BASALTIC ROCKS, 
nation of the sill, and Lune head, (or W. S. W.) It is seen on 
Eggleston common, crosses Eggleston burn with observed bearing 
■ • E. or E„ 20° N., breadth thirty-three feet, nearly vertical. In 
ie hill above the dyke is exposed in a plantation, between cheeks 
of shale converted to a whitish soft rock, such as that often found 
below the Whin sill, called ‘pencil bed,’ in which many vertical 
joints appear parallel to the dyke. Along the south face of the dyke 
some lead ore was obtained, for which shafts were sunk and a level 
driven. The ore lay in what may be called mineralized trap. Further 
to the east the range of the dyke continues to be traceable by the 
valley of the Redburn, north of Hamsterley, and near Witton-le-Wear. 
"W hitworth and Tudhoe, to Hett and Quarrington, always preserving- 
one direction, viz. E. 19° 20°, 21° or 22“ N. At Quarrington it passes 
through Crow Trees colliery, dividing and charring the five quarter 
and high main coal seams, diminishing in breadth as it approaches 
the surface. It does not divide the superjacent limestone ; but 
whether this arises from the contraction of the fissure, or from an- 
teriority of date, is not certainly known. Its breadth at the surface 
at Crow trees is six and a half feet, at Tursdale nine and a half 
feet, at I3itchburn fifteen feet, at Hamsterley twenty-three and a half 
feet, and at Eggleston burn thirty-three feet. Thus its breadth 
diminishes from the basaltic region toward the E. N. E,, and it also 
contracts upwards or toward the surface. It is supposed to extend 
up Lunedale, by Greengate, and Womersgill. The substance of this 
d)-ke is a fine grained basalt of bluish aspect, it is not of prismatic 
structure, but full of vertical and transverse fissures which are often 
lined by ochraeeous partings. 
Another dyke, also appearing to originate from the great Whin 
sill at its eastern end, is seen on the banks of the Tees, half a mile 
below the confluence of the water of Lunedale, and is imagined 
to range through the limestone country north of Lunedale. It is 
next observed crossing Eggleston burn, a little east of that noticed 
above. It has a bearing of E. 5“ N„ is nearly vertical; breadth 
fitty-four feet; a narrow part on the south side is soft, the northern 
