Versatile German scientist (1821–1894) known for his discoveries related to visual and aural perception, electrodynamics, and the conservation of energy. ALS signed “H. Helmholtz,” one page, 4.5 x 7, March 31, 1864. Letter to an unidentified friend. In part: “My former plans to stay some days with Professor Roscoe at Manchester have been crossed by the circumstance that Professor Roscoe was called to appear as a witness at a trial in Liverpool.” A few creases and wrinkles, some light toning to bottom, and pencil notations on reverse, otherwise fine condition. RRAuction COA.
