36 WARREN D. SMITH 
ing in a southeasterly direction down into Sorsogon, and this is 
crossed in two very important places—the first trail leads from 
Nueva Caceres to Pasacao, and the second from Albay to Pilar. 
These passes have been most important in the settlement of certain 
parts of the east coast. There has always been very little trading 
along the east coast and, by examining the map alluded to before, 
there are seen to be several isolated spots occupied by Tagalogs and 
it is my opinion that these Tagalogs have come across the mountains 
rather than by the longer way of the sea. From what we know of 
the history of the United States, mountains are great control- 
factors in the distribution of people. I have but to call attention 
to the Cumberland Gap leading from the Appalachian valleys into 
the ‘‘blue grass” regions of Kentucky and Tennessee. For a 
certain period in the history of the United States, practically the 
entire flow of the population was through this pass. 
The central Cordillera —The central Cordillera begins about the 
latitude of Lingayen Gulf and extends north to the northernmost 
point of Luzon. It is not a single range but consists of two or three 
parallel ranges. The eastern Cordillera and the central Cordillera 
start from what Adams calls the ‘‘central knot” which is the 
Caraballo Sur in northern Nueva Ecija. The principal range of 
this central Cordillera is the Polis Range about 25 miles east of 
Cervantes. In this range is Mount Polis or Amuyao, which is 
probably the highest peak in Luzon; Mount Data, which is 7,366 
feet high, is another high peak in this Cordillera, and Mount 
Pulog east of the Agno River is also one of the highest points in the 
Philippine Islands (Fig. 2). On a recent trip into the northern 
country, I made a boiling-point observation on a peak 45 miles 
north of Baguio and found the elevation to be 8,236 feet, and there 
were a half-dozen peaks around me which were much higher. 
This Cordillera extends, as I have said, to the north coast, and keeps 
its high elevation practically throughout the whole extent. It isa 
region of great rainfall and steep slopes—much greater slopes than 
the material will stand on, so that landslides are of exceedingly 
frequent occurrence. The vegetation is very scanty, and prac- 
tically the only forest tree is the pine (P. imsularis). 
The formations are largely igneous, diorite in the bottom of the 
