9 x 13.3 x 11.4
Iron and copper
INDEX 1788 : O.IV.270
Annulus cupreus tribus pedibus insistens, et pila ferrea, quae frigida per annulum transit, calefacta non transit.
A little copper ring seated on three feet, and a ball of iron that passes through the ring when cold, but not when hot.
This is the famous 's Gravesande's ring through which an iron sphere passes exactly when it is cold, but not when it is heated, which demonstrates the dilatation of metals by the action of the heat.
The apparatus consists of a little copper tripod and an iron sphere provided with a little hook. A wire with the ends bent in order to suspend the sphere when it is heated also existed.
From Colégio dos Nobres, catalogue n.º 260.
Carvalho, Rómulo de, História do Gabinete de Física da Universidade de Coimbra, Universidade de Coimbra, Biblioteca Geral, Coimbra, 1978, p. 439.