Celsiis. I. Anders, a Swedish astronomer, born Nov. 27, 1701, died in Upsal, April 25, 1744. His grand-uncle, Magnus Celsius (1621-79), an astronomer, was the discoverer of the Helsing runes. His uncle, Olaf Celsius (1670-1756), a theologian, was one of the founders of the scientific society of Upsal, author of Hierobotanicon (Upsal, 1745-7), and the first to recognize the genius of Linnaeus. His father, Nils Celsius (1658-1724), was a mathematician and naturalist. Anders was professor of astronomy at Upsal 1730-'32, when he visited Doppelmayr in Nuremberg, where he published Observationes Luminis Bo-realis. He next went to Rome, and in 1734 to Paris, where he subsequently joined Mauper-tuis and his associates in the measurement of the Lapland degree of longitude. On his return to Upsal he published De Observationibus pro Figura Telluris determinanda in Gallia habitis. The observatory of Upsal was established in 1740 under his auspices. He was the first to employ the centigrade, also known as the Celsius thermometer.

II. Olaf de, a Swedish historian, cousin of the preceding, born in 1716, died in 1794. In 1747 he became professor of history at Upsal, was afterward raised to the nobility, and in 175G founded the first literary journal in Sweden. In 1777 he became bishop of Lund, and in 1786 a member of the Swedish academy. His principal works are a history of Gustavus I. (2 vols., Stockholm, 1746-'53; 3d ed., 1792; German translation, Copenhagen, 1753), and a history of Erie XIV. (1774; German and French translations, 1777).