1848.] Proceedings of the Asiatic Society. 705 



distance ftom the Penclawdd seam, which is one of the lowest in that series. 

 During the present year another boulder of cannel coal, was discovered in 

 the Penclawdd seam, which the workman who found it positively affirms to 

 have been in the vein of bituminous coal. The boulder is 13 inches long, 

 7 wide, and 3 thick, one corner having been broken off after it had become 

 rounded by attrition, probably a short time prior to its arrival at the spot 

 in which it was found ; a siliceous cement has coated a part of the surface of 

 this fracture, has filled the cavity caused by another fracture and also attach- 

 es a piece of rock to the boulder. The Penclawdd five feet vein, is about 300 

 yards in geological position below the quarries of the Town Hill sandstone, 

 and throughout this depth there would appear to be frequent instances of 

 drift and false beds of coal : in some specimens the pebbles of the older or 

 drift coal having from their greater hardness, penetrated into and distorted 

 the drift plants, which have since become coated with the newer coal. One 

 or two other pieces of cannel coal have been found at Penclawdd, but as 

 these were discovered in the heap of bituminous coal, after it had been raised 

 to the surface, and from exposure to the air had heated, and slacked, they 

 may have originally formed parts of large boulders, and their present angular 

 form is no certain proof of their having been derived from other beds in the 

 immediate locality. In the subjacent measures of the South Wales coal 

 field, some seams associated with regular seams of cannel coal are known to 

 exist about 700 yards below the Penclawdd vein, and laying conformably with 

 it. In alluding to the boulder he discovered Mr. Logan remarks : 



" To suppose that the boulder is derived from the lower seams, after they had 

 been indurated, converted, and crystallized, would, it is apprehended, be carry- 

 ing the age of the whole deposit to the extent that has never yet been conceived 

 and is perhaps inadmissible for it is not easy to account for any mode in which 

 a fragment of them, without a disturbance of the stratification, which yet exhi- 

 bits none of a requisite order, could be displaced and conveyed to the newer 

 beds whilst forming. It is therefore, safer to refer the boulder to some anterior 

 deposit of coal, perhaps no longer in existence.* To attempt to determine 

 whether these boulders of cannel coal are derived from the lower measures, 

 or from some anterior deposit, I have not been able to collect sufficient data, 

 but some pieces of the top stone of the Penclawdd vein may be interesting, 

 as they show that a conglomerate of small pebbles of ironstone, apparently 

 identical in quality with the large deposits of ironstone of the lower mea- 

 sures, has been deposited within a few inches of the top of the Penclawdd vein 

 of coal. If the boulders have been derived from the lower veins of the 



* See Journal for January, p. 60, in which, with reference to our Indian Ball Coal, 

 the same view is expressed.— H. P. 



