Pingke, Alexander Guy

, a French mathematician and astronomer, was born at Paris, in 1711. In 1727 he became a member of the canons regular of the congregation of France. He was intended for the church, hut the freedom of his opinions displeased his superiors, and after a few years’ study of theology, he devoted himself entirely to the sciences. In 1749 he was appointed a member of the academy of sciences in Rouen, and was elected to fill the office of astronomer, and attained to first-rate excellence. His earliest production, as an author, was the “Calculation of an Eclipse of the Moon,” on the 23d of December 1749. Lacaille had calculated it at Paris; but the calculations differed by four minutes: Lacaille., however confessed his error, and received Pingre into his friendship. In May 1753 he was elected correspondent of the Academy of Sciences at Paris, after having sent them an observation of the transit of Mercury, which he made at Rouen. He was next appointed librarian of the abbey of St. Genevieve, obtained the construction of an observatory, and was furnished by the abbot and chapter with a six-foot telescope, while he had the loan of an excellent quadrant from the academy. At the desire of Le Monnier, he next engaged in calculating “A Nautical Almanack,” to enable navigators more easily to ascertain the longitude by means of lunar observations. He calculated a table of the eclipses visible of the sun and moon from the commencement of the Christian aera to 1900, and afterwards a table of the eclipses visible from the northern pole to the equator, for a thousand years before our aera. | The utility of these labours for verifying historical dates, induced the Academy of Inscriptions to insert a part of them in the forty-second volume of their Memoirs. He published the “State of the Heavens” for 1754: in this the moon’s place was calculated with the utmost exactness according to the tables of Dr. Halley for noon and midnight, with the right ascension in seconds of time twice a day. In 1753 he published “A Memoir relating to the Discoveries made in the South Sea, during the Voyages of the English and French round the World.” In 1760, Pingre left France for the island of Rodriguez, in the Indian ocean, to observe the transit of Venus, that was to take place in the following year; and on the 6th of June of that year he made his observations, from which he concluded that the parallax, of the sun was 10“. 2. At the same time the English astronomer Mason concluded, from the observations which he made at the Cape of Good Hope, that the parallax was 8”. 2. La Lande, in his “Astronomy,” published in 1764, adopted a medium between these conclusions, and supposed l,he parallax to be 9“, in which he was followed by astronomers in general, till more numerous observations, made on the transit of 1769, led to a different result. After the return of Pingre from the East, he published a description of Pekin, in which he shewed the position of that capital from the result of a number of calculations of eclipses; and ascertained its longitude by other calculations, with a degree of precision to which none of the labours of the scientific missionaries had any pretensions. In 1769 he sailed for the island of St. Domingo, on board the Isis man of war, to observe the transit of Venus, and performed the service committed to him in the most able and satisfactory manner possible. An account of this voyage, which proved of considerable importance to the science of geography, as well as astronomy, appeared in 1773, in two vols. 4to. After comparing the results of the immense number of calculations made by the observers of the transit in 1769J the sun’s parallax has been concluded to be about 8”. 6. In 1771, Pingre made another voyage, on board the Flora frigate, with a view of extending the interests of geographical and astronomical knowledge, having with him, as the companion of his pursuits, the chevalier de Borda, a celebrated engineer and geometrician. The account of their proceedings, observations, and experiments, was | published in 1778, in two vols. 4to. In 1784, M. Pingre published his “Cometography, or historical and theoretical treatise on Comets,” in two vols. 4tc, which is his most considerable work, and contains calculations of the orbits of all the comets of which an. account has been preserved. After a long life, spent in the most important services to the world, he died in the month of May 179tf, leaving behind him a high character for integrity, having enjoyed the esteem of the public, as well as that of his friends. He was author of many other works besides those that have been already noticed. ¹