706 Proceedings of the Asiatic Society. 



series, they may probably have been supplied from partial destruction of the 

 lower measures at the south-west corner of the basin, previous to the forma- 

 tion of the veins included in the Pennant series of sandstones. It may have 

 occurred, that during the gradual subsidence of the land beneath the estuary 

 or basin in which the successive strata of coal, sand, and shale have been 

 deposited, communication between such basin and the larger seas have been 

 formed or enlarged, and that the detritus of the lower measures, thus exposed 

 to the action of the sea, has from time to time supplied the boulders and drift 

 during the formation of the Pennant series. The greater coarseness of the 

 Pennant sandstones, and the frequent conglomerates and marks of drift, infer 

 that these deposits have occurred frequently under the action of the rough 

 sea, rather than of the quiet lake, and if the boulders of granite should, upon 

 examination, be found to be equivalent to that of Pembrokeshire, it would 

 rather point to the line of drift. The destruction of a portion of the lower 

 beds before the deposit of the higher, might, as I have ventured to suggest 

 have been effected without disturbing the conformity of the lower and Pen- 

 nant measures on the existing portions of the coal field. The question whe- 

 ther a large portion of the coal measures has or has not been cut off by the 

 anticlinal line of Cefu Bryn, would not affect the suggestion ; as this upheav- 

 ing of the old red sandstone equally distorts the higher and lower measures, 

 and probably occurred when the present coal field was again raised above the 

 level of the waters. But if the suggestion is admitted as deserving of further 

 enquiry, namely, that these boulders are derived from the lower veins of the 

 same coal field, the inference (and a question of considerable interest it is) 

 would follow, that sufficient time has elapsed between the deposit of each 

 vein to allow the perfect crystallization and formation of the vein below 

 it. It also yields information interesting with reference to the ascertaining 

 of the manner of the formation of the coal ; as it would infer, that the ma- 

 terial of which, in this instance, the bituminous vein was formed, was origin- 

 ally too soft and yielding, notwithstanding its present hardness and density, 

 to fracture the boulder during the period of pressure necessary for its forma- 

 tion, and also that the chemical agents acting, or escaping during the formation 

 of the bituminous coal, do not appear to have in any way affected the cannel 

 coal deposited within it." 



It will be noted that Mr. Benson speaks of boulders of Cannel Coal, which 

 renders these facts still more extraordinary. I have not been able to examine 

 our boulders, yet having some other researches on hand which are not yet 

 completed. 



H. PlDDINGTON. 



