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in applying to the above a solution which has been named by Mr. Talbot the "Gallo-Nitrate of Silver;" it is prepared in the following manner: Dissolve one hundred grains of crystalized nitrate of silver in two ounces of distilled water, to which is added two and two-third drachms of strong acetic acid. This solution should be kept in a bottle carefully excluded from the light. Now, make a solution of gallic acid in cold distilled water: the quantity dissolved is very small. When it is required to take a picture, the two liquids above described should be mixed together in equal quantities; but as it speedily undergoe decomposition, and will not keep good for many minutes, only just sufficient for the time should be prepared, and that used without delay. It is also well not to make much of the gallic acid solution, as it will not keep for more than a few days without spoiling. A sheet of the iodized paper should be washed over with a brush with this mixed solution, care being taken that it be applied to the marked side. This operation must be performed by candle light. Let the paper rest half a minute, then dip it into one of the dishes of water, passing it beneath the surface several times; it is now allowed to drain, and dried by placing its marked side upwards, on the drying apparatus. It is better not to touch the surface with bibulous paper. It is now highly sensitive, and ready to receive the impression. In practice it is found better and more economical not to mix the nitrate of silver and gallic acid, but only to brush the paper with the solution of the nitrate. Mr. Talbot has recently proposed some modifications in his method of preparing the calotype paper. The paper is first iodized in the usual way; it is then washed over with a saturated solution of gallic acid in distilled