X, A, 3 Smith: Reconnaissance, of Mountain Province 189 



This might be, in very general terms, the geologic history of the western 

 part of northern Luzon. 



At the end of this monograph I shall try, in a summary, to correlate 

 the formations noted on Luzon with those of Java, the only island in the 

 Indian Ocean whose geology is thoroughly known. 



GEOGRAPHY 



TOPOGRAPHY 



This region is typically mountainous, and from the character 

 of the relief we must consider it as being in the stage of "topo- 

 graphic youth," as a glance at Plate II, which is characteristic, 

 will at once make evident. Whatever might be said in general 

 elucidation of this type of topography has already been said and 

 written many times about similar forms of relief in geologically 

 young parts of the earth and would only mean needless repetition 

 here. However, a few facts should be noted. 



There are two distinct types of topography in the region 

 covered by this paper, and these are directly to be attributed 

 to the character of the geologic formations. In the country to 

 the west of the Polls Range the formations are mainly volcanic, 

 and we find there an irregular, rugged, accentuated relief. The 

 elevations vary from 370 meters to 2,400 meters or more. 



East of this range the formations are folded sediments, giving 

 rise to a more regular topography, and in places the hills and 

 mountains are nothing more than tilted blocks of sandstone. On 

 the eastern slopes these present long, gentle inclines, but to the 

 west they form steep escarpments with here and there a saw- 

 toothed skyline. As one goes farther to the east, approaching 

 the valley of the Cagayan, the mountains become mere foothills, 



Cagayan Valley, which I have not personally explored, though 

 I have overlooked it from a number of points, is clearly synclinal. 



In the eastern portion, between the high and low country just 

 referred to, there is a stretch which has been called by Worcester 

 "No Man's Land." The people inhabiting this tract will be 

 referred to in a subsequent paragraph. The topography consists 

 of medium-sized hills, from 370 to 430 meters in height, which 

 are due to a cross folding of the originally flat-lying sediments. 

 This cross folding produces hummocky hills and little pockety 

 valleys or hollows. 



CLIMATE 



The climate of this region shows a complete gradation from 

 subtropical in the bottoms of the large valleys, as, for instance, 

 at Cervantes, to temperate in the more elevated portions. The 

 lowest temperature that I experienced was at 5.30 on the morning 



