Bouguer, Peter

, a celebrated French mathematician, was born at Croisic, in Lower Bretagne, the 10th of February 1698. He was the son of John Bouguer, professor royal of hydrography, a tolerable good mathematician, and author of “A complete Treatise on Navigation.” Young Bouguer was accustomed to learn mathematics from his father, from the time he was able to speak, and thus became a very early proficient in those sciences. He was sent soon after to the Jesuits’ college at Vannes, where he had the honour to instruct his regent in the mathematics, at eleven years of age. Two years after this he had a public contest with a professor of mathematics, upon a proposition which the latter had advanced erroneously; and he triumphed over him; upon which the professor, unable to bear the disgrace, left the country. Two years after this, when young Bouguer had not yet finished his studies, he lost his father, whom he was appointed to succeed in his office of hydrographer, after a public examination of his qualifications, being then only fifteen years of age; an occupation which he discharged with great respect and dignity at that early age.

In 1727, at the age of twenty-nine, he obtained the prize proposed by the academy of sciences, for the best way of masting of ships. This first success of Bouguer was soon after followed by two others of the same kind; he successively gained the prizes of 1729 and 1731; the former, for the best manner of observing at sea the height of the stars, and the latter, for the most advantageous way of observing the declination of the magnetic needle, or the variation of the compass. In 1729, he gave an “Optical | Essay upon the Gradation of Light;” a subject quite in which he examined the intensity of light, and determined its degrees of diminution in passing through different pellucid mediums, and particularly that of the sun in traversing the earth’s atmosphere. JVIairati gave an extract of this first essay in the Journal des Savans, in 1730. In this same year, 1730, he was removed from the port of Croisic to that of Havre, which brought him into a nearer connection with the academy of sciences, in which he obtained, in 1731, the place of associate geometrician, vacant by the promotion of Maupertuis to that of pensioner; and in 1735 he was promoted to the office of pensioner-astronomer. The same year he was sent on the commission to South America, along with messieurs Godin, Condamine, and Jeussieu, to determine the measure of the degrees of the meridian, and the figure of the earth. In this painful and troublesome business, of ten years duration, chiefly among the lofty Cordelier mountains, our author determined many other new circumstances, beside the main object of the voyage such as the expansion and contraction of metals and other substances, by the sudden and alternate changes of heat and cold among those mountains; observations on the refraction of the atmosphere from the tops of the same, with the singular phenomenon of the sudden increase of the refraction, when the star can be observed below the line of the level; the laws of the density of the air at different heights, from observations made at different points of these enormous mountains; a determination that the mountains have an effect upon a plummet, though he did not assign the exact quantity of it; a method of estimating the errors committed by navigators in determining their route; a new construction of the log for measuring a ship’s way; with several other useful improvements. Other inventions of Bouguer, made upon different occasions, were as follow: the heliometer, being a telescope with two object-glasses, affording a good method of measuring the diameters of the larger planets with ease and exactness: his researches on the figure in which two lines or two long ranges of parallel trees appear his experiments on the famous reciprocation of the pendulum and those upon the manner of measuring the force of the light &c. &c.

The close application which Bouguer gave to study, undermined his health, and terminated his life the 15th of | August 1758, at 60 years of age. His chief works, that have been published, are, 1. “The Figure of the Earth, determined by the observations made in South America,1749, in 4to. 2. “Treatise on Navigation and Pilotage,Paris, 1752, in 4to. This work was abridged by M. La Caille, in 1 vol. 1768, 8vo, and was reprinted in 1769 and 1781, and in 1792 with the notes of Lalande. 3. '“Treatise on Ships, their construction and motions,1756, 4to. 4. “Optical treatise on the Gradation of Light,” first in 1729; then a new edition in 1760, in 4to.

His papers that were inserted in the Memoirs of the Academy, are very numerous and important. They appear in their volumes from 1726 to 1757.

In his earlier years, Mr. Bouguer had lived in a state of seclusion from general intercourse with the world, and he had thus acquired a cast of temper, which marked his character in more advanced life. Although he was universally acknowledged to possess superior talents, and to be distinguished by an assiduity and zeal, no less successful than indefatigable, in various departments of useful science, he indulged a degree of suspicion and jealousy, with regard to his reputation, which disgusted some of those with whom he was under a necessity of associating, and which disquieted his own mind. Fully sensible of the importance and utility of his own performances, he was apt to consider others, who were engaged in similar pursuits, as competitors with himself, and to grudge them the reputation which they justly acquired, from an apprehension that his own credit would be thus diminished. Hence arose his disputes with La Condamine, one of the companions of his voyage, and associate in his labours in America; and the mortification he experienced from the public suffrage that seemed to have been bestowed on that academician. His character in other respects was distinguished for modesty and simplicity. The truths of religion were instilled into him along with the first principles of geometry, and had made such an impression upon his mind, r r to regulate and adorn his moral conduct. On his death-bed he cherished the same views which had thus guided him through life, and he closed his career with philosophical fortitude, and with a piety and resignation truly Christian. In the year 1784, a very singular book was published at Paris, entitled “Relation de la conversion et de mort de Bouguer,” by P. La Berthonie. His piety naturally offended | Lalande, who, in noticing this book, ascribes his piety to fear; this was a common opinion with the French deists, and had very pernicious influence on the minds of their disciples. Laiande, however, if our information be not incorrect, lived to experience the fear he once ridiculed. 1

1 Hutton’s Mathematical Dict. Rees’s Cyclopedia. Brewster’s Edinburgh Encyclopaedia. —Dict. Hist.