664 GEOLOGY. 



with the first extant monuments of organic life, which have not hitherto been discovered 

 in the Cumbrian district, though the same strata are there extensively developed. The 

 division includes the high mountains of Carnarvonshire and Merionethshire, where the 

 slates are abundantly interstratified with masses of porphyry ; and where south Britain has 

 its loftiest elevation, Snowdon rising to the height of 3557 feet. In this series of strata, 

 both in Wales and Cumberland, the richest metalliferous veins occur, excepting the lead 

 and iron ores of the carboniferous system. Greenwich Hospital receives a large revenue 

 from the estates of the unfortunate Earl of Derwentwater, transferred to that esta- 

 blishment upon their forfeiture to, the crown, and which abound in productive lead ore. 

 Corresponding strata in Brittany and the Hartz are also highly metalliferous. The 

 upper components of the system, the Bala limestone, consisting of a vast thickness of 

 dark laminated beds in Wales, present many fossil remains of a few species, but none 

 have been found in those patches of the strata which occur in Westmorland. The Plyn- 

 lymmon Rocks, hard, slaty, fine or coarse-grained, occupy the greatest part of the chain 

 of the Berwyns, of which Plynlymmon is the central mass. They have few metallic 

 riches, and appear to be nonfossiliferous. 



The whole region of the slates exhibits a magnificent physiognomy, having been 

 largely invaded by the igneous rocks, which have variously elevated the strata, and burst 

 through them in great masses, or flowed into them, forming inter-stratifying layers and 

 dykes. " Supported by granite," says Phillips, " and mixed with igneous masses, the 

 slaty rocks of the English lakes rise to more than 3000 feet in height, and present a 

 variety of outline and intricacy of combination which, in connexion with clear lakes and 

 considerable waterfalls, leave to Switzerland little superiority." At Burrowdale, Scaw- 

 fell, Patterdale, and Helvellyn, the slate is associated with greenstone, amygdaloid, and 

 argillaceous porphyry, which constitute the towering crags and lofty precipices of those 

 districts, and form the rocks over which the cataracts fall. The contour of Snowdonia 

 exhibits a similar style of landscape, and indicates the amazing energy with which 

 disturbing causes have acted upon it, the intruding porphyries here, as in Brittany, 

 Cornwall, and in the Lammermuir Hills on the southern boundary of the plain of the 

 Lothians, having been subject to subsequent disturbance equal to that of the strata. 

 " We began a toilsome march," says Pennant, speaking of his ascent of Snowdon," clam- 

 bering among the rocks. On the left were the precipices over Cwm (valley) Brwynog, 

 with Llyn (the pool) du yr Arddwy at their foot ; on our right were those over the 

 small lakes Llyn Glas, Llyn y Nadroedd, and Llyn Cock. The last is the highest on 

 this side of the mountain, on whose margin we were told that, in fairy days, those dimi- 

 nutive gentry kept their revels. This space between precipice and precipice forms a 

 short and no very agreeable isthmus, till we reached a verdant expanse, which gave 

 us some respite before we laboured up another series of broken crags ; after these is 

 a second smooth tract, which reaches almost to the summit, which, by way of pre- 

 eminence, is styled y Wyddja, or the conspicuous. It rises almost to a point, or, at 

 least, there is but room for a circular wall of loose stones, within which travellers usually 

 take their repast. 



" The mountain from hence seems propped by four vast buttresses, between which are 

 four deep cwms, or hollows : each, excepting one, had one or more lakes lodged in its 

 distant bottom. The nearest was Ffynnon Lias, or the green well, lying immediately 

 below us. One of the company had the curiosity to descend a very bad way to a 

 jutting rock that impended over the monstrous precipice, and he seemed like Mercury 

 ready to take his flight from the summit of Atlas. The waters of Ffynnon Lias from this 

 height appeared black and unfathomable, and the edges quite green. From thence is a 

 succession of bottoms, surrounded by the most lofty and rugged hills, the greatest part of 



