MICHELL, John, an eminent English man of science of the 18th century. He received his university education at Queen’s College, Cambridge. His name appears fourth in the Tripos list for 1748-49; and in 1755 he was moderator in that examination. He was a fellow of his college, and became successively Woodwardian professor of geology (in 1762) and rector of Thornhill in Yorkshire. He was elected a member of the Royal Society in the same year as Henry Cavendish (1760). He died in 1793. In 1750 he published at Cambridge a small work of some eighty 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 variety of acute and accurate magnetic observations, and is particularly distinguished by a lucid exposition of the nature of magnetic induction. He is now best known as 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, who made, by means of Michell’s apparatus, the celebrated determination that now goes by the name of Cavendish’s experiment {Phil. Trans., 1798)....