of South Wales near Pontypool. 435 



this promontory, is a corresponding fault of' about 220 feet passing- up the 

 ravine in a parallel direction to the fault on the north side of Pen y Tranch. 

 So far as the present survey carries us, the three or four principal faults 

 pass apparently along- the troughs of the valleys. Without entering upon the 

 debatable ground of the origin of valleys, and the agency of existing causes 

 in modifying the earth's surface, we have certain facts, by no means unim- 

 portant in the controversy, showing that extensive fissures range along those 

 ravines, or, by a transposition of terms, that the rivers have formed their 

 channels in ancient fissures. 



Thicknesfi of Strata. — The series of beds exhibited is probably not less than 

 1800 feet thick above the limestone. Within this space are about 20 beds of 

 coal, varying in thickness from 1 to 10 feet, and amounting in the aggregate 

 to about 60 feet. Not more than 6 of these are usually worked ; the greater 

 portion of the mineral treasures being comprised within an inconsiderable part 

 of the general section. At Abersychan the principal workable beds are con- 

 tained in a thickness of 119 yards, at the bottom of the series. They consist 

 of 13 beds of bituminous coal, of the aggregate thickness of 42 feet 8 inches, 

 and will readily supply upwards of 30,000 tons per acre. Alternating with the 

 coal-seams are numerous courses of argillaceous iron ore, capable of supplying 

 15,000 tons of mine per acre. 



Almost all these beds, whether of iron ore or of coal, bear different names 

 in different localities. This is not remarkable, when we observe the variations 

 of position and thickness at inconsiderable distances in what are considered 

 to be the same veins. On placing, side by side, several sections derived from 

 iron-works in this neighbourhood, it will be seen that in the thickness of the 

 mineral series, collectively, there is a certain agreement ; but that in the po- 

 sition of the members of the same series, indwidually, there are frequently 

 striking variations ; the coal-beds being often widely separated at some points, 

 and at others, brought either almost into contact, or new veins are introduced. 

 This will be best exemplified by a series of sections, which, when reduced to 

 a common scale, admits of ready comparison. 



Aggregate thickness of the strata containing the principal mineral and coal 

 beds, from the "Bottom Vein Mine" to the " Black Pins" inclusive: 



Yds. Ft. In. 



At Abersychan and Pen Tvvyn Works 119 2 



. ,, ., , fist section 119 1 5 



At Verteo;, two miles north s 



° l2nd section 120 2 6 



At Blaen Afon, four miles north 154 4 



At Coalbrook Vale, six miles north-north-west 127 2 G 



At Rumney Vale, ten miles north-west 215 2 2 



