Jefferson, Thomas, as third President

Autograph letter signed ("Th: Jefferson"), 1 page (9 3/4 x 7 7/8 in.; 246 x 200 mm) on a bifolium of wove paper, Washington, 13 June 1803, to Thomas Whitney, "Mathematical instrumt. maker" (at Philadelphia), integral blank with autograph address and reception docket; lightly browned, tiny pinholes at intersecting folds, seal tear with marginal loss. Half blue morocco folding-case, red morocco spine labels.

Sold, Christie's New York, 19 December 1986, lot 102 (undesignated consignor)

The Papers of Thomas Jefferson. Jefferson's Memorandum Books, ed. Bear & Stanton, 2:1130-131

President Jefferson orders a navigating instrument—very possibly for the use of the Lewis and Clark Corps of Discovery. "I observe in the European catalogues of Optical, Astronomical &c. instruments, they advertise 'Artificial horizons by parallel glasses and quicksilver to take double altitudes by, £1-16. sterl.' I suppose it possible that this may be to supply the want of a good horizon at land and enable us to use Hadley's quadrant here as well as at sea. should this be the case, and you happen to have one, or if you can procure one I shall be glad to receive it by mr. Claxton, and will have the price remitted to you as soon as known. mr. Claxton took charge of a limb of the fixed machinery of the Quadrant, which has got broke on it's passage, and which he was to desire you to repair."

Hadley's quadrant, invented by John Hadley about 1730, was an octant designed for maritime navigation; Jefferson evidently saw that it might be modified for land navigation as well. To supply the artificial horizon he had read about (which would allow the lateral and longitudinal altitude to be taken when the real horizon was either restricted in visibility or not visible at all), Jefferson turned to Thomas Whitney, perhaps the nation's preeminent scientific instrument maker following the death of David Rittenhouse in 1796. Whitney is known to have supplied a number of instruments to the Lewis and Clark expedition, very few of which survive; however, a fine brass-and-silver compass made by Whitney and carried by William Clark is now in the Smithsonian.

Still, given Jefferson's sweeping intellectual curiosity, the artificial horizon could as well have been for his personal use. His memorandum books record a $27 payment to Whitney in July 1804 "for mathematical instruments for myself." Moreover, Thomas Claxton, to whom he deputed the purchase of the horizon from Whitney, was his purchasing agent for furnishing the White House.