granite. It has been recognized also, however, as a primary constituent of granite itself.
A curious variety of andalusite known as chiastolite is specially characteristic of clay-slates near a contact with granite. The elongated prismatic crystals enclose symmetrically arranged wedges of carbonaceous material, and in cross-section show a black cross on a greyish ground. Cross-sections of such crystals are polished and worn as amulets or charms. Crystals of a size suitable for this purpose are found in Brittany and the Pyrenees, while still larger specimens have been found recently in South Australia. The name chiastolite is derived from the Greek χιάστος, crossed or marked with the letter χ: cross-stone and macle are earlier names, the latter having been given on account of the resemblance the cross-section of the stone bears to the heraldic macula or mascle. (L. J. S.)
ANDAMAN ISLANDS, a group of islands in the Bay of Bengal. Large and small, they number 204, and lie 590 m. from the mouth of the Hugli, 120 m. from Cape Negrais in Burma, the nearest point of the mainland, and 340 m. from the northern extremity of Sumatra. Between the Andamans and Cape Negrais intervene two small groups, Preparis and Cocos; between the Andamans and Sumatra lie the Nicobar Islands, the whole group stretching in a curve, to which the meridian forms a tangent between Cape Negrais and Sumatra; and though this curved line measures 700 m., the widest sea space is about 91 m. The extreme length of the Andaman group is 219 m. with an extreme width of 32 m. The main part of it consists of a band of five chief islands, so closely adjoining and overlapping each other that they have long been known collectively as “the great Andaman.” The axis of this band, almost a meridian line, is 156 statute miles long. The five islands are in order from north to south: North Andaman (51 m. long); Middle Andaman (59 m.); South Andaman (49 m.); Baratang, running parallel to the east of the South Andaman for 17 m. from the Middle Andaman; and Rutland Island (11 m.). Four narrow straits part these islands: Austin Strait, between North and Middle Andaman; Homfray’s Strait between Middle Andaman and Baratang, and the north extremity of South Andaman; Middle (or Andaman) Strait between Baratang and South Andaman; and Macpherson Strait between South Andaman and Rutland Island. Of these only the last is navigable by ocean-going vessels. Attached to the chief islands are, on the extreme N., Landfall Islands, separated by the navigable Cleugh Passage; Interview Island, separated by the very narrow but navigable Interview Passage, off the W. coast of the Middle Andaman; the Labyrinth Island off the S.W. coast of the South Andaman, through which is the safe navigable Elphinstone Passage; Ritchie’s (or the Andaman) Archipelago off the E. coast of the South Andaman and Baratang, separated by the wide and safe Diligent Strait and intersected by Kwangtung Strait and the Tadma Juru (Strait). Little Andaman, roughly 26 m. by 16, forms the southern extremity of the whole group and lies 31 m. S. of Rutland Island across Duncan Passage, in which lie the Cinque and other islands, forming Manners Strait, the main commercial highway between the Andamans and the Madras coast. Besides these are a great number of islets lying off the shores of the main islands. The principal outlying islands are the North Sentinel, a dangerous island of about 28 sq. m., lying about 18 m. off the W. coast of the South Andaman; the remarkable marine volcano, Barren Island (1150 ft.), quiescent for more than a century, 71 m. N.E. of Port Blair; and the equally curious isolated mountain, the extinct volcano of Narcondam, rising 2330 ft. out of the sea, 71 m. E. of the North Andaman. The land area of the Andaman Islands is 2508 sq. m. About 18 m. to the W. of the Andamans are the dangerous Western Banks and Dalrymple Bank, rising to within a few fathoms of the surface of the sea and forming, with the two Sentinel Islands, the tops of a line of submarine hills parallel to the Andamans. Some 40 m. distant to the E. is the Invisible Bank, with one rock just awash; and 34 m. S.E. of Narcondam is a submarine hill rising to 377 fathoms below the surface of the sea. Narcondam, Barren Island and the Invisible Bank, a great danger of these seas, are in a line almost parallel to the Andamans inclining towards them from north to south.
