[page] 74

1751 DARWIN (CHARLES, 1809-1882). Naturalist and Author. Wrote "Descent of Man," etc.

EIGHT LETTERS SIGNED (TWO ENTIRELY AUTOGRAPH), TO JAMES CROLL, F.R.S.

22 pp., 8vo. Dated from Kent and Surrey, 1868-1877. | £12 10s

A most interesting series of letters on geological matters.

To James Croll 6 February [1869]

"…I was reminded of my crude notion that the cause of elevations, volcanic phenomena &c. was cosmical, by my son telling me about Capt. Clark's paper in Phil. Trans. on the globe being a little flattened at the equator, & that this stands in relation to relative position of continents & oceans.

"It wd. be a great gain if someone could shew a cause of the many changes of level in the crust of the earth…

[To James Croll 24 November 1868]

"If we are to admit that all the scored rocks throughout the more level parts of the United States result from true glacier action it is a most wonderful conclusion, & you certainly make out a very strong case; so I suppose I must give up one more cherished belief. . . Am I right in supposing that you believe that the glacial periods have always occurred alternately in the northern & southern hemispheres; so that the erratic deposits which I have described in the S. parts of America, & the glacial work in New Zealand could not have been simultaneous with our glacial period. From the glacial deposits occurring all round the northern hemisphere, & from such deposits appearing in S. America to be as recent as in the North, & lastly, from there being some evidence of the former lower descent of glaciers all along the Cordillera, I inferred that the whole world was at this period cooler. . . Do you believe that during the glacial period in one hemisphere, the opposite hemisphere actually becomes warmer, or does it merely retain the same temperature as before? …

[To James Croll 31 January [1869]]

"I wish that you would turn your astronomical knowledge to the consideration whether the form of the globe does not become periodically slightly changed, so as to account for the many repeated ups & downs of the surface in all parts of the world. I have always thought that some cosmical cause would some day be discovered."? Etc.