Algernon Sidney, an English statesman, born about 1622, executed on Tower hill, London, Dec. 7, 1683. He was the second surviving son of the second earl of Leicester of that creation, by the eldest daughter of the earl of Northumberland, and grandncphew of Sir Philip Sidney. In 1632 he accompanied his father to Denmark, where the latter was accredited as ambassador, and four years later to France. In 1641 he served in Ireland as captain of a troop of horse in a regiment commanded by his father; and at the outbreak of the civil war, while on his way with his brother to join the king's forces, he was detained at Liverpool by order of parliament. The king believed this had been done through the connivance of the young men, who, resenting his distrust, at once declared for the parliament. Algernon Sidney was commissioned a captain in May, 1644, and fought with gallantry at Marston Moor, where he was severely wounded. In 1646 he was appointed lieutenant general of horse in Ireland, and governor of Dublin. In the same year he entered parliament for Cardiff, and in May, 1647, received the thanks of parliament for his services in Ireland, and was made governor of Dover castle.

He acted as one of the judges of the king, but refrained from signing the warrant for his execution, although he subsequently characterized it as "the justest and bravest action that ever was done in England or anywhere else." His opposition to the protectorship of Cromwell compelled him to relinquish his legislative duties; and in April, 1653, he retired to his father's residence at Penshurst. He resumed his seat at the first meeting- of the restored parliament in 1659, and on May 13 was nominated one of the council of state. On June 5 he was sent as one of the commissioners to negotiate a peace between Sweden and Denmark, and was absent from England at the time of the restoration. Unwilling to return to his native country while it remained under " the government of a single person, kingship, or house of lords," he remained a voluntary exile for nearly 18 years. Intent upon establishing an English republic, in 1665 he sought the assistance of the Dutch government and the influence of the French ministers toward that end'. Failing in both instances, he retired to the south of France, where he lived till 1677, when, at the solicitation of his father (a centenarian), a permission for him to return home was obtained from the king.

He soon became an active opponent of the court, but was defeated in two attempts to obtain a seat in parliament. He is charged with accepting 500 guineas for favoring the intrigues of Barillon, the French ambassador, who about this time was in clandestine correspondence with prominent members of the popular party seeking to crush the duke of York and the Roman Catholics, the parliament, and the ministry. But it has been alleged that, if true, the act was not criminal, as it required no betrayal of his principles, and as he needed the money and its acceptance was not repugnant to the practice of the age. The discovery of the Rye House plot, in June, 1683, gave the king an opportunity to exact vengeance for years of restraint and humiliation; and Sidney, with his illustrious companion in misfortune, William Lord Russell, was arrested on a charge of complicity with the conspirators, and imprisoned in the tower. At his trial, over which Jeffreys presided, but a single living legal witness to the conspiracy for an insurrection, the infamous Lord Howard, could be produced; but garbled extracts from a theoretical work on government in manuscript, which had been found among Sidney's papers, were read in evidence against him.

These, though containing assertions of the right of a people to depose an unworthy sovereign, were unconnected by other evidence with the conspiracy itself; under the ruling of the court, they were nevertheless deemed sufficient to convict. Sidney met his death " with the fortitude of a stoic." His attainder was reversed by the first parliament of William and Mary. His " Discourses concerning Government" were published in 1698, and a fourth edition, with additions by Thomas Hollis, including his "Apology," dated on the day of his death, and a number of letters and miscellaneous pieces, in 1772. His "Essay on Virtuous Love" was published in vol. viii. of the Somers collection of tracts (1742). The fragmentary distich, . . . manus haec inimica tyrannis Ense petit placidam sub libertate quietem, which he wrote in the university album at Copenhagen, is perhaps the best remembered extract from his writings. The report of his trial, after Jeffreys had struck out whatever he pleased, was published in 1684; it is also given in "Howell's State Trials." - His life has been written by George Wilson Meadley (8vo, London, 1813), and by G. Van Sant-voord (12mo, New York, 1851). See also Arthur Collins, " Memoirs of the Lives and Actions of the Sidneys," prefixed to his " Letters and Memorials of State," etc. (2 vols, fol., London, 1746), and Blencowe, "Sydney Papers" (8vo, 1825).