Antique Georgian mahogany cased hydrometer bulbs, also known as philosophical bubbles or gravity beads. The circular turned mahogany box with domed lid opens to a velvet-lined interior with nine numbered glass beads (originally 12). They were used for testing the proof of spirit. The inside of the lid has the remains of a paper label and listed the spirits and their corresponding numbers. They were invented by Alexander Wilson of Glasgow in the 1750s.
British, circa 1750 - 1780
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