C. T. Clough—The Whin Sill of Teesdale. 439 
thickness of the shale present is about 14 ft. The shale layer which 
is immediately below the Whin at the South end can be traced 
running on, and we may be certain that it isno higher than the base 
of the main Whin in the middle of the section.’ We will take this 
South. Ty] North. 
cena 
Ant Na A nu ce | la i I ih i hy | 
ANE oe le = Aa i He 
TS sth ki 
Fic, 4.—Diagram Section at the High Force. 
a. Basalt. b. Shale. ce. Limestone. 
[Where the natural section is slightly obscure, the edges of the Whin are given in 
broken lines. ] 
shale layer as one geological horizon and the top of the limestone as 
another. Between these two horizons we ought to find the same 
sedimentary beds at any place in the section, because there is no 
sign of any change taking place in the character or thickness of the 
beds. Instead of this, we have at the South end of the section 
about 20 ft. of shale between these horizons, and in the middle only 
14 ft. There is, therefore, 6 ft. of shale missing in the middle of the 
section, and we have just about this thickness of Whin instead of it. 
An instance somewhat similar to the preceding two has been noted 
by my colleague Mr. D. Burns, in connexion with the “ Little Whin 
Sill” of Weardale. He says (Proceedings of the North of England 
Institute of Mining and Mechanical Engineers, vol. xxvil. 1873, 
On the Intrusion of the Whin Sill) :—-‘‘In Weardale, what has been 
called the Little Whin Sill crops out from Rookhope to Stanhope, 
and it may extend much further eastward, between two posts of the 
Three Yard Limestone. This limestone is pretty uniformly of the 
thickness which its name implies, but where it includes the Whin, 
there is at some points only two feet of limestone on the top, and one 
foot below. This shows that the limestone is either abnormally 
thin, or that the Whin in some way has destroyed a fathom of it: the 
latter intepretation is certainly much more probable than the other.” 
I do not think that any theory of pre-existing fissures will help us 
to explain facts like these. Such fissures would have often to be of 
very large dimensions, to be inclined at all angles from vertical to 
horizontal, and to occur in all the sedimentary beds alike, in sand- 
stone and shales as well as limestones. What agent could produce 
1 It is probably a little lower, because, as indicated in the diagram, the Whin base 
seems to have run down slightly towards the South in one place, 
