RIVEE SYSTEMS 527 



a. Pasig. e. Eio Grande de Pampanga. 



6, Cagayan. /. Bicol. 



c. Agusan. g. Abra. 



d. Cotabato. Ji. Agno. 



a. Pasig. — This is the shortest, swiftest, narrowest, and yet the most 

 important of the island waterways. Its total length is not over 15 miles, 

 having its source in Lagnna de Bay and debonching into Manila Bay. 

 The fall of this stream is slight, flowing as it does through almost flat 

 country. While it does not carry the greatest volume of water-borne 

 freight in the islands, it does transport the largest passenger traffic. In 

 its lower part, within the limits of Manila, the river usually is choked 

 with inter-island boats and launches. Vessels drawing over 15 feet never 

 come into the river, only launches and very shallow-draught boats pro- 

 ceeding above Manila. The tide runs up this stream as far as Fort Wil- 

 liam McKinley, about 7 miles. At this point the river cuts through 

 gently folded tuff beds, affording about 50 feet of section. This is impor- 

 tant geologically because it gives an excellent opportunity for the study 

 of the composition of the plain. This rock also is of considerable eco- 

 nomic importance. 



&. Cagayan. — This river is about 220 miles long, flowing from the 

 south almost due north, save for its meanderings, and draining the ex- 

 tensive Cagayan Valley of northeastern Luzon, the great tobacco district 

 of the archipelago. It is navigable for ocean-going vessels of shallow 

 draught as far as the town of Tuguegarao, about 70 miles, and for boats 

 drawing not over 3 or 4 feet as far as Echaque, 160 miles. The Cagayan 

 unmistakably occupies a structural valley modified by erosion. Along its 

 west bank the country generally is high because the river has swung over 

 to that side of the valley. It is said that the dip of the sediments in the 

 bluffs near Tuguegarao is westward, and it is quite likely that there is a 

 fault-line which has influenced the position of the river. Professor Koto, 

 of Japan, has expressed the opinion, verbally to the writer, that this may 

 be a rift valley and a continuation soutliward of an important fault seen 

 by him on the eastern side of Formosa. 



c. Agusan. — This river likewise flows from south to north along a well 

 defined tectonic line and is very similar to the Cagayan except that it is 

 less open to navigation. It is navigable for launches only for a short dis- 

 tance above Butuan, about 25 miles, and beyond that only by native dug- 

 outs. It has one marked feature which sets it apart from the other rivers 

 considered here, the large swampy tract composing the so-called lakes — 

 Pinayat, Dagun, Sadocun, and Linao. These "lakes'' are situated be- 

 tween Talacogan and Veruela, being really little more than a series of 



