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CHAPTER V. 



On the Basaltic Dyke. On the economical Uses of the Mineral Pro- 

 ducts in the Eastern part of Yorkshire. 



O NE 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 of 

 the rock, and observed its bearings at Cockfield fell, Bolam, Langbargh, 

 and Lilhoue 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, a'rid certainly in appearance and composition they much 

 resemble each other. On the east it does not reach the sea side, but 

 terminates obscurely, after crossing near its source the easternmost branch 

 of Littlebeck. Its general direction is E. S. E. and W. N. W. ; but in 

 several places considerable deviations in this respect are observable. The 

 breadth is commonly about sixty feet, as at Cockfield fell, Langbargh 

 quarry, 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 vein, resting on black 

 shale. The sides of the dyke are seldom perpendicular, but generally 

 slope downwards toward the north. At Langbargh quarry this slope 

 is about 1 in 8. The strata through which the dyke passes are generally 

 dislocated, so that a given layer is found considerably higher on the 

 south side than on the north. 



As might be expected, this hard rock has been less wasted by the 

 deluge and the changes of the atmosphere, than the softer strata which 



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