464 ADAMS AND PRATT. 



of the bottom gravel indicates that it was deposited by streams flowing 

 above sea level. The upper part of the deposits contains evidences of 

 tidal conditions and some of the streams are tidal for a long distance 

 inland. These facts point to a submergence of the coast. It is be- 

 lieved that this submergence was regional, that it affected the northern 

 coast of Camarines Province and gave the drowned appearance to the 

 shores along Caramuan Peninsula. On the map of the physiographic 

 districts (fig. 1) the 30-fathom line is shown to pass nearly parallel 

 with, this coast and outside of the islands lying off the shore. The 

 emergence of the coast, which is indicated by the littoral deposits of 

 the lowland at Daet and to the north, is later and may be local. 



Nalasvetan mineral district. — This district is situated about 34 kilo- 

 meters south 19° west from Mambulao, not far from the waterehed of the 

 Cordillera, at an elevation of about 300 meters. The mineralization 

 occurs along silicious zones. At this f)lace a considerable amount of 

 mining, practically all by open cuts, was done during the Spanish 

 regime. The country rock is andesite. The locators of the present 

 claims have done the greater part of their prospecting on a big body 

 of ore which extends through jSTalasvetan hill for a distance of about 

 1.5 kilometers, striking north 40° west and standing nearly vertical. 

 The main ore body, as is shown by recently driven tunnels, is about 

 6 meters wide. It carries free gold and has the characteristics of a large, 

 low-grade deposit. Thus far no sulphides have been encoimtered. Some 

 manganese oxide is found aside from iron oxide and clay gouge. 



Ragay Gulf mineral district. — A considerable area of placer ground 

 has been staked for gold dredging near the head of Eagay Gulf and 

 some tests by boring have been made. Copper ore, principally carbonate, 

 has been found as float near Talcauayan. Farther inland thin beds 

 of coal have been seen and float coal of good quality has been picked 

 up. Placer claims for dredging have been located on the Vinas Eiver 

 and the streams entering Talcauayan Bay. There is gold-bearing gravel 

 along the streams inland from Talcauayan, but it is shallow and in 

 small areas. The rocks just to the east of Talcauayan are termed 

 greenstones in this report. They are cut by quartz porph3a-ies. They 

 have been subjected to djmamic action and the specimens of greenstone 

 could not be determined microscopically. I^o veins have been opened 

 in them. 



Historic eruptions of Mayon. — This volcano, by reason of the number 

 of its eruptions, is considered the most active cone in the Philippines. 



Abella, in his monograph written in 1882, gives an account of the historic 

 eruptions, and Padre Jose Coronas includes a resume with his account of the 

 eruption in 1897. In chronologic order their characters may be noted as follows: 



