My dear G.

I send index.— You need not look over the pages of Ch. XX. There will be no occasion for Revise & do not correct anything except actual errors— I send 2^d. vol. of Descent for Printers have not sent old Proofs. If at all intelligible, it is useless to make any expression in Index better. Make any corrections very clear. Return proofs as soon as you can to Clowes address—ie “Stamford St. Blackfriars, London.”—²

Please return 2^d. vol. of Descent by Post.—

And now can you answer me 2 queries in physics. I am nearly sure that some crystals & I think fibrous iron conduct heat more easily or quickly in certain directions than in others.— Is not this so?

Secondly, I believe a very hot body radiates heat quicker than a less hot body; but how is this in conduction. Is heat conducted away more quickly or easily from a very hot than from a less hot body? It is too long a story to explain why I want this information; it is to illustrate, as mere analogy, the transmission of the motor impulse through the leaves of Drosera.³

Yours affect | C. Darwin