: 
Geology of High Teesdale. 159 
the inferior strata, which present themselves in the same order in 
which they appeared below the High Force; partly also by the 
intervention of a small fault which elevates the beds on the west 
side of its range. 
The west side of Forcegarth-hill exhibits, under a different 
form, a repetition of the beds, which are laid bare in the natural 
sections below the High Force. The relations of this part of the 
valley, will be best understood by a reference to the accompanying 
section, (Pl. 1x. Fig. 3.) the line of which passes from Forcegarth- 
hill to the bed of the river below the High Force. 
TII. I have now only to consider the phenomena produced 
by the great transverse fault, and the geological relations of the 
highest parts of Teesdale. 
Above Forcegarth-hill, the Tees is no longer confined to 
a narrow channel, by lofty precipitous banks, but finds its way 
through an open valley, the lower parts of which are, in some 
places, so much occupied by turf-bog or diluvial gravel, as to 
give us little information respecting the internal structure of the 
country. One or two secondary vallies, which branch out from 
this part of Teesdale, may, at the time of the great denudation, 
have assisted in producing this striking alteration in its external 
character. The change is, however, principally to be ascribed 
to a great transverse fault, which raises the trap to a great ele- 
vation (perhaps not less than forty or fifty fathoms) above its 
former level, and exposes the more yielding beds of shale lime- 
stone and sandstone to the immediate action of the waters. 
This fault crosses the Tees, about a mile and a half above 
High Force, ranges past Hunt Hall, and then ascends by the 
right bank of a rivulet towards Middleton Fell. In its further 
range towards the north, it is said to be prolonged to the Bur- 
treeford dyke, an assertion which may admit of doubt, since the 
dislocations produced by that dyke, are, according to the state- 
ment of Mr. Winch, of an opposite kind to those in Teesdale, 
Great trans- 
verse fuult. 
