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Darwin Correspondence Project

From Henry Landor   10 March 1869

Amherstburg | Ontario | Canada

March 10th 1869

Dear Sir

I wish to call your attention to a mode of transportation of boulders and with boulders dirt and animal & vegetable life, not noticed in your wonderful book on Origin of Species, but which must have very considerable influence in distributing species over large areas in this part of the world, and doubtless in every other country in similar circumstances.

The theories on the formation of ground ice in running streams, are none of them without objections, which cannot at present as far as I can see be explained, but I will not allude to them further than is necessary to explain facts of observation.

When the temperature falls to Zero or 10 degrees above it, a curious phenomenon occurs in rivers, after two or even one nights frost. In those parts where the current is too rapid for the formation of surface ice, the water freezes at the bottom, adhering to the ground or stones on the bottom. As day after day of sharp frost continues, the ground ice thickens; at first it is more or less tubular, the tubes in the direction of the current. It would seem that there are tubular currents of small diameter and the water freezes between them, allowing pipes as it were for the passage of the swifter water. The diameter of these is small, and the cakes of ice often break off the stones or bottom of the river, and fill the surface of the stream with this porous ice. In those masses of ice which continue to adhere to the bottom thickening continues daily, and in time by its power of flotation, it raises itself and the stone or dirt to which it was anchored to the surface. The block of ice and dirt or boulder as the case may be, then floats away to the nearest part of the river where the surface is frozen over. Then it becomes frozen in with the mass of surface ice, with its blocks of earth or stone enclosed, until the general thaw in the spring. The ice on the surface in one night loses its tubular character, if it has even retained it, until flotation, and any one seeing the boulder or dirt attached to it, would find it impossible to say whether it came from the bank or bottom of the river, unless he had watched it to its position.1

In the spring these blocks are carried away, some dropping in the river itself; many carried into the great lakes,2 and far into them, before they thaw sufficiently to drop their burden of earth or boulders. Those streams that flow into the Mississippi carry their contents into that river which may carry them through degrees of latitude before they thaw & deposit.

I am not a man of science, only a common sense observer, but I am sure that here we have a mode of distribution that ought not to be overlooked. Every year this goes on in every river of Canada, and in all the States in similar latitude & condition of climate, and has gone for nameless centuries. The accumulated results of centuries of this work must tell, and this also shews that boulders are brought from considerable distances, and in lapse of time in considerable quantities, and are distributed over large areas. Ice is drifted by every changing wind across the largest of these great lakes again and again in every winter. Even this year a man has been drifted on ice across Lake Huron. Therefore these boulders are dropped all over the bottom of these lakes. It may be said that the result

CD annotations

3.12 The block … enclosed, 3.15] underl pencil
Top of letter: ‘Only Probable [interl] Distribution by Ground-ice in Canada— | from Dr. Landor’ ink


CD mentioned icebergs as a means of transport in Origin, pp. 362, 381–2, 393–4, and 399.
The Great Lakes between the United States and Canada include Lakes Ontario, Erie, Huron, Michigan, and Superior; Amherstburg lay at the east end of Lake Erie.


Suggests that ground ice, in Canada and similar countries, is a mode of distribution of boulders and animal and vegetable life.

Letter details

Letter no.
Henry Landor
Charles Robert Darwin
Sent from
Amherstberg, Ontario
Source of text
DAR 205.2 (Letters): 244
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6652,” accessed on 17 January 2019,

Also published in The Correspondence of Charles Darwin, vol. 17