MICHELL, JOHN English natural philosopher and geologist, was born in 1724, and educated at Queens' College, Cambridge He was a fellow of his college, and was appointed Woodwardian professor of geology in 1762, and in 1767 rector of Thornhill in Yorkshire, where he died on April 29, 1793. He was elected a fellow of the Royal Society in 1760. In 1750 he pub lished at Cambridge a work of some 8o pages entitled A Treatise of Artificial Magnets, in which is shown an easy and expeditious method of making them superior to the best natural ones. Besides the description of the method of magnetization which still bears his name, this work contains a lucid exposition of the nature of magnetic induction. He was the founder of seismology. Michell was the original inventor of the torsion balance, which afterwards became so famous in the hands of its second inventor Coulomb. Michell described it in his proposal of a method for obtaining the mean density of the earth. He did not live to put his method into
practice ; but this was done by Henry Cavendish (Phil. Trans., 1708). His most important geological essay was that entitled Conjectures concerning the Cause and Observations upon the Phaenomena of Earthquakes (Phil. Trans., li. 176o).
Michell's other contributions to science are: "Observations on the Comet of January 176o at Cambridge, Phil. Trans. (176o) ; "A Rec ommendation of Hadley's Quadrant for Surveying," ibid. (1765) ; "Proposal of a Method for measuring Degrees of Longitude upon Parallels of the Equator," ibid. (1766) ; "An Inquiry into the Probable Parallax and Magnitude of the Fixed Stars," ibid. (1767) ; "On the Twinkling of the Fixed Stars," ibid. (1767), "On the Means of Discov ering the Distance, Magnitude, etc., of the Fixed Stars," ibid. (1784).
See Charles Davidson, The Founders of Seismology (1927).