T. Mellard Reade- — JEolian Sandstone. 197 



perfectly indistinguisliable from the Twt Hill rock," which he holds 

 to be unconformably overlaid by black Cambrian shales, and thus 

 according to his view proving the Pre-Cambrian age of the grit. 

 In company with Prof. Hughes, I visited these quarries towards the 

 close of last year. We found the conglomerate and grit and the 

 black shales against them, but saw no unconformability. The black 

 shales crushed and broken at the junction are faulted against the 

 conglomerate in the manner shown in Fig. ?>. 



Fig. 3. Section in Quarry \ E.S.E. of Nebo, Amlwch. 



a. Black slate, b. Jointed and veined grit conglomerate in parts. /. Faidt. 



In the larger quarry the grit and conglomerate are much'traversed 

 by joints running in the same direction as the fault, which joints 

 might easily be mistaken for lines of bedding, and the shale would 

 then appear to be resting on the " upturned edges " of the con- 

 glomerate. These sections, therefore, do not bear out Dr. Callaway's 

 interpretation. 



3. About a mile and a quarter from Llanerchj'medd, on the S.W. 

 road, not far from Bryngwallen, the granitoid series is exposed in a 

 quarry on the S. side of the road. On the opposite side, in a field, 

 about 50 yards from the road, another quarry has been opened in 

 beds of grit and conglomerate. The latter is composed of pebbles 

 of quartz, imbedded in a matrix containing crystals of pyrites, and 

 resembles in all respects the conglomerates of Penlon, Nebo, and 

 Twt Hill. It passes up, as does the conglomerate in the other 

 sections, into grit and sandstone. The sandstone only a few feet 

 from the conglomerate includes a fossiliferous band containing 

 Ortliides. This fixes the position of the sandstones and with them 

 the quartz conglomerate into which they pass. Even if it be 

 denied that this conglomerate and the Twt Hill conglomerate are 

 identical in spite of their singular resemblance to one another, this 

 discovery removes the only really strong a priori argument against 

 referring the Twt Hill bed to the Cambrian series, viz. the absence 

 of felsite pebbles. The Bryngwallen conglomerate, which passes 

 up into fossiliferous sandstone, is composed of pebbles of quartz, 

 imbedded in a felspathic matrix and is not distinguishable in the 

 field from the Twt Hill conglomerate. 



III. — ^OLiAN Sandstone. 

 By T. Mellard Eeade, C.E., F.G.S. 



AS bearing upon the subject of Mr. J. Arthur Phillips's interest- 

 ing and valuable paper in the last number of the Quarterly 

 Journal of the Geological Society, entitled, " On the Constitution 

 and History of Grits and Sandstones," a description of a cliff section 

 of blown sand now to be seen on the coast at Crosby may not be 



