in Yorkshire and Durham. 3] 
No other dyke has, I believe, been yet described, which Extent and 
intersects so many secondary formations, and preserves such an 
extraordinary uniformity of direction and inclination. The whole 
length, reckoning from the quarry at Gaundlass Mill, is more 
than fifty miles: and if any one should object to this, as includ- 
ing a considerable space in which the continuity is not apparent ; 
there will still remain from Coatham Stob a distance of about 
thirty-five miles, through which it is almost certain that the trap 
ranges without any break or interruption. Perhaps it might 
with more justice be objected, that the first computation falls 
below the truth ; in consequence of the probable extension of the 
dyke to the N. W. through the Woodland Fells and Egglestone 
Burn te the banks of the Tees. Should this supposition be ad- 
mitted, we shall have an uninterrupted dyke extending from 
High Teesdale to the confines of the ,eastern coast; a distance 
of more than sixty miles, 
The angle at which it cuts the strata is of course variable, 
and in many places cannot possibly be ascertained. At Barwick, 
near the Tees, its inclination to the horizontal beds of sand- 
stone is more than eighty degrees; and the angle at which it 
intersects the beds of shale and sandstone in the eastern moors 
is still greater; occasioned, perhaps, by the south-eastern dip, 
which generally prevails among the strata in that region*. 
Secondary fermations, when interrupted in the manner 
above described, seldom preserve the same level on the oppo- 
site sides of their line of separation. Thus at Cocktield Fell, 
the coal-beds on the north side of the dyke are eighteen feet 
below the corresponding beds on the south side. In the excava- 
tions at Preston and Barwick there is no indication of any great 
change having been produced in the relative level of the beds of 
sandstone: nor can any conclusive evidence be obtained on this 
* See the Survey of the Yorkshire coast by Young and Bird. 
