(b. Glasgow, Scotland, 1 March 1771; d, Princeton, New Jersey, 17 February 1814)
Maclean’s father, John Maclean, a surgeon, and his mother, Agnes Lang Maclean, both died when he was young. He was raised by George Macintosh, the father of Charles Macintosh, the inventor of the waterproofed cloth named after him.
Maclean attended Glasgow Grammar School and entered the University of Glasgow when he was about thirteen. At the university, under the influence of Charles Macintosh, who was four years older, he joined the Chemical Society and presented several papers. In 1787 he left Glasgow to travel and study at Edinburgh, London, and Paris. At Paris he made contact with Lavoisier and Berthollet, who won him over to the antiphlogistic theory of the “new chemistry” He returned to Glasgow in 1790, and on 1 August 1791 he received his diploma authorizing him to practice surgery and pharmacy. The same day he became a member of the faculty of physicians and surgeons.
In April 1795 Maclean left Scotland for America, at least in part because of his sympathy for the United States. Benjamin Rush advised him to settle in Princeton, seat of the College of New Jersey. After delivering a course of lectures in Princeton during the summer of 1795, Maclean was chosen professor of chemistry and natural history at the college. He is recognized as the first professor of chemistry, outside of a medical school, in any American college. He was also appointed professor of mathematics and natural philosophy; such comprehensiveness was necessary since there was only one other professor, who also served as president.
Maclean’s Two Lectures on Combustion, published at Philadelphia in 1797, was important in the overthrow of the phlogiston theory. Publication of the work led to a discussion by Maclean, Priestley, James Woodhouse, and Samuel Mitchill in the New York Medical Repository.
In his teaching at Princeton, Maclean divided chemistry into “dead” and “living” matter, foreshadowing the later division into organic and inorganic. His dead matter was further divided into “simple” and “compound” substances. Of the thirty-seven simple substances he discussed, some twenty are now recognized as elements, including oxygen, hydrogen, aluminum, tungsten, platinum. The rest would now be classified as compounds—lime, soda, potash, and a number of acids.
In 1802 Maclean met with Benjamin Silliman, who, although he was not yet qualified for that role, had been appointed professor of chemistry at Yale. Maclean prepared a reading list for him.
Maclean resigned from the College of New Jersey in 1812 and shortly after joined the faculty of the College of William and Mary in Williamsburg, Virginia. Because of ill health he stayed there only a little over a year. He returned to Princeton, where he died soon after.
Maclean married Phoebe Bainbridge, the sister of Commodore William Bainbridge, on 7 November 1798. They had two daughters and four sons. The eldest son, John, became the tenth president of Princeton.
Maclean’s published work was Two Lectures on Combustion (Philadelphia, 1797). The chief source of biographical information is a memoir by his son, John Maclean, A Memoir of John Maclean, M. D., the First Professor of Chemistry’ printed privately (Princeton, 1876). See also William Faster, “John Maclean—Chemist,“in Science,60 (3 Oct. 1924), 306-308; John F. Fulton and Elizabeth H. Thomson, Benjamin Silliman (New York, 1947), and Theodore Hornberg, Scientific Thought in the American Colleges 1638-1800 (Austin, 1945). Princeton University Library has several of Maclean’s letters.
Vern L. Bullough