Take a long narrow bottle, such as an old-fashioned Eau-de-Cologne bottle, and put into it two and a half drachms of camphor, and eleven drachms of spirits of wine; when the camphor is dissolved, which it will readily do by slight agitation, add the following mixture: - Take water, nine drachms: nitrate of potash (saltpetre), thirty-eight grains; and m.uriate of ammonia (sal ammoniae thirty-eight grains. Dissolve these salts in the water prior to mixing with the cam phorated spirit; then shake the whole well together. Cork the bottle well, and wax the top, but afterwards make a very small aperture in the cork with a red-hot needle. The bottle may then be hung up, or placed in any stationary position. By observing the different appearances which the materials assume, as the weather changes, it becomes an excellent prognosticator of a coming storm or of a sunny sky.