In 1820, a French physicist invented an astatic needle which canceled out the Earth's magnetic field, enabling the creation of the sensitive Galvanometer

In 1820, a French physicist invented an astatic needle which canceled out the Earth's magnetic field, enabling the creation of the sensitive Galvanometer. The invention was part of André-Marie Ampère's work on electricity and magnetism. Ampère also developed the solenoid, studied electric currents, formulated laws of electrodynamics, proposed an electrical telegraph and helped establish the study of electromagnetism.