GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 69 



dillera near that place. The writer, after considerable field work, has 

 concluded that the cura's statement may be dismissed as having no value 

 in the literature. • 



Smith, who made a hurried trip through Subig, on his way to ascend 

 Mount Pinatubo, states in his report that he judged from the appearance 

 of the country that there are limestones and shales in the region sur- 

 rounding the bay. The writer found none and was unable to learn of 

 any through inquiry. 



Finally it should be mentioned that Eoth, without any seeming basis, 

 and without any subsequent substantiation unless it be the statement 

 by the cura reported by Von Drasche, says, in discussing the occurrence 

 of limestones in Luzon, that probably the abrupt peaks in the region 

 which corresponds to the position of the Pinatubo group of mountains 

 are composed of the same limestones which are found near Antipolo and 

 Bosoboso in the eastern cordillera. This .statement is without value 

 since the peaks are now known to be formed of eruptives. 



Marine conglomerates. — The only reference to a locality of marine 

 conglomerates on the flanks of the western cordillera is in the report on 

 the Sisiman quarry by Ickis. He says, "along the path north of the 

 blacksmith shop and directly below Mr. Nelson's home, occurs a 10-foot 

 bank having the appearance of a conglomerate, while further north on 

 the same path the bank is very soft resembling tuff. Both these occur- 

 rences may result from weathering and washing down of the andesite." 

 Ickis did not recognize the significance of this conglomerate as he 

 probably would have had he seen more typical exposures. It is found 

 east of Sisiman Bay and also on the point west of the entrance to Ma- 

 riveles Bay, where in a cove it forms a sheer bluff 30 meters high. The 

 writer first studied the conglomerate on Corregidor Island, which locality 

 will now be discussed. 



An erroneous idea in regard to the character of Corregidor Island is 

 presented by several writers, none of whom, however, has made a careful 

 examination of the locality. It seems to have had its inception in the 

 statement by Von Kotzebue that it contains a crater. This idea, which 

 has even become popular, is most fully elaborated by Von Drasche, who 

 says, 



"The entrance to the bay has a width of 10 sea miles but is narrowed by two 

 islands. One of them, Corregidor, is nearly three and a half sea miles long and 

 is composed of lava beds. Von Kotzebue, according to J. Roth, mentions a crater 

 upon it. Although I likewise did not visit this island, nevertheless, I had 

 opportunity to pass both to the north and south of it and noticed only slightly 

 dipping lava beds. To the south of it lies the small island, Pulo Caballo." In 

 his paper he has a text figure which shows both islands with the soundings taken 

 from the chart of the Bay of Manila by Claudis Montero. 



"According to this sketch it appears that the two islands were once joined to the 

 east, but now they are separated by a depth of 59 meters. Also the soundings 

 suggest that the two islands once formed a circular mountain with a deep crater 



