twelve years his senior, who was destined to be his co-worker or rival, according to circumstances, during his life. In 1806 he and Biot were appointed by the emperor to co-operate with the Spanish commissioners, Chaix and Rodriguez, in continuing the measurement of the arc of the meridian, for the establishment of the metric system. In this expedition he found arduous work, and underwent hard sufferings from the fortunes of war, the story of which we will let M. Jamin tell further along. He returned to France in the summer of 1809, and was received into the Academy of Sciences, in departure from its rules, at the age of twenty-three years. The emperor, who always manifested a remarkable esteem for him, considering how he had behaved when a school-boy, appointed him Professor of Analysis and Geodesy in the Polytechnic School, a position, or the equivalent of which, he held for twenty years. He also became director of the observatory and delivered lectures on astronomy, which were heard with equal interest by astronomers and by persons who knew nothing of mathematics, and were fully understood by the latter.
In 1830 he took the place of Fourier as perpetual secretary of the Academy, in which position it became his duty to pronounce eulogies upon deceased members, the felicity of the style and the scientific accuracy of which gained for him a world-wide reputation.
In 1830 M. Arago became a member of the Chamber of Deputies for the Pyrénées-Orientales. He took his seat on the Extreme Left, and became a conspicuous advocate of measures tending to the extension of public liberty and to electoral reform. He was also prominent in discussions relating to the marine canals, public instruction, and railroads. When the revolution that expelled the Orleans dynasty took place in 1848, M. Arago was made a member of the provisional government by popular acclamation, and was given charge of the bureaus of the marine and of war. He took part in all the events of that stirring epoch, sat among the moderate members, opposed the most radical republicans, while he always enjoyed their respect, was a member of the executive commission appointed by the Constituent Assembly, and marched to the barricades at the head of his troops during the bloody days of June. But so many struggles and shocks had broken his physical and moral energies, and he afterward sat in the Legislative Assembly without taking an active part. He declined to take the oath to the new government in 1852, as inconsistent with his past acts and professions, and was excused from it, and was allowed to keep his place in the observatory unsworn. He died in the next year, October 2, 1853.
The scientific, personal, and social aspects of Arago's life have been admirably portrayed by M. Jamin in his eulogy, and most of what follows on those points is drawn from that address. The first scientific labors coming under his notice were in association with Biot, the continuation of Borda's investigations of the indices of refraction
