Description:
A curvy, lamp-shaped glass jar with a bell-shaped glass base stoppered by a perforated glass cap through which goes a brass rod with a large brass ball outside. From this brass rod inside the jar hang two pith balls from thin metal threads at the level of the widest section of the jar. At the same height, on opposite ends of the jar, are openings on the glass covered with brass caps, and which allow the insertion of identical thin rods with small brass balls at their ends. The brass caps have binding posts outside and long screws that alter the distance of the small brass ball from the edge of the glass.
One of the two pith balls has fallen to the bottom of the jar. The instrument as a blue triangle and the letter "E" written in (the letter next to the e has been crossed out).