Dear Sir.

I have just finished reading your first and smaller work, on The Origin of Species,¹ &c. and would herein express my pleasure at the natural and scientific view of the subject therein advocated.

In the interest of Science, I suppose that I am justified in addressing you, for the purpose of calling your attention to some few facts, which possibly bear affirmatively on the points discussed.

First, I would call attention to the Humming birds of Puget Sound. Your map will show you that Puget sound lies near the Pacific Ocean, adjacent to Vancouvers Island, British Columbia.²

A description of these Humming-birds will be found among the papers of the Smithsonian Institute.³ I can not indicate more nearly, for I am but a cursory reader, not a special student. Now the particular fact is this, that there are about (40) forty varieties, or species of these birds on the western coast of the continent of America, and only three or four species or varieties on the eastern Coast, notwithstanding that they are birds of passage.⁴

2^d. The Bobolink, or Carolina rice bird, is never seen on the Pacific coast, though very common on the Atlantic coast. It is my impression, but I am not certain, that it is never seen west of the Alleghany Mountains.⁵ I do not know of any works wherein this is mentioned.

3^d I can not find that the American Bison ever ranged east of the Aleghany Mountains, and it is certain that they suddenly passed west of the Mississipi River during the present century, abandoning forever their former range on the East of that river.

At about the same period, they suddenly contracted their range from the west of the Rocky Mountains, over a space of probably about 700 or 800 miles of latitude. This fact again I have never seen mentioned, but from my own observation, and from information derived from old hunters, I know it to be true. And I judge that the contraction on the eastern limit, could not have been caused by the pressure of civilized man on their flank, because we know that the almost simultaneous contraction of the western limit was not induced by such a cause. Records of the contraction of the eastern limit may be found in books.⁶

4^th. A short distance west of the Missouri River the Oak and the Hickory suddenly cease, although they are very plentiful to the eastward.

The same holds true of other plants. The termination is abrupt, but the line of termination is waved.⁷

5^th The Hudson River (in the eastern part of the state of New York) is, and always has been, the eastern limit of the Turkey buzzard, and of the opossum. The same river is also the western limit of some small animals, and of some plants.⁸ But it is quite singular and striking in the case of the Turkey buzzard. These are facts which you can verify in the reading of an extensive library, especially of American Authors.

I conceive that they have some bearing on the theory which you advance, and offer them solely in the interest of science.

George P. Bissell. M.D.

Charles Darwin M.A. | Down, Broomley, Kent, England