Arago, ah'ra go, DOMINIQUE FRANCOIS (1786-1853), a celebrated French scientist and statesman who gained especial fame as an investigator in physics and astronomy. He made important discoveries in magnetism and optics and was a popular writer on these subjects. He graduated from the polytechnic school and was appointed to a commission which was making certain measurements of longitude that were to serve as the basis of a decimal metric system. While engaged in this work he was taken prisoner as a spy by the Spaniards, underwent hardships and narrow escapes, but finally reached Marseilles. On returning to Paris he was at once elected a member of the Institute. In 1830 be became perpetual secretary of the Academy of Sciences and director of the observatory. He was elected a member of the Chamber of Deputies in 1831, and there made many famous speeches in behalf of education, science, and, especially, the rights of the people. Arago was president of the Council General of the Seine until 1849 and was the chief instrument in the emancipation of slaves. After the revolution of 1848 he was appointed minister of war and marine. He favored liberal institutions as exemplified in the United States. Arago was the author of about sixty scientific works and memoirs.