Scilly Islands (Silly), a Cornish group, lie about 27 miles WSW. of Land's End. They occupy, as a group, about 30 sq. m. of sea-room, and consist of six large islands - St Mary's (1528 acres; pop. 1290), Tresco (697 acres; pop. 328), St Martin's (515 acres; pop. 175), St Agnes (313 acres; pop. 148), Bryher (269 acres; pop. 103), and Samson (78 acres, uninhabited) - and some thirty small ones, besides innumerable rocks and ledges. None reaches more than 160 feet above the sea. They are wrongly identified with the Cassite-rides or ' Tin Islands ' of the ancients. The idea of a land of Lyonesse between the islands and the mainland submerged within historic times is now abandoned. The present name 'scilly' belongs strictly to a small, very inaccessible, rocky island in the north-west, and is probably derived from Cornish silya, 'a conger eel.' Athelstan conquered the islands in 938, and established monks upon Tresco. The islands were handed over to Tavistock Abbey by Henry I., and in 1568 leased by Queen Elizabeth to Sir Francis Godolphin. In 1834 they were leased to Mr Augustus John Smith, who made Tresco his home for thirty-eight years, built churches and schools, suppressed smuggling, encouraged agriculture, and forbade overcrowded holdings. He was succeeded in 1872 by his nephew.
The climate is mild, but necessarily damp, and the weather is changeable and frequently stormy; but the temperature is extremely equable, averaging 58° F. in summer and 45° F. in winter. The leading natural features of the scenery are the fantastically weathered rocks and rock-basins and the bold coast-lines. There are remains of cromlechs and stone circles. There has been a lighthouse on St Agnes since 1680, on Bishop Rock since 1858, and on Round Island since 1887; there are also lights on the Wolf, the Seven Stones (floating), and the Longships of Land's End. Hugh Town, on St Mary's, is the only town on the islands; there is good anchorage in the roadstead. Wrecks used to be a fruitful source of wealth. One of the most famous was that of three ships of Sir Cloudesley Shovel's fleet in 1707, when 2000 men, including the admiral, were drowned. Smuggling was formerly largely indulged in. Kelp-making, introduced in 1684, has been given up; so, too, has shipbuilding. Nowadays most of the young men emigrate. Farming is practised, and early potatoes and broccoli are exported; but the chief industry now is the cultivation of narcissus and other lilies - 100 tons of flowers being shipped in a single spring. See works by Borlase (1756), White (1850), Tonkin (Penzance, 1887), and Besant (1890).