2 antique professional instruments ball of outlet Gravesande

antique technical instrument

two specimen !

" the ball of 's Gravensande "

The device consists of a small metal ball on a chain or handle and a metal ring on a support. The ring is just large enough that when the ring and the ball are at the same temperature, the ball passes through the ring. However, if the ball is heated by dipping it in boiling water or playing on the flame of an alcohol lamp on it, the metal will expand and the ball will no longer pass through the ring. Once the ball is cooled, it will get back in the ring

ca 1940

perfect condition

25 cm high/ diameter ball 3 cm 10 inch high/ the ball 1,2 inch

base 14 cm x 8 cm/ 5,5 inch x 3,2 inch outlet