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Darwin Correspondence Project

To Charles Pritchard   12 October [1866]1


Oct. 12th.

My Dear Mr Pritchard,—

I have read with much interest your sermon, with its appendices, & I thank you sincerely for having sent it me.2

I should be a very cross-grained man to object to a single word that you have said. You pay me the most elegant compliments, and attack me with much spirit and force. Even if I could you would not thank me for making a long defence; but I may make two remarks. When I refer to the extremely simple eyes of the articulata (i.e., insects, spiders, etc.), you translate this into the human eye.3 Should there be a second edition, I hope you will correct this, for I have always spoken of the human eye as the pinnacle of difficulty.

You speak of the necessity of various parts of the eye changing simultaneously in order that it may become adapted for even slightly changed work; but many a short-sighted person can see an object distinctly at a distance which renders the image confused to others.4

What a very curious case about the increasing length of day!5 I have that profound respect for mathematics which profound ignorance gives, but I cannot help observing that when applied to uncertain subjects, such as geology, it gives as uncertain results as geologists arrive at by other means; for instance, how Thomson and others differ about the thickness of the crust of the earth and the rate of cooling.6

My son George has been much interested by your sermon, and begs to be very kindly remembered to you.—7

With my best thanks, pray believe me, yours very sincerely, | Ch. Darwin

That is a very foolish episode of mine about the Wealden, and was struck out in later editions.8


The year is established by the relationship between this letter and the letter from Charles Pritchard, 8 October 1866.
Pritchard had misinterpreted a remark from Origin, p. 188, in which CD suggested that the change from a simple optic nerve to an eye of any member of the Articulata could be plausibly explained as the result of natural selection. Pritchard assumed CD meant an eye ‘as perfect as the human eye’ (C. Pritchard 1866, p. 32). CD had expanded his discussion of the possible development of the eye in Origin 4th ed., pp. 216–18.
CD noted Pritchard’s argument (C. Pritchard 1866, p. 33) in his discussion of the possible incremental steps in the development of the eye in Variation 2: 222–3.
CD refers to another argument Pritchard made against Darwinian theory, based on astronomical evidence that the length of a day was constantly increasing (see letter to Charles Lyell, 12 October [1866] and n. 8).
The physicist William Thomson (later Lord Kelvin) had recently calculated the age of the earth based on its cooling from a molten ball. He concluded that the earth could not possibly have existed with its crust in a similar state as at present for the length of time proposed by geologists (W. Thomson 1865).
George Howard Darwin had been a student at Clapham Grammar School while Pritchard was headmaster there (see letter from Charles Pritchard, 8 October 1866 and n. 5).
In Origin, p. 287, CD had written that the denudation of the Wealden district in Kent took longer than 300 million years. In response to criticism, he revised his estimate downwards to 150 or 100 million years in Origin 2d ed., p. 287. No reference was made to the Wealden in the third or later editions of Origin (see Peckham ed. 1959, pp. 483–4). See also Correspondence vol. 12, letter from A. C. Ramsay, 10 July 1864 and n. 3.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Origin 2d ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1860.

Origin 4th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 4th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1866.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

Pritchard, Charles. 1866. The continuity of the schemes of nature and of revelation. A sermon preached, by request, on the occasion of the meeting of the British Association at Nottingham. With remarks on some relations of modern knowledge to theology. London: Bell and Daldy.

Thomson, William. 1865. The ‘Doctrine of uniformity’ in geology briefly refuted. [Read 18 December 1865.] Proceedings of the Royal Society of Edinburgh 5 (1866): 512–13.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Responds to CP’s sermon. Corrects CP’s confusion of what CD said about eyes of the Articulata with human eye,

and questions applicability of CP’s mathematical arguments about length of geological time needed for evolution.

Agrees he was foolish about the Wealden, now struck from later editions [Origin, pp. 285–7].

Letter details

Letter no.
Charles Robert Darwin
Charles Pritchard
Sent from
Source of text
A. Pritchard comp. 1897, p. 93
Physical description
LS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 5240,” accessed on 13 September 2023,

Also published in The Correspondence of Charles Darwin, vol. 14