480 
THE GEOLOGIST. 
elevation of about 800 feet above its waters (estimated), were found 
to be all clearly ice-raoulded, that is to say, worn down into smooth 
mamroillated 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 feet 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 productfons 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 cliflTs. I satisfied myself, by a 
careful inspection, that this bank, to w^hich 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 
gTavel and sub-angular or rounded pebbles in a clayey matrix, also 
enclosing large blocks of porpliyry 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, Pusses, and Glaciers. 
