Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Hermann von Helmholtz (1821-1894) was a protege of Humboldt's distinguished for his research in optics and the physiology of vision and acoustics, the law of conservation of energy, and electrodynamics. He made important discoveries about the structure and mechanism of the human eye and invented the opthalmoscope. He suggested the investigation of light beyond the visible range to his student Heinrich Hertz.