PENTLAND-SKERRIES, islets, in the district of St-Mary's, parish of South-Ronaldshay, county of Orkney. The Pentland Skerries are several small islets, situated at the east end of the Pentland Firth; and the largest of them contains eleven inhabitants. It is a mile long and half a mile broad, and has a lighthouse where two fixed lights are exhibited, a hundred feet apart, and seen at the distance of from sixteen to eighteen nautical miles: the lighthouse was erected in 1794, previously to which time the Skerries were most formidable to mariners. No anchorage can be found in any part of the Firth; and when a west or south-west wind causes an increase in the current, scarcely any vessel is able to withstand the tremendous surge, which dashes with such violence against the coast, that the spray is often carried a great distance inland, and falls like a shower of rain. This strait has been the terror of the boldest sailors, and the grave of thousands; it connects the Atlantic with the North Sea, and from the Hebrides and Cape Wrath the flow of the former comes rolling in one unbroken and irresistible stream.