Page:The National Geographic Magazine Vol 16 1905.djvu/177

lakes and marshes, waterfalls, and elevated beach lines, showing that the whole archipelago is in a condition of unrest.

The coasts of the archipelago are for the most part intricate; how intricate may be realized from the statement that these islands, with an area of about 115,000 square miles, have a coast line more than double the length of that of the main body of the United States. They are in part the result of volcanic action and in part the work of coral animals. Vulcanism has brought up the land from great depths in the form of thousands of large and small islands, fringed with coral reefs, some of which have been brought to the surface, while others lie immediately below it.

With such a broken coast, harbors of one sort or another are numerous. Most of them are of sufficient depth to admit large vessels, but are so difficult and dangerous of entrance, owing to the reefs which obstruct them and to the absence of lights, channel buoys, range stakes, and accurate charts, as to be of little value except to those who know them well. Owing to the alternating character of the winds which prevail throughout most of the archipelago, the northeast trade wind from October to June and the southwest wind during the rest of the year, many, if not most, of the harbors furnish shelter during only a part of the year.

All the principal islands and groups of islands have harbors for the largest vessels in all kinds of weather at all seasons, except the island of Bohol, which has no harbors, and there are many harbors which are safe only according to the season of the year.

The dominating feature of the currents in the islands is the great equatorial current, which, sweeping across the Pacific from east to west in a broad belt, divides east of these islands. The northern portion, which farther north is known as the Japan current, sends numerous streams through the passages among the islands, thus forming a complicated system of currents almost impossible of description. The system is still further complicated by surface drifts, set in motion by the southwest wind in the summer and fall, making currents in various directions among the islands at different times of the year.

Tides in the archipelago are exceedingly irregular, differing greatly in different places, owing to the directions in which tidal waves move, and differing also greatly at different times of the month. For details regarding them reference should be made to the sailing directions prepared by the United States Coast and Geodetic Survey.

There are few rivers in the Philippine Islands, the Cagayan of northern Luzon, the Rio Grande de Mindanao, and the Augusan of Mindanao being the only three which can be classed as large streams. These, which are in approximately the same class, have a length exceeding 200 miles, and owing to the abundance of precipitation carry large volumes of water even during the low stage. The Pampanga River of central Luzon is nearly as large, and this is followed in magnitude by the Ango of central Luzon and the Arbra in the northern part of the same island. Probably there are no other streams in the islands which exceed iod miles in length.

Mr G. R. Putnam, in charge of the United States Coast and Geodetic Survey in the Philippine Islands, at the instance of the Director of the Census, made a count and measurement of all the islands and islets comprised in this archipelago, including everything, however small, which at high tide appeared as a separate island. The total number