John Michell was an English natural philosopher and clergyman, educated at Queen's College, Cambridge, who discovered that the force between magnetic poles varies as 1/r ². In 1767, Michell became Rector of Thornhill, now a suburb of Dewsbury, Yorkshire. Sometime in the early 1770s, he played music with the great astronomer William Herschel and gave Herschel his first telescope. In 1784, Michell deduced the existence of what are now called black holes from Newton's corpuscular theory of light, and suggested that some stars might have dark companions. He also devised and built the torsion balance for determining the universal gravitational constant G, but died before having the chance to use it. The balance was passed to the Cambridge physicist F. J. H. Wollaston, and from him to Henry Cavendish, who used it at his house in London and is often, mistakenly, identified as its inventor.