SCILLY ISLANDS 291 SCINTILLATION The need for some improvement in the old rule-of-thumb methods is generally recognized, and industry undoubtedly owes a debt to those who have studied the subject from the scientific viewpoint. In some cases it has been quick to adopt and profit by their suggestions, and even in the most conservative factories, it will be found that many of their ideas have permeated, to the general benefit. SCILLY ISLANDS, a group of islands belonging to Cornwall, England; 25 miles W. S. W. of Land's End. They oc- cupy about 30 square miles of sea room, and consist of six large islands — St. Mary's (1,528 acres), Tresco (697 acres), St. Martin's (515 acres), St. Agnes (313 acres), Bryher (269 acres), and Samson (78 acres) — and some 30 small ones, be- sides innumerable rocks and ledges, of which about 100 are named. They are composed entirely of a coarse type of granite, a continuation of that running through Devon and Cornwall. The name Scilly belongs strictly to a small, very inaccessible, double, rocky island in the N. W. of the group. Athelstan conquered the islands in 938, and established monks on Tresco, the ruins of whose abbey still remain. Olaf Trygvason (995-1000), who forced Chris- tianity on Norway and introduced it into Iceland, is said to have been converted by a hermit on one of .he islands. They were handed over to the wealthy abbey of Tavistock by Henry I., but reverted to the crown upon the dissolution of the monasteries in 1539. In 1568 Queen Elizabeth leased them to Sir Francis Go- dolphin, who built the Star Castle on St. Mary's — over the doorway stands "E. R., 1593." They remained in his family for more than 250 years — hence the hamlet of "Dolphin" town on Tresco. They shel- tered Prince Charles in 1645 before he fled to Jersey, and Cromwell's Tower on Tresco was set up by the Parliamentary forces. In 1831 they were leased to Au- gustus John Smith, a radical reformer though somewhat of an autocrat, and the best friend the islands have ever had. He made Tresco his home for 38 years, and his tropical gardens there are unique in northern Europe. He built churches and schools, suppressed smuggling, encour- aged agriculture. 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 lead- ing natural features of the scenery are the fantastically weathered rocks and rock basins and the bol^ coast-lines. There are remains of cromlechs and stone circles; and a perfect kistvaen (contain- ing human bones showing traces of fire action) was opened on Samson in 1862. Tresco Abbey and its gardens are con- sidered the leading objects of interest for the tourist. There has been a lighthouse on St. Agnes since 1680, on Bishop Rock since 1858, and on Rock Island since 1887; there are also lights on the Wolf, the Seven Stones (floating), and the Longships off Land's End. Hugh Town on St. Mary's, the only town on the is- lands, with plain, substantial and uninter- esting houses (mostly two-storied), has a church, two chapels, two hotels, banks, shops, schools, telegraph, and Jubilee Hall. Wrecks used to be very numerous and were a fruitful source of wealth. One of the most famous was that of three ships of Sir Cloudesley Shovel's fleet in 1707, when 2,000 men, including the admiral, were drowned. The Scillonians also lived by pilotage, but steam and more light- houses now help vessels to avoid the is- lands. Smuggling was formerly largely indulged in. In the early years of the 19th century, before the days of iron ships, there were three shipbuilding-yards on St. Mary's. Kelp making, introduced in 1684, has been given up. Farming is practiced, and early potatoes and broc- coli are exported; but the principal in- dustry now is the cultivation of narcissus and other lilies — 100 tons of flowers be- ing shipped in a single spring. Politi- cally the islands belong to the St. Ives division of Cornwall. Pop. about 21,000. SCINTILLATION, a twinkling of the stars; a familiar phenomenon to all who have directed their attention to the firma- ment above us. Under ordinary atmos- pheric conditions this flickering is pos- sessed only by the so-called fixed stars. A planet shines steadily and by this mark can readily be picked out. When near the horizon, however, planets have been observed to scintillate slightly; while stars at low altitudes invariably twinkle more vigorously than stars overhead. This at once points to the atmosphere as an important factor, since the phenom- enon is more pronounced when the light has to traverse a greater depth of air. Again, when viewed through sufficiently large telescopes stars cease twinkling al- together. The action of the telescope is to concentrate on the eye a much larger pencil of rays than could naturally enter it. Instead of one slender ray the eye receives the integral effect of a great number of rays, whose individual features are lost in the general average. In the case of a planet, again, the rays which fall on the retina converge from all parts of a disk of sensible size; and in the in- tegral effect of this pencil the individual
