EDEN VALLEY AND YORKSHIRE-DALE DISTRICT. 63 



tain horizon, have heen carried far to the north of the nearest rock 

 of the kind in place, and borne up hill to a point considerably above 

 that reached by any of the parent rock in the neighbourhood. One 

 of these boulders occurred at Lad Gill, near the Tan -Hill colliery, at 

 an elevation of about 1600 feet above the sea. 



Other striae pointing in a generally north-north-easterly direction 

 are found on "Whitsundale Edge, and on the north side of Bakstone 

 Beck ; these are proved to have been caused by northward-flowing 

 ice, by blocks of Millstone-grit having been carried across the Beck 

 northward to rocks lower in the series. No other rock of the kind 

 exists in place nearer than some which occurs in Teesdale, with the 

 exception of that which is faulted in the valley of the Eden at the 

 foot of Stainmoor : this grit, however, is much stained by Permian 

 influences, so that blocks of it may be distinguished at a glance from 

 any of the Swaledale Millstone-grit. 



At Tan-Hill colliery, and on a hill a little to the north of it 

 named Grey-grits on the Ordnance six-inch maps, several well-stri- 

 ated rock-surfaces occur, with the scratches ranging in a generally 

 north-easterly direction. The central line of watershed of Northern 

 England passes through part of this ground ; and although there is 

 no marked kind of rock in the drift to show which way the ice-sheet 

 moved here, it amounts almost to a certainty that it came from the 

 higher ground to the south-west — because in the opposite direction the 

 surface gradually slopes for miles to the north-east, and there is no 

 high ground again in that direction nearer than part of the Durham 

 end of the great ridge that extends eastward from Cross Eell. 



To the east-south-east of the strise-bearing ground just mentioned 

 lies the head of the comparatively wide dale known as Arkendale. 

 The upper part of this widens out and merges into the slightly 

 undulating tract of moorland most of which goes by the name of 

 Stain moor. The hills on the north side of Arkendale Head bear 

 sets of strise which have a generally north-easterly direction ; the 

 form of the ground shows that the ice that produced these must 

 have flowed right across the Dale and over the north side of it into 

 the basin of the Tees. The striae in the other parts of Swaledale 

 included in the map do not call for any particular mention : most 

 of them show clearly enough that, away from the influence of the 

 great icy stream that flowed northward from the high ground 

 about the head of the dale, the lower ice tended more or less to flow 

 in the direction of the principal valleys. 



The details of the glaciation of the Dale district have been dwelt 

 upon at greater length here than their importance might at first 

 sight seem to warrant, because it was desirable to prove where the 

 ice sheet that swept across the hills and valleys of Eastern Lanca- 

 shire had its line of departure. If this can be made clear, and it 

 can be shown that another similar ice sheet started from the same 

 line of high ground, flowed alike over wide dales and high fells, and 

 finally crossed from the basin of the Swale into that of the Tees on 

 Stainmoor, many of the difficulties that are met with in accounting 

 for the distribution of the Eden-valley drifts will be removed. 



