Other greater 
Dislocations. 
Causes of 
them. 
192 Professor SEDGWICK on the 
excavated most of the secondary vallies, that the conditions of 
any great geological problem are seldom completely before us. 
From the composition of a rock (like the Whin-Sill) and from 
its obvious effects, we may refer it to a certain class of operations: 
but it may be utterly impossible to point out the modifying forces 
by which it has been brought into its existing form. In such 
a case, it is enough for us to shew, that the phenomena are not 
physically incompatible with the causes we assign for them. 
The fractures and dislocations which intersect the mountain- 
limestone and coal formations, are not confined to the region above- 
described. Similar dislocations abound in every part of the moun- 
tain-chain which borders on the different branches of the Wear 
and the Tyne. Though striking and important in themselves, 
they are as nothing compared with the rupture which has severed 
the calcareous chain of Cross Fell from the zone of metalliferous 
limestone, which sweeps round the northern side of the slate moun- 
tains of Cumberland. This enormous fault, has not only rent 
asunder the whole formation, through a distance of twenty or 
thirty miles, but appears, in some places, to have elevated the 
beds of metalliferous limestone on the north-east side of its range, 
more than two thousand feet above the level of the correspond- 
ing beds on the other side. The range of this fault is, in a great 
measure, concealed by the new red sandstone, which extends 
from the foot of Stammoor to Solway Frith: but its termination 
may be seen in the neighbourhood of Brough, where mountain 
masses of the strata have been rent asunder and brought down 
with an inverted dip into the bottom of the valley. 
It is hardly possible to help speculating on the mechanical 
forces which have produced such gigantic effects. Some such 
modification of voleanic agency, as I have before alluded to, may, 
perhaps, have produced them; and the supposition seems con- 
