The following is the patent process for obtaining a negative picture:--Take a sheet of paper, with a smooth surface, and a close and even texture, and without the water-mark, and wash one side of it, by means of a soft camel’s-hair brush, with a solution composed of one hundred grains of crystallized nitrate of silver dissolved in six ounces of distilled water, having previously marked with a cross the side which is to be washed. When the paper has been dried cautiously at the fire, or spontaneously in the dark, immerse it for a few minutes (two minutes, at a temperature of sixty-five degrees,) in a solution of iodide of potassium, consisting of five hundred grains to one pint of distilled water. The paper is then to be dipped in water, and then dried, by applying blotting-paper to it lightly, and afterwards exposing it to the heat of a fire, or allowing it to dry spontaneously. The paper thus prepared is called iodized paper, and may be kept for any length of time in a portfolio not exposed to light. When a sheet of paper is required for use, wash it with the following solution, which we shall call No. 1; take one hundred grains of nitrate of silver, dissolved in two ounces of distilled water, and add to this one-third of its volume of strong acetic acid. Make another solution, No. 2, by dissolving crystallized gallic acid in cold distilled water, and then mix the two solutions together in equal proportions, and in no greater quantity than is required for immediate use, as it will not keep long without spoiling. This mixture, called gallo-nitrate of silver, by the patentee, is then to be spread, by a soft camel’s-hair brush, on the marked side of the iodized paper; and, after allowing the paper to remain half-a-minute to absorb the solution, it should be dipped in distilled water and dried lightly; first with blotting-paper, and then by holding the paper at a considerable distance from the fire. When dry, the paper is ready, and it is advisable to use it within a few hours.