Merionethshire and Denudation. 321 



fi cations, and of the Carboniferous series, all of which 

 have been much disturbed and extensively denuded. 



The Cambrian rocks of Merionethshire, for example, 

 marked 2 on the map, were once buried deep beneath 

 more than 20,000 feet of Lower Silurian strata. Let any- 

 one climb to the rugged centre of this Cambrian area, and 

 stand on the summit of the great grit-formed cliffs of 

 Ehinog-fawr or of Y-Grraig-ddrwg (the bad cliff). From 

 thence turning to the south and south-east, he will see 

 the long ridgy peaks of the interstratified felstones and 

 ashes of Cader Idris and Aran Mowddwy, further north- 

 east the serrated edges of Moel Llyfnant and the 

 Arenigs, and the circle is continued on the northern 

 side of the Cambrian strata by the noble heights of the 

 Manods and the Moelwyns near Ffestiniog and Port- 

 madoc. On three sides the great anticlinal boss of 

 Cambrian grits is set in a curved frame of Silurian 

 slates and volcanic beds, and on the fourth it is bordered 

 by the sea. All these rocks, and much more besides, 

 once overlaid the Cambrian beds, in the form of a great 

 anticlinal curve, and have since been removed by denu- 

 dation ; and thus it happens that between the estuary of 

 the Mawddach below Dolgelli, and that of Traeth- 

 bach at Portmadoc, we find this inner group of gritty 

 hills, more than half enclosed by that somewhat distant 

 ring of higher mountains, which are highest, as a rule, 

 simply because of the hard quality of the great inclined 

 beds of porphyries, of which they are so largely com- 

 posed. (Fig. 62.) 



In this brief account of a fragment of North Wales 

 of about 1,200 square miles, lies the essence of the 

 matter, for with differences of detail, the whole of 

 the strata suffered an equal amount of disturbance and 

 denudation, and the history simply comes to this. Much 



