To Leonard Horner   23 December [1859]

My dear M^r Horner.

I must have the pleasure of thanking you for your extreemly kind letter. I am very much pleased that you approve of my Book & that you are going to pay me the extraordinary compliment of reading it twice.

I fear that it is tough reading; but it is beyond my powers to make the subject clearer. Lyell would have done it admirably.

You must enjoy being a gentleman at your ease; & I hear that you have returned with ardour to work at the Geological Society.¹ We hope in the course of the winter to persuade M^rs. Horner² & yourself & daughters to pay us a visit.

Ilkley did me extraordinary good during the latter part of my stay & during my first week at home; but I have gone back latterly to my bad way & fear I shall never be decently well & strong.

With many thanks for your very kind letter | Pray believe me | My dear M^r Horner | Yours very sincerely | Charles Darwin.

P.S. When any of your party write to Mildenhall,³ I should be much obliged if you would say to Bunbury that I hope he will not forget, whenever he reads my Book, his promise to let me know what he thinks about it; for his knowledge is so great & accurate that everyone must value his opinion highly. I shall be quite contented if his belief in the immutability of species is at all staggered.⁴