William Hembel (1764–1851), merchant and physician, was a lifelong resident of Philadelphia. He studied medicine but chose not to take a degree due to his impaired hearing. Hembel worked as a shopkeeper by 1791 and retired from the import business around 1839 with an estate estimated six years later to be worth $50,000. He retained an interest in medicine with special emphasis on chemistry, and he advised and cared for the city’s poor at no charge. Elected to the American Philosophical Society in 1813, Hembel served as curator, 1814–15, and councillor, 1817 and 1823–51. He was also elected to the Academy of Natural Sciences of Philadelphia in 1824, serving as vice president, 1831–40, and president, 1840–49 (William S. W. Ruschenberger, A Notice of the Origin, Progress, and Present Condition of the Academy of Natural Sciences of Philadelphia [1852], 59–60, 76; Henry Simpson, The Lives of Eminent Philadelphians [1859], 515; APS description begins American Philosophical Society description ends , Minutes, 16 Oct. 1813 [MS in PPAmP]; APS description begins American Philosophical Society description ends , Proceedings 73 [1934]: 381, 387–90; Members and Correspondents of the Academy of Natural Sciences of Philadelphia [1877], 8, 41; Clement Biddle, The Philadelphia Directory [Philadelphia, 1791], 56; S. Harris, Harris’s Commercial Directory, and Merchants’ Guide, for Philadelphia, 1838 [1838], 29; Wealth and Biography of the Wealthy Citizens of Philadelphia [2d ed., 1845], 11; Philadelphia North American and United States Gazette, 14 June 1851).

Joseph Cloud (1770–1845), chemist and agriculturist, was living in Delaware in 1796 when President George Washington appointed him melter and refiner at the United States Mint at Philadelphia, a position he held from 1797 until he resigned in 1835. In 1806 Cloud was elected a member of the American Philosophical Society, which he served as secretary, 1812, and curator, 1814–22. He died on his farm in Delaware County, Pennsylvania (Historical Collections of the Joseph Habersham Chapter, Daughters American Revolution [1902], 2:427; Edgar F. Smith, Chemistry in Old Philadelphia [1919], 86–90; JEP description begins Journal of the Executive Proceedings of the Senate of the United States description ends , 1:219, 4:489 [30 Dec. 1796, 2 Jan. 1797, 22 Dec. 1835]; APS description begins American Philosophical Society description ends , Minutes, 17 Jan. 1806 [MS in PPAmP]; APS description begins American Philosophical Society description ends , Proceedings 73 [1934]: 377, 381; Philadelphia Public Ledger, 2 Aug. 1845; Farmers’ Cabinet, and American Herd-Book 10 [1845]: 92).

flÖtz, German for “stratum” or “layer,” was the name given by Abraham Gottlob Werner to one of the periods in his theory of the Earth’s geological development and to the sedimentary rocks formed during that period by the erosive action of water on primitive rocks (DSB description begins Charles C. Gillispie, ed., Dictionary of Scientific Biography, 1970–80, 16 vols. description ends ; William MacLure, Observations on the Geology of the United States of America; with Some Remarks on the effect produced on the nature and fertility of Soils, by the decomposition of the different Classes of Rocks [Philadelphia, 1817; Poor, Jefferson’s Library description begins Nathaniel P. Poor, Catalogue. President Jefferson’s Library, 1829 description ends , 5 (no. 173)], esp. pp. 19–21).