Witches, however, were not alone in their power of floating. According to a popular belief in the north-west Highlands, insane people cannot sink in water. Sir Arthur Mitchell, in the "Proceedings of the Society of Antiquaries of Scotland," volume iv., refers to the case of a certain madman--Wild Murdoch by name--concerning whom strange stories were told. He was born on the small island of Melista, near the coast of Lewis, used only for occasional habitation in connection with the pasturing of cattle. Anyone born in the island is believed to become insane. The superstition about not sinking was certainly put to a severe test in Wild Murdoch's case. "It is said," remarks Sir Arthur, "that his friends used to tie a rope round his body, make it fast to the stern of the boat, and then pull out to sea, taking the wretched man in tow. The story goes that he was so buoyant that he could not sink; 'that they tried to press him down into the water;' that he could swim with a stone fastened to him; that when carried to the rocky holms of Melista or Greinan, round which the open Atlantic surges, and left there alone, he took to the water and swam ashore." CHAPTER X. WATER-SPIRITS. Influence of Scenery--Science and Superstition--Loch-nan-Spoiradan --Lochan-nan-Deaan--Lochan-Wan and its Sacrifice--Jenny Greenteeth --Poetry and Superstition--Tweed and Till--Dee and Don-- Folk-practices for Finding a Drowned Body--Deeside Tradition-- Salt used by Tweed Fishers for Good Luck--Guardian-Spirit of Conan--Peg Powler--Water-kelpies--Nikr--Halliwell Boggle--Robin Round Cap--Round Hole, near Flamborough--Aberdeenshire Kelpy Legends--Some Sutherland Kelpies--Story about an Islay Kelpy-- Mermaids in the North.