Atmospheric electrometer, after Peltier and Kohlrausch

A ‘black box’. That is the name we give nowadays to an apparatus of which you cannot see at the outside how the inside works. The same holds for this beautifully made electrometer, made by the Belgian instrument maker Theodore Henri Schubart (1835-1899). The purpose of an electrometer is to establish the magnitude of a charge or a voltage. This specimen, based on the design of Jean Charles Athanase Peltier (1785-1845) from 1836, with little alterations by Rudolf Kohlrausch (1809-1858), was especially made for measurements of atmospheric electricity. The apparatus is based on the principle of electrostatic repulsion of like charges, the same principle that was applied in the torsion balance of Coulomb (cat. no 726). A small magnet ensures that a return to the initial situation after each measurement.