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Shan Macdonald, Curatorial assistant for Scientific Instruments selected this object from the Hunterian Museum's collection. Shan writes - These mid-eighteenth century glass beads manufactured by Alexander Wilson in Glasgow were used primarily in the assaying and taxing of alcoholic spirits.
Each glass bead was hand-blown, its dimensions equating to a particular density or viscosity of liquid. Having identified the correct specific gravity of the liquid in question, by floating the bead in a measured quantity, its alcoholic percentage could be calculated.
The use of these beads made it difficult for unscrupulous manufacturers of alcoholic spirits to deceive the government inspectors and avoid paying their levy.