Two gifted 18th-century Londoners, Lord Charles Cavendish and his preeminent son, the Honorable Henry Cavendish, were descendants of paired revolutions, one political and the other scientific. Scions of a powerful revolutionary family, they gave a highly original turn to their understanding of public service. Lord Charles began his career as a Member of Parliament and ended it as an officer of the Royal Society, and his son Henry made a complete life within science, in the course of which he demonstrated skills that rank him with the greatest scientists of all time. In the history of British aristocracy, in high tide following the revolutionary settlement, there was no action more remarkable than Henry Cavendish gently laying delicate weights in the pan of his incomparable precision balance. Illustrations.