Page:EB1911 - Volume 20.djvu/475

 New South Wales); Easter Island (to Chile); the Galapagos Islands (to Ecuador). In an area to be defined roughly as lying about the Tropic of Cancer, between Hawaii and the Bonin Islands, there are scattered a few small islands and reefs, of most of which the position, if not the existence, is doubtful. Such are Patrocinio (about 28° 30′ N., 177° 18′ E.) and Ganges (39° 47′ N., 154° 15′ E.), among others which appear on most maps. Marcus Island, in 23° 10′ N., 154° E., was annexed by Japan in 1899 with a view to its becoming a cable station.

The following paragraphs review the oceanic islands generally, and are therefore concerned almost entirely with the central and mid-western parts of the ocean. It is impossible to estimate the total number of the islands; an atoll, for instance, which may be divided into a large number of islets, often bears a single name. The number of names of islands and separate groups in the Index to the Islands of the Pacific (W. T. Brigham), which covers the limited area under notice, is about 2650, exclusive of alternative names. Of these, it may be mentioned, there is a vast number, owing in some cases to divergence of spelling in the representation of native names, in others to European discoverers naming islands (sometimes twice or thrice successively) of which the native names subsequently came into use also.

The islands may be divided broadly into volcanic and coral islands, though the physiography of many islands is imperfectly known. There are ancient rocks, however, in New Caledonia, which has a geological affinity with New Zealand; old sedimentary rocks are known in New Pomerania, besides granite and porphyry, and slates, sandstone and chalk occur in Fiji, as well as young volcanic rocks. Along with these, similarly, hornblende and diabase occur in the Pelew Islands and gneiss and mica

slate in the Marquesas, which afford a type of the extinct volcanic islands, as does Tahiti. In other areas, however, there is still volcanic activity, and in many cases volcanoes to which only tradition attributes eruptions can hardly be classified as extinct. Hawaii contains the celebrated active crater of Kilauea. In Tonga, in the New Hebrides, and in the long chain of the Solomons and the Bismarck Archipelago there is much activity. Submarine vents sometimes break forth, locally raising the level of the sea-bottom, or even forming temporary islands or shoals. Earthquakes are not uncommon in the volcanic areas. Most of the volcanic islands are lofty in proportion to their size. The peaks or sharp cones in which they frequently culminate, combined with the rich characteristic vegetation, are the principal features which have led all travellers to extol the beauty of the islands.

In the central and western Pacific the northern and southern limits of the occurrence of reef-forming corals are approximately 30° N. and 30° S. It may be added that this belt narrows greatly towards the east, mainly from the south, in sympathy with the northward flow of cold water off the coast of South America. But apart from this the limits are seen to accord fairly closely with the geographical definition of the area under consideration. Here the broad distinction has been drawn between volcanic and coral islands; but this requires amplification, both because the coral islands follow more than one type, and because the work of corals is in many cases associated with the volcanic islands in the form of fringing or barrier reefs. As to the distribution of coral reefs within the Pacific area, in Micronesia the northern Marianas (volcanic) are without reefs, which, however, are well developed in the south. The Pelew islands have extensive reefs, and the Carohne, Marshall and Gilbert islands are almost entirely coral. In Melanesia, as has been seen, the volcanic type predominates. Coral reefs occur round many of the islands (e.g. the Louisiade and Admiralty