In 1791 he explained Pictet's experiment by arguing that all bodies radiate heat, no matter how hot or cold they are. However, he abandoned it for law, and this too he quickly deserted to devote himself to education and to travelling. He there became acquainted with Joseph Louis Lagrange, and was thus led to turn his attention to physical science.
After some years spent on political economy and on the principles of the fine arts (in connection with which he wrote, for the Berlin Memoirs, a remarkable dissertation on poetry) he returned to Geneva and began his work on magnetism and on heat. Interrupted occasionally in his studies by political duties, in which he was often called to the front, he remained professor of philosophy at Geneva until he was called in 1810 to the chair of physics. He died at Geneva in 1839.
[Royal Society; Prussian Academy of Sciences]
Frederick II of Prussia secured him in 1780 as professor of philosophy, and made him member of the Akademie der Wissenschaften in Berlin.