GEOLOGY OF PART OF SOUTH DURHAM. 195 



been put through the dyke, and the coal found no higher on the 

 one side than on the other, than what is to be accounted for by 

 the general rise of the Measures. 



At Evenwood Colliery a drift was put through the dyke near 

 to Buckheads Farm, at which point it was not found in one 

 mass, but split up into three or more walls of whinstone with 

 pieces of coal strata between. 



Near the village of Bolam it is wrought extensively in an open 

 quarry. To the east it is seen as a dyke about ten yards wide, 

 cutting through beds of sandstone and shale, some of which are 

 considerably altered by heat. To the west the whin spreads out 

 north and south, forming a large tabular mass about one hundred 

 yards across, and fifty or sixty feet deep. Fragments of coal 

 are here sometimes found in the whin very beautifully coked. 



The latter locality is the most easterly where we have seen 

 the Cockfield Dyke, but about a mile more to the east, between 

 Legs-a-Cross and Houghton Bank, there is an old quarry hole, 

 half filled with rubbish and water, that is said to have been for- 

 merly wrought for whinstone. The rock at present exposed is 

 a very coarse, easily decomposing grit, which looks, from its 

 altered aspect, as if it had been subject to igneous action. 



The general course of the dyke, from the last named place to 

 the Gaunless, near Haggerleases Lane, is to the west of W.N.W. 

 From the latter point its bearing becomes still more westerly. 

 From Diamond Pit to Wooley Hill its course is unknown, or it 

 may possibly not reach upwards to the present land surface ; 

 but as the latter locality is to the W.S.W. of the former, it is 

 evident that a deflection to the south of west must there take 

 place. 



We have observed no traces of the dyke in the Magnesian 

 Limestone. But at Broom Dykes, near to where it would strike 

 the outcrop of that formation, assuming its course to continue as 

 before, a disturbance takes place in the limestone which may 

 possibly be in some way connected with it. 



On the right of the road leading from Hilton to the Black 

 Horse, and nearly opposite Wackerfield Lane, there is an old 



