THE GEOLOGY OF LUZON, P.1. 35 
naissance from Laguna de Bay to Infanta, and Pratt and Adams 
have been on the Caramoan Peninsula. A few boats have skirted 
the east coast of Luzon, but very fragmentary observations have 
been brought back. 
It is needless to say that we know very little about the elevation 
of this Cordillera, except that it is much lower than the central 
Cordillera, and in several places, to which I shall refer later, the 
range is quite low. 
We know practically nothing about the formations in the 
northern part of this range. Ferguson found a volcanic peak, 
Mount Kawa, near the northernmost point. Ickis has made a 
cross-section from Tanay to Infanta (Fig. 5), showing closely folded 
sediments, diorite, and andesites. Adams and Pratt found con- 
siderable andesite in the central part of the range in Ambos 
Camarines. 7 
If we examine the map showing the distribution of civilized and 
wild peoples, published in the second volume of the first Philippine 
Census, 1903, we note that the whole eastern Cordillera from Cape 
Engano to Casiguran Bay, and, except for two or three spots as far 
down as Infanta, is inhabited by Negritos. Then, continuing along 
the coast almost to San Miguel Bay, there is a long strip pretty well 
taken up by Tagalogs. Then, in the Caramoan Peninsula, the 
Negritos are found again with some Bicols. At any rate the 
population is very scanty. 
Beginning at the north, we find several well-defined passes 
through this range, and these passes are the location of trails leading 
from the interior to the coast. The first one runs from the head- 
waters of the Ilagan River eastward to Palanan Bay. Then about 
50 miles south is another one leading across from the headwaters of 
the Cagayan River to Casiguran Bay. Only a few miles south of 
that is another which runs across from Cabanatuan to Baler. The 
next important pass is following the Chico River from Penaranda to 
Dingalen Bay. Farther south is the route followed by Ickis from 
Tanay on Laguna de Bay to Infanta. Another one extends from 
Pagsanjan to Mauban. Then from Lucena to Atimonan. In 
Ambos Camarines, this Cordillera splits up into two: one following 
as already described, the Caramoan Peninsula; the other stretch- 
