By means of a brass ring, a small glass cylinder placed vertically is attached to the centre of the cover. At the top of it another brass ring holds the device for the suspension of the needle and the regulation of its height.
The case, with the mobile accessories on the inside, is attached with four L-shaped rods to the brass frames of the two coils having a V profile with the face towards the centre of the flat and vertical instrument and the other curving towards the outside. They are attached, with the inner face at a distance of 12 centimetres, to a brass support which lies, by means of a vertical staff, on a cast-iron tripod painted black equipped with levelling screws. The entire system can rotate around that staff, but can also be fixed in any position.
Each coil consists of two groups of turns the terminals of which are connected to eight brass clamps, numbered from one to eight, which are attached to a wooden support at the bottom between the frames of the two coils. They allow connection of the two groups of turns of each coil in series or one of the groups of one coil in series with the corresponding group of the other coil. The average diameter of the turns is 26 cm, the average distance between the turns of the two coils is 13 cm and the overall height of the instrument is 37.5 cm.