A Manual Of Photography

12 HISTORY OF PHOTOGRAPHY. molecules of visible light, with the property of being polarized by reflection, and of escaping from reflection in the same positions as the luminous molecules, &c.” Irom the time when the difficulty of fixing the photographs stopped the progress of Davy and Wedgwood, no discoveries were made until 1814, when'M. Niepce, of Chalons, on the Soane, appears to have first directed his attention to the pro- duction of pictures by light. It does not seem that his early attempts were very successful; and after pursuing the subject alone for ten years, he, from an accidental disclosure, became acquainted with M. Daguerre, who had been for some time endeavouring, by various chemical pro- cesses, to fix the images obtained with the camera obscura. In December, 1829, a deed of copartnery was executed between M. Niepce and M. Daguerre, for mutually investigating the subject. M. Niepce had named his discovery Heliography.1 In 1'827, he presented a paper to the Noyai Society of London, on the subject ; but as he kept his process a secret, it could not, agree- ably with one of their laws, be received by that body. This memoir was accompanied with several photographs on metal (plated copper and pewter) and on glass plates ; which were afterwards distributed in the collections of the curious, some of them still existing in the possession of Mr. Robert Brown, of the British Museum. They prove M. Niepce to have been then acquainted with a method of forming pictures, by which the lights, semi-tints, and shadows, were represented as in nature; and he had also succeeded in rendering his Heliographs, when once formed, impervious to the further effects of the solar rays. Some of these specimens appear in a state of advanced etchings; but this was accomplished by a process similar to that pursued in common etchings. The ease with which nitric acid could be applied to etch these Heliographie plates will be apparent when the process of obtaining the pictures is clearly understood. 1 Sun-drawing: a more appropriate name than Photography, since there are reasons for believing that light is not the agent producing those so- called “light-drawn" pictures.