MINDANAO AND SULU: II. PHYSIOGRAPHY. 349 



THE VALLEY OF THE AGUSAN". 



Mr. Maurice Goodman 8 to some extent has already described this 

 great intermontane flat. However, he does not give any definite figures 

 as to its width. It is very wide, as is attested by the fact that the distant 

 mountain peaks could be seen with difficulty. This broad valley must 

 be in the neighborhood of 300 kilometers in length. It is inhabitated 

 by Christian Visayans, Manobos, Mandayas, Manguangans, and Bukid- 

 nons, the first named having immigrated there. 



Some so-called lakes are found about midway in the length of this 

 great stream, but according to all travelers in this region they are to be 

 regarded as large, low, swampy areas over which the river has spread. 

 The lakes are supposed to have originated in a local subsidence at the time 

 of the earthquake of 1892, which was very much like that causing the 

 formation of Eeelfoot Lake in western Tennessee in the United States. 

 The description given me by an American civil engineer, formerly super- 

 visor of Surigao Province, confirms this view. He said that many trees 

 of a kind not usually growing in water could be seen submerged so that 

 only the top branches were visible. This is not at all unreasonable in 

 view of the fact that the valley of the Agusan is a focus of great seismic 

 activity, and the line of equal magnetic intensities follows its trend. 7 



There is little transportation over this plain. The river with its 

 tributaries is at present practically the only route of travel. Hemp and 

 rice are the chief agricultural products. 



SMALL RIVERS. 



Besides the two main rivers of central and eastern Mindanao and the 

 Agusan, in the northeastern district, there are several shorter and un- 

 navigable ones in various parts of the island. The following will be 

 considered: (1) The Sahug-Tagum system, (2) the Agus, (3) the 

 Mataling, (4) the Cagayan, (5) the Iponan, (6) the Tumaga. Others, 

 which are much longer than the last mentioned, but as yet of little 

 commercial importance, have been omitted. 



(1) The Sahug-Tagum system.— This system, which is known as the 

 Sahug in the upper waters and the Tagum in the lower part, has its 

 source on the southern slopes of Mount Kuanabayan. This is the route 

 Ickis and Goodman took in the early part of 1908 to pass from the Gulf 

 of Davao to the upper waters of the Agusan. A much shorter way, 



• A Reconnaissance from Davao, Mindanao, over the Divide of the Sahug River 

 to Butuan, including a survey from Davao to Mati. This Journal, Sec. A (1908), 

 3, 501. 



T Mr. Goodman found that abnormally high water was sufficient to explain 

 these lakes. It is quite probable that in 1902, when the civil engineer visited 

 them, there was a flood. M. Saderra Maso, S. J. Isoclinie and Isogonic lines 

 in the Island of Mindanao, Phil. Weather Bureau, Manila (1902), p. 246. 



