Volume 14 Australasia - dana ward's homepage

THE PIIILIPriXKS. 245ridge is also broken b}' numerous openings, the broiidcst and deepest of wlaichlies off the coast of Mindanao. As shown by the submarine explorations of theChallenijer, the two basins enclosed between the Philijipinesand Borneo resemblethe Mediterranean in the temperature of their lower depths. The cold waters ofthe oceanic depths are unable to penetrate across the intervening isthmuses intothese inland seas, where the thermometer nowhere records less than 50^ F.These three lines of partly emerged, partly submarine, ridges, stretchingIndonesia towards the Philippines, continue their main axis in the interior offromthisarchipelago, and constitute a great part of its relief. Mindanao, least kno\^n ofthe whole group, although one of the most remarkable for its volcanic phenomena,is formed, at least in the west and centre, by the prolongation of the two easternridges, indicated seaward by the Sulu and Sanguir Archipelagoes.The Sulu axis,whose normal direction is south-west and north-east, comprises all the westernpeninsula of Mindanao, while the Sanguir axis, running south and north, strikesthe southern point of the same I'egion at the Saragani volcano. Beyond thispoint it first continues its northerly trend and then gradually sweeps round to thewest. East of this mountain range another parallel chain occupies all the easternsection of Mindanao bordering on the Pacific Ocean.A broad survey of the whole orographic system shows in the same way that,from the southern point of Mindanao to the northern extremity of Luzon, the reliefof all the islands is disposed in a line with or parallel to the southern isthmuses.Thus the coast range of the east side of Mindanao is continued north-west in agraceful curve through the islands of Leyte, Masbate, Ticao, and Burias ; in theeast is developed a parallel curve formed by the island of Samar, the Camarinespeninsula in Luzon, and the Isla del Polillo. On the other hand the islands ofBohol, Cebu, Negros, and Panay are disposed in a line with or parallel to theSulu Archipelago, while Miudoro and the main section of Luzon form the northeasternextension of Paragua and Borneo. In many places volcanic or othermasses mark the points of intersection, and it is noteworthy that in Luzon, mostrugged of the Philippines, all the cordilleras converge like the ribs of a dome inthe culminating crest of Caraballo.Xorthof the Philippines the mountain ranges,interrupted by broad straits, are continued through Formosa and the Liu-Kieugroup towards Japan.The whole surface of the Philippines is essentially mountainous, the only plainsthat occur being the aUuvial districts at the river mouths, and the spaces left at theintersection of the ranges. Most of the surface appears to be formed of old rocks,especially schists, and, in the north of Luzon, granites. Extensive coal-fields arefound in the central islands, especially Cebu and Negros, and in many places thesecarboniferous beds seem to have been buried under more lecont lavas. LaterKmestones have also been developed by the coral-builders round all the seaboard,and there is clear evidence that along extensive stretches of the coastline theseformations have been upheaved to a considerable height above sea-level. Theyform at some points broad horizontal tables round the headlands, and here arcfound shells and other marine remains belonging to the same species still living in