D. Mackintosh — Drifts of the Borders of the Lake-district. 253 



explained by what Dr. Eobert Brown calls " a monstrous regurgita- 

 tion of waves," caused by ice falling down from tbe tops of cliffs or 

 ridges, and struggling to become launched, at the time when the 

 valleys were occupied by the sea ? 



At one spot, near the lake, on the E. or upstream side of a 

 glaciated boss of rock, a section has been exposed of a deposit of 

 drift. (See Fig. 2.) 



E. of Strands one may see plateaux and knolls of stratified and 

 contorted sand and gravel, with sub-angular stones and boulders of 

 granite from the E., and porphyry from the N". In some places 

 pinel appears underneath. W. of Strands, a fine section of pinel, 

 surmounted by loam, may be seen on the road-side. About a 

 quarter of a mile W. of Strands, the granilite is distinctly striated 

 E. 10° N., which accords with the direction above assigned to the 

 glaciation of the bosses near Greendale. 



Philosophy of Screes. — Wastdale Screes escarpment rises to an 

 average height of about 1,650 feet above the lake. Near the top 

 the slope is about 40°, in the middle 50°, towards the base 40°. 

 The solid rock generally comes half-way down, and the broken rocks 

 or screes run half-way up. The screes are chiefly in deltas, under 

 rakes or gulleys, from which they have been precipitated by frost, or 

 washed down by rain torrents. (See Fig. 3.) In the process of scree- 

 N.w. S.E. 



Roches Moutonn^es. 



Fig. 3. — Section of "Wastdale. 



making, the tops of previously-existing cliffs have been bevelled off, 

 and their bases shored up. At the lower end of the lake the Screes 

 consist of greyish-blue, sometimes nearly black, fine-grained felstone 

 graduating into ill-defined porphyry. Pebbles and boulders from 

 the Screes may be readily traced all the way S. as far at least as 

 Chester, their derivation being witnessed by the peculiar granilite 

 and granite with which they are associated. 



With the exception of a very little comminuted matter, which in 

 some places has been washed clown from above, the Screes have not 

 been mixed with fine sand or clay. They nearly all consist of bare 

 stones. Eain cannot grind stones, and the lake is almost equally 

 incapable, as may be seen at its lower end, where it has thrown up 

 a heap of very small, bare, angular fragments, with three teri'aces 

 marking different water-levels. The brook from Illgill, above 

 Wastwater-foot, has made a section in scree-matter (a part of which 

 it has probably itself brought down), revealing its bare stony 

 character. In the* greater part of the Lake District, the screes are 



