Jonathan Williams (1750–1815), a native of Boston, went to London in 1770 to receive mercantile training under the guidance of his great-uncle Benjamin Franklin. From 1776 he was a merchant and American arms inspector in Nantes, returning to the United States with Franklin in 1785. Williams became a member of the American Philosophical Society in 1787, subsequently serving several terms as secretary and councillor and becoming a vice president just before his death. President John Adams appointed him a major in the 2d Regiment of Artillerists and Engineers in 1801, and later that year TJ appointed him superintendent of the military post at West Point. Williams was promoted to lieutenant colonel and became first superintendent of the new United States Military Academy in 1802, resigned a year later because of his lack of authority over nonengineering cadets and officers, and returned in 1805 when TJ offered him greater control over the entire academy. He rose to colonel in 1808 but resigned his position at West Point in 1812 and became a brigadier general in the New York militia. Williams had written TJ on the use of the barometer to measure Virginia elevations in 1796, and his scientific interests subsequently found an outlet in the United States Military Philosophical Society, which he founded in 1802 and to which TJ belonged. He won election to the United States House of Representatives in 1814 but died before taking office (ANB description begins John A. Garraty and Mark C. Carnes, eds., American National Biography, 1999, 24 vols. description ends ; DAB description begins Allen Johnson and Dumas Malone, eds., Dictionary of American Biography, 1928–36, 20 vols. description ends ; PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 32 vols. description ends , 27:839, 28:594–9; APS description begins American Philosophical Society description ends , Minutes, 20 July 1787, 6 Jan. 1815 [MS in PPAmP]; Heitman, U.S. Army description begins Francis B. Heitman, comp., Historical Register and Dictionary of the United States Army, 1903, 2 vols. description ends , 1:1041; Williams to TJ, 12 Dec. 1802, and TJ to Williams, 25 Dec. 1802 [DLC]; Washington Daily National Intelligencer, 20 May 1815).

Francis D. Masson gave another instance of the usefulness of the thermometer in navigation in a 20 June 1810 letter to Williams from Clifton, England, reporting that on a recent transatlantic voyage he had successfully used changes in water temperature to predict the approach of icebergs (RC in NWM: Williams Papers; in French). Williams published translated extracts from this letter and its enclosed “Thermometrical Journal” with a brief covering letter of 3 Sept. 1810 to the editor of the New-York Gazette (reprinted in Philadelphia Poulson’s American Daily Advertiser, 14 Sept. 1810). He later republished Masson’s observations with further remarks of his own in an article entitled “On the Utility of Thermometrical Observations at Sea,” Archives of Useful Knowledge 1 (1811): 254–7 (Dfts of this article are in NWM: Williams Papers). Williams had proposed this method in Thermometrical Navigation, being a series of experiments and observations, tending to prove, that by ascertaining the relative heat of the sea-water from time to time, the passage of a ship through the Gulph Stream, and from deep water into soundings, may be discovered in time to avoid danger, although (owing to tempestuous weather,) it may be impossible to heave the lead or observe the heavenly bodies; extracted from the American philosophical transactions (Philadelphia, 1799; Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, 1952–59, 5 vols. description ends no. 649). Thomas Beverly randolph was appointed a cadet at the United States Military Academy in 1808 and rose from second lieutenant to captain in the United States Army between 1812 and his resignation in 1815 (Heitman, U.S. Army description begins Francis B. Heitman, comp., Historical Register and Dictionary of the United States Army, 1903, 2 vols. description ends , 1:815). TJ wrote him a letter of introduction to Williams on 23 Feb. 1809 (DLC), to which Williams’s missing letter to TJ of 6 Mar. 1809, recorded in SJL as received from Philadelphia on 8 Mar. 1809, may have been a response. The biblical reference, a little leaven would leaven the whole lump, is to 1 Corinthians 5.6.