A catechism of photography

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Cassell, Petter & Galpin, 1859 - 97 pages
 

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Page 39 - I advise, where practicable, that the hens should have carbonate and phosphate of lime strewn about for them to peck at. This enriches the albumen and renders it more limpid. Each egg must be broken separately into a shallow cup, and the yolk retained in the shell as well as the germ ; then poured into a measure until the required quantity of limpid albumen is obtained.
Page 31 - ... brightest sunshine. I developed the image at ten in the evening, and with perfect success. The experiment was made on one of the hottest days in the early part of July. I have made several experiments on this subject, and with the tame result.
Page 31 - ... nitrate of silver this period may be considerably prolonged. It will, of course, be understood by all who have followed the processes described up to this point, that the papers which are prepared for keeping are not those which are the most sensitive; hence it is necessary to expose such a much longer time in the camera than those prepared by the stronger solution of silver.
Page 7 - A ray D thus entering, and suffered to pass unobstructed, would form on a plane surface a circular disk of white light E, but the prism being so placed that the ray may enter and quit it at equal angles, it will be refracted in such a manner, as to form on a screen MN, properly placed, an oblong image called the solar spectrum, and divided horizontally into seven coloured spaces, or bands of unequal extent, succeeding each other in the order represented : red, orange, yellow, green, blue, indigo,...
Page 44 - BO called, as before stated, quite insoluble in any mixture of alcohol and sulphuric ether. Secondly, an explosive cotton, likewise insoluble, but differing chemically from the first, obtained by a mixture of certain strength when used cold. If warm, however, either from the heat produced spontaneously on mixing the two acids, or by raising the temperature artificially to about 130, the cotton then immersed becomes perfectly soluble, producing a third variety ; if, however, it be thoroughly dried...
Page 43 - Hadow, who has devoted considerable attention to this subject, says : — " The difference in properties is owing to the gradual weakening of the acid mixture in consequence of the nitric acid being removed by the cotton, with which it becomes intimately combined, at the same time that the latter gives out a proportionate quantity of water.

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