[ Autographs ] NIKOLA TESLA (1856 - 1943) American engineer and inventor who discovered the principle of a rotating magnetic field, invented the Tesla Coil and with Edison developed electric lighting. Fine content T.L.S. "N. Tesla" on his illustrated Tesla laboratory letterhead, 1p. 4to., [Brookhaven], Feb. 26, 1912 to Edwin A. Elsbach in San Francisco. Tesla opens expressing his regret for the tardiness of his letter, citing his "very pressing and important work". He adds:"...As you appreciate greatly my system, you probably also know by this time that wireless messages, the world over, are at present transmitted by devices of my own invention but the system as a whole has not been properly understood and, so far as I know, it has not yetbeen applied. I have written a few articles a record of which I have not on hand...two of them appeared in the Electrical World..." In 1897Tesla invented a system of wireless telegraphy whose merits, he indicates here, had yet to be fully appreciated. Folds, otherwise finecondition.