Hydrometer, an useful instrument for measuring the gravity, density, strength, etc. of spirits, or other liquids.

For this purpose, various hydrometers have been contrived on different principles; but the most simple of which appears to be that devised by Mr. William Jones, mathematical instrument - maker, Holborn. It requires only three weights to discover the strength of spirits, from alkohol down to water, and is adjusted to the temperate state of the air, or to 60° of Fahrenheit's thermometer. Farther, as an alteration of this temperature has a very material effect on the gravity of" spirits, by causing them to appear much stronger during warm weather, and the reverse in cold seasons, it was formerly requisite to place a thermometer in the spirits, previously to immersing the hydrometer, and to make a certain, but inaccurate, allowance for the several degrees the mercury may be above, or below, the temperature before mentioned. In order to remedy this inconvenience, Mr. Jones has contrived to unite the thermometer with his instrument ; and, from experiment, to adapt the divisions to the different degrees above or below the temperate state. Thus, his hydrometer is rendered easy in its application, and sufficiently accurate for the common purposes of distillers, or dealers in spirits.