Étienne Léopold Trouvelot (1827–1895) Induced images produced by a direct discharge from the negative terminal of the Ruhmkorff coil onto a thin sheet of ebonite covering the two photosensitive plates. Figure I, c. 1885. Contemporary print on citrate paper, mounted on cardboard, signed and inscribed in ink on the backing at the bottom. 22.3 x 17 cm