528 W. D. SMITH — GEOLOGIC INFLUENCES IN THE PHILIPPINES 



swamps. Tradition has it that the area subsided during an earthquake, 

 giving rise to these lake-swamps in a manner similar to that of the for- 

 mation of Eeelfoot Lake, in Tennessee, United States of America. No 

 authentic records of this event were found by the writer. The Agusan 

 forms the only highway whereby one may travel for any distance in the 

 province. The main article of commerce brought down it is hemp. The 

 Agusan Valley is of rather recent origin, Pleistocene deposits being com- 

 mon along the river banks. The valley is, according to Maso,^ the region 

 of greatest seismicity in the archipelago. No active volcanoes are situ- 

 ated in or close to this region. 



d. Cotabato. — Beginning in the extreme northern part of Luzon, this 

 stream flows south until it reaches about the center of the island, at which 

 point it makes a more than right-angled turn and continues somewhat 

 north of west into Polloc Bay. It is the largest river of the island and is 

 navigable for shallow-draught stern-wheelers for over 100 miles into the 

 interior. The valley it occupies is wide and generally fiat-bottomed, bor- 

 dered by a rather marked escarpment on the southern side, which evi- 

 dently was an old sea margin, being made up largely of coral material. 

 The flat plain through which it meanders through several channels is one 

 of the most fertile tracts in the archipelago, and it is here that the Gov- 

 ernment recentl}^ has established some large rice colonies in an effort to 

 increase the productivity of the island and at the same time to colonize 

 the island with Christian Filipinos. The main town on the river, situ- 

 ated on the south bank some 12 miles from the mouth, is Cotabato, which 

 some day should be the largest city on the island, as it has what most of 

 the Philippine towns do not possess, namely, a great and potentially rich 

 tributary region to draw on. Above this there are only scattered Moro 

 villages. 



e. Eio Grande de Pampanga. — Rising in the "Central Knot" of the 

 mountains of Luzon, the Caraballo Sur, this flows down the eastern mar- 

 gin of the central plain, very close to the eastern cordillera, and thence 

 sliglitly west of south to Manila Bay. Its lower end breaks up into a net- 

 work of canals, which anastomose with those of one or two other smaller 

 streams that flow from the center and western margin of the southern 

 half of this plain. In its lower portion it is a fine example of a ""braided" 

 stream. It is navigable for steamers of light draught as far as Mount 

 Arayat, a distance of about 75 miles, and for rafts as far up as Caba- 

 natuan, about 150 miles. For the most part this river is wide, shallow, 

 with low mud banks. Just to the east and parallel to the river is the long 

 and narrow Candaba swamp. 



8 Fr. Sadera Maso, S. J. : Bulletin of Weather Bureau, 1910, p. 283. 



