or PICTLAND FRITH, is a narrow strait of six miles between the mainland of Scotland and the Orkney islands. This strait is the great thoroughfare of shipping between the eastern and western seas, the terror of mariners, and has been the grave of thousands. The navigation of this frith was formerly extremely dangerous by the island of Stroma, and two rocks called the Skerries, lying near the middle of it; but it is now greatly improved, and comparatively safe, in consequence of a lighthouse erected on the Skerries.