﻿388 SMITH. 



I found that the courses of the Mantija and Mangliji side streams were 

 almost entirely controlled by structural conditions. As 'can be seen by 

 a cross section of almost any part of the field, the coal measures are 

 folded to a considerable degree in some places. The Magliji is located 

 on the crest of a small local anticline and the reason for this position is 

 that there is usually along the crest of an anticline a fracture system 

 which would give a stream a foothold. 



It would be interesting to know to what extent jointing and faulting 

 had affected the orientation of drainage in this area, but unfortunately 

 there are few good exposures, and quarries and mining operations have 

 not yet proceeded far enough to throw much light on the underground 

 condition. 



To one accustomed to read topographic features much of the underlying 

 structure and formations of a country is revealed, whereas to another 

 person a surface examination would disclose nothing. For instance, 

 the abrupt change in the contours at the point where the Ustaganon comes 

 into the Danao should be noted; west of that point the rock is igneous, 

 a hard, fairly structureless diorite, east of that point to a place as far as 

 the end of the railroad, the contours are fewer and farther apart, showing 

 gentle slopes and o^^tlines, the underlying formation is that of the coal 

 measures, consisting largely of soft shales. Again, the crowded contours 

 just south of the end of the railroad track at Camansi should be 

 considered. They mark a great, white cliff of limestone, which usually 

 gives this character to the topography. I may state that such topog- 

 raphy is not very favorable to engineering projects. 



geology: general. 



For purposes of convenience, and also because of a natural distinction 

 between the areas, I shall treat the geology of this region under the 

 following heads : 



1. The Acsubing-Muao region. 



2. The Mount Licos region. 



3. The Cajumayjumayan region. 



4. The Sili Creek region. 



THE ACSUBING-MUAO BEGION. 



This portion of the district, lying south of the Cot-Cot Eiver, is 

 largely covered by a sheet of andesite and it therefore is much more 

 simple to deal with. Although this part of the area was evidently 

 entirely covered by this sheet of andesite, the streams have greatly dis- 

 sected it, cutting down through it for over 200 meters (nearly 700 feet) 

 to the unconformable coal series below. Isolated residual patches of the 

 upper limestone are scattered at long intervals, resting upon the andesite. 



The streams are naturally for the greater part deeply incised with V- 

 shaped cross sections as a result of the character of the formation which 

 is predominantly igneous. 



