Take dry saltpetre, ½ oz.; strong oil vitriol, ¾ oz.; mix in a tumbler, ad 1 20 grains of dry cotton wool, stir with a glass rod five minutes, remove the cotton, and wash from all traces of the acid in four or five waters; then dry carefully under 120°. This is gun cotton. To make collodion, dissolve 20 grs. gun-cotton in 6 oz. sulphuric ether, to which add alcohol, ¾ oz.; let it stand a short time, and pour off the clear into bottle No. 1 for use. In bottle N'o. 2, put 1 oz. alcohol, and as much iodide of ammonium as it will dissolve; then add as much iodide of silver (made from nitrate of silver and iodide of potassium) as the solution will take up. Get another bottle, No. 3, with a wide mouth; into it put 1 oz. out of No. 1, to which add 15 or 20 drops out of No. 2. The collodion thus formed is call collodio-iodide of silver. Having well cleaned a plate of glass of the size of the frame in your camera, coat it completely and very evenly on one side, by pouring the collodion on the centre from the boltle; pour back any excess of liquid from one corner of the glass, and in this way yon coat the plate in a uniform manner. To prepare the plate thus coated for the camera, plunge it carefully and quickly into a bath of the following proportions, then allow it to remain covered in the solution ahout two minutes: Distilled water, 1 oz.; nitrate of silver, 80 grs.; alcohol, 30 drops; dissolve and filter. Obtain a good focus, place the plate in the frame and the frame in the camera, pull up the slide in front, and expose a proper length of time; hav-ing dosed your slide, remove the frame to your dark room, take out the plate, and develop the picture with the following solution, holding the plate perfectly level, the collodion side upward, and pour-ing enough of it on the plate to cover it; in a short time the picture will be developed: Water, 1 oz.; copperas, 14 grs.; saltpetre, 10 grs.; acetic acid, ½ drachm; nitric acid, 2 drops; then wash with water, and pour over it some of the solution of hyposulphite of soda made thus: Water, 1 pt.; hyposulphate of soda, 4 oz., allow it to remain for two minutes, then wash off thoroughly, and your picture is finished. By this process, a most beautiful picture is obtained in a space of time varying from a fraction of a second up to 15 seconds, with the most perfect detail of all the parts.

Paper For Photographing

Wash the paper with a solution of nitrate of silver, 5 grs.; distilled water, ½ oz.; dry the paper, and wash it with iodide of potassium, 5 grs.; distilled water, ½ oz.; dry with a gentle heat; repeat the wash with the silver solution; and, when dry, the paper is ready for use. The sensitive surface is an iodide of silver, and is easily affected by light.