68 D. C. Davies—The Millstone Grit of North Wales. 



Southern aspect. The details will be given in my paper " on the 

 relation of the Boulder-clay of the North of England to the great 

 Chalky clay of the South," when published in the Quarterly Journal 

 of the Geological Society. 



VI. — On the Millstone Grit of the North Wales Border. 

 By D. C. Davies, Oswestry. 



THE MHlstone Grit of the North Wales Border follows the 

 eastern slope of the Carboniferous Limestone, from Crickheath 

 and Sweeney, South of Oswestry, to the shores of the Irish Sea ; it 

 is also thrown up into the range of hills which the traveller by the 

 Great Western Eailway may see to the west of the line between 

 Oswestry and Chester. This range serves as a natural boundary 

 between this part of England and Wales, and forms a second line of 

 natural fortification, strengthened on the English side by numerous 

 outposts of low hills of clay, gravel, and sand, which give place, 

 upon the Welsh side, to precipitous escarpments of Moimtain Lime- 

 stone, beyond which the change in the language, dress, and manners 

 of the people is marked and sudden. 



These hills are composed for the most part of an accumulation of 

 sandstones, of very variable superficial breadth, affected as that 

 breadth has been, firstly, by the area of their original deposition ; 

 secondly, by the amount of denudation they have since suffered; 

 thirdly, by the extent to which they are covered by the Coal 

 Measures ; and fourthly, by the disturbances which have elevated the 

 sandstones and the Coal Measures, leading to the subsequent denu- 

 dation of the latter from off their surface. Thus, in the southern 

 half of its course, say, from a point south-west of the town of 

 Wrexham to Sweeney, the Millstone Grit presents the appearance of 

 a continuous band of variable breadth, while, in its northern con- 

 tinuation, through a country crossed by numerous faults, it appears 

 in disjointed patches, among the Coal Measures, as well as in a main 

 band following the course of the Limestone towards Mold, Holywell, 

 and the sea. 



By the construction of a branch line from the Cambrian Railway, 

 a most instructive section of the Grit has been exposed at Sweeney, 

 perhaps the most complete hitherto obtained. By a reference to this 

 section (See Woodcut, Fig. 1) it will be seen, that above the main 

 body of Carboniferous Limestone there rests a deposit of coarse red 

 and purple Sandstones, containing layers of pebbles ; this is followed, 

 in ascending order, by a considerable thickness of Calcareous Sand- 

 stones, containing in places thin layers of limestone, and these in 

 their turn are overlain by a series of yellow, mottled, and brown 

 beds ; the whole being capped by a deposit of pinky- white sand- 

 stone, becoming in places pure white. Unfortunately, in this section 

 the junction between the Grit and the Limestone is not seen, owing 

 to a covering of drift, but if we travel a little towards the north- 

 west we find, first, at Treflach, the deep red sandstone beds passing 

 downwards into a purplish calcareous sandstone; and, in Craigforda 



