TO DR. CHAPMAN.
Monticello, December 11, 1809.
Sir,—Your favor of November 10th did not come to hand till the 29th of that month. The subject you have chosen for the next anniversary discourse of the Linnean Society, is certainly a very interesting and also a difficult one. The change which has taken place in our climate, is one of those facts which all men of years are sensible of, and yet none can prove by regular evidence, they can only appeal to each other's general observation for the fact. I remember that when I was a small boy, (say 60 years ago,) snows were frequent and deep in every winter—to my knee very often, to my waist sometimes—and that they covered the earth long. And I remember while yet young, to have heard from very old men, that in their youth, the winters had been still colder, with deeper and longer snows. In the year 1772, (37 years ago,) we had a snow two feet deep in the champain parts of this State, and three feet in the counties next below the mountains. That year is still marked in conversation by the designation of "the year of the deep snow." But I know of no regular diaries of the weather very far back. In latter times, they might perhaps be found. While I lived at Washington, I kept a diary, and by recurring to that, I observe that from the winter of 1802-3, to that of 1808-9, inclusive, the average fall of snow of the seven winters was only fourteen and a half inches, and that the ground was covered but sixteen days in each winter on an average of the whole. The maximum in any one winter, during that period, was twenty-one inches fall, and thirty-four days on the ground. The change in our climate is very shortly noticed in the Notes on Virginia, because I had few facts to state but from my own recollections, then only of thirty or thirty-five years. Since that my whole time has been so completely occupied in public vocations, that I have been able to pay but little attention to this subject, and if I have heard any facts respecting it, I made no note of them, and they have escaped my memory. Thus, sir, with every disposition to furnish you with any information in my possession, I can only express my regrets at the entire want of them. Nor do I know of any source in this State, now existing, from which anything on the subject can be derived. Williams, in his History of Vermont, has an essay on the change of climate in Europe, Asia and Africa, and has very ingeniously laid history under contribution for materials. Doctor Williamson has written on the change of our climate, in one of the early volumes of our philosophical transactions. Both of these are doubtless known to you.
Wishing it had been in my power to have been more useful to you, I pray you to accept the assurances of my esteem and respect.