My dear Darwin

Though very unwilling to give you trouble, I cannot quite cease writing to you and hoping for a few lines whenever you are able to write.

Erasmus² gave a better account of you when I saw him in the Spring— I hope this may have continued, and that your wretched health, has been less wretched than usual.

Nothing but mental rest will ever give you any comfort and you have got into such a normal state of requiring the stimulus of mental activity, that you must have it, & the poor body go to the wall.

How goes on the Book?³ Requiring so many additions and corrections, that it never approaches its end I suppose.

I am anxiously looking for your work on domestic animals, which will I suppose soon be out.⁴ Possibly it may be so already, for I am sadly behind hand with knowledge of what is going on in the literary world. Except Sir P Egerton⁵ I have no literary bot Hist^y friends here—& he is never at home for more than a few weeks.

I was deeply grieved a few days since, to hear of poor Susans suffering state, from Frank Parker.⁶ I knew she was very ill, but I hoped not in such pain as he told me she was.

Erasmus I thought looking extremely well. He gets younger, not having a Book to destroy him.

We have all been at Whitby.—a famous place in any point of view.— I just left it before Sir C. Lyell arrived there.⁷ I should have much liked to see him again. There were some grand specimens of Ichthyosaurus & Plesiosaurus there for ⁠⟨⁠  ⁠⟩⁠ Inspection.

Possibly you may be interested in the fact of Smerinthus Ocellatus & Populi being now regularly bred between. They are cognate species—The eyed Hawk Moth & the Poplar. I imagine there is little difficulty in procuring the mules. I have a lot of the caterpillars of each & hope next year to try whether the mules will breed again.⁸

Possibly this may be proved by others this year.

When you write, if you ever do, tell me how you all are—and also how Caroline⁹ & her belongings are.

My Brood are all well I am thankful to say— it is a good deal to say of 16.¹⁰

With our kindest regards to Mrs Darwin¹¹ Believe me Ever yours affec^ly | W. D. Fox