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Among the 2 000.000 of unproductive beings which are supported in Europe at public expense, to parade public places and amuse the idle, M. Niepce de St. Victor is an exception. Captain of the guards at Paris, he employs his leisure hours at the barracks in extending the domain of photography, and continues thus in the course which his uncle, Niepce, opened by the part which he took in the invention of the daguerreotype. Numerous discoveries have preceeded from his researches. He has , just now completed a work, the first part of which appeared in 1847, treating of the effect of using different vapors, and especially that of iodine, in photography. He has shown that the vapor of iodine diffuses itself over the black lines in an engraving, to the exclusion of the white, and that we may reproduce the image on paper prspared with starch, or on glass covered with it, and thus form a design, the colored part of which will be iodide of starch. These designs are however not permanent. But M. Niepce has pursued the subject, and by the following method they are rendered unalterable:— If the design obtained as just mentioned is plunged into a solution of nitrate of silver, it disappears; but on exposing the paper or glass for some seconds to the light, the original design of iodide of starch is changed into iodide of silver ; and by further exposure to the light, this iodide, being much more sensitive than the nitrate of silver contained in the paper or in the layer of starch on the glass, is acted upon before the nitrate; it is then only needed to plunge the glass or paper into a solution of gallic acid to bring out the original design, which is then treated with hyposulphite of soda, just as for photographic pictures. The pictures are thus rendered as permanent as ordinary photographs.
