Philosophical Beads, by John Galleti, Glasgow, c. 1860

Set of fifteen glass beads in wooden box. Eleven are numbered to correspond with the table pasted in the lid of the box, and relate to the divisions on the British Excise Hydrometer. The bead which neither sank nor rose in the liquid under test indicated its specific gravity, or degree above or below proof at a particular temperature. Four of the beads indicate actual specific gravity readings, and may not belong to this set.