While Lavoisier was engaged in experiments on oxygen, Cavendish, too, was devoting his attention to the constituents of air, but in a somewhat different manner. His early experiments led him to the discovery of the composition of water; and it has already been pointed out how necessary a knowledge of the true nature of hydrogen is to the understanding of the phenomena of combustion. His second paper deals with the inactive constituent of air, the mephitic portion, now known as nitrogen or azote. But before considering these, a sketch of his life will prove of interest. The Honourable Henry Cavendish was a very singular man, retiring and uncommunicative to a degree; hence little is known of his early life. He was the elder son of Lord Charles Cavendish, who was the third son of the second Duke of Devonshire. His only brother, Frederick, was also an eccentric, but a very benevolent man, and the two brothers, though they seldom met, lived on excellent terms with each other. Henry Cavendish was born at Nice in October 1731. His mother died when he was two years old. Nothing is known of his childhood and youth, save that he attended Hackney School from 1742 to 1749, and that he went to Cambridge in the end of 1749, and remained till 1753, without taking a degree. After leaving Cambridge, it is supposed that he lived in London for ten years. It is known that his allowance from his father amounted to £500 a year, and that his rooms were a set of stables fitted up for his accommodation. It is probable that this was his own choice, and that he made use of them chiefly as a laboratory and a workshop. Although at his father’s death and by the legacy of an aunt he acquired a large fortune, he never spent more than a fraction of it. He left more than a million sterling to his relative, Lord George Cavendish; but they saw each other only once a year, and the interview seldom lasted more than ten minutes. The writer of his obituary notice, M. Biot, epigrammatically said:--“Il était le plus riche de tous les savans, et le plus savant de tous les riches.” [Illustration: H. Cavendish] He was a regular attendant at the meetings of the Royal Society, of which he was made a Fellow in 1760, and was a constant diner at the Royal Society Club. It is said that he used to talk to his neighbour at table so long as others did not join in the conversation; but if the conversation took a general turn, he was silent. His death took place in February 1810, and was as solitary as his life. It is related by his servant that Cavendish, on feeling his end approaching, dismissed him from the room, telling him to come back in half an hour. He disobeyed instructions, and, being anxious, found some pretext to enter the room. Cavendish ordered him away in a voice of displeasure; and on returning, the man found his master dead.