To G. H. Darwin   2 May [1876]1

6. Q. Anne St

May 2d

My dear George

I am very glad indeed that you have come to such a point in your work, as to get a little rest to your mind.— I do not think any geologist wd. be shocked at your assumption of 1 foot of elevation per century, or at your table land, as I believe the plateau of Mexico is 10,000 & a large area of Thibet fully that much.—2 I do not know whether it wd. make calculations easier, but seeing how commonly deep sea comes close up to the higher sides of continents, you might make your elevated area abruptly separated from your depressed area.— You are aware that, as Lyell has shown, the world can be divided so that almost all the land lies in one hemisphere & all the water in the other.3 I suppose the mean height of all the land might be assumed to be 1000 ft & the depth of all the ocean at 2000 fathoms. & it wd not be difficult to estimate the difference in specific gravity of rock & water. What a curious problem (but I suppose very difficult) it wd be to ascertain what the effect wd. be of reversing the present positions of land & water.

I think that as in your Cousin paper,4 it will be of considerable importance to geologists &c & to know that the gradual elevation cannot cause any great change of climate

Ever your affect | C. Darwin

It will be very interesting to know what Adams thinks of your method.5

1
The year is established by the relationship between this letter and the letter from G. H. Darwin, 1 May 1876.
2
George was calculating the influence of geological changes on the earth’s axis of rotation, and had asked CD to comment on his assumptions concerning the rate of elevation (see letter from G. H. Darwin, 1 May 1876).
3
Charles Lyell had pointed out that if the globe was divided into two by ‘projecting the hemispheres on the plane of the horizon of a point in lat. 52° N. and in long. 6° W. of Greenwich’, one hemisphere would contain as much land as water, while in the other the proportion of sea to land would be eight to one (C. Lyell 1872, 1: 261–2).
4
George had published a paper on marriages between first cousins (G. H. Darwin 1875a); he concluded that chances of deleterious effects on their offspring had not been shown to be greater than in other marriages (see Correspondence vol. 22, letter to G. H. Darwin, [6 December 1874] and n. 5).
5
George intended to consult John Couch Adams before undertaking the calculations for his study of the effects of geological change on the position of the earth’s axis of rotation (see letter from G. H. Darwin, 25 April 1876 and n. 3).

Manuscript Alterations and Comments

1.3 of elevation] after del ‘per’
1.5 commonly] after del ‘how’
1.12 (but…difficult)] parentheses over commas
1.12 it wd be] interl
2.2 gradual] above del ‘first’
2.2 cause] after del ‘ca’

Please cite as “DCP-LETT-10493,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10493