John Michell was a clergyman and Fellow of the Royal Society whose interest in natural philosophy centred on the stellar heavens. Michell interpreted what he saw with his telescopes in the terms of the then-dominant Newtonian picture of the universe, in which all material bodies, including the distant stars, attracted each other by inverse-square gravitational force-universal gravitation. This was the generally accepted picture by the middle of the eighteenth century. The Diminution of the velocity of light, in case it should be found to take place in any of the fixed stars, is the principal phenomenon whence it is proposed to discover their distance. The velocity of light in any medium, in whatever direction it falls upon it, will always bear a given ratio to the velocity it had before it fell upon it, and the sines of incidence and refraction will, in consequence of this, bear the same ratio to each other with these velocities inversely.