The Rio Grande de Mindanao rises in the centre of the island and empties itself on the west coast by two mouths, and is navigable for some miles by light-draught steamers. It has a great number of affluents of little importance.
The only river in Negros Island of any appreciable extent is the Danao, which rises in the mountain range running down the centre of the island, and finds its outlet on the east coast. At the mouth it is about a quarter of a mile wide, but too shallow to permit large vessels to enter, although past the mouth it has sufficient depth for any ship. I went up this river, six hoursʼ journey in a boat, and saw some fine timber near its banks in many places. Here and there it opens out very wide, the sides becoming mangrove swamps.
The most important Lakes are:—In Luzon Island the Bay Lake or Laguna de Bay, supplied by numberless small streams coming from the mountainous district around it. Its greatest length from E. to W. is 25 miles, and its greatest breadth N. to S. 21 miles. In it there is a mountainous island—Talim,—of no agricultural importance, and several islets. Its overflow forms the Pasig River, which empties itself into the Manila Bay. Each wet season—in the middle of the year—the shores of this lake are flooded. These floods recede as the dry season approaches, but only partially so from the south coast, which is gradually being incorporated into the lake bed.
Bombon Lake, in the centre of which is a volcano in constant activity, has a width E. to W. of 11 miles, and its length from N. to S. is 14 miles. The origin of this lake is apparently volcanic. According to tradition it was formed by the terrific upheaval of a mountain 7,000 or 8,000 feet high, in the year 1700. It is not supplied by any streams emptying themselves into it (further than two insignificant rivulets), and it is connected with the sea by the Pansipít River, which flows into the Gulf of Balayan at lat. 13° 52′ N.
Cagayán Lake, in the extreme N.E. of the island, is about 7 miles long by 5 miles broad.
Lake Bató, 3 miles across each way, and Lake Buhi, 3 miles N. to S. and 2½ miles wide, situated in the eastern extremity of Luzon Island, are very shallow.
In the centre of Luzon Island, in the large valley watered by the above-mentioned Pampanga and Agno Rivers, are three lakes, respectively Canarem, Mangabol, and Candava; the last two being lowland meres flooded and navigable by canoes in the rainy season only.
In Mindoro Island there is one lake called Naujan, 2½ miles from the N.E. coast. Its greatest width is 3 miles, with 4 miles in length.
In Mindanao Island there are the Lakes Maguindanao or Boayan, in the centre of the island (20 miles E. to W. by 12 N. to S.); Lanao, 18 miles distant from the north coast; Liguasan and Buluan towards the south, connected with the Rio Grande de Mindanao, and a group of four small lakes on the Agusuan River.
The Lanao Lake has great historical associations with the struggles between Christians and Moslems during the period of the Spanish dominion, and is to this day a centre of strife with the Americans.