290 The Philippine Journal of Science isib 



Practically every attempt at prospecting has had to contend 

 with the difficulty that the tunnels ran out of coal sooner or 

 later under circumstances which made it difficult to decide 

 whether the coal bed had been faulted or had failed by pinching 

 out. It will readily be understood that a nearly vertical fault, 

 more or less parallel to the strike of an inclined coal bed, might 

 so displace the coal on either side of the fault plane that the 

 bed would appear to pinch out gradually. 



The true nature of the discontinuities in Philippine coal beds 

 cannot be determined by geologic study alone. Outcrops are 

 notoriously unreliable where the surface relations are so obscured 

 by slides, by talus, and by the growth and decay of heavy 

 vegetation, as they are in the Philippines. In certain individual 

 cases it is clear that beds have been faulted, and less commonly 

 unmistakable evidence that the original bed was of restricted 

 lateral dimensions is to be found in gradually decreasing thick- 

 nesses along outcrops. But to decide which is the common cause 

 of nonpersistence and usually to decide which factor is respon- 

 sible in a particular case, underground exploration is necessary. 



The exploration which has been carried out in the past throws 

 some light on this problem, and it seems desirable to bring the 

 results together for comparison and study. The work of ex- 

 ploration having been restricted to a few localities, the study 

 cannot be made exhaustive, but an attempt to interpret the 

 data which are available should be useful as a guide to future 

 exploration. 



The Spaniards performed and recorded the results of a great 

 deal of exploration in coal beds, and their works should be 

 reviewed briefly in this connection. 



About the year 1874 an association called "La Paz" was or- 

 ganized to exploit certain deposits of coal which outcrop in the 

 vicinity of San Esteban, a barrio of Bacon, Sorsogon. The out- 

 crops appear to represent several beds, but the principal work 

 was confined to a single bed, which, according to Jose Centeno, 

 an engineer in the Spanish mining inspectorate, varied in width 

 from 4 to 8 meters. All of the beds are nearly vertical and 

 strike about north 20° west. The coal lies near the base of the 

 Tertiary sedimentaries, and at the western edge of the sedi- 

 mentary area — below the coal — there are outcrops of holocrys- 

 talline rocks which probably are part of the base upon which 

 the beds were laid down. 



The workings executed by the La Paz association, according 

 to Centeno, included 6 shafts varying in depth from 22 to 34 

 meters and 5 galleries and crosscuts aggregating 66 meters in 



