480 



THE GEOLOGIST. 



elevation of about 800 feet above its waters (estimated), were found 

 to be all clearly ice-moulded, that is to say, worn down into smooth 

 mamraillated bosses, often showing striations or grooves ; but above 

 this line, which appeared very constant for a long distance, the rocks 

 assume the form of crags, sharp and precipitous. (See figure.) 

 The contrast here alluded to may be well observed on the flanks of 

 the rock-masses west of Greendale. And if we suppose that it marks 

 the upper limits of the glacier, we have a measure of the thickness 

 of the ice at this point. The level of the lake is 160 feeb above the 

 sea, and its depth 270 feet, or 110 feet below this. This would give 

 for the total thickness of the ice 800 + 270= 1070 feet, and for its 

 surface, 800 + 160 = 960, or 1000 feet above sea-level. By similar 

 admeasurements, it is probable the thickness of all the extinct glaciers 

 may be calculated.* The length of the glacier (measured from its 

 nevee, at Wastdale Head, to the point where the first traces of 

 glaciation were observed) appears to have been upwards of six miles, 

 and it had its source amongst the snow-clad heights of Scawfell, Yew- 

 barrow, Kirkfell, and Great Gable. From these reservoirs also pro- 

 ceeded, in all probability, glaciers into Ennerdale, Crummockdale, and 

 Borrowdale. 



In Wastdale, there is a remarkable scarcity of some of the more 

 prominent productions of glaciers, at least as compared with many of 

 the neighbouring valleys. There is very little drift, or moraine 

 matter, with one exceptional case presently to be noticed, and perched 

 blocks are of rare occurrence. In general, the native rock is bare, but 

 invariably iceworn from the water's edge up to the limit already 

 assigned. 



But the large moraine which has been thrown across the valley 

 near its entrance, and which forms the embankment for the lake, 

 amply compensates for the absence of these glacial monuments in other 

 parts of the valley. Viewed from above, it looks like an artificial 

 bank, as its upper surface has been levelled, and planted with trees. 

 It is nearly 500 yards in length, with a breadth varying up to 100 

 yards, and a height of sixty feet above the surface of the lake. The 

 water finds an outlet in a channel between the southern end of the 

 moraine and the base of the Screes, which here tower aloft to a height 

 of about 1000 feet, a wall of beetling cliffs. I satisfied myself, by a 

 careful inspection, that this bank, to which the lake, at least partially, 

 owes its existence, is a true terminal moraine. It is either this or 

 man's work, and the latter it certainly is not. It is composed of 

 gravel and sub-angular or rounded pebbles in a clayey matrix, also 

 enclosing large blocks of porphyry and other rocks. To the south, it 

 terminates, as already stated, opposite the base of the Screes, and its 

 northern extremity reposes upon ice-moulded bosses of syenite. The 

 period at which this moraine was thrown across the valley was pro- 

 bably that third stage in the changes of the Glacial Epoch, when, after 



* Similar admeasurements have been made in North Wales by Professor 

 Ramsay, — Peals, Passes, and Glaciers. 



