560 
which is Grantley Lake. At this point there has been a 
violent upheaval. For at the south side of the Lake, in a 
quarry on the top of the hill, the rough grit is seen to dip 7° 
to the west. About sixty yards to the east of this, the 
arenaceous flags are thrown up, and dip at an angle of 37° 
west. Between the quarry and the lake there is a precipi- 
tous descent of two hundred feet, down which the rocks have 
been thrown in wild confusion, which is now partly concealed 
with the overgrowth of trees. Although all the valleys in 
this district were to some extent modified during the glacial 
period, and in the time which has elapsed since, it seems to 
me that their general forms were pretty much the same 
before the glacial period as they are now, and that their 
denudation has been going on at least from the period of the 
lias. The Oolitic hills of east Yorkshire were not improbably 
derived from the slow disintegration of the hills of west 
Yorkshire. As these rose slowly from the sea, their upper 
parts would be exposed to the action of rain and rivers, their 
sides and ends to the action of the waves. In the elevation 
of these hills there were probably many pauses, the result of 
which would be to produce a series of raised beaches with 
intermediate slopes and cliffs, such as are readily traceable 
along the sides of "Wensleydale ; and upon which there would 
at that time be left masses of sand, shingle, and boulders, 
such as are now found on any rocky coast. The amount of 
material which has been carried away by the denudation of 
the deposits under consideration, is at least equal to that 
which is now left in these districts. In Nidderdale, between 
Brimham and Guy's Cliff, the whole series has been cut 
through, so that at the bottom of the valley near Dacre the 
Scar limestone appears. 
One reason for thinking that these valleys were excavated 
before the glacial period is this : upon the Magnesian lime- 
stone, and partly upon the red grit, there is a bed of glacial 
