Around 1784 C. A. Coulomb devised the torsion balance, discovering what is now known as Coulomb's law : the force exerted between two small electrified bodies varies inversely as the square of the distance, not as Aepinus in his theory of electricity had assumed, merely inversely as the distance. According to the theory advanced by Cavendish, "the particles attract and are attracted inversely as some less power of the distance than the cube." A large part of the domain of electricity became virtually annexed by Coulomb's discovery of the law of inverse squares.