Geology of High Teesdale. 171 
It has been stated above (p. 157.) that the Whin-Sill rises out in 
the bed of the river, about half-way between Bowlee Beck foot 
and Winch Bridge, The beds resting on the Whin, appear in 
the following order, beginning with the lowest. (1) Shale and 
hazle alternating; the shale in a state of extreme induration. 
(2) Limestone, in texture entirely granular. (3) Indurated shale. 
(4) Limestone less granular than the preceding, and part of it 
unchanged. (5) Shale, soft, earthy, and in every respect like the 
beds of slate-clay in other parts of the district. I have thought 
it proper to give this section, because it is taken from the only 
place below the great transverse fault, (the Burtreeford dyke,) 
where I had an opportunity of examining the effects produced 
by the Whin-Sill upon the superior strata. 
5. The phenomena exhibited at the junction of the trap with 
the inferior strata at Forcegarth-hill, and at the High Force, 
are well deserving of attention, (See the Section, Pl. 1x. Fig. 3.) 
As the several escarpments in this part of the dale, only give 
a repetition of the same general facts, I shall confine myself to 
a notice of the mineralogical character of the beds which appear 
under the trap on the south-east side of Forcegarth-hill. 
(1) The upper part of the escarpment (where the inferior 
beds are first seen on the side of the hill,) is composed of prismatic 
trap. (2) Under the trap appears a bed of sandstone nine feet 
thick. It is in a state of extreme induration, difficult of fracture, 
and in its texture differs entirely from the ordinary sandstone beds 
of the district. (3) Under the sandstone is a bed about 18 feet 
thick, which, from its hardness and texture, might at first sight 
be mistaken for greywacké slate. I do not, however, believe 
that it differs in its composition in any respect from slate clay; 
especially as it contains nodules of ironstone arranged exactly in 
the same manner in which they appear among the soft argillaceous 
beds of the metalliferous series." We may, therefore, conclude, 
y2 
Sections at 
Forcegarth-hill 
and High 
Force. 
