GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 109 



Tomas was about 38 meters. At Santa Rita it was encountered at a 

 slightly shallower depth which was not definitely reported. The forma- 

 tion is a recent littoral deposit containing beds of, shells and much 

 organic matter buried in silts. The gas probably has its origin in the 

 decomposition of the organic matter, and there is little probability that 

 the amount will be sufficient to prove of commercial value since flows 

 of gas encountered at shallow depths in similar formations are usually 

 soon exhausted. 



In the well which was drilled at Bay in the area of alluvial deposits 

 bordering Bay Lake, an intermittent flow of gas was encountered at a 

 depth of 69 meters. No record of this well has been received by the 

 division of mines, but it is presumed that the gas at Bay has an origin 

 similar to that of Santo Tomas and Manalin, with the difference that 

 at the latter place the deposits were formed on the border of the lake 

 while in the former they are brackish water deposits belonging to the 

 river delta area bordering Manila Bay. 



STONE. 



Guadalupe and Meycauayan stone. — The principal building stone 

 used in Manila in former years has been the water-laid volcanic tuff ob- 

 tained along the banks of the Pasig. It is a soft stone which can readily 

 be cut with axes and bolos, and the facility of transportation on the 

 Pasig to Manila has rendered it a cheap structural material. A similar 

 stone reputed to be of a somewhat better quality is obtained to the east 

 of Meycauayan, and it has also been used in Manila. Many quai-ries 

 have been opened within the area of the tuff deposits, but, with the ex- 

 ception of the Guadalupe stone from the Pasig River banks and the Mey- 

 cauayan, none of the products have received trade names. The tuff has 

 low compression and tensile strength and when used in large buildings 

 requires the construction of a very thick wall. The fortifications built 

 by the Spaniards around the Walled City of Manila are of this stone 

 and it was used in public buildings and the numerous churches in the 

 capital, and had been shipped by water transportation to many towns 

 in the provinces. It is fast falling into disuse except for low walls and 

 fences. 



Sisiman andesite. — A large commercial quarry at Sisiman, which lies 

 to the east of Mariveles on the north shore of the entrance to Manila Bay, 

 was opened for obtaining stone for building the breakwater and harbor 

 impovements at Manila. Stone from this locality had been used during 

 Spanish times as a building stone and for paving blocks in Manila. 

 A good sample of its use as a building stone is found in the Spanish 

 Bank building, where it was employed principally in columns and in 

 trimming. It has a soft, gray appearance when weathered. Its princi- 

 pal defect is its tendency to scale which is exhibited in some blocks. 



