Two small rods lying on the axis of the central wheel can be weighted down with light weights at one end, while on the other they are fixed to a support held by a column 12.3 cm in height by means of a horizontal pin that leaves it free to rotate.
The instrument is put into movement by a spring that has one end attached to the axis of the central wheel and the other to the frame of the instrument.
It is possible to increase the wheel's moment of inertia by applying four small, identical brass balls on pins on the outside of the wheel by pressure.
In the same way, it is possible to study the inertia produced by the air by applying four identical brass vanes instead of the balls.
The instrument is protected by a glass case.
An identical apparatus appeared in the catalogue of the watchmaker Deleuil in Paris in 1863.