Geology of High Teesdale. 153 
of the river, (opposite Breckholm and Low Houses) where the beds 
are set on edge in a form which unequivocally indicates the 
presence of a fault, and where the contiguous strata are tilted 
exactly in that way which would be occasioned by a downcast on 
the north side of the line of dislocation. 
That the great Teesdale fault is continued far beyond the 
places last-mentioned cannot admit of doubt, though the exact line 
of its direction is in some measure hypothetical. Perhaps it may be 
considered to terminate in the bed of the river at Holwick Head, 
about half a mile below the High Force. For the trap there puts 
on the appearance of thin vertical beds, which so often mark the 
presence of a fault; though the quantity of depression on the north 
side must be incomparably less than it is in some of the lower parts 
of the valley. 
By some of the practical men of the country, the great Teesdale 
fault is supposed to cross the river at Holwick Head, to range on 
the south-west side of High and Low Hag, and from thence to be 
continued along a depression of the country as far as Hunt Hall; 
where it is supposed to meet the great transverse dyke to be de- 
scribed in a subsequent part of this Paper. Iam unwilling to 
admit the truth of this hypothesis. First, because it does not seem 
adequate to the explanation of some of the intricate phenomena 
exhibited in this part of the valley. Secondly, because the strata 
on the north side of the line, extending from Holwick Head to 
Hunt Hall, do not appear (as in the case of the great Teesdale 
fault) to be at all points thrown down below the level of the cor- 
responding beds on the south side. 
Before I proceed to consider the manner in which the trap 
is associated with the other strata, it may be proper to remark, that 
there are many other veins or faults which produce a considerable 
effect in modifying the relative position of the strata in the parts of 
the valley above described. To attempt to enumerate the whole of 
Vol. 11. Part I. U 
Other Veins and 
Dislocations. 
