SIDNEY, or SYDNEY, ALGERNON, an English military officer; born in Pens hurst, Kent, in 1622. He accompanied his father, the 2d Earl of Leicester, in his embassies to Denmark and France. He was also early trained to a military life, and served with some distinction in Ire land, where his father was lord lieuten ant. In 1643 he returned to England and joined the Parliamentary forces. In 1644 he was lieutenant-colonel of a regiment of horse in Manchester's army, and was se verely wounded at Marston Moor. In 1645 he was given the command of a cav alry regiment in Cromwell's division of Fairfax's army, and was returned to Par-. liament for Cardiff. He was nominated one of the commissioners to try Charles I., but took no part in the trial, though he approved of the sentence. He refused all concurrence in the government of Crom well, retiring to Penshurst, but when the return of the Long Parliament in May, 1659, gave expectations of the establish ment of a republic, he again took his seat and was nominated one of the council of state. He was soon after appointed a
commissioner to mediate a peace between Denmark and Sweden, and while he was engaged in this embassy the Restoration took place. Conscious of the offence he had given the royal party, he refused to return and remained an exile for 17 years. At length, in 1677, the influence of his friends procured him permission to return to England. After the death of Shaftes bury in 1682, he entered into the confer ence held between Monmouth, Russell, Es sex, Hampden, and others, and on the discovery of the Rye House Plot he was arrested and sent to the Tower on a charge of high treason. He was tried before the notorious Chief Justice Jeff reys, and his trial was conducted with a shameless absence of equity which has conferred on him all the glory of a mar tyr. He was executed on Tower Hill, Dec. 7, 1683. His "Discourses Concern ing Government" were first printed in 1698.