My dear Sir—

Our mutual friend D^r 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 D^r 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 D^r Sir | Yours truly | B. Silliman Jun

Chas Darwin Esq