514 British Association Reports. 
that if such pressure could be communicated it would not be effective 
in excavating the lake-basin at Wastdale. On the whole, he con- 
cluded that for a satisfactory explanation of the full effect of ice in 
valleys and lakes it would be necessary always to treat each case as 
a special problem by no means purely geological, but including and 
requiring important and quite practicable mechanical determinations. 
‘Il. On tur Gzorocy or Coarsrooxparz, By the Rey. W. Purton. 
oj UST where the valley of the Severn contracts towards the narrow 
gorge by which it passes through the great Limestone ridge of 
Wenlock Edge, it is met by the lateral valley of Coalbrookdale run- 
ning down from the high table-land which forms the chief part of the 
Shropshire or Coalbrookdale Coal-field. The Dale, which is for the 
most part scooped out of the Wenlock shale, is joined about midway 
down by the Lightmoor hollow through which the railway passes, and 
which is excavated in the Lower Coal-measures, here faulted down, 
and is flanked at its entrance into the Severn valley by the rounded 
hill called Strethill on the north, and by Linceln Hill on the south. 
At Strethill we find that mass of Glacial Drift, 200 feet in height 
above the Severn, which forms the subject of Mr. G. Maw’s paper in 
the Quarterly Journal of the Geological Society, for May 1864, and 
which has served to prove that at one time during the Glacial epoch 
Wenlock Edge was the coast-line of the Irish sea, and the Severn 
Valley a marine strait. At Lincoln Hill, resting on the Wenlock 
Shale, the Wenlock Limestone is seen dipping at a high angle to the 
south. It is now worked in an extensive series of caverns, but in 
the old surface-workings we have an interesting section showing the 
Lower Coal-measures resting on the Limestone in the following 
order :— 
. Impure sandy limestone. 
. Limestone (chalkstone) 12 feet. 
Conglomerate and sandstone, 18 feet, 6 inches. 
. Clunch, with balls of sandstone, 18 feet. 
Coal, ‘ Lancashire Ladies,’ 6 inches. 
More clunch and sandstone, 12 feet. 
A red and yellow ‘ pimply’ rock, about 4 feet. 
Whitish sandstone, 1 foot 8 inches. ‘ Crawstone Measure Crust.’ 
“Crawstone ’ ironstone, 3 feet. 
Sandstone, ‘ Flint Coal Flint.’ 
A walk of about a mile through the woods on the same side of the 
Dale will bring us to the quarry in Lightmoor Wood. Here we see, 
first, a white and brown Sandstone with plant-markings, 5 to 6 feet 
thick ; the Crawstone-measure crust; then the Crawstone ironstone; 
above this a whitish Sandstone with fossil stems and roots of trees 
(Sigillaria and Stigmaria). It was from this quarry that the large 
fossil tree now in the possession of H. Whitmore, Esq., M.P., which 
was figured in the ‘ Illustrated London News’ some two years ago, 
was procured. This last stratum is much stained by petroleum with 
which the rocks are saturated. Above it lies the ‘Little Flint’ coal, 
SO WADI OOOH 
HI 
