To W. D. Fox 23 September 
Down Bromley Kent
My dear Fox
I was very glad to get your letter a few days ago. I was wishing to hear about you, but have been in such an absorbed, slavish, overworked state, that I had not heart without compulsion to write to anyone or do anything, beyond my daily work.— Though your account of yourself is better, I cannot think it all satisfactory, & I wish you could soon go to Malvern again.—1 My Father used to believe largely in an old saying that if a man grew thinner between 50 & 60 years of age his chance of long life was poor, & that on the contrary it was a very good sign if he grew fatter;2 so that your stoutness, I look at as very good omen.—
My health has been as bad as it well could be all this summer; & I have kept on my legs, only by going at short intervals to Moor Park; but I have been better lately, & thank Heavens, I have at last as good as done my Book, having only the index & two or three Revises to do.— It will be published in 1st week in November & a copy shall be sent you.— Remember it is only an Abstract (but has cost me above 13 months to write!!) & facts & authorities are far from given in full. I shall be curious to hear what you think of it, but I am not so silly as to expect to convert you.— Lyell has read about half of the volume in clean sheets & gives me very great kudos.3 He is wavering so much about the immutability of species; that I expect he will come round.— Hooker has come round & will publish his belief soon—4
So much for my abominable volume, which has cost me so much labour that I almost hate it.—
On October 3d. I start for Ilkley but shall take 3 days for journey! It is so late that we shall not take house; but I go there alone for 3 or 4 weeks; then return home for a week & go to Moor Park for 3 or 4 weeks, & thus I shall get a moderate spell of Hydropathy; & I intend, if I can keep to my resolution of being idle this winter. But I fear ennui will be as bad as a bad stomach.— Emma has suffered much from headach of late; but I hope will soon be better.— I very much fear that my eldest girl Etty will never be strong; & Lenny has been often ailing for last 2 years with intermittent (but only symptomatically so) pulse.— My poor constitution like everything else is transmitted by inheritance.—
My eldest two Boys give me in every way much satisfaction.
Farewell my dear old friend. I truly hope that you will steadily get stronger. I shd. much like another note before very long. Farewell | Ever yours affecty | C. Darwin
Remember if ever you can find out whether a cross between any two coloured horses produces a dun, I shd. particularly wish to hear.—5
His book [Origin] is nearly done. Is not so silly as to expect to convert WDF. Lyell is wavering; Hooker has come round.
Asks WDF to find out if a cross between differently coloured horses produces a dun.