BOUGUER, Pierre, an eminent French mathematician, was born in 1698. His father, one of the best hydrographers of his time, was regius professor of hydrography at Croisic in Lower Britanny, and author of an excellent treatise on navigation. Young Bouguer was bred to mathematics from his infancy, and at an early age was appointed to succeed his father as professor of hydrography. In 1727 he gained the prize given by the Academy of Sciences for his paper “On the best manner of forming and distributing the Masts of Ships and two other prizes, one for his dissertation “On the best method of observing the Altitude of Stars at Sea,” the other for his paper “On the best method of observing the Variation of the Compass at Sea.” These are published in the Prix de Γ Académie des Sciences. In 1729 he published Essai d ’ optique sur la gradation de la lumière, the object of which is to define the quantity of light lost by passing through a given extent of the atmosphere. He found the light of the sun to be 300 times more intense than that of the moon. He was soon after made professor of hydrography at Havre, and succeeded Maupertuis as associate geometer of the Academy of Sciences. He was afterwards promoted in the Academy to the place of pensioned astronomer, and went to reside in Paris. In 1735 Bouguer sailed with Godin and De la Condamine for Peru, in order to measure a degree of the meridian near the equator. Ten years were spent in this operation, a full account of which was published by Bouguer in 1749, Figure de la Terre déterminée. His later writings were nearly all upon the theory of navigation. He died in 1758....