This essay discusses Priestley's experiments concerning phlogiston, also called "the principle of inflammability," which was once thought to be a volatile substance that was part of all combustible matter and was released as flame in combustion.

Louis Hasbrouck was in his last year at Princeton in 1796-1797 when he attended the course of chemistry lectures given by John Maclean. In only his second year at Princeton, Maclean was rapidly becoming known for introducing the latest currents in chemical theory, including the system of Antoine Laurent Lavoisier, and he was one of the first Americans to insist that students take part in active experimentation. Louis Hasbrouck was in his final year at Princeton in 1796-1797 when he attended John Maclean's lectures on chemistry. His notebook from the second half of that course includes a detailed record of the lectures from January 24-March 14 and June 22-24, 1797, covering Maclean's discussion of the chemistry of metals, "chemical combination," combustion, and botanical chemistry. Although his notes are not complete, Hasbrouck was enrolled at a singularly interesting period in the history of American chemistry. This was only the second time that Maclean had offered his course, in which he introduced the new chemical system of Lavoisier, and it includes a relatively complete version of Maclean's most important lecture, "Of combustion." This devastating attack on Joseph Priestley and phlogistic theory appeared in print in 1797 as Two Lectures on Combustion: Supplementary to a Course of Lectures on Chemistry.

Correspondence of Joseph Priestley, scientist, Unitarian minister, and republican theorist. The collection includes 41 letters written to John Vaughan, 1791-1800, 5 letters to other correspondents, and manuscripts and photostats of 68 items in the Municipal Library, Warrington, England, on theological issues, the internal development of the United States, the French Revolution and its aftermath, Unitarianism, science, his publications, and American Philosophical Society.