A Manual Of Photography

282 PRACTICE OF PHOTOGRAPHY. velop; arrest it in four or five minutes, wash it well in three waters, and fix with hyposulphite of soda as follows: <6 Sixth. Three drachms of hyposulphite of soda to one ounce of water. Allow the proof to remain in this solution until all the yellow iodide disappears, wash it well, rear up to dry, and it is finished. " Success is sure to attend any one practising this method, provided the eggs are fresh and the glass is clean : if the glass is not clean, or the eggs are stale, the albumen will split off in fixing. , ... “ Caution.—Wash all the vessels, as soon as done with, with nitric acid, and then with water. Every precaution should he used to avoid dust. The albumen of a duck s egg is more sensi- tive than that of a hen ; and from an experiment of to-day, lam almost certain that of a goose is more sensitive than either. — Athenaeum, No. 1220. Section IV.—Miscellaneous Modified Processes. Several other preparations have been employed, with variable success, and recommended for procuring an absorbent film upon glass plates—amongst others the serum of milk has been used by M. Blanquart Everard; others combine with their albumen or gelatine, grape sugar and honey; the object of these being to quicken the process, which they appear to do in virtue of their power of precipitating the metals from their solutions. Blanquart Everard has lately communicated the following to the Paris Academy of Sciences, as an instantaneous process :— “Fluoride of potassium added to iodide of potassium, in the preparation of the negative proof, produces instantaneous images on exposure in the camera. To assure myself of the extreme sensibility of the fluoride, I have made some experiments on the slowest preparations employed in photography that of plates of glass covered with albumen and iodide, requiring exposure of at least sixty times longer than the same preparation on paper. On adding 'the fluoride to the albumen and iodide, and substi- tuting for the washing of the glass in distilled water after treat- ment with the aceto-nitrate of silver, washing in fluoride of po- tassium the image immediately on exposure in the camera ob- scura, I have indeed obtained this result (but under conditions less powerful in their action) without the addition of the fluoride to the albumen, and by the immersion only of the glass plate in a bath of fluoride after its passage through the aceto-nitrate