Glass and Mercury Antique Hydrometer in Original Wooden Box linen pillowcases unexpected surprise

unexpected surprise

lighter one is 1 3/4" diameter

Like nothing else

Widely collected by museums

Glass and Mercury Antique Hydrometer in Original Wooden Box linen pillowcases unexpected surpriseAt first I thought this antique Griebel Instrument Co. hydrometer was an old thermometer, until I noted that the numbers on the side run 0 to 6 rather than showing temperatures. Ive since learned that a hydrometer is used for measuring the relative density of liquids based on buoyancy: you pour liquid into a container, lower the hydrometer into it until it floats, and then the point at which the surface of the liquid touches the stem of the hydrometer