My dear Sir

Whilst reading your book it occurred to me that your immense collection of facts would be of inestimable value to anyone going to write on the subject, or who was making a special study of it, from having formed some distinct opinion, & therefore wished to learn all the evidence.¹ But to the general & intelligent reader, the collection would I think, be unnecessarily large, & tends to make the work heavy. It likewise interferes to a certain extent with the force & clearness of the general argument. Therefore, as far as my judgment goes, it would be advisable to publish a shortened work, with only one or two of the most illustrative & curious cases under each head.— You could always refer to the other work for additional evidence.

I should very much like to have some conversation with you, but I am very doubtful whether it will be possible, as I have been very unwell of late with my head much affected, & conversation or any excitement tries me too much.— If you think it worth while when in London, to send me a line, I will tell you how I am; or I may possibly be in London at that time. Yesterday a gentleman came down unexpectedly to see me, & I could not avoid half-an-hour’s conversation, but it knocked me up to an extreme degree.²

I mention this to show that I speak from experience.—

My dear Sir | Yours very sincerely | Ch Darwin