CHAPTER X. 
GEOLOGICAL OBSERVATIONS ON THE PHILIPPINE AND 
SOOLOO ISLANDS. 
Tue Philippine Islands constitute a large archipelago of triangular 
shape to the east of the China Sea, and the Sooloo Group is pro- 
perly the southern limit of this. archipelago, between Mindanao and 
the north of Borneo. The region has been long known to abound 
in volcanoes; but it is less well-understood that far the larger part 
of the land consists of ancient Plutonic and stratified rocks. The 
Sooloos appear to be wholly volcanic. The southern extremity of 
Luzon is also volcanic, and there are cones on Mindoro, Mindanao, 
and other islands. But the greater part of Luzon north of Manilla is 
said to be covered with granites, gneiss, talcose rocks, sandstones and 
shales containing coal deposits, and yielding also ores of lead and 
copper. Specimens of the coal and ores were received by us through 
the kindness of Don Inigo Azaola and It] Sefor Roxas, of Manilla. 
Luban contains copper pyrites in talcose and chlorite slate; and the 
same formation is continued in Mindoro, where it passes into serpen- 
tine, specimens of which were contained in the cabinet of Sefior 
Roxas. Gold occurs here in quartz, and probably in the talcose rock. 
We sailed by Panay, one of the large islands of the archipelago, and 
observed nothing volcanic in the appearance of its mountains, which 
had similar features to the main range of Mindoro. Some of the 
peaks were estimated at eight thousand feet in height. One of our 
boats touched at San José, a village on the western shores, and 
brought off a number of pebbles from the beach, which were varieties 
of the talcose rock, with quartz and jasper; and the jasper, as in Cali- 
fornia, may appertain to the talcose formation. On Mindanao, at 
Caldera, besides rolled fragments of basalt, porphyry, and chalcedony, 
