Hydrostatic balance, Jan van Musschenbroek, Leiden, 1725-1740
From the bequest of Willem Jacob 's Gravesande
V09295

Tradition has it that Archimedes, after an important discovery in hydrostatics, ran naked and shouting 'Eureka!' through the streets of ancient Syracuse. In about 1730 the Leiden professor Willem Jacob 's Gravesande was looking for a striking demonstration of precisely Archimedes' discoveries. Whether he adopted the streaking is not known, but in any case he opted for this elegant apparatus. The most important component is the brass cylinder, which fits exactly into the bucket hanging above it. The balance can now be in equilibrium on two ways: if the cylinder is in the bucket, and if it is hanging below it submerged in water. But in the latter case the bucket must be filled with water. And that means that the upward force of the water on the cylinder is equal to the weight of the displaced water, exactly what Archimedes had worked out.