NORTHUMBERLAND AND DURHAM. 33 



yellow sand ; but it is not seen either underlying or penetrating 

 the Magnesian Limestone, which, caps the same cliff a little to 

 tBe northward of the dike. It is 12 feet wide, and runs in the 

 direction of south 40° east to north 40° west, with a slope south- 

 ward of 85°. The dikes we have noticed are basalt, but this is 

 more allied to greenstone or diorite. 



The Coaly Sill Bile varies in width from 7 feet to 21 feet, 

 and has a general direction of E.S.E. It seems to be the same 

 as that which comes to the surface at Ouseburn, and at Simonside, 

 in the county of Durham. Buddie has described it, and notices, 

 that it pursues an undulating course, only occasionally appearing 

 on the surface. In Benwell colliery it is 200 feet, and in Walker 

 colliery 630 feet below the Tyne level. The coal in contact with 

 it is reduced to " cinder." 



Two small dikes with an east to west direction, about 13 feet 

 apart, one being 5 feet and the other 6 feet wide, dipping north 

 78°, are in Walbottle Bene: these have the character of greenstone. 



The Brunton Bihe, on IS'orth Tyne, which cuts through the 

 Mountain Limestone beds from north 40° east to south 40° west, 

 is 16 feet wide, and throws down the strata on the west side 

 above 20 feet. It crosses the South Tyne passing "Warmley, and 

 probably extends to Whitfield, where a basaltic dike is seen on 

 the West AUen. 



The Lewis Bxirn Bike has a long and somewhat irregular course, 

 but with a general direction of east north-east ; and it is trace- 

 able from Short Cleugh, on Lewis Burn, to Troughead and Dar- 

 den, in Redesdale, a distance of 12 miles. At Short Cleugh, in 

 the deep gullies made by water torrents, this dike is exposed at 

 several points ; it widens as it descends, and attains the width of 

 50 feet ; a small branch comes from the main trunk, and is seen 

 in the hill side. The Mountain Limestone strata, which it cuts 

 through, are greatly dislocated ; on its south side sandstone beds 

 are flat, while on the other they are nearly perpendicular. 



Of the two principal basaltic dikes in Durham we have some 

 definite information. 



