574 MR. A. R. DWERRYHOUSE ON THE GLACIATION OF [ Aug. 1902, 
the opposite side of Herdship Fell. Langdon Beck, the only important 
tributary of Harwood Beck, rises on the high ground between 
Teesdale and Weardale, in the neighbourhood of Ireshope Moor. 
Below the junction of Harwood Beck the Tees is again confined 
by the basalt-rocks of the Whin Sill (which has been let down by a 
fault), and emerges to plunge over the edge of that Sill at High 
Force (1).! 
Below this point Teesdale is much more open, but the river has 
a very steep fall. The western side of this section of the Dale is 
bounded by the precipitous escarpment of the Whin Sill, and the 
eastern side is also steep (fig. 3). 
Fig. 3.—Section through Newbiggin (Teesdale). 
[Vertical seale=twice the horizontal. | 
Several small streams join the Tees on both banks between High 
Force and Middleton-in-Teesdale, and about a mile below that 
town the River Lune comes in. At Middleton-in-Teesdale itself, 
Hudeshope Beck joins the Tees. It rises on Outberry Plain (2144 
feet) and flows in a deep valley nearly parallel to Teesdale. Farther 
east, and rising near the same point is Great Eggleshope Beck, 
running in a deep V-shaped valley. 
This beck, by its junction with Little Egeleshope Beck, forms a 
stream known as East Skears, which flows into the Tees near the 
village of Eggleston. This is the last important tributary on the 
left bank of the Tees, until Barnard Castle is reached. 
The greater part of the surface of Upper Teesdale is formed of 
the limestones, shales, and sandstones of the Carboniferous Series, 
with their accompanying sheets of basalt. The basaltic rocks form 
most of the salient features in the scenery of the Dale, especially in 
that portion which lies between Cauldron Snout and High Force. 
At the foot of Cronkley Scar (3), according to the Geological 
Survey, there occurs a patch of Skiddaw Slates and Borrowdale 
voleanic rocks, brought in by the disturbance known as the 
Burtree-Ford Dyke. Doubts are sometimes expressed as to the 
existence of the Borrowdale Rocks in this part of the Dale, and 
some observers are of opinion that the so-called ‘Skiddaw Slates’ are 
Carboniferous shales which have been altered by contact with some 
mica-trap dykes which penetrate them. I was unable to see any 
Borrowdale Rocks i situ, as the part of the Dale where they are 
mapped is very much obscured by Glacial Drift and by talus from 
1 This and subsequent numerals in parentheses refer to the map, Pl. XXX. 
