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Fahrenheit's Hydrometer, is generally constructed of glass, and differs from Nicholson's in having at its lower extremity a ball weighted with mercury instead of the basket. It resembles it in having a dish at the top, in which weights are to be placed sufficient to sink the instrument to a definite mark on the stem.

Hydrometer

Fahrenheit's Hydrometer, is generally constructed of glass, and differs from Nicholson's in having at…