Henry Cavendish [1731-1810]
An English physicist and chemist, born in Nice. He was the son of Lord Charles Cavendish and grandson of the 2nd Duke of Devonshire. He was a recluse, and most of his writings were published posthumously. His great contributions to science resulted from his many accurate experiments in various fields. His conclusions were remarkably original. His chief researches were on heat, in which he determined the specific heats for a number of substances (although these heat constants were not recognized or so called until later); on the composition of air; on the nature and properties of a gas that he isolated and described as "inflammable air" and that Lavoisier later named hydrogen ; and on the composition of water, which he demonstrated to consist of oxygen and his "inflammable air." In his Electrical Researches (1879) he anticipated some of the discoveries of Coulomb and Faraday. His experiments to determine the density of the earth led him to state it as 5.48 times that of water. His Scientific Papers were collected in two volumes (Electrical Researches and Chemical and Dynamical) in 1921.
Cavendish is also credited with one of the earliest accurate calculations of the density of the earth. The current best estimate for the Earth's mass is 5.9725 billion trillion tonnes, a difference of only about 1% from Cavendish's measurements.