am on the right road, I shall not care 

 what the mob of naturalists think. The penultimate chapter,* 

 though I believe it includes the truth, will, I much fear, make 

 you savage. Do not act and say, like Macleay versus 

 Fleming, " I write with aqua fortis to bite into brass." 



Ever yours, 



C. Darwin. 



C. Darwi?i to C. Lyell. 



Ilkley, Yorkshire. 



Oct. 20th [1859]. 



My DEAR LYELL, I have been reading over all your let- 

 ters consecutively, and I do not feel that I have thanked you 

 half enough for the extreme pleasure which they have given 

 me, and for their utility. I see in them evidence of fluctua- 

 tion in the degree of credence you give to the theory ; nor am 

 I at all surprised at this, for many and many fluctuations I 

 have undergone. 



There is one point in your letter which I did not notice, 

 about the animals (and many plants) naturalised in Australia, 

 which you think could not endure without man's aid. I can- 

 not see how man does aid the feral cattle. But, letting that 

 pass, you seem to think, that because they suffer prodigious 

 destruction during droughts, they would all be destroyed. In 

 the " grandes secos " of La Plata, the indigenous animals, such 

 as the American deer, die by thousands, and suffer apparently 

 as much as the cattle. In parts of India, after a drought, it 

 takes ten or more years before the indigenous mammals get 



* Chapter XIII. is on Classification, Morphology, Embryology, and 

 Rudimentary Organs. 



