Alexander Slidell Mackenzie, an American naval officer, born in New York, April 6, 1803, died in Tarry town, N. Y., Sept. 13, 1848. His name was originally Slidell; that of Mackenzie, the name of his mother, was added to his own in 1837, at the request of a maternal uncle. He entered the navy as a midshipman in 1815, and made his first cruise to the Mediterranean in the frigate Java, commanded by Capt. Oliver II. Perry. In 1822 he took command of a merchant vessel to improve himself in seamanship. He was made lieutenant in 1825, and commander in 1841, and in both grades was in active duty in the Mediterranean, the West Indies, the Brazilian waters, and the Pacific. In 1842 he commanded the brig Somers, manned chiefly by naval apprentices; and on his passage from the coast of Africa in the autumn of that year, the existence of a mutinous plot on board was discovered, the principals of which were immediately placed in close confinement. A council of officers was called, which, after a careful investigation, decided that the conspiracy had already attained a formidable growth; and as the mutinous spirit evidently increased, even while the investigation was in progress, the immediate execution of the three persons principally implicated was recommended.

This recommendation was carried into effect at sea, Dec. 1, 1842. The Somers soon afterward arrived in New York, when a court of inquiry was immediately ordered to investigate the affair. The result was a full approval of the conduct of Mackenzie. Subsequently a court martial was held upon him at his own request, and the trial resulted in his acquittal. He was ordnance officer at the siege of Vera Cruz, and commanded a division of artillery, detached from the fleet, on the storming of Tabasco in 1847. He published "A Year in Spain " (2 vols., 1829; enlarged ed., 3 vols., 1836); "Popular Essays on Naval Subjects " (2 vols., 1833); " The American in England " (2 vols., 1835); " Spain Revisited " (2 vols., 1836); "Life of John Paul Jones" (2 vols., 1841); "Life of Oliver H. Perry " (2 vols., 1841); and " Life of Stephen Decatur " (1846). He also left in manuscript a journal of a tour in Ireland.