The horizontal cylinder contains the quadrants and the needle; the two vertical cylinders contain the platinum wire on which the needle is suspended, the ends of which are fixed at the centre of two agate insulating windows that seal the electrometer at top and bottom.
To one of the bases of the horizontal cylinder are attached:

1)     the plugs for connections to the plates, which are insulated by small blocks of agate;

2)      the plug for earthing the case;

3)      a lever that allows connection of the two quadrants to each other and to the case.

On the lateral surface of the horizontal cylinder we find on one side, at the level of the mirror, a glass window and on the other side a small glass receptacle communicating with the inside and capable of containing a hygroscopic substance.