1872.] TIDDEMAN ICE-SHEET IN NOETH lANCASHIRE ETC. 477 



eighteen inches or two feet. Most remarkable examples of this, to 

 which Mr. Hughes first called my attention*, occur on JSTorber ; and the 

 Silurian boulders there, some of which must have been brought from 

 lower levels in thecountrynorth of them,appear to have a rude arrange- 

 ment along lines which coincide with the- direction of the scratches 

 and the line in which they must have travelled fi-om the parent rock. 



North, southj and west of Settle many scratches are to be found. 

 They have nearly all a general north-and- south direction. Some of 

 them may have been produced by later glaciers, lying as they do 

 along the bottom of the valley ; but others are at elevations up to 

 1300 feet, and, taken with the scratches on Ingleborough, on the other 

 side of the Eibble valley, would imply a glacier eight miles broad and 

 750 feet deep. A point worthy of notice is that these scratches are 

 taking a course parallel to the general direction of the watershed, 

 which is not two miles to the east of them. 



Bowland Knotts.- — From the Central Fells south of Ingleborough a 

 long ridge dividing the Lune and Eibble drainage strikes east towards 

 the Eibble valley near Settle. It is composed of the lowest bed of 

 the Millstone Grits, dipping gently north. Along its edge are many 

 bold and picturesque bastions of rock, forming a :fine foreground to 

 the beautiful panorama of the Pennine chain which is seen from 

 here. Close to the highest point, which is crossed by a mountain- 

 road running from Clapham to Slaidburn, on a prominent bluff of 

 conglomerate, I found the most remarkable evidences of ice-action in 

 the whole district. Scratches were seen under drift at an elevation 

 of 3400 feet; the direction was S. 15° E. across the ridge. On 

 another rocky eminence, one third of a mile south-east of the first are 

 more scratches, on the southern side of the ridge ; their direction is 

 S. 5° E., and the elevation is about 1325 feet. 



If these were produced by a local glacier, what were its gathering- 

 grounds ? Not the Fells immediately west ; for then the scratches 

 woiild be at right angles to their present course. Looking along 

 them to the north, the nearest ground even equalling this in height is 

 a portion of Ingleborough seven and a half miles distant; and between 

 this and that lies a broad valley excavated to the depth of about 

 1000 feet. Ingleborough, with its 900 feet only of additional height, 

 could hardly fill up that valley and make itself felt at that distance. 

 If we look south again along the scratches, there is no ground of equal 

 height to help us nearer than Pendle Hill, at ttuelve miles distance, 

 and across tiuo broad valleys. The height at which these scratches 

 occur across this ridge is greater than the height of some of the passes 

 across the Fells to the west of it. There can be very little doubt 

 that the ice-stream passed entirely over these Fells. 



In the broad valley between Ingleborough and Bowland Knotts, to 

 which I have just alluded, are two distinct sets of scratches at right 

 angles to one another. One runs south-east, the other south-west. 

 The south-east set were probably made when the ice-sheet was not 

 at its maximum, i. e. when there was not sufficient lateral pressure 

 or " shouldering" to thrust the ice over Bowland Knotts, and when 



* " Notes on the Geology of parts of Yorkshire and Westmoreland," Proc. 

 Geol. and Poht. Soc. of the West Eiding, 1867. 



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