Topography.—The islands forming Great Andaman consist of a mass of hills enclosing very narrow valleys, the whole covered by an exceedingly dense tropical jungle. The hills rise, especially on the east coast, to a considerable elevation: the chief heights being in the North Andaman, Saddle Peak (2400 ft.); in the Middle Andaman, Mount Diavolo behind Cuthbert Bay (1678 ft.); in the South Andaman, Koiob (1505 ft.), Mount Harriet (1193 ft.) and the Cholunga range (1063 ft.); and in Rutland Island, Ford’s Peak (1422 ft.). Little Andaman, with the exception of the extreme north, is practically flat. There are no rivers and few perennial streams in the islands. The scenery is everywhere strikingly beautiful and varied, and the coral beds of the more secluded bays in its harbours are conspicuous for their exquisite colouring.
Harbours.The coasts of the Andamans are deeply indented, giving existence to a number of safe harbours and tidal creeks, which are often surrounded by mangrove swamps. The chief harbours, some of which are very capacious, are (starting northwards from Port Blair, the great harbour of South Andaman) on the E. coast: Port Meadows, Colebrooke Passage, Elphinstone Harbour (Homfray’s Strait), Stewart Sound and Port Cornwallis. The last three are very large. On the W. coast: Temple Sound, Interview Passage, Port Anson or Kwangtung Harbour (large), Port Campbell (large), Port Mouat and Macpherson Strait. There are besides many other safe anchorages about the coast, notably Shoal Bay and Kotara Anchorage in the South Andaman; Cadell Bay and the Turtle Islands in the North Andaman; and Outram Harbour and Kwangtung Strait in the archipelago. The whole of the Andamans and the outlying islands were completely surveyed topographically by the Indian Survey Department under Colonel Hobday in 1883–1886, and the surrounding seas were charted by Commander Carpenter in 1888–1889.
Geology.—The Andaman Islands, in conjunction with the other groups mentioned above, form part of a lofty range of submarine mountains, 700 m. long, running from Cape Negrais in the Arakan Yoma range of Burma, to Achin Head in Sumatra. This range separates the Bay of Bengal from the Andaman Sea; and it contains much that is geologically characteristic of the Arakan Yoma, and formations common also to the Nicobars and to Sumatra and the adjacent islands. The older rocks are early Tertiary or late Cretaceous but there are no fossils to indicate age. The newer rocks, common also to the Nicobars and Sumatra, are in Ritchie’s Archipelago chiefly and contain radiolarians and foraminifera. There is coral along the coasts everywhere, and the Sentinel Islands are composed of the newer rocks with a superstructure of coral. A theory of a still continuing subsidence of the islands was formed by Kurz in 1866 and confirmed by Oldham in 1884. Signs of its continuance are found on the east coast in several places. Barren Island is a volcano of the general Sunda group which includes also the Pegu group to which Narcondam belongs. Barren Island was last in eruption in 1803, but there is still a thin column of steam from a sulphur bed at the top and a variable hot spring at the point where the last outburst of lava flowed into the sea.
Climate.—Rarely affected by a cyclone, though within the influence of practically every one that blows in the Bay of Bengal, the Andamans are of the greatest importance because of the accurate information relating to the direction and intensity of storms which can be communicated from them better than from any other point in the bay, to the vast amount of shipping in this part of the Indian Ocean. Trustworthy information also regarding the weather which may be expected in the north and east of India, is obtained at the islands, and this proves of the utmost value to the controllers of the great trades dependent upon the rainfall. A well-appointed meteorological station has been established at Port Blair since 1868. Speaking generally, the climate of the Andamans themselves may be described as normal for tropical islands of similar latitude. It is warm always, but tempered by pleasant sea-breezes; very hot when
