Hermann von Helmholtz

Hermann von Helmholtz was a Prussian army surgeon who became the greatest German scientist of his century, working in physiology, physics and mathematics: he measured the speed of nerve impulses, invented the ophthalmoscope, explained hearing and colour vision, and in 1847, at twenty-six, gave the first general statement of the conservation of energy. On the Conservation of Force, the lecture of 1862 that the Harvard Classics print, explains that principle for a general audience. He was also a philosopher of perception, an admirer of Kant, and the teacher of Hertz and Planck.