Sedbergh School, Station Rd, Sedbergh LA10 5HG, United Kingdom
Thomas attended Sedbergh School.
University of Edinburgh, Old College, South Bridge, Edinburgh EH8 9YL, United Kingdom
Garnett atriculated at the University of Edinburgh in 1785.
After attending Sedbergh School, Thomas was at fifteen articled at his own request to the John Dawson of Sedbergh, Yorkshire, who was a surgeon and mathematician. Garnett obtained knowledge of chemistry and physics, and matriculated at the University of Edinburgh in 1785. He took the Doctor of Medicine in 1788 and finished his medical education in London in 1789.
After graduating Garnett wrote the article “Optics” for the Encyclopaedia Britannica. He supplemented his medical practice, conducted in the north of England, with chemical analyses and lecture demonstrations, using equipment that he himself had designed and built. While waiting for passage to America, where he hoped to teach chemistry, he accepted the professorship of natural philosophy at Anderson’s Institution in Glasgow. He resigned in 1799 to join the Royal Institution, then being organized. Count Rumford, who knew Garnett by reputation only, accepted his suggestions about necessary facilities and the design of the lectures.
On 4 March 1800 Garnett opened the lectures. His first season was highly successful. Unfortunately, he became the victim of bouts of melancholy induced by the death of his wife in childbirth on 25 December 1798, and his second lecture season was not well received. Rumford’s high-handed treatment of him only increased the tension growing between Garnett and the managers of the Royal Institution, leading to his resignation on 15 June 1801. Garnett subsequently set himself up in Great Marlborough Street as a lecturer, and he also edited the first volume of the Annals of Philosophy, Natural History, Chemistry, Literature, Agriculture, and the Mechanical and Fine Arts.
Garnett's Royal Institution lectures were published after his death under the title of Zoonomia, or the Laws of Animal Life.
In 1795 Garnett married Grace Cleveland. They had two daughters. Grace died in childbirth in 1798.