X, A, 4 Pratt: Petroleum and Residual Bitumens 269 



through the overlying beds, and wells penetrating such zones 

 might obtain larger flows than the undisturbed shale would yield. 



The deposits of solid bitumens indicate the former presence 

 of a large quantity of petroleum in the Leyte formations. But 

 they indicate also the escape and consequent loss of much of the 

 original supply. Just what proportion may remain is undeter- 

 mined. When all is said and done, definite evidence as to the 

 quantity of petroleum present in Leyte and in Tayabas will be 

 obtained only by drilling test wells. 



The evidence as to the quantity of solid bitumens present in 

 Leyte is somewhat more definite, but here again lack of explora- 

 tion makes impossible the exact estimates that are desirable. 



The tonnage of deposits like those outcropping at A and B 

 cannot be estimated in advance of exploration. The width of 

 the fissure or vein at B as revealed in the floor of the shallow 

 pit opened there is about 60 centimeters. The gilsonite veins 

 in Utah, according to George H. Eldridge,-' range in width from 

 45 centimeters to over 5 meters and contain a total quantity of 

 more than 30,000,000 tons. While the vein at outcrop A in 

 Leyte is thin, its width is of the same order of magnitude as 

 the width of the veins in Utah. In Utah, however, the outcrops 

 even of the small veins can be traced for several kilometers, 

 while the vein at outcrop A can be followed a few meters only 

 on the surface. Yet the vein at A may be found to be persistent 

 underground, for it is well known that outcrops are usually 

 obscure in the Philippines. The outcrop of the coal bed mined 

 at East Batan, Albay, for instance, could be traced on the surface 

 only a comparatively short distance, yet the workings in the 

 mine ultimately proved an area of 50 or more hectares with the 

 coal always regular and continuous. Only by exploration can the 

 extent of the vein at B be ascertained. Without exploration 

 there is in sight at the present time only a few tons of bitumen. 



At C and D the quantity of bitumen in sight is insignificant, 

 but no prospecting of the outcrops has been attempted. 



Limited exploration on several outcrops in the region of 

 E, F, and G has recovered only 100 tons or so of bitumen and 

 has indicated that some of the deposits contain not much more 

 than this quantity of material. The work has been only super- 

 ficial, however, and it may be possible to follow the irregular 

 bodies beneath the surface into deposits of larger proportions. 



The outcrop at K has not been explored, but the surface in- 

 dications promise little in the way of tonnage. 



' 22d Annual Rept. U. S. Geol. Surv. (1900-1901), pt. 1, 342 et seq. 



