COULOMB, CHARLES AUGUSTIN DE, was born at Angoulase in 1736, studied at Paris, and entered at an early age into tho army. After serving with distinction for three years in the West Indies, he returned to Paris, where he became known by a treatise on the equi librium of vaults (1776). In 1779 he was employed at Rochefort, where he wrote his 'Th6orie des Machines Simples,' a treatise on the effects of friction and resistances, which gained the prize of the academy, and was subsequently printed separately in 1809. A project of navigable canals had been offered to the Etats of Bretagne, and Coulomb was appointed by the minister of marine to examine the ground. His report was unfavourable, which so displeased some influential persons that he was placed in confinement : the pretext was, that he had no order from the minister of war.
The Etats afterwards saw their error, and offered Coulomb a large recompense, but he would accept nothing but a seconds' watch, which afterward served him in all his experiments. In 1784 he was intend ant des eaux et foutaines ; in 1786 he obtained the reversion of the place of coneervateur des plans et reliefs, and was sent to England as a commissioner to obtain information on the hospitals. At the revo lution he lost his public employments, and devoted himself to his domestic affairs. He was one of the first members of the Institute, and an inspector-general of public instruction. He died August 3, 1806, having supported a high moral and social character through life. There are many men into whose biographies we are obliged to insert more account of their labours than will be necessary in the case of Coulomb. All his researches are of a permanent character, and belong to treatises of mechanics and electricity. We have no pro minent acts of mind to record which individualise his discoveries, though they were marked by a union of patient industry and experi mental sagacity of no common order, accompanied by a strong sense of the necessity of mathematical experiment, or numerical determina tion of mechanical phenomena. He was, we may say, the founder of
the school of experimental physics in France, a country which, till his time, had been by no means pre-eminent in that branch of discovery. His retie trchea on friction, and resistances in general, were the first in which the subject had been pursued manually by one with the know ledge of mathematics necessary to combine or separate the results according to the subject and the method. In electricity ho was the first who invented the method of measuring the quantity of action, and from it he deduced the fact of electrical attractions and repulsions, following the Newtonian law. He ascertained the non-penetration of these agents into the interior of solid bodies, and on these two conclusions the mathematical theory of electricity is now based. He even deduced the second phenomenon from the first. He extended in a great degree to magnetism his conclusions on electricity. The instrument by which these brilliant results were obtained was of his own invention, the Torsion Balance, the principle of which is a needle hanging from a flexible thread, in which tho force of torsion necessary to produce a given effect in producing oscillation's of the needle being first ascertained, the instrument remains a determinate measurer of any small forces; or, if the absolute force of torsion be unknown, it may be made to give comparative determinations. This construction, In the hands of Cavendish, determined the mean density of the earth, and is now as much of primary use in delicate measurements of force, as the common balance in analytical chemistry. There is, perhaps no one to whom either the determination of resistances in mechanics, or the theory of electricity, is so much indebted as to Coulomb. Tin account of his life Is from the article in the ' Biog. Univ.' by M. Biot.