CAVENDISH, Henry, English chemist: b. Nice, Italy, 10 Oct. 1731; d. London, 10 March 1810. He was a grandson of the 2d Duke of Devonshire, and after his education at Peter house College, Cambridge, devoted himself ex clusively to scientific research. He lived in quiet retirement, having no interests besides his scientific studies. He never married, and left a fortune of f1,175,000. He was rather eccen tric, and had a hesitation in his speech. His first researches dealt with arsenic, and in 1765 he made some notable investigations concerning heats of liquefaction and vaporization which were not published until considerably later. He discovered the peculiar properties of hydrogen, and the qualities by which it is distinguished from atmospheric air. To him we owe the important discovery of the composition of water. Scheele had already observed that, when oxygen is mixed with double the quantity of hydrogen, this mixture burns with an explo sion without any visible residuum. Cavendish repeated this experiment with the accuracy for which he was distinguished. He confined both the gases in dry earthen vessels, to prevent the escape of the product of their combustion, and found that this residuum was water, the weight of which was equal to the sum of the weights of the two gases. Lavoisier confirmed this con
clusion in later times. Cavendish also obtained the anhydride of nitrous acid from nitrogen and oxygen by the electric spark.
Cavendish determined to constant K in the Kmml law of gravitation f=.—, where m and nil clt are the masses of two bodies, d the distance between them and f the measure of their mutual gravitational attraction, and was thus able to determine the mean density of the earth. He found it to be 5.45 times as great as the density of water —a conclusion which differs but little from that obtained by Maskelyne in another way. The apparatus used consisted of two large fixed masses of lead and two smaller masses near these at the ends of a rod sus pended by a wire at its middle. It was devised by the Rev. John Mitchell. Cavendish was a member of the Royal Society of London, and in 1803 was made one of the eight foreign members of the National Institute of France. His writings consist of treatises in the 'Philo sophical Transactions,' from 1766 to 1792. They are distinguished by acuteness and ac curacy. Consult 'The Electrical Researches of Henry Cavendish,' edited by J. Clerk-Maxwell (Cambridge 1879) ; Wilson, of Cavendish' (London 1846).