HYDROGRAPHY. In the smaller and narrower islands the mountain chain which is the back bone of each island is the great central water parting, streams flowing to the sea on either side of it in short, straight courses. :Mindoro, for example. has about 60 independent little rivers. The drainage of the larger islands is more com plicated, the parallel arrangement of the moun tain ehains giving space for the development of considerable streams. Among them is the Rio Grande de Cagayan (q.v.), with a drainage basin of 10,000 square miles, or much more than one third of Luzon. All the interior waters of North eastern Luzon are tributary to the Cagayan, reaching the China Sea on the north coast of the island. All the interior waters of Central Luzon, south of the Cagayan basin, are included in the system of the Rio Grande de la Pampanga, which empties through a wide delta into Manila Bay. The mountains are so near the sea in East Luzon that the rivers of that coast are of small import ance excepting the 13icol in the southeast, which floats small vessels; but in the northwest the Agno has 11 feet of water on its bar at high tide, which gives some importance to the port of Dagupan at its mouth. The Pasig is only 12 miles long, but as it corrects Bay Lagoon (q.v.),
or Laguna de Bay, with Manila Bay through the chief port of the island. it is a commercial high way of importance. The river systems of Min danao, confined within the parallel ranges, have chiefly a north and south direction and are more important for navigation than those of Luzon. The Rio Grande de Mindanao. one of the largest rivers in the Philippines, drains the central basin of the island, carries the waters of many tribu taries to the Celebes Sea on the west coast, and is navigable for gunboats as far as Lake Lagu san. The Rio Agusan f q.v.) rises about 25 miles from the south coast, and reaches the sea on the north coast, nearly dividing the island. It is navigable for a few miles from its mouth. The most important lakes in Luzon are: Laguna de Bay. 25 miles long and 21 miles wide, which re ceives numerous small streams from the moun tains around it, and Bombon, 14 by 11 miles in extent, Taal volcano rising amid its waters. The largest lakes of Mindanao are Maguindanao, in the centre, and Malanao, near the north coast. Smaller lakes are scattered over the islands,