PRATT, Orson, American Mormon apos tle: b. Hartford, N. Y., 19 Sept. 1811; d. Salt Lake City, Utah, 3 Oct. 1881. After a com mon-school education, he followed the lead of his brother, Parley P. Pratt (q.v.), and joined the Mormons in 1830, accompanied them in the westward migration and in 1835 became one of the original 12 apostles. With Erastus Snow he was the first to enter the valley of the Great Salt Lake. From 1840-78 he accomplished eight missions to Great Britain and in 1864-65 one to Austria. During his visits to England he edited at various times The Millennial Star, the circulation of which he increased greatly. He began in Washington in 1852 the publica tion of The Seer, a monthly, of which 18 num bers appeared. From 1874 until his death he was historian and general church recorder. He was also for many sessions a member of the Utah Territorial legislature and seven times its speaker. In spite of the lack of educa
tional opportunities which he had experienced in his early life, he became a well-versed scholar of higher mathematics, astronomy and Hebrew. In 1854 he announced his "law of planetary rotation" to the effect that the cubic roots of the densities of the planets are as the square roots of their periods of rotation. Among his works are 'New and Easy Method of Solution of the Cubic and Biquadratic Equations) (Lon don 1866) ; 'Key to the Universe' (1879), and a large number of tracts and pamphlets deal ing with the Mormon doctrine. He also edited and published in Salt Lake City The Doctrine and Covenants of the Church of Jesus Christ of Latter-Day Saints, Containing the Revelations Given to Joseph Smith, Jr., the Prophet.>