Envisaging the West: Thomas Jefferson and the Roots of Lewis and Clark


Letter from Thomas Jefferson to Jonathan Williams

Thomas Jefferson to Jonathan Williams, July 3, 1796
Thomas Jefferson Papers, Library of Congress
Thomas Jefferson discusses "barometrical measurements" of the Virginia mountains. Jefferson also notes his ongoing interest in agricultural researches.

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Monticello, July 3, 1796.

Dear Sir,

I take shame to myself for having so long left unanswered your valuable favor on the subject of the mountains. But in truth, I am become lazy to everything except agriculture. The preparations for harvest, and the length of the harvest itself, which is not yet finished, would have excused the delay however, at all times & under all dispositions. I examined, with great satisfaction, your barometrical estimate of the heights of our mountains; and with the more, as they corroborated conjectures on this subject which I had made before. My estimates had made them a little higher than yours (I speak of the blue ridge). Measuring with a very nice instrument the angle subtended vertically by the highest mountain of the blue ridge opposite to my own house, a distance of about 18. miles southwestward, I made the highest about 2000. f. as well as I remember, for I can no longer find the notes I made. You make the south side of the mountain near Rockfish gap, 1722. f. above Woods'. You make the other side of the mountain 767 f. Mr. Thomas Lewis dec'd, an accurate man, with a good quadrant, made the north side of the highest mountain opposite my house something more (I think) than 1000. f.; but the mountain estimated by him & myself is probably higher than that next Rockfish gap. I do not remember from what principles I estimated the peaks of Otter Maps: at 4000. f.; but some late observations of Judge Tucker's coincided very nearly with my estimate. Your measures confirm another opinion of mine, that the blue ridge, on it's south side, is the highest ridge in our country compared with it's base. I think your observations on these mountains well worthy of being published, and hope you will not scruple to let them be communicated to the world.--You wish me to present to the Philosophical society the result of my philosophical researches

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since my retirement. But, my good Sir, I have made researches into nothing but what is connected with agriculture. In this way, I have a little matter to communicate, and will do it ere long. It is the form of a mould-board of least resistance. I had some years ago conceived the principles of it, and I explained them to mr. Rittenhouse. I have since reduced the thing to practice, and have reason to believe the theory fully confirmed. I only wish for one of those instruments used in England for measuring the force exerted in the draughts of different ploughs, &c., that I might compare the resistance of my mould board with that of others. But these instruments are not to be had here. In a letter of this date to mr. Rittenhouse, I mention a discovery in animal history, very signal indeed, of which I shall lay before the society the best account I can, as soon as I shall have received some other materials which are collecting for me. I have seen, with extreme indignation, the blasphemies lately rended against the memory of the father of American philosophy. But his memory will be preserved and venerated as long as the thunders of heaven shall be heard or feared.

With good wishes to all of his family, and sentiments of great respect & esteem for yourself, I am, dear Sir, your most obedient, and most humble servant.
Th: Jefferson