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Mar., 1939] CENTENARY OF PHOTOGRAPHY 255
"pinhole lens" on a white wall or on white paper fastened opposite the hole.
Cameras, front boards, bellows, and plate holders have since been constantly improved. From the beginnings of photography the camera obscura was equipped with a single lens, but soon thereafter came the periscopic lens, the meniscus prism, and double objectives.
Astrologers were displaced, largely through the greed for precious metals, by the alchemists, forerunners of the chemist — in our specialized field the photochemist.
Northern Italy, which provided colored ribbons and fabrics for Europe during the eighteenth century, was naturally interested in the action of dyes and colors, and to Beccarius is ascribed the priority of discovery of the light sensitivity of chloride of silver. An earlier work, in Latin, by Agricola (1490-1555) deals with silver ores. This work was translated into English by President and Mrs. Hoover. Here is one of the examples of a comatose condition, because a closer study of this work might have hastened an understanding of the action of light on the silver salts. It is quite certain that the alchemists of the sixteenth century knew of the aqueous production of silver chloride.
Again we see a dormant period in the progress of the discovery of photography, which extends to the end of the eighteenth century. One of the men to whom great credit is due in this celebration, discovered— again not photography but as he named it — heliography. Joseph Nicephore Niepce (1765-1833), educated for the priesthood, therefore equipped with a knowledge of the humanities and a training in elementary science, was drawn into the vortex of the wars of the French Revolution. He was discharged from the army at his request, being debilitated by a fever which at the time raged both in the army and among the civilian population.
Niepce's part in the invention of photography is best stated in his own words. He described his process as "automatically fixing by the action of light the image formed in the camera obscura and the reproduction by printing with the aid of known processes of engraving." Niepce experimenting with lithography (1813-1815), then new in the reproductive process, attempted to obtain designs on stone and metal by the action of light instead of by manual drawing, and thus produced etched intaglio plates. He used diaphragms in his lens and added bellows to his camera. His first camera images were obtained in 1816, at the end of which year, being unable to fix his paper