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Darwin Correspondence Project

From Benjamin Silliman Jr   27 October 1860

Office of Silliman’s Journal, New Haven, Ct.,

Oct 27 1860

My dear Sir—

Our mutual friend Dr Wyman has informed me of your desire to learn something more of the Rats found in Mammoth Cave—1 I kept a pair of these rats for some weeks in Louisville after my visit to the Cave in 1850—2 We captured them in a trap at a place more than half a mile from the entrance to the Cave—3 The surface of dry dust on the ledges of rock bore abundant record of their tracks but we never could surprise them or obtain a sight of them until by setting a trap we caught them with the flavor of an apple—

We made a great number of experiments to satisfy ourselves that they were blind being at first unwilling to believe that their large lustrous eyes—as large as Squirrels eyes—could be sightless— Our conclusion was clearly to the point of their blindness

Mr Reginald Mantell son of Dr G A Mantell4 was there with me in Ky and being at leisure he devoted himself to the study of these animals until an accident (from dogs) destroyed them—   He became fully satisfied that after about a month of exposure to a graduated light they came to a dim perception of objects—as they would blink or dodge on the approach of bodies toward the eyes while at first they took no heed of such unless their long silky lashes were touched—   So far as I know—no naturalist has described this animal which is no rat in the ordinary sense and it is much to be desired that Someone would spend the time there required for a thorough study of their habits—

I send you a copy of a letter I wrote at the time to Prof Guyot in which some facts are mentioned which may perhaps interest you5

Dana is improving steadily6—is in excellent spirits—but says he is like Nebedchnazzer turned out to grass—7 I confidently expect his perfect restoration in another year—

With high regard | I am Dr Sir | Yours truly | B. Silliman Jun

Chas Darwin Esq

CD annotations

1.4 a place … Cave—] double scored brown crayon
3.3 month] underl brown crayon


Silliman had formerly been professor of chemistry in the medical school of the University of Louisville, Kentucky (DAB).
CD quoted this information in the third edition of Origin, pp. 154–7. See also letter to Benjamin Silliman Jr, 4 December [1860].
Reginald Neville Mantell, the son of the geologist Gideon Algernon Mantell, was a family friend of Silliman’s.
Silliman refers to a letter to Arnold Henri Guyot published in the American Journal of Science and Arts in 1851 (Silliman 1851). Guyot was professor of geology and geography at Princeton University. There is a copy of the paper in the Darwin Pamphlet Collection–CUL.
James Dwight Dana was Silliman’s brother-in-law.
hey shall make thee [Nebuchadnezzar] to eat grass as oxen‘ (Dan. 4:25).


DAB: Dictionary of American biography. Under the auspices of the American Council of Learned Societies. 20 vols., index, and 10 supplements. New York: Charles Scribner’s Sons; Simon & Schuster Macmillan. London: Oxford University Press; Humphrey Milford. 1928–95.

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.


On the suggestion of Jeffries Wyman, he writes about the rats that he captured in Mammoth Cave in 1850. They were indeed blind. Reginald Mantell studied them and learned that with long exposure to graduated light, they became somewhat sensitised. Sends copy of an abstract which he wrote as a letter to A. H. Guyot ["On the Mammoth Cave of Kentucky", Am. Journal of Sci. and Arts 2d ser. 11 (1851)]. [See 3007.]

Letter details

Letter no.
Benjamin Silliman, Jr
Charles Robert Darwin
Sent from
New Haven, Ct.
Source of text
Darwin Pamphlet Collection–CUL (bound with Silliman 1851)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 2966B,” accessed on 6 July 2020,

Also published in The Correspondence of Charles Darwin, vol. 8