160 Professor SEDGWICcK on the 
though both may have been produced by forces nearly allied 
to each other*. 
ae On the west side of the great fault above-mentioned, the 
dale has a singularly wild and desolate character, and at first 
sight presents no object which would arrest attention, except 
the rocks of Low Cronkley, which form a kind of breast-work 
in front of the mountains ranging on the south side of the 
valley. The upper part of the escarpment of Low Cronkley, is 
composed of a great bed of trap. This is supposed to represent 
the Whin-Sill; and from its elevation above all the rocks 
of the same kind, between Forcegarth-hill and High Force, the 
quantity of dislocation produced by the great transverse fault 
has been estimated. The escarpment which commences at Low 
Cronkley, is prolonged, without interruption, for about four 
miles, and forms the most magnificent feature in this part. of 
Teesdale. The north side of the river is comparatively devoid 
of interest. By following the brook which descends from Har- 
wood Chapel, we may, however, discover the whin-stone at 
an elevation which is not lower than the summit of Cronkley 
Fell. 
Glen between About two miles above the place where this brook joins the 
ae ans Tees, the valley sweeps round to the south-west, and the river 
si once more descends through a narrow glen, being hemmed in 
by the rocks of Widdy Bank on one side, and the basaltic 
terrace of High Cronkley on the other. No other part of Upper 
Teesdale can bear a comparison with this glen, either for the 
grandeur of its features, or for the interest which arises out of 
its physical structure. The lowest parts of it are formed by 
alluvial gravel and vegetable soil, resting on nearly horizontal 
beds of limestone, sandstone, and shale. Immediately upon 
these stratified rocks, there rests, on each side of the river, 
* See the Transactions of the Geological Society, Vol. 1V. p. 78. 
