GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 105 



River was accomplished as the land emerged. This theory of the origin 

 of Laguna de Bay is somewhat similar to one proposed by other writers, 

 who have considered the lake once to have been an arm of the sea, but 

 it supposes a differential movement of the land to the west instead of 

 the formation of a long bar, or spit, of water-laid tuff which upon being 

 elevated, cut off the lake from Manila Bay. 



Returning to the evidence presented by the finding of marine fossils 

 on the shores of the lake, the writer wishes to question the fact of the 

 shells having been deposited in marine banks. While studying Jalajala 

 Peninsula, and inquiring concerning deposits of shells, he was told of 

 a place situated well up on the flank of the mountain and near the trail 

 passing from over the peninsula, where numerous shells could be found. 

 The locality was visited and the place was seen to bear many indications 

 of having been the site of human habitation. The shells were exposed 

 on the surface or slightly buried in the soil, and occurring with them was 

 found the bone of a carabao. At the present time there are some houses 

 near by which are occupied during a part of the year when rice is 

 cultivated on the hillsides. It seems altogether probable that the ac- 

 cumulation of shells is in the nature of a kitchen-midden. 



In the first part of this article reference is made to a statement by 

 Smith that he found marine-cut terraces on the east face of a limestone 

 ridge in Binangonan Peninsula, and shells of Crassatellites lying on one 

 of these terraces. The writer, upon examining the locality, could see 

 no evidence of marine-cut terraces, but he did find some shells lying in 

 the trail, and it was his opinion that they had been dropped there by 

 travelers. It would be very interesting to find beds containing shells 

 on the shores of Laguna de Bay and their presence would be entirely in 

 accordance with the probable history of the lake; but until authentic 

 cases of the discovery of fossil shells are reported it would be well to 

 rely on other evidences to prove the elevation of the region. The occur- 

 rence of deposits of water-laid tuff at considerable elevations near the 

 borders of the lake at other localities than the western shore is a 

 sufficiently definite proof of the emergence of the land bordering the 

 lake basin. 



kMINERAL RESOURCES. 

 IRON. 



Lanatin iron deposits. — In his Ligera Resena de la Mineria de las 

 Islas Filipinos, Abella says under the heading "iron" : "The deposits 

 in the present district of Morong were in reality the first to be exploited 

 and smelted, the object being to manufacture munitions of war." 



In discussing the Angat iron deposits, McCaskey quotes the above statement, 

 and in his report publishes two analyses of iron which he found in the records 

 of the Spanish Inspection de Minns. Both of these samples were probably from 

 93217 4 



