278 The Philippine Journal of Science 1915 



lations of petroleum and of bitumens derived from petroleum 

 appears to be governed partly by anticlinal structure and partly 

 by the intrusions. The petroleum has a paraffin base and a 

 large proportion of burning oils. The different bitumens are 

 semiliquid, viscous, and solid and cannot readily be classed 

 according to the recognized mineral types. They all contain 

 paraffin and are clearly derived from the associated petroleum. 

 They are found filling fissures along bedding planes and in 

 pockets, impregnating porous limestone and sandstones, in mix- 

 ture with fragments of unchanged clay-tuft' near the present 

 surface, as cements in breccias of mineral-impregnated clay-tuff 

 or shale, and in cavities in concretions in the clay-tuff. The 

 pure bitumens cannot be used for paving purposes, but would 

 be valuable in the manufacture of other products. One large 

 deposit of bituminous limestone, or rock asphalt, has been found 

 which can probably be used as a paving material. Some of the 

 deposits of bitumens appear to be of limited size, but others 

 are very probably large enough to be of commercial importance. 

 No exploration has been carried on in Leyte, but there is 

 enough chance of obtaining petroleum to justify a thorough 

 geologic study and probably enough chance to justify drilling 

 at favorable sites. The least-promising feature of the field from 

 this point of view is the apparent lack of porous beds adequate 

 in extent to serve as reservoirs for large accumulations of pe- 

 troleum, but there are many thin beds of sandstones intercalated 

 with the Vigo shale, and further study may prove the aggregate 

 volume of pore space in these beds to be large enough to afford 

 abundant storage capacity. 



