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As something has been said in one or two numbers of the “Scientific American,” in relation to " Storm Pointers," (usually called t: Storm Glass,") I send you the correct ingredients :—2 drachms of camphor; i drachm pure nitrate of potash; 4 drachm muriate of ammonia, and triturate them together until: they are thoroughly pulverized; the operation may be assisted by the addition of a few drops of alcohol. When well triturated, the mixture is to be dissolved in about two ounces of proof spirits (good whiskey) and put into a tall vial, such as eau-de-Cologne bottle, or into a glass tube about ten inches in height, and three-fourths of an inch in diameter, the mouth of which is to be covered with a piece of bladder perforated with a pin. The indications which it gives are of this nature —If the atmosphere toe dry and the weather promising to be fine, all the solid part of the composition which appears in the glass will be closely collected at the bottom, and the liquid above will be quite clear; but on the approach, of a change to rain, the solid matter will appear gradually to rise, and small I crystalline stars will be observed to float [ about in the liquid, which otherwise will remain pellucid. On the approach of winds, flocks of the composition, apparently in the form of a leaf, will appear on the surface of the liquid, which, in this case, will seem thick and in a state of lermentation. These indications often begin to exhibit themselves twenty-four hours before the actual breaking forth of the storm ; and after a short experience in observing the changes of appearance of the materials in the glass, not only the magnitude of the coming storm will readily be estimated but likewise its direction; for the quarter of the compass irom which the wind blows will always be indicated by circumstance of the solid particles lying more closely to i the side of the glass opposite to that whence the tempest comes. During the winter the composition is rendersd white by the multitude of small white stars which are constantly floating about in the liquid: this is particularly remarkable during white frost and snow, in summer, on the contrary, when the weather is warm and serene, the liquid is clear, and the solid matter lies at the bottom of the glass. Some of these indications are as yet unaccounted lor; but the Leading principle is the solubility of camphor in alcohol and its insolubility in water, combined with the well-known meteorological fact, that the drier the atmosphere the more aqueous vapor does it take up, and vice versa; when, therefore, the weather is warm and dry_ a quantity of the water of the menstrum is drawn off in the form of vapor, and consequently more of the camphor enters into solution; and, on the contrary, when the air is surcharged with moisture, that moisture begins to be deposited, and the menstruum again will be weakened, and a quantity of tbe camphor is precipitated from the solution in the form of little crystal- I line stars. This may easily be proved by making an alcoholic solution of camphor, and adding a few drops of water. G. M, Hallowell, Me.
