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Darwin Correspondence Project

From G. H. Darwin   1 June 1876

Trin. Coll. Camb

Friday June 1. 761

My dear Father,

I must write a line to say that the great mare’s nest of which I wrote turns out wonderfully.2 I have worked it with care & today I got to the arithmetic; I was so tremendously excited I really could hardly finish it, but I have done so & been thro’ it again, & I find that when the earth had half its present density (assuming the nebular hypoth)3 that it was spinning at an obliquity of 15o instead of 23o28′.

Now this fits in wonderfully with a lot of things I have thought of, but wh. are too long to tell. Amongst the things to wh. it will lead are the classification & explanation of the various planets according to their obliquities— this will in fact be almost the experimentum crucis4—a rough approximation to the date of the solidification of the earth, & some faint idea of the temperatures of the various planets   You may imagine with all this seething in me that I’m pretty excited.

Adams was very kind about reading my other paper & I took it to him yesterday, & of course I shall get him to look at this.5

It’s really too tremendous a discovery to be true & I can’t believe it.

I hope Frank’s Teazle discovery will go on well, & it sounds very interesting.6

I was very much interested to read Paget’s letter, & it shows what a very severe accident it was, but it’s a great comfort to hear that he thinks it will be all right with care. I’m afraid poor old Billy will find life rather a bore for the next few months7

I am going up to London tomorrow to see the machine8 but am coming down again at night. I’m wonderfully strong now & you see I can work now, but I’m not well by a long way yet

Yrs affectionately | George Darwin

Of course I’d made a mistake wh. makes it rather less astoundg but the rest remains good


In 1876, 1 June was a Thursday. See also George’s letter of 31 May 1876, dated Thursday (31 May was a Wednesday). It is impossible to tell from internal evidence which part of the date George got right.
See letter from G. H. Darwin, 31 May 1876. He published his theory in ‘On a suggested explanation of the obliquity of planets to their orbits’ (G. H. Darwin 1877).
Nebular hypothesis: the theory of Pierre Simon Laplace that the solar system was formed by the contraction and breaking up of a rotating nebula (Chambers). The obliquity of planets was not accounted for in the nebular hypothesis.
Experimentum crucis: crucial test (Latin).
John Couch Adams was Lowndean Professor of astronomy and geometry at Cambridge University. George’s other paper was ‘On the influence of geological changes on the earth’s axis of rotation’ (G. H. Darwin 1876b).
Francis had discovered protoplasmic filaments protruding from the glandular hairs lining the cups of the common or fuller’s teasel (Dipsacus sylvestris, now D. fullonum; see letter from Francis Darwin, [28 May 1876], and F. Darwin 1877b).
See letter from James Paget, 30 May 1876. William Erasmus Darwin had been injured on 10 May 1876, when his horse fell (Emma Darwin’s diary (DAR 242); letter to W. D. Fox, 26 May [1876]).
George was in correspondence with Horace Darwin about a machine he had had made by a machinist in Clerkenwell, London (letter from Horace Darwin to G. H. Darwin, 25 May 1876 (DAR 258: 861)). An appointment to see it on 30 May had been cancelled because Horace was ill (letter from Emma Darwin to H. E. Litchfield, [30 May 1876] (DAR 219.9: 135)). It was a device to demonstrate planetary motion (letter to G. H. Darwin, [4 June 1876], and letter from Horace Darwin to G. H. Darwin, 6 March 1876 (DAR 258: 858)).


Chambers: The Chambers dictionary. Edinburgh: Chambers Harrap Publishers. 1998.

Darwin, George Howard. 1877. On a suggested explanation of the obliquity of planets to their orbits. Philosophical Magazine 5th ser. 3: 188–92.


Greatly excited by the astronomical implications of his work.

Letter details

Letter no.
George Howard Darwin
Charles Robert Darwin
Sent from
Trinity College, Cambridge
Source of text
DAR 210.2: 54
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 10522,” accessed on 4 June 2023,

Also published in The Correspondence of Charles Darwin, vol. 24