254 The Philippine Journal of Science i9i6 



Bulan coastal plain in order to examine and get specimens of 

 a so-called conglomerate which is exposed on the east side of 

 the divide. It is not a water-laid deposit but a flow breccia or 

 a volcanic conglomerate, containing igneous pebbles and bowl- 

 ders, more or less rounded, in a matrix of igneous rock. I have 

 not studied the rock under the microscope, but macroscopically 

 the pebbles and bowlders appear to be andesite inclosed in a 

 matrix of scoria. The andesite being more resistant stands out 

 in relief in the exposures of the conglomerate. 



TRIP TO THE CRATER OF BULUSAN 



I had planned to make an attempt to reach the top on Monday 

 if the weather permitted. A start was made about 8 o'clock from 

 Patag barrio. The trail up to the last house, a height of 765 

 meters, was good. From the last house to the cogon grass, the 

 guide had previously brushed out a trail for Mr. Elmer, a 

 botanist from Manila. The green vegetation stopped at 1,010 

 meters, and the cogon grass stopped at 1,260 meters. This 

 cogon appeared dead, but showed no signs of sintering. On 

 the south slope much of it was covered by sand and gravel, 

 which had been carried down recently by water and landslides. 



The crater was reached at 12.30, after four hours of almost 

 steady climbing. The aneroid gave an altitude of 1,450 meters 

 at the crater's rim, which is from 10 to 15 meters down on the 

 flank; however, the atmospheric conditions were so changeable 

 that readings were not very reliable. 



On the rim of the crater is a small, irregular vent whose 

 long dimension trends north 20° west up the slope. There are 

 three openings: the largest, 10 by 4 meters, and two small 

 crevices, measurable in centimeters. From all of these vents 

 there was a steady rush of steam and sulphur dioxide (SO2) 

 vapor. Around the orifices there were being deposited fine 

 crystals of sulphur. In this type of sulphur formation, which 

 is designated as the "solfatara type," crystals of sulphur are 

 formed from sublimation. The formation of "solfataras" was 

 formerly thought to be due to the reaction of gases, namely, 

 hydrogen sulphide (H2S) and sulphur dioxide, in which 

 water and free sulphur were formed according to the reaction 



2H2S+S02=2H20+3S 



but Brun * has shown that this reaction cannot take place in 

 nature. 



* Brun, A., Chem. Zeitg. (1909), No. 15, 29, quoted by Hunt, W. F., Econ. 

 Geol. (1915), 10, 544. 



