EARLY HISTORY OF PHOTOGRAPHY Photography may be described as the offspring of optics and chemistry. If the camera obscura had not been ready to hand, to cast a miniature picture on the sensitive plate or film, the discovery of the actinic power of light on certain substances would have been valueless, except as a scientific curiosity. The camera obscura (Latin = dark chamber) hole was discovered. The idea of en closing the lens in a small box, with a screen of tracing paper or ground glass, first occurred to Porta, as already stated, in 1569. The box form of camera obscura appears to have been used as an enter taining toy, or as a ready means of tracing landscapes and views, for nearly three centuries before the discovery of photo graphy. The apparatus is mentioned by the Abbe Nollet, in his " Lecons de Physique," published at Paris in 1755. A quaint form of camera obscura, with fold ing legs, designed by A. M. Guyot, for out door work in tracing landscapes, is shown by Fig. 1. This illustration is copied from
a work published in London in 1774 entitled " Hoope•'s Rational Recreations." As will upon glass, and of making profiles by the agency of light upon nitrate of silver." This process was really what is now re ferred to in photography as printing, and consisted simply of obtaining prints or silhouettes of suitable objects by exposing them to light in contact with paper pre pared with a solution of nitrate of silver (see Fig. 2). Attempts had been made by both Wedgwood and Davy, without suc cess, to secure a reproduction of the image formed in a camera obscura ; al though the latter was enabled to copy the images of small objects, produced by means of the solar microscope, when the pa-per was placed a short distance from the lens. All endeavours to render the prints permanent were, however, unsuc cessful.