Page:A history of the theories of aether and electricity. Whittacker E.T. (1910).pdf/76

 the names boreal and austral were assigned, were postulated by the Hollander Anton Brugmans (b. 1732, d. 1789) and by Wilcke. These fluids were supposed to have properties of mutual attraction and repulsion similar to those possessed by vitreous and resinous electricity.

The writer who next claims our attention for his services both to magnetism and to electricity is the French physicist, Charles Augustin Coulomb (b. 1736, d. 1806). By aid of the torsion-balance, which was independently invented by Michell and himself, he verified in 1785 Priestley's fundamental law that the repulsive force between two small globes charged with the same kind of electricity is in the inverse ratio of the square of the distance of their centres. In the second memoir he extended this law to the attraction of opposite electricities.

Coulomb did not accept the one-fluid theory of Franklin, Aepinus, and Cavendish, but preferred a rival hypothesis which had been proposed in 1759 by Robert Symmer. "My notion," said Symmer, "is that the operations of electricity do not depend upon one single positive power, according to the opinion generally received; but upon two distinct, positive, and active powers, which, by contrasting, and, as it were, counteracting each other, produce the various phenomena of electricity; and that, when a body is said to be positively electrified, it is not simply that it is possessed of a larger share of electric matter than in a natural state; nor, when it is said to be negatively electrified, of a less; but that, in the former case, it is possessed of a larger portion of one of those active powers, and in the latter, of a larger portion of the other; while a body in its natural state remains unelectrified, from an equal balance of those two powers within it."

Coulomb developed this idea: "Whatever be the cause of electricity," he says, "we can explain all the phenomena by