German physicist (1857 - 1894) who was the first person to provide conclusive proof of the existence of electromagnetic waves. Rare ALS signed "H. Hertz," one page, 5.25 x 8.25, October 27, 1891. Letter in English to astronomer Henry Crew, in part: "By the same post I send you a set of the required papers. You will only find the first paper wanting, of which I am sorry I have no copy left. The French resume, which I added will do for it. I give you my best thanks for the publication of the Observatory which you sent me." In fine condition. Accompanied by the original mailing envelope. The only Hertz letter we have handled.Format: ALS