1. Silver nitrate....................... 200 grains Water............................... 1½ ounce. 2. Ammonia bromide...................... 120 grains. Water................................ 1½ ounce. Gelatine............................. 12 grains. I emulsified the two together in the usual way, allowed the whole to cool, and then poured the thin emulsion into about ten ounces of alcohol, stirring the while. As I had anticipated, a flocculent precipitate was formed, which settled to the bottom of the vessel in a few minutes. This was, in fact, sensitive bromide of silver mixed with a very small quantity of gelatine (about five per cent.), and could, I found, be treated in the same manner as a bromide precipitate from an aqueous solution; it might be washed, either by decantation or by filtration, easily dried, and doubtless could, when dry, be kept for an indefinite time, and be at any time used by mixing with gelatine and water in any proportion thought fit. I found that a less amount of gelatine than four grains to the ounce was sufficient to carry the bromide down, while five grains to the ounce carried it down in something which I considered too near an approach to a plastic mass. It will be noticed that in the experiments which I have described the emulsion had not been boiled, so that the sensitiveness of the bromide was probably not great. As the experiment was done in daylight it was of no practical use for making emulsion; but I have since made several batches in this manner and have found them most satisfactory. When sensitiveness is sought by boiling I rind it necessary to add a small quantity of gelatine after boiling and before precipitating, as that which has been kept for some time at a high temperature seems to have lost the viscosity necessary to carry down the silver bromide in such a form that it can he easily separated from the alcohol and water. The practical manner of making an emulsion by this method may be as follows. Make up the following mixtures: I. Silver nitrate...........................................400 grains. Water..................................................... 3 ounces. II. Ammonia bromide..........................................240 grains. Gelatine..................................................24 grains Water..................................................... 3 ounces. Hydrochloric acid enough to slightly acidify the solution. III. Gelatine................................................. 20 grains. Water.................................................... ½ ounce. IV. Hard gelatine (say Nelson's X opaque, or Mr. A. L. Henderson's)................................240 grains. Soft gelatine (Nelson's No.1)........................... 240 grains. Water.....................................................24 ounces.