83 
DYKES, MINERAL VEINS, &c. 
part is hard blue Whin with large crystals of felspar. It divides a 
coarse grit rock, (firestone of Aldstone moor, Ingleborough grit of 
Yorkshire) and consolidates it exceedingly. This same sandstone is 
often equally hardened by veins, so as to cause great expense in drifts. 
Obscure traces of this dyke may be found on the moors along a line 
E. 10° N., and at Woolley hills, two miles east, we find on this line the 
great Cockfield fell Whin dyke. At Woolley hills the dyke bears 
S. of E. : it is quarried extensively, appears very wide, and somewhat 
arched above. The stone is blue, not very compact, and includes large 
crystals of felspar; it resembles in some respects the basalt of Coley 
hill near Newcastle. The coal of Butterknowl is charred by it, 
especially on the north side ; it is there fifty feet wide, ranges S. 
65° E , seems divided into several parts or strings above, but is solid 
underneath. A remarkable circumstance connected with it is the 
contraction of its mass to a breadth of nine feet in this colliery at 
fifty feet depth, and it is supposed to retain only a very narrow 
breadth for some distance westward toward Woolley hills. Its direction 
undulates, and changes in the colliery at Butterknowl to S. 88° W. — 
which carries it to Woolley hills. In one place it is shifted horizontally 
twenty-two fathoms, by a slip of seven fathoms ranging north and 
south. 
At Cockfield fell the dyke expands laterally, and seems to overlay 
a part of the coal series ; it presents a very remarkable pyriform expan- 
sion at Bolam above West Aukland, crosses the Tees between Yarm 
and Stockton, is quarried at Stainton and Langbargh, lies in prisms 
across Clifton rigg, ranges down Eskdale to Egton, and thence on the 
moors across May beck, where it terminates its long course of seventy 
miles in oolitic rocks. Effects corresponding to igneous agency accom- 
pany its whole course. (See Illust. of Geol. of Yorksh. Vol. I.) 
Besides these Whin dykes Mr. Hutton mentions one passing east 
and west through Warcop fell and cutting Long fell and Roman 
fell. A basaltic dyke also crosses by Tyne head, in a direction N. N. W. 
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