24 Mr. N. J. Winch on the Geology of 



the place of contact is at present inaccessible. In the neighbouring 

 colliery both portions of the vein hold their course through the 

 seam there worked, and the coal is charred by their influence. 



Some of the blocks from the quarry are quite black, and of an 

 earthy fracture, and contain nodules of quartz and chalcedony, 

 varying in magnitude from the size of a pin's head to that of a 

 large pea. Other specimens of the rock are hard, coarse grained, 

 and of an iron-grey colour ; but in neither varieties have I found 

 the mineral resembling adularia, so abundant in the basalt of Coley 

 hill. 



A basaltic dyke 6 feet wide may be seen among the rocks of 

 the coal formation at the south-eastern corner of the promontory 

 on which Tynemouth castle stands. Another, about 3 yards wide, 

 appears in the cliffs near Seaton sluice ; its direction is west-north- 

 west, and it may again be seen in Hartley burn. A small whin 

 dyke was formerly quarried near Bedlington ; and another is found 

 in Cowpen colliery, which has charred the coal in contact with it. 



Passing to the south of Newcastle about 2 miles beyond Durham, 

 a basaltic vein may be seen, when the water is low, at Butterby in 

 the bed of the Wear. This vein is remarkable for a salt spring 

 that issues from its interstices, and for a string of galena (first 

 noticed by Mr. Fenwick of Dipton) that fills a crevice beside it. 

 Two miles further to the south near the junction of the Auckland 

 and Darlington roads, is another dyke, the direction of which is 

 nearly east and west, and on which two quarries are worked, each 

 about 10 feet wide. 



Of the Cockfield dyke a section and description have been given 

 in the History of Durham, by the late Mr. Dixon, from which 

 work I derive the following particulars. 



This dyke passes in a north-west and south-east direction from 



