MALAY ARCHIPELAGO, the largest group of islands in the world, lying south-east of Asia and north and north-west of Australia. It includes the Sunda islands, the Moluccas, New Guinea and the Philippine islands, but excludes the Andaman Nicobar group. The equator passes through the middle of the archipelago; it successively cuts Sumatra, Borneo, Celebes and Halmahera, four of the most important islands.
The islands of the archipelago nearly all present bold and pic turesque profiles against the horizon, and at the same time the character of the scenery varies from island to island and even from district to district. Volcanoes running south-east through Sumatra, east through Java and the southern islands to Timor, curving north through the Moluccas, and again north, from the end of Celebes through the whole line of the Philippines, follow a line roughly resembling a horseshoe narrowed towards the point. A disastrous eruption occurred in Aug. 1928 from Mt. Rokatinda, in the island of Palu Wai, north of Flores. The loftiest mountain in the archipelago would appear to be Kinabalu in Borneo (13,698 ft.). An important fact in the physical geography of the archi pelago is that Java, Bali, Sumatra and Borneo, and the lesser islands between them and the Asiatic mainland, all rest on a great submerged bank, nowhere more than 1 oo fathoms below sea-level and seldom exceeding 5o fathoms, which may be considered a con tinuation of the continent ; while to the east the depth of the sea has been found at various places to be from i,000 to 3,557 fathoms. As the value of this fact was particularly emphasized by Wallace, the limit of the shallow water, which is found in the narrow but deep channel between Bali and Lombok, and strikes north to the east of Borneo, has received the name of "Wallace's Line." The Philippines on the other hand, "are almost sur rounded by deep sea, but are connected with Borneo by means of two narrow submarine banks" (A. R. Wallace, Island Life). The archipelago, in effect, is divided between two great regions, the Asiatic and the Australian, and the fact is evident in various branches of its geography—zoological, botanical, and even human. It is believed that there was a land-connection between Asia and Australia in the later part of the Secondary epoch, and that the Australian continent, when separated, became divided into islands before the south-eastern part of the Asiatic.
The most notable fact in the geological history of the archi pelago is the discovery in Java of the fossil remains of Pithecan thropus erectus. The strata in which it was found belong to the late Pliocene or to the early Pleistocene. Among the rocks of economic importance may be mentioned granite of numerous kinds, syenite, serpentine, porphyry, marble, sandstones and marls. Coal is worked in Sumatra and Borneo; china clay in Java. Dia monds are obtained in Borneo, garnets in Sumatra, Bachian and Timor, and topazes in Bachian, antimony in Borneo and the Philippines; lead in Sumatra, Borneo, Celebes and the Philippines; copper and malachite in the Philippines, Celebes, Timor, Borneo and Sumatra; nickel in Celebes, and, most important of all, tin in Banka, Billiton and Singkep. Iron is pretty frequent in various forms, occurring in Celebes and particularly in south-east Borneo. Wolframite and manganese are known, the latter in Java. Gold is not uncommon in the older ranges of Sumatra, Banka, Cele bes, Bachian, Timor and Borneo; silver is found in Java and Suma tra. Platinum and quicksilver are found in Borneo. Petroleum is a valuable product of Sumatra and Java, and is found in large quantities in Borneo, saltpetre in Sumatra and Flores, and sulphur, naphtha, alum, lignite and mag netite, in Sumatra, and asphalt in Buton (Celebes).
Climate, Flora, Fauna.— The most striking general fact as regards climate in the archipelago is that wherever that part of the south-east monsoon which has passed over Australia strikes, the climate is comparatively dry, and the vegetation is less lux uriant. The east end of Java has less rainfall than the west ; the distribution of the rain on the north coast is quite different from that on the south, and a similar difference is observed between the east and west of Celebes. The north-west monsoon, beginning in October and lasting till March, brings the principal rainy season in the archipelago.