My dear Darwin,—

Your precious MS. has arrived safe.¹ I will return it registered in a few days. I am much obliged to you for the privilege of reading it; and in regard to the notes prepared for the new edition,² I am amused to find how many of the topics are the same as those treated of in the letters of yourself, Hooker, and Bunbury, in commenting on the observations by Agassiz of marks of glaciation in the Organ Mountains.³ By the way, you allude to Hooker’s discovery of moraines in the Sikhim Mountains, which I believe are only about 7^o farther from the equator than the Organ Mountains.⁴ It is very interesting to read Hooker’s letter dated 1856, and to see the impression which the MS. made on him, causing him to feel, as he says, ‘shaky as to species’ so long before the ‘Origin’ was published.⁵ We certainly ran no small risk of that work never seeing the light, until Wallace and others would have anticipated it in some measure.⁶ But it was only by the whole body of doctrine being brought together, systematised, and launched at once upon the public, that so great an effect could have been wrought in the public mind.

I have been doing my best to do justice to the astronomical causes of former changes of climate, as I think you will see in my new edition, but I am more than ever convinced that the geographical changes are, as I always maintained, the principal and not the subsidiary ones.⁷ If you snub them, it will be peculiarly ungrateful in you, if you want to have so much general refrigeration at a former period.⁸ In my winter of the great year, I gave you in 1830 cold enough to annihilate every living being.⁹ The ice now prevailing at both poles is owing to an abnormal excess of land, as I shall show by calculation.¹⁰ Variations in eccentricity have no doubt intensified the cold when certain geographical combinations favoured them, but only in exceptional cases, such as ought to have occurred very rarely, as paleontology proves to have been the case.¹¹

Ever most truly yours, | Charles Lyell.