55 



which was several hundred feet in diameter, and but little dis- 

 turbed from its original nearly horizontal position. 



It should be remarked, that while the under surface of the coal 

 resting almost in contact with the primary rock, assumes its un- 

 evenness of outline, the upper surface is also affected by similar un- 

 dulations, though to much less extent, which only goes to show that 

 the deposition of the coal did not sufficiently fill up the original 

 inequalities upon the floor, to make a perfectly level surface for the 

 reception of deposites which succeeded. 



Of the nature of the dislocations or faults, too little is at present 

 known to enable one to generalize or say much upon this truly im- 

 portant topic. The greatest number of pits being upon the eastern 

 border of the coal field, it is there that the faults or troubles, as they 

 are generally denominated in this region, are best seen. Along 

 this outcrop of the coal, there would seem to extend over a great 

 space one or more very remarkable lines of dislocation, throwing 

 up the coal to the west by a heavy fracture, so as to make of the 

 same seam a double outcrop, and over a distance of perhaps half a 

 mile, bringing the subjacent granite itself again into view. We wit- 

 ness, therefore, over a portion of the eastern side of the coal field, 

 two parallel ranges of collieries, less than a fourth of a mile asunder. 

 The Black Heath mines, the Union mine and the Deep run pits 

 are said to lie along the outer crop, though it is questionable 

 whether one and the same fracture extends over so many miles of 

 strata. The probability is, that several nearly parallel fractures will 

 be found traversing this side of the region, and tending to the in- 

 tricacy and difficulty of successful mining. In fact, three extensive 

 faults affect the strata near the Black Heath mines, the outer one 

 causing the upthrow before stated, and the others producing heavy 

 downthrows to the west. 



It would seem, that transverse to these more important and 

 serious fractures, which generally pursue a direction nearly parallel 

 to the general line of outcrop of the coal, there are innumerable other 

 more trivial breaks and displacements, sometimes straight, but of- 

 tener irregular in direction and dip, which still further intersect the 

 strata, dividing them into a multitude of nearly detached and broken 

 basins. An exact knowledge, more particularly of the great lon- 

 gitudinal faults, is especially desirable for directing with system the 

 mining operations of this coal field. 



There is one general fact of much practical interest disclosed in 



