Provenance:Thomas Jefferson; by descent to John Hartwell Cocke at the Dispersal Sale in 1827; by descent to Mrs. Lucy Cocke Elliott; by gift to the Thomas Jefferson Foundation in 1952
Accession Number: 1952-67
Historical Notes: 1774 Thomas Jefferson resigned from the position of Albemarle County surveyor, but he used the theodolite, a highly sophisticated surveying instrument that measured both horizontal and vertical angles, for the rest of his life. In The Worlds of Thomas Jefferson at Monticello, Lucia Stanton, Monticello's Senior Research Historian, wrote that Jefferson "fixed the true meridian of Monticello, calculated the position of features of the Monticello landscape and surrounding mountains, and may have used it in his observation of the solar eclipse in June 1778. In 1815, in one of his most elaborate trigonometric exercises, he used the theodolite to determine the elevation of the Peaks of Otter in the Blue Ridge Mountains."
This sophisticated scientific instrument is on display in Jefferson's Cabinet, or study, and it suggests Jefferson's lifelong interest in science, particularly as a means of expanding the range of knowledge and improving the condition of mankind. This and other scientific instruments fill the Cabinet, which was the epicenter of Jefferson's Enlightenment activities.
Jefferson's captivation with science was only one aspect of his pursuit of the ideals of the Enlightenment, an eighteenth-century intellectual movement also known as the Age of Reason. Jefferson and other Enlightenment thinkers believed that knowledge was power and that human reason could be applied to improve the condition of mankind.
The theodolite and other scientific instruments in the Cabinet vividly reflect Jefferson's passion for science and for its practical application. For example, Jefferson wrote to another scientist in 1817 that "I have been drawn by the history of the times from physical and mathematical sciences, which were my passion, to those of politics and government towards which I had naturally no inclination." 
Undated. "A Theodolite by Ramsden, the spirit level 2 1/4 I.[nches] 26-5...a common Theodolite or Graphometer 8 I.[nches] 54 D."
1778 January 12. "Pd. Revd. Mr. Andrews of Theodolite L45."
1778 February 5. "Observations on the variation of the needle...it was 3 degrees-31' 34" E. of the North Pole..."
1778 March 6. "Attempts to fix with the assistance of an accurate theodolite the true meridian at Monticello by the help of Willis's mountain..."
1778 April 18. "Having accurately adjusted the spirit level of the Theodolite so that on a line of 300 f. it answered exactly, backwards and forwards. I found with it that the upper surface of the pedestal cap of the most western column of the house, was on a level with the 8th. joint of bricks above the water table of the South outchamber, or the 17th. joint counting from the ground. Or in other words, it was 2 f 2.1 I. above the water table of the out-chamber at the Western angle."
1778 July 19. (Jefferson to David Rittenhouse). "The theodolite, for which I spoke to you also, I can now dispense with, having since purchased a most excellent one."
1778 November 12. "Placing the Theodolite on the top of the house, the Eastern spur of the High mountain intersects the Horizon 19 degrees. Westward of Willis's mountain. Note the observation was made on the intersection of the ground (not the trees) with the horizon."
1781 October 2. Jefferson made observations of Blue Ridge, possibly with theodolite; mentions "the upright hair of the instrument."
1783 November 8. (Jefferson to Isaac Zane). "I send you also the ball and screw of your theodolite."
1786 March 27. "Pd. for a camp theodolite L4-4."
1799 February 16. "Gave Ouram ord. on do. for 4.D. for brass for theodolite."
1805 December 12. "Drew ord. on bk. U.S. in favr. of Thos. Freemand 54. D. for graphometer."
1806 March 10. "Sent to Monticello...[box 24] theodolite...[box 25] legs of theodolite."
1809 December 27. Jefferson observed variation of needle: "4-by theodolite, 4 degrees by small circumferenter, 1 degree by large do."
1811 March 21. (Jefferson to Robert Patterson). "I am limited to what can be done with a fine Equatorial...Theodolite with telescopes both by Ramsden..."
1811 December 29. (Jefferson to Rev. James Madison). "I have a fine theodolite and equatorial both by Ramsden..."
↑ This article is based on John Rudder, Monticello Research Report, May 2003
↑ Jefferson to Dr. Caspar Wistar, Monticello, June 10, 1817. Thomas Jefferson Papers, Library of Congress. Polygraph copy available online.
↑ Please note that this list should not be considered comprehensive.