Luzon and Mindanao united would be larger in area than all the rest of the islands put together. Luzon is said to have over 40,000 square miles of land area. The northern half of Luzon is a mountainous region formed by ramifications of the great cordilleras, which run N. to S. All the islands are mountainous in the interior, the principal peaks being the following, viz.:—
| Feet above sea level | |
| Halcon (Mindoro) | 8,868 |
| Apo[1] (Mindanao) | 8,804 |
| Mayon (Luzon) | 8,283 |
| San Cristóbal (Luzon) | 7,375 |
| Isarog (Luzon) | 6,443 |
| Banájao (Luzon) | 6,097 |
| Labo (Luzon) | 5,090 |
| South Caraballo (Luzon) | 4,720 |
| Caraballo del Baler (Luzon) | 3,933 |
| Maquíling (Luzon) | 3,720 |
Most of these mountains and subordinate ranges are thickly covered with forest and light undergrowth, whilst the stately trees are gaily festooned with clustering creepers and flowering parasites of the most brilliant hues. The Mayon, which is an active volcano, is comparatively bare, whilst also the Apo, although no longer in eruption, exhibits abundant traces of volcanic action in acres of lava and blackened scoriae. Between the numberless forest-clad ranges are luxuriant plains glowing in all the splendour of tropical vegetation. The valleys, generally of rich fertility, are about one-third under cultivation.
There are numerous rivers, few of which are navigable by sea-going ships. Vessels drawing up to 13 feet can enter the Pasig River, but this is due to the artificial means employed.
The principal Rivers are:—In Luzon Island the Rio Grande de Cagayán, which rises in the South Caraballo Mountain in the centre of the island, and runs in a tortuous stream to the northern coast. It has two chief affluents, the Rio Chico de Cagayán and the Rio Magat, besides a number of streams which find their way to its main course. Steamers of 11-feet draught have entered the Rio Grande, but the sand shoals at the mouth are very shifty, and frequently the entrance is closed to navigation. The river, which yearly overflows its banks, bathes the great Cagayan Valley,—the richest tobacco-growing district in the Colony. Immense trunks of trees are carried down in the torrent with great rapidity, rendering it impossible for even small craft—the barangayanes—to make their way up or down the river at that period.
The Rio Grande de la Pampanga rises in the same mountain and flows in the opposite direction—southwards,—through an extensive plain, until it empties itself by some 20 mouths into the Manila Bay. The whole of the Pampanga Valley and the course of the river present a beautiful panorama from the summit of Arayat Mountain, which has an elevation of 2,877 feet above the sea level.
The whole of this flat country is laid out into embanked rice fields and sugar-cane plantations. The towns and villages interspersed are numerous. All the primeval forest, at one time dense, has disappeared; for this being one of the first districts brought under European subjection, it supplied timber to the invaders from the earliest days of Spanish colonization.
The Rio Agno rises in a mountainous range towards the west coast about 50 miles N.N.W. of the South Caraballo—runs southwards as far as lat. 16°, where it takes a S.W. direction down to lat. 15° 48′—thence a N.W. course up to lat. 16°, whence it empties itself by two mouths into the Gulf of Lingayen. At the highest tides there is a maximum depth of 11 feet of water on the sand bank at the E. mouth, on which is situated the port of Dagupan.
The Bicol River, which flows from the Bató Lake to the Bay of San Miguel, has sufficient depth of water to admit vessels of small draught a few miles up from its mouth.
In Mindanao Island the Butuan River or Rio Agusan rises at a distance of about 25 miles from the southern coast and empties itself on the northern coast, so that it nearly divides the island, and is navigable for a few miles from the mouth.