TO C.LYELL.Down, October 9th [1866].
One line to say that I have received your note and the proofs safely, and will read them with the greatest pleasure; but I am certain I shall not be able to send any criticism on the astronomical chapter (192/1.
"Principles of Geology," by Sir Charles Lyell; Edition X., London, 1867.
Chapter XIII.

deals with "Vicissitudes in Climate how far influenced by Astronomical Causes."), as I am as ignorant as a pig on this head.
I shall require some days to read what has been sent.

I have just read Chapter IX.

(192/2.

Chapter IX., "Theory of the Progressive Development of Organic Life at Successive Geological Periods."), and like it extremely; it all seems to me very clear, cautious, and sagacious.