182 '^h^ Philippine Journal of Science wu 



bank of Bontoc River. The view in this narrow valley, with its sides that 

 jut forth Kroovelike and upon which are built in steep terraces the well-kept 

 rice fields of the Igorots, is truly splendid. 



The shortest way to Bontoc is from Sabantran, provided one follows down 

 the river; by this route it is easy to make the journey to Bontoc in from 

 five to six hours. 



This trail, if it may so be called, is absolutely impassable at high water, 

 and even at low water must be traveled afoot on account of the extraordi- 

 narily large bowlders. We had brought along horses for our trip in Bontoc, 

 but we had to send them back to Sabangan after trying in vain for one hour 

 to get the animals over the high bowlders. The banks of the river in the 

 vicinity of Sabangan consist of a red, completely decomposed trachyte-tuflF, 

 which has an appearance of stratification due to gradations of color. All 

 along the river are found enormous fragments of a coarsely crystalline 

 rock, which is made up of quartz, orthoclase, much plagioclase, and a dark 

 green mineral (chlorite ?) crystallizing in small flexible laminae. Just out 

 from Sabangan I entered upon the road for Bontoc through Sagada, which 

 is passable for horses. To reach the road it is necessary to cross over to 

 the left bank of a small river, Sabangan River, traversing the yellow tuff 

 formation for a short distance, beyond which one encounters a beautiful 

 quartz-trachyte, which is of considerable extent. This rock is dense, white, 

 and hard, with a splintery fracture. In the dense groundmass one can 

 distinguish white sanidine, glistening like glass, a gi'ay, opaque feldspar 

 crystallized in little columns, quartz in irregular grains, and little crystals 

 of augite — certainly a rare mineral combination. Under the microscope 

 the groundmass resolves itself into a maze of colorless and brown crystals, 

 the latter perhaps being augite microliths. The gray feldspars stand 

 out of the matrix in a most remarkable manner; they are separated from 

 the rest of the groundmass by a sharp, dark border. Augite is rather scarce, 

 while magnetite is present in beautiful crystals. All the disseminated 

 minerals are strongly corroded by the groundmass and contain numerous 

 inclusions. Fig. 3 on Plate III shows very beautiful feldspars in the 

 turbid groundmass. 



In the vicinity of Anquilen the trail proceeds in a northerly direction 

 high up on the west wall of the valley. 



In the middle of the carefully cultivated, terraced rice fields, with their 

 artificial irrigation system, along this small tributary of the Rio Bontoc, 

 nestle the hamlets Sagada, Balugan, and Anquilen, one above the other. 

 One again crosses bedded series of trachyte-breccias, intercalated with 

 yellow tuffs, and dipping in a southwesterly direction. 



No doubt they constitute the northerly continuation of the bedded complex 

 noted between Cayan and Sabangan. At Sagada extensive coralline lime- 

 stone cliffs are again encountered. These may be traced south almost to 

 Balugan and toward the north to Tetenan. From a distance these give one 

 the impression of a large cemetery with numerous gravestones. 



These coral cliffs likewise show stratification with clearly discernible 

 thick beds, usually with a southerly inclination of 15°-20°; between the 

 strata I found a thin layer of greenish tuff. Weathered trachjrte is en- 

 countered between Tetenan and Bontoc. The greenstone base of the Agno- 

 bed series may be seen at two places also, but over limited areas only. 

 Passing eastward, one very soon reaches Bontoc River at a point where a 

 tributary with exceedingly steep banks enters at right angles from the left. 



