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In 1894, I met Mr. Sellers who described his devices to me and gave me photographs of them and also strips of pictures used therein.
An acquaintance of Cohiian Sellers, and likewise a Philadelphian, Henry R. Heyl, also made camera plates (of a dancing couple in action) making from the negatives w^et-plate lantern slides which he mounted disc-wise, and revolved, step-by-step, in the light of a projection lantern. He gave a public demonstration at the Academy of Music, Philadelphia. Feb. 5, 1870.* I have paper prints off the negatives, which he gave me in 1895.
An examiner in the U. S. Patent Office, some ten years after allowing me a patent on a perforated picture strip in continuous and synchronous motion with a plurality of lenses passing a fixed open
Projector with plurality of lenses.
ing in a camera, called my attention to an anticipating French publication, of March 1, 1864, in w^hich Sr. Ducos illustrated and described much the same thing, i. e., a flexible picture band carried along by a sprocketed drum, synchronously with a plurality of lenses.^
The first use of the now almost universally employed geneva gear or star-and-cam in projectors appears to have been made by A. B. Browm, in 1869.^ However, the use of this type of intermittent gear is practically the only interest his contribution has for the historian.
Marey, a French scientist, employed the zoetrope, the slotted cylinder described earlier herein, w^ith solid figures instead of pictures, modeled in imitation of successive phases of an animal in action, which not only gave the action but the placticity of solid bodies. One of his instruments of this type is still to be seen in the Museum of the Paris Physiological Station.
A variation of the picture-carrying drum, employed as a projector, had a series of vertical mirror-strips for reflecting the light beam which carried the picture to the screen. It depended for success
* Franklin Institute Transaction of this year (1870). ^Unpublished French Patent, Julv 5, 1864. « U. S. Patent 93,594, 1869.
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