AR'AGO, DOMINIQUE, a celebrated French astronomer and natural philosopher, was b. Feb. 20, 1786, at Estagel, near Perpignan, in the department of the eastern Pyre nees. At the early age of 17, lie entered the polytechnic school at Paris, where the spirit, promptitude, and vivid intelligence he exhibited in his answers to the questions of Legendre, excited the admiration of every one. In 1804, he became secretary to the observatory at Paris. Two years afterwards, be was engaged, with Biot and others, by the French government, to carry out the measurement of an arc of the meridian, which had been commenced by Delambre and Mechain. A. and Biot had to extend it from Barce lona to the Balearic isles. The two savants established themselves on the summit of Mt. Galatza, one of the highest of the Catalonian branch of the eastern Pyrenees. Here they lived for many months, communicating by signals with their Spanish collabo rateurs, across the Mediterranean in the little isle of Ivies, though many a night the furious tempests destroyed their hut along with the labors of weeks. Visitors they had none, except two Carthusian monks, who were wont to come up and spend a portion of the evening in converse with them. Before A. had completed his calculations, Biot had returned to France, and war had broken out betwixt the two nations. A. was now held to be a spy; his signals were interrupted; and with great difficulty he succeeded in mak ing his escape to Majorca, where he-voluntarily imprisoned himself in the citadel of Belver, near Palma. At last he obtained his liberty on condition of proceeding to Algiers, which lie did; but was captured, on his return to France, by a Spanish cruiser, and sent to the hulks at Palamos. He was, however, liberated after a time, and sailed once more for France; but almost as he was entering the port of Marseille, a tempest arose which drove the vessel across the Mediterranean all the why to Algiers. The former dey, to whose demands he had owed his liberation from the hulks, was dead; his successor, a ferocious tyrant, placed him on his list of slaves, and intended to employ him as interpreter. After some time, he was released at the request of the French consul, aud. narrowly escaping another capture by au English frigate, finally found his way to Marseille in July, 1809. As a reward for his suffering in the cause of science, the academy of sciences suspended its standing rules in his favor; and though only 23 years of age, he was elected member in the place of Lalande, who had just died, and was appointed professor of analytical mathematics in the polytechnic school. Afterwards, his attention was devoted more to astronomy, magnetism, galvanism; and the polarization of light. In 1811, he read a paper to the academy, which may be considered the foundation of "chromatic polariza tion." In 1812, he commenced his extraordinary course of lectures on astronomy, etc., which fascinated all Paris—the savants, by their scientific rigor and solidity; the many, by their brilliancy of style. In 1816, along with Guy Lussac, A. established the Annales
de Chinzie et de Physique, and confirmed the truth of the undulatory theory of light. In the same year he visited England for the first time, and made the acquaintance of various persons distinguished in science, especially Dr. Thomas Young. In 1818 appeared his Rccueil d'Obserrations geodesiques, astronomzqueset physiques. In 1820, he turned his facile and inventive genius into a new channel, and made several important discoveries in electromagnetism. Oersted had shown that a magnetic needle was deflected by a voltaic current passing along a wire. A. pursued the investigation, and found that not only a magnetic needle, but even non-magnetic substances, such as rods of iron or steel, became subject to deflection also, exhibiting, during the action of the voltaic current, a positive magnetic power, which, however, ceased with the cessation of the current. Some time after, he demonstrated, that a bar of copper, and other non-magnetic metals, when moved circularly, exert a noticeable influence on the magnetic needle. For this discov ery of the development of magnetism by rotation, he obtained, in 1825, the Copley medal of the royal society of London; and in 1834, when he again visited Great Britain, espe cial honors were paid to him by the friends of science in Ildinburgli and Glasgow. Four years previous to this second visit to Great Britain; he had received the honor he most coveted—that of being made perpetual secretary of the academy. It was while holding this office that he wrote his famous eloges of deceased members, the beauty of which has given him so high a place among French prose-writers. As a politician, also, his career was remarkable. He was a keen republican, and took a prominent, part in the July revo lution (1830). In the following year he was elected by Perpignan as member of the chamber of deputies, where he occupied a position on the extreme left. In the February revolution of 1848. he was chosen a member of the provisional government, and appointed minister of war and marine. In this position he resisted the proposed measures of the socialist party, regarding the constitution of the United States as the beau-ideal of democ racy. His popularity in his own province was the means of preventing the discontented population of the east Pyrenees from proceeding to lawless and violent measures. On the question of the presidency, A. opposed Louis Napoleon, declared himself against the policy of the new ministry, and refused to take the 'oath of allegiance after the coup d'etat of 1852. The emperor, in a letter, paid a high eulogium on his talents and virtues, and made a special exception in his case. A. died Oct. 3, 1853. In his general charac ter A. was sociable, energetic, and fond of fame. He was the intimate friend of Alex ander von Humboldt.