John David Hahn (295)

Johann David Hahn (9 July 1729–9 March 1784) was an educator, and a member of the American Philosophical Society, elected in 1770. Born in Heidelberg, Germany, he relocated to the Netherlands to pursue medicine and philosophy at Leiden University. After graduating with his doctorate, he began teaching at Utrecht University, working as Professor of philosophy, astronomy, and experimental physics (1753-1775), and then Professor of botany of chemistry (1759-1775). After his time at Utrecht, he returned to Leiden and served as Professor of medicine at Leiden University, where he remained for the rest of his life. Hahn wrote prolifically on chemistry and toxicology and held public experiments and lectures on experimental physics and astronomy. He corresponded with many of his contemporary natural philosophers, including Benjamin Franklin. After nearly a decade in Leiden, his health began to fail and he died.