A Manual Of Photography

 278 PRACTICE OF PHOTOGRAPHY. still, a sheet of positive albuminized paper, which is described hereafter. . , - You then put it in the pressure frame, placing above it a piece of black cloth pasted on one side of a thick sheet ot glass; then shut the frame, giving to the proof a slight pressure; after which, expose it to the light. In order to follow its action you may just raise it by one corner of the glass, to judge ot the tint which the image takes: when you think it sufficiently exposed, take it out of the. frame, and fix it the same as the positive paper. , ,- Niepce de Samt Victor has recently published a process in which he employs starch instead of albumen on the glass plates. The main features of this process are as follows:—About 7U o-rains of starch are rubbed down with the same quantity ot distilled water, and then mixed with three or four ounces more water; to this is added 51 grams of iodide of potassium dis- solved in a very small quantity of wat.er, and the whole is boded until the starch is properly dissolved. With this the glass plates are carefully covered, and then placed to dry on a perfecty horizontal table. When thoroughly dried, the aceto-nitrate ot silver is applied by wetting a piece of paper, placing .tins.on the starch, and over it another piece of paper wetted wthdistiUed water. This mode of preparation furnishes, it is said, tablets ot great sensibility ; but the starch is liable to break off from the glass, and there is much difficulty in spreading it uniformly in the first instance. Section II.—Mb. Malone’s Process. Some very ingenious experiments have been made by Mr. Malone, from whose communication the following remarks are 1 “ To the white of an egg its own bulk of water is to be added, the mixture, beaten with a fork, is then strained through a piece of linen cloth, and preserved for use in a glass stoppered bottle; then a piece of plate glass, cleaned with a solution of caustic potash, or any other alkali, is to be washed with water and dried with a cloth. When the glass is about to be used, breathe on it, and rub its surface with clean new blotting paper; then, to remove the dust and fibres which remain, use cotton- wool or a piece of new linen. Unless this latter, and, indeed, every other precaution, is taken to prevent the presence o cus, the picture will be full of spots, produced by a greater absorp-