Ar'ago, FRANÇOIS JEAN DOMINIQUE, a celebrated French astronomer and physicist, was born
February 26, 1786, at Estagel near Perpignan, in the department of Pyrénées Orientales. At the early age of seventeen, he entered the Polytechnic School at Paris, and in 1804 became secretary to the Observatory. Two years afterwards he was engaged, with Biot, by the French government, to carry out the measurement of an arc of the meridian, which had been commenced by Delambre and Méchain. Arago and Biot had to extend it from Barcelona to the Balearic Isles. The two savans established themselves on the summit of Mount Galatza, one of the highest of the Eastern Pyrenees, and here they lived for many months. War broke out betwixt France and Spain, and Arago was held to be a spy; his signals, supposed to be meant to guide the French invading army, were interrupted; and with great difficulty he succeeded in reaching Majorca. Having gone to Algiers, he was captured, on his way back to France, by a Spanish cruiser; and it was not till June 1809 that he finally arrived at Marseilles. As a reward for his sufferings in the cause of science, he was elected a member of the Academy of Sciences, though only twenty-three years of age, and was appointed professor of Analytical Geometry in the Polytechnic School.
His laurels were, however, won mainly in the fields of astronomy, magnetism, and optics. In 1812 he commenced his extraordinary course of lectures on astronomy and cognate subjects, which fascinated all Paris. In 1816, along with Gay Lussac, he established the Annales de Chimie et de Physique, and confirmed the truth of the undulatory theory of light. In 1818 he published his Recueil d'Observations Géodésiques, Astronomiques, et Physiques, and, with Biot, made geodetic observations on the coasts of England and Scotland. In 1820 he made several important discoveries in electro-magnetism—especially the phenomenon of rotatory magnetism. He may be said to have proved the relation between the aurora borealis and magnetic variations. He greatly promoted the acceptance of the undulatory theory of light, and made important advances in the doctrine of the polarisation of light. Other minor achievements were made in the department of photometric measurements of the brightness of the stars, the elastic force of steam and other gases. In 1830 he became chief director of the observatory, and received the post of Perpetual Secretary of the Academy. It was while holding the latter office that he wrote his famous éloges of deceased members. He took a prominent part in the July revolution (1830). Elected by Perpignan as member of the Chamber of Deputies, he occupied a position on the extreme left. In the revolution of 1848, he was chosen a member of the provisional government, and in this position he resisted the proposed measures of the Socialist party. Arago opposed Louis Napoleon, and refused to take the oath of allegiance after the coup d'état of 1852. He died 3d October 1853, and was honoured with a public funeral. His works were edited by Barral (17 vols. 1854–62), including the Astronomie Populaire and the Notices Biographiques. See Audiganne's Arago, son Génie et son Influence (2d ed. 1869).
JACQUES ÉTIENNE VICTOR ARAGO, brother of the great savant, was born 10th March 1790. In 1817 he accompanied an expedition round the world. Afterwards, we find him first at Bordeaux, and then at Toulouse, writing vaudevilles, besides publishing poems and romances. From 1835 to 1837 he managed the theatre at Rouen. His Promenade autour du Monde (1822), and Souvenir d'un Aveugle (1838), are well known. In 1849, though blind, he formed a company of speculators, and departed for California, to search for gold.
On his return he published Une Vie Agitée (1853). He died in Brazil in January 1855.—ETIENNE, another brother of the astronomer, was born 9th February 1802, and made himself well known as a popular author. He held an appointment under the provisional government of 1848, and was afterwards exiled. In 1859 he returned to France, and in 1878 became archivist in the École des Beaux Arts. He died 5th March 1892.—EMANUEL, son of the astronomer (1812-96), became known as a zealous republican in 1848, and was after 1852 active as a barrister. In 1870 he became a member of the committee of national defence, and afterwards held appointments under the government.