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CHAPTER V. 
On the Basaltic Thyhe.—On the economical Uses of the Mineral Pro- 
ducts in the Eastern part of Yorkshire. 
One of the most remarkable features on a geological map of England 
is the line of the great trap dyke, from beyond Cockfield fell in Durham 
to the Sneaton moors in Yorkshire, a distance of sixty miles. That this 
subterranean wall of basalt is really connected through the whole of this 
length few will be inclined to dispute who have studied the character o 
the rock, and observed its bearings at Cockfield fell, Bolam, Langbargli, 
and Silhoue cross ; but it is not traceable between all these points on the 
surface of the ground. It is a common opinion, that this dyke is united, 
toward the west, with the “ great whin sill,” or basaltic formation of 
Upper Teesdale, from the eastern end of Avliich another long dyke 
appears to arise. On the east it does not reach the sea side, but ter- 
minates obscurely, after crossing near its source the easternmost branc i 
of Littlebeck. Its general direction is E. S. E. and W. N. W ; but m 
several places considerable deviations in this respect are observable. The 
breadth is commonly about sixty feet, as at Cockfield fell Langbargh 
ouarry and Egton ; but it diminishes to less than thirty feet at the 
eastern extremity. At Bolam in Durham, it expands into a large pyri- 
form mass, having the appearance of an interposed bed resting on black 
shale. The sides of the dyke are seldom perpendicular, but generally 
slope downwards toward the north. At Langbaigli quaiiy t ns P 
is about 1 in 8. The strata through avliich the dyke passes are generally 
dislocated, so that a given layer is found considerably higher on the 
south side than on the north. 
As mi old be expected, this hard rock has been less wasted by watery 
currents and the changes of the atmosphere, than the softer strata which 
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