My dear G.

Your letter has told us a lot of interesting news.— I am extremely glad that your work is coming to a satisfactory end. Its value I expect under a geological point of view is mainly negative, as Geologists require a much greater change of climate within a rather recent period.— There were Luxuriant forests in Spitbergen during the middle Tertiary period.²

There is a map in Wallace’s new book on Geographical Distribution, showing depth of sea according to all recent data & a calculation of its average depth viz 12,000 ft.— Humboldt estimated average height of land at 1000 ft. See p. 36 & 37 of this book.—³ I think the most interesting & probable supposition w^d. be to submerge in the N. $\frac{1}{2}$ or $\frac{1}{4}$ hemisphere taking St George’s Channel⁴ as centre of subsidence to depth of 12000 ft, & raise at the antipodes $\frac{1}{2}$ or $\frac{1}{4}$ of hemisphere (where ever there is water) to height of 1000 ft & see the result.— There is reason to suspect that there has been great & recent subsidence in Antarctic region & near N. Zealand.—⁵

I hardly dare venture to hope that your astronomical problem about obliquity &c will really work.⁶

Your affect. | C. Darwin

Frank has made a really fine zoological discovery.—⁷