Thomas Ewell (1785–1826), physician, author, and gunpowder manufacturer, was a native of Prince George County who received a medical degree from the University of Pennsylvania in 1805. His publications included Plain Discourses on the Laws or Properties of Matter: containing the Elements or Principles of Modern Chemistry (New York, 1806; Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, 1952–59, 5 vols. description ends no. 833), The Ladies Medical Companion (Philadelphia, 1818), Statement of Improvements in the Theory and Practice of the Science of Medicine (Philadelphia, 1819; Poor, Jefferson’s Library description begins Nathaniel P. Poor, Catalogue. President Jefferson’s Library, 1829 description ends , 5 [no. 194]), and an annotated edition of David Hume, Philosophical Essays on Morals, Literature, and Politics, 2 vols. (Georgetown, D.C., 1817; Poor, Jefferson’s Library description begins Nathaniel P. Poor, Catalogue. President Jefferson’s Library, 1829 description ends , 9 [no. 485]; TJ’s copy in DLC: Rare Book and Special Collections). Having married a daughter of former secretary of the navy Benjamin Stoddert in 1807, Ewell served as a surgeon in the United States Navy, 1808–13, concurrently practicing medicine privately in the District of Columbia for part of this time. He also owned and managed the Anacostia Bridge. Ewell founded a gunpowder mill near the nation’s capital in 1812 and received a patent for an improved method of manufacturing the explosive the following year. While under contract to provide gunpowder to the Navy Department, he was accused of corruption, a charge that he strenuously denied. After spending about a year in Philadelphia, Ewell returned to Washington in 1819. Financial difficulty, alcoholism, and bouts of depression began to take a toll on his health from about 1820. Having relocated to Prince William County, Ewell unsuccessfully sought employment at the University of Virginia from TJ late in 1824. He died two years later at his home in Centreville. During the Civil War his son Richard S. Ewell was a lieutenant general in the Confederate army (Donald C. Pfanz, Richard S. Ewell: A Soldier’s Life [1998], 4–8; Howard A. Kelly and Walter L. Burrage, American Medical Biographies [1920], 373–4; University of Pennsylvania Catalogue description begins Will J. Maxwell, comp., General Alumni Catalogue of the University of Pennsylvania, 1917 description ends , 567; Callahan, U.S. Navy description begins Edward W. Callahan, List of Officers of the Navy of the United States and of the Marine Corps from 1775 to 1900, 1901, repr. 1969 description ends , 187; National Intelligencer & Washington Advertiser, 12 Feb. 1810; Petersburg Daily Courier, 9 Nov. 1814; Madison, Papers, Pres. Ser., 4:322–3, 5:565–6, 598–9; List of Patents description begins A List of Patents granted by the United States from April 10, 1790, to December 31, 1836, 1872 description ends , 130; Washington Daily National Intelligencer, 5 May 1819; Ewell to TJ, 12 Dec. 1824; TJ to Ewell, 5 Jan. 1825; Baltimore Patriot & Mercantile Advertiser, 8 May 1826).