WATSON THE HJ]iIATITE DEPOSITS OP GLAMORGANSHIRE. 245 



in South Wales," the dolomitic coDglomerate is classed with the 

 poikihtic or new red sandstone series, and a lithological resemblance 

 is pointed out between this rock and consolidated beaches, the 

 resemblance being further traced in their mode of occnrrence. Messrs. 

 Buckland and Conjbeare, also, in their notice of the south-western 

 coal -districts of England, observe that the conglomerate ''generally 

 forms a thick bank or talus near the base of those hills from the 

 debris of which it has been derived ; while at a distance from them 

 it grows thinner, and at length wholly disappears." But, without 

 actually dissenting from the presumed beach-origin of the conglo- 

 merate, I submit that the recent mining excavations in the neigh- 

 bourhood of Llantrissant and Llanharry, as well as the openings 

 and sections at Newton Nottage, exhibit so much evidence of former 

 denudation, that there is strong reason for believing that the patches 

 and thin coverings of the magnesian rock now presented to us, are 

 merely the remains of a thicker formation, which has been attenu- 

 ated to its present condition by aqueous causes ; and, following up 

 this view, there is nothing, in the absence of palseontological grounds, 

 to show why this rock, which is notably magnesian in its composition 

 should not be the representative of the magnesian limestone of true 

 Permian age in the North of England, and be wholly unconnected in 

 time with the overlying sands and marls at the base of the lias. This 

 reasoning seems further supported by the frequent cases of uncon- 

 formabihty in the position of the latter group of rocks. In the 

 absence of organic tests, it is fair to assume, all other things being 

 equal, the contemporaneity of formations lithologically related, though 

 not identical. 



The outliers of the lias, and the scooped-out surface of the dolomite, 

 where exposed in section, and where the hollows are seen filled with 

 drift-gravel, mark periods of destruction. And to these we have 

 additional witnesses in the loose blocks of the conglomerate which 

 fret the surface of such situations as Newton Nottage Downs, and 

 the blocks of fine soft pinkish-white argillo-quartzose stone which 

 occur scattered over the western part of those downs,* If we follow 



* This rock, mostly in a disintegrated state, often occupies hollov/s in the lime- 

 stone, where it is considered to be in situ, and it is questionahle whether it does 

 not belong to the Millstone-grit or its equivalent. In North Staifordshiie, the 



