Celsius, ANDERS, the constructor of the centi-grade thermometer, was born at Upsala in Sweden, 27th November 1701. He was the grandson of
Magnus Celsius (1621-79), a professor of Astronomy and decipherer of the Helsing runes, and the nephew of Olof Celsius (1670-1756), professor of Theology at Upsala, author of the Hierobotanicon, and an early friend and patron of the great Linnæus. Anders became in 1730 professor of Astronomy at Upsala. Two years later he set out on a scientific tour, visiting the observatories of Nuremberg, Rome, and Paris. After his return he published his De Observationibus pro figura telluris determinanda in Gallia habitis (Upsala, 1738). In 1740 he had the satisfaction of seeing a splendid observatory erected at Upsala, and here he laboured till his death, 25th April 1744. The Transactions of the Swedish Academy contain many papers by Celsius on astronomy and physics. It is, however, as the first constructor (1742) of the thermometer now chiefly used by scientific men, that he is best known. In it the space between the freezing-point and the boiling-point of water is divided into one hundred spaces, hence Celsius's thermometer is often called the centigrade or centesimal scale. See THERMOMETER.