in Yorkshire and Durham. 29 
into the magnesian limestone; have led some to imagine, that the 
prolongation of the dyke of Cockfield Fell is for several miles 
concealed beneath the beds of that formation. These basaltic 
veins, which do not penetrate the magnesian limestone, prove 
one of two things. Either that they took their present form 
before the deposition of the limestone; or that they were injected 
from below, but not with sufficient energy to break through the 
superincumbent limestone. Neither of these suppositions can 
apply to a great dyke intersecting an enormous mass of secondary 
strata which are newer than the magnesian limestone, and probably 
rest upon it. If therefore we admit the identity of the Cockfield 
Fell and Cleveland dykes; we must suppose that in the whole 
interval, between Houghton-le-side and Coatham Stob, it is con- 
cealed by a thick covering of diluyium: an opinion which no 
one will have much difficulty in admitting who has observed the 
enormous accumulation of transported materials in all the neigh- 
bouring district *. 
At Preston the trap emerges from beneath nearly fifty feet Range of the 
of diluvian brick earth; and would probably have remained the Eaten” 
concealed, had it not been laid bare in the bank of the river." 
On both sides of the Tees it is more than seventy feet wide, and 
ranges through horizontal strata of sandstone in a direction about 
S.E. by E. These horizontal strata must be referred to the new 
red sandstone formation, though they exhibit but faint traces of 
the usual ferruginous tinge. From Barwick the dyke passes 
through the quarries of Stainton, Nunthorp, and Langbargh, to 
the foot of the Cleveland hills; making in its progress a con- 
siderable flexure to the north. At Stainton the north face of the 
dyke is interrupted by a fissure about five feet wide, which is 
filled with light coloured argillaceous materials, with a transverse 
SS ee ee eee 
* See Plate II. Fig. 1. 
