Scilly Isles, a group of small islands, belonging to Cornwall, England, 25 m. W. by S. of Land's End. (For map, see England, Section VI.) They form an outlying portion of the granite highlands of Cornwall; and contain a few metalliferous veins or lodes, which could never have yielded much ore. An old theory that the Scilly Isles could be identified with the "Cassiterides" or "Tin Islands" of Herodotus is abandoned, and the origin of their name has never been authoritatively settled. The islands are wild and picturesque, with sheer cliffs and many large caves hollowed out by the Atlantic. Owing to the reefs and shoals by which these shores are surrounded, navigation becomes perilous in rough weather, and many disasters have occurred. In 1707 Sir Cloudesley Shovel perished in the shipwreck of his flagship and two other men-of-war, while two fireships of his squadron were driven aground, and the remainder only narrowly escaped. The graveyard of an old Puritan church on St Mary's contains the bodies of 311 persons, drowned in the wreck of the "Schiller" in 1875; and a local proverb tells that for every man who dies a natural death on the islands the sea takes nine. Much, however, has been done to minimise the danger, especially by lighting the coast. On St Agnes there is a lighthouse, and on an outlying rock to the south-west is the lonely Bishop Light, constructed with infinite difficulty in 1858, and rebuilt thirty years later.
The islands are composed wholly of granite - outliers of the granite highlands of Cornwall. Most of the granite is coarse and porphyritic, but towards the centre of the original igneous mass it is finer and non-porphyritic. The finer granite occurs on the north-west side of St Mary's, the southern part of Tresco, Bryher and Samson and the north-west side of Annet. Elvans of quartz-porphyry are found in the granite. On the north-east end of White Island a fragment of the altered killas, which once covered the whole area, is still visible. A gravel deposit with chalk flints and Greensand cherts which caps some of the higher ground on St Mary's may possibly be of Eocene age. Raised beach, blown sand, fragmental granitic waste or "head" and an iron-cemented glacial deposit are found resting upon the granite.
The climate of the islands is unusually mild, snow being rarely seen, and the temperature varying from about 46° F. in winter to 58° in summer. As a result, vegetation is luxuriant; fuchsias, geraniums and myrtles attain an immense size, and aloes, cactus and prickly pear flourish in the open. All these, together with palms, may be seen in the gardens of the governor on Tresco Island, which are quite subtropical in character, and, therefore, unique in the British Isles. Great flocks of sea-birds haunt the remoter parts, and on some of the islands there are deer. On Tean there is a warren of white rabbits; and some of the rarer land-birds occasionally visit the islands, such as the golden oriole, which has been known to breed here.
The islands are served by steamers from Penzance, and telephone and telegraph communication is established with the mainland. The raising of early asparagus and other spring vegetables, and of flowers, has taken the place of potato culture as the principal industry. In spring the fields of narcissus and other flowers add greatly to the beauty of the islands. There is also a small coasting trade; and fishing is carried on to some extent, its most important branch being the taking of lobsters for the London market.
The islands which may be distinguished from mere rocks number about 40, and the group has a total area of 4041 acres; but only five islands are inhabited - St Mary's, Tresco, St Martin's, St Agnes and Bryher. The total population in 1901 was 2092. Hugh Town in St Mary's is the capital, occupying a sandy peninsula crowned by the height known as the Garrison, with Star Castle, dating from the days of Elizabeth. The town possesses a harbour, which is used by the Penzance steamers, and a roadstead where large vessels can lie at anchor. The government of the islands is vested in a county council created in 1890, consisting of a chairman, vice-chairman, 4 aldermen, and 18 councillors. For parliamentary purposes the isles are included in the St Ives division of Cornwall.
On Tresco there are the ruins of an abbey, and of two fortifications called Oliver Cromwell's Tower and King Charles's Tower; and here also is a church built in 1882 and dedicated to St Nicholas. Numerous rude pillars and circles of stones, resembling those of Cornwall, are to be noticed; and barrows are common, the most remarkable of these prehistoric remains being a barrow on the Isle of Samson, 58 ft. in girth, and containing, amongst other relics, the only perfect "kistvaen," or sepulchral chamber of stone, which has been disinterred from any Cornish tomb.
Although the Scilly Isles have been regarded as the remains of Lyonesse, as identical with the Cassiterides, and as the object of an expedition and of conquest on the part of Athelstan in pursuance of a vow made at the shrine of St Burian, it is not until the reign of Henry I. that we have indisputable evidence concerning them. The king gave all the churches of Scilly and the land, as the hermits held it in the days of the Confessor, to the abbot and church of Tavistock. A confirmation of this grant and a further grant to the monks of all wrecks except whole ships and whales was made by Reginald, earl of Cornwall. In 1180 the bishop of Exeter confirmed a grant by Richard de Wicha of tithes, hitherto withheld, and of rabbits. Secular priests were temporally substituted for regulars by the abbot of Tavistock in 1345. Sharing the dignity of lords of Scilly with the abbot, holding apparently the better half of St Mary's Island, which was already furnished with a castle and a prison, and like the abbot practically beyond the jurisdiction of the hundred courts, the family of Blanchminster (de Albo Monasterio), at the beginning of the 14th century, held of the earldom of Cornwall lands in Scilly at a yearly service of 6s. 8d. or 600 puffins. The Year Books tell us that in cases of felony the punishment under this family was for the convicted person to be taken to a certain rock in the sea with two barley loaves and one pitcher of water and to be left on the rock until drowned by the tide. The Blanchminsters resisted and imprisoned the coroner of Cornwall and in 1319 were granted a coroner of their own. In 1345 they are found petitioning the king for a remedy owing to an invasion by 600 of the king's Welsh troops, who, being becalmed at Scilly, had carried away everything, and so impoverished the tenants that they were unable to pay their yearly rent of X40. In 1547 Silvester Danvers, as representing the Blanchminsters, being one of the coheirs, sold his moiety of Scilly to Sir Thomas Seymour, by whose attainder in 1549 this and probably the other moiety fell to the crown. The suppression of the religious houses had already placed the church's land and revenues at the king's disposal. During the Civil Wars, Hugh Town stood for the king, and in 1645 afforded a temporary shelter to Prince Charles, until his escape to Jersey. In 1649 the islands were occupied by a royalist, Sir Richard Grenville, and formed the base from which he swept the surrounding seas for two years, before a fleet under Admiral Blake and Sir John Ayscue forced him to surrender. In ancient times a haunt of pirates, the islands were afterwards notorious for smuggling. In 1687 the whole of Scilly was granted to Sidney Godolphin for eighty-nine years from the expiration of the lease for fifty years granted to Francis Godolphin in 1636 by Charles I. In 1831 Augustus Smith succeeded the Godolphins as lessee or lord-proprietor, and under his and his nephew's wise autocracy the islands prospered.