X, A, 5 Pratt: Persistence of Philippine Coal Beds 295 



evidence of fracture or displacement, but nearer the mouth, and 

 especially in the vicinity of the main fault, the rocks vi^ere 

 disturbed, slickensided, and broken. It is estimated that the coal 

 had been displaced by this fault through a distance of about 40 

 meters measured along the fault plane. 



Once having reached the coal beyond the fault, the tunnel was 

 advanced as a stope (driven in parallel) on the full dip of the 

 bed and carried 98.4 meters farther when old workings were 

 encountered (fig. 2). It was concluded that the old workings 

 probably had been driven up the dip from the face of the long 

 Spanish transversal tunnel which, therefore, must have reached 

 the bed as the records show. Unfortunately it became necessary 

 to suspend the exploration at this point, although the results of 

 the work so far completed had been fairly satisfactory. 



At the outcrop of the faulted block the bed has a thickness 

 of 5.60 meters between roof and floor, both of which are sandy 

 shale and sandstone. About 4.75 meters of this is coal, of 

 which 4.6 meters could be removed economically in mining. 

 There are several parting planes, and there is one narrow parting 

 of carbonaceous shale. About 0.2 meter of carbonaceous shale 

 near the middle of the bed, and 0.6 meter of carbonaceous shale 

 and thin coal at the bottom, would have to be removed as waste. 

 In the driving of the tunnels the middle coal was mined by re- 

 moving the central layer of carbonaceous shale. This permitted 

 the upper coal as high as the parting to fall, after which the 

 lower coal was taken up down to the lower parting. 



The changes which the bed manifested as the work advanced 

 are shown clearly in the accompanying sections (fig. 3). The 

 bed where first encountered beyond the fault is only 3.5 meters 

 thick between floor and roof and contains only 1.95 meters of 

 coal. At the face of the slope, farther down the dip, the bed is 

 still thinner — 2.7 meters between floor and roof — but the thick- 

 ness of the coal is maintained fairly well at 1.91 meters. Thus, 

 while the general tendency is toward a gradually reduced thick- 

 ness of the bed, the coal itself suffers little diminution below the 

 position of the fault and becomes freer from intermixed shale. 

 The only evidence of disturbance beyond the first fault was a 

 slight roll, undoubtedly the result of a movement too restricted 

 in extension to cause a true fault. However, the conditions of 

 deposition appear to have varied alarmingly within a short dis- 

 tance, and the desired constancy is not proved. 



The outcrop of this bed of coal can be traced but a few 

 meters. Yet a kilometer away along the strike exploration was 

 started on two other outcrops adjacent to each other, each of 



