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



At Bamborough 9^ miles north-north-west of Dunstanborough, a 

 well was sunk in the Castle hall to the depth of 150 feet, by which 

 it was ascertained that the overlying rock of basalt was 75 feet thick, 

 and rested upon a fine grained red and white sandstone, parts of 

 which fell into small round fragments on being immersed in water. 



In the Heugh, the promontory on which Holy Island Castle is 

 built so as to command the harbour, the basalt seems also to rest on a 

 soft fine grained sandstone ; on the east side of the island the sea has 

 scooped deep caverns in the latter rock ; trials have there been made 

 for coal, and small quantities of galena have been discovered, as I 

 have before mentioned. 



Basaltic dykes, which occur in the Coalfield, are also found inter- 

 secting the lead mine measures, instances of which may be seen on 

 Aldstone moor, in Allendale, and in Weardale. A well defined 

 dyke may be seen a little above South-Tyne-head smelting-house, 

 traversing the Tyne bottom limestone without altering its level. 

 The dyke is there 36 or 37 feet wide, and is by many thought to be 

 the same that crosses the Allen close to the bridge at Whitfield and 

 the Wear at Burtree-ford still further to the south. This basalt is of 

 a. coarse grained texture and greenish black colour. At Egglestone 

 three miles below Middleton a very strong vein of basalt may be seen 

 crossing the Tees in a diagonal direction ; and the mountainous 

 moors in the upper part of the vale are covered with fragments and 

 immense blocks of this species of rock for the distance of many 

 miles. 



I have already mentioned that the basalt appears to fill dykes at 

 Stagshaw bank and at Jemming. Further to the north, in the village 

 of Embleton, not far from Dunstanborough, an extensive quarry is 

 worked in a basaltic dyke. The course of the vein is north and 

 south, about a mile to the west of the craggy ridge on the sea coast, 



