270 



THE GEOLOGIST. 



Lake district. Taking the moraine of Llyn Idwal as one of several examples, 

 he shows that it is situated at about one thousand feet below the elevation 

 attained b y the Northern Drift. Now if this moraine had been formed previous 

 to the deposition of this marine deposit (which attains an elevation of two 

 thousand three hundred feet), it would most certainly have been entirely 

 obliterated. It is, therefore, evident that moraines of this kind belong to a 

 period subsequent to the Northern Drift. Bearing this in mind, and recollecting 

 the clear evidence which the roches moutonnees, frequently enclosed by marine 

 drift, afford of having been formed by glaciers before the deposition of the same 

 formation, we have here a sequence of three distinct, though connected, periods: 

 the first, in which the glaciers descended down the main valleys ; the second, 

 when the land of Wales had sunk at least two Ihousand three hundred 

 feet, during which the till or drift was spread over the flanks of the mountains; 

 and the third when the land had been elevated, and glaciers again descended 

 from the heights ploughing out the drift, and forming moraines for embankments 

 to lakes and tarns. 



The striations of the rock-surfaces of Anglesea appear to be altogether dis- 

 connected with the glacier system of Caernarvonshire. The striae and grooves 

 generally range west thirty degrees south, and are probably the result of ice- 

 bergs stranding and scoring the bottom as they floated from the mountains of 

 Westmoreland. 



The existence of former glaciers amongst the mountains of Westmoreland 

 and Cumberland have been announced by Agassiz and Buckland. Both these 

 authors, notice in several localities on the southern and eastern sides of the 

 district, examples of scored and grooved surfaces, and the mammilar bosses 

 which occur at Penrith and Windermere. The author thinks, however, that 

 Dr. Buckland has extended the glacial theory frequently beyond its true limits, 

 and has mistaken, in the valley of the Eden, Walney Island, and elsewhere, 

 remarkable forms of drift-gravel and boulders for glacial moraines; and altogether 

 dissents from the astounding supposition that a glacier stretched from the 

 skirts of Shap Fell across the valley of the Eden, by means of which the granite 

 blocks were distributed over the high table-land of Stainmore Eorest, and the 

 valley of the Tees. 



The rocks of a large district surrounding the interior mountains are remark- 

 ably ice-moulded, polished, and striated, as far as the head of Morecombe Bay 

 to the south, and the vale of the Eden to the north ; and the drift, a marine 

 boulder-clay, rises to the height of one thousand two hundred feet on the 

 southern slopes of the hills. 



Several well-marked moraines may be observed at elevations considerably 

 below the upper limit of the drift. All those occupying this position must, in 

 consequence, be of more recent date than this marine deposit. Of examples of 

 this class, the most remarkable is the large terminal moraine at the lower ex- 

 tremity of Grisedale. This gorge, one of the most desolate and savage in 

 Cumberland, descends from the heart of Helvellyn towards the head of Ulles- 

 water. The rocks of porphyry which form the bottom and flanks of the valley, 

 up to an elevation of about five hundred feet on either side, are remarkably 

 ice-moulded, affording numerous examples of perched blocks and lateral moraines. 

 Striations are not, however, of frequent occurrence, owing to the nature of the 

 rocks. On descending towards the mouth of the valley, "the terminal moraine 

 arrests the attention, and appears like a congeries of large rounded hummocks, 

 strewn with boulders, rising up the sides of the valley to about one hundred 

 and fifty feet above the bed of the river. After the melting of the glacier, this 

 moraine, in all probability, produced a lake. But the torrent has hewn a 

 channel and levelled the ground over a breadth of about one hundred yards. 



The position of this moraine is not more than six hundred feet above the sea- 



