Sheerness, a port on the N.W. of the Isle of Sheppey, Kent., 52 miles from London, at the point of junction between the Medway and the Thames. Here a fort was bnilt after the Restoration, but was taken by De Ruyter in 1667. It was afterwards strengthened and a dockyard begun; but the existing basins date from 1830, and, though covering 60 acres, will not accommodate vessels of the largest class. The fortifications are very strong, and the abbey-church is the oldest in England.