218 Prof. Sedgwick on Trap Dykes in Yorkshire and Durham. 
fore 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 concealed by a thick 
covering of diluvium : an opinion which no one will have much 
difficulty in admitting who has observed the enormous accu- 
mulation of transported materials’ in all the neighbouring di- 
strict. 
Range of the Dyke through the Eastern Moors. 
At Preston the trap emerges from beneath nearly fifty feet 
of diluvian brick earth; and would probably have remained 
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 direc- 
tion about S.E. by E. These horizontal strata must be re- 
ferred to the new red sandstone formation, though they ex- 
hibit 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 considerable 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 argil- 
laceous materials, with a transverse slaty texture. These sub- 
stances bear no resemblance either to the sound or decom- 
posing specimens of the dyke itself. 
On the east side of Nunthorp it gradually rises above the 
level of the neighbouring country, and might be mistaken for 
a gigantic artificial mound, had not the quarries exposed its 
interior structure. A well defined ridge, about four hundred 
feet above the level of the neighbouring plains, marks its pas- 
sage over the south flank of Rosebury Fopping. Still further 
to the east it is traced by a gap in the outline of the moors: 
for the upper beds of sandstone appear to have been shattered 
and carried off, and the dyke only rises to the highest level of 
the great bed of alum-shale. After passing through this gap 
and descending into Lownsdale, we found the trap forming a 
mass of bare rock which rose twenty or thirty feet above the 
vegetable soil. From thence it may be followed without diffi- 
culty many miles down the valley of the Esk, in a line bearing 
about E.S.E. Afterwards, by the turn of the valley at Egton 
Bridge, it is once more brought through the high moorlands ; 
and its course is marked in that desolate region by a low ridge 
resembling an ancient Roman road. A quarry which is 
opened at Silhoue, near the seventh milestone on the road 
from Whitby to Pickering, proves the whole thickness of the 
dyke to be about forty feet, and its inclination and direction 
nearly the same as in the other localities. Beyond this place 
it 
