Fascinating Historical Physics Instrument – ’s Gravesande’s Ball and Ring with Oil Lamp (ca. 1875–1900)

A fantastic physics demonstration instrument featuring a small oil lamp: the Ball and Ring of ’s Gravesande, named after the Dutch physicist Willem Jacob ’s Gravesande.

The ’s Gravesande Ring is a classic physics apparatus designed to demonstrate the thermal expansion of metals. It consists of a metal ball that fits through a metal ring at room temperature. When the ball is heated, it expands and can no longer pass through the ring—visually illustrating the effect of heat on matter.

The base is made of cast iron, and on top sits a small oil lamp. In my view, this is likely the original oil lamp, as it fits perfectly around the ring holder.
I tested the instrument: indeed, after heating for some time, the ball no longer fits through the ring—although it takes quite a while, and the ball becomes blackened with soot during the process.

The ring can be unscrewed and moved up and down the central rod so that it can be positioned around the ball.
The wick holder is marked with the letter R, Brevete, and Paris, suggesting French manufacture.

Altogether, a very special and rare piece.
Exact age unknown, but likely 1875–1900.

Total height: 28 cm
Ball diameter: 30 mm