204 "^he Philippine Journal of Science vns 



some small vents near the river 30 meters or so upstream from 

 the salt springs. The whole countryside shows evidence of 

 dying vulcanism. 



Road metal. — For the most part the only highways in this 

 country are horse trails; consequently there is at present little 

 demand for road metal, but we can assert with entire assurance 

 that there will never be any dearth of suitable material when 

 it is needed. There is no lack of "trap rock," which term the 

 road engineer employs to designate several varieties of igneous 

 rock. A very good stone for the traffic utilizing it is now used 

 on the streets of Bontoc. It is a whitish rock, some phases of 

 which resemble dacite, and affords a firm, hard, quickly drying 

 surface. It is abundant just south of the town. 



Building stone. — Stone for construction purposes is quarried 

 in two localities. One of these is a gray, impure sandstone, 

 derived from the debris of andesitic rocks, which occurs at Kian- 

 gan; the other is a tuffaceous sandstone at Sagada. The two 

 are superficially much alike. 



At Lubuagan the school authorities are planning to use a 

 similar stone for building a schoolhouse. My opinion, which 

 has been asked for by local authorities, is that this stone, while 

 superficially much like the stone in the other localities mentioned, 

 is really of very inferior quality. It is a grayish, tuffaceous 

 sandstone, fairly fine-grained, in places coarse, and composed 

 of andesitic detritus. The chief mineral fragments are lime- 

 soda feldspars and hornblende with little or no quartz. A block 

 of this stone, with a bearing surface of 11.8 centimeters by 

 12.8 centimeters, was subjected to a compression test with the 

 result that it yielded at 348 kilograms per square centimeter with- 

 out giving a cone. In fact it broke along parallel planes, indicat- 

 ing that the pressure had been applied parallel to the bedding 

 planes (there was nothing to indicate beforehand how these lay). 

 Although this figure is low, it is higher than that (329 kilograms 

 per square centimeter) given for a superior sandstone when com- 

 pressed along the bedding planes. It is reasonable to suppose 

 that the Lubuagan tuff would withstand a greater load if it were 

 applied at right angles to the bedding planes, and it follows that in 

 construction the stone should be laid with the bedding plane 

 horizontal. 



The most unfavorable feature of the Lubuagan stone is its 

 tendency to crack and sprawl on exposure. 



I have no figures for the Sagada stone, but as it hardens on 

 exposure it ought to serve very well in structures of moderate 



