Take a long, narrow bottle, and put. into it 2½ drs. of camphor; spirits of wine, 11 drs. When the camphor is dissolved, add to it the following mixture: Water, 9 drs.; saltpetre, 38 grs.; sal-ammoniac, 38 grs. Dissolve these salts in the water prior to mixing with the camphorated spirit; then shake all well together, cork the bottle well, wax the top, hut afterwards make a very small aperture in the cork with a red-hot needle. By observing the different appearances which the materials assume as the weather changes, it becomes an excellent prognosti-cator of a coming storm or of a sunny sky.