116 
connected with a deep seated plutonic root. At the moment of 
eruption, this vent was the passage through which vast quantities 
of semi-liquid volcanic material was discharged at the surface. 
H. B. Woodward (“ Geology of England and Wales,” p. 569), gives 
twoexamples of the discharge of igneous dykes, one in The Cheviot 
Hills, and the other the great whin sill in Northumberland and 
Durham. In the case of the igneous dyke on Mendip denudation 
has removed most of the discharge and a large portion of 
the rock on which it rested leaving only a portion exposed at 
the surface. 
The origin of the basic rocks of the West of England as stated 
by Teall, p. 228, and the recognised principles of igneous dykes 
previously referred to, will place beyond a doubt that the great 
earth movements which has resulted in the “ crumpling,” or, the 
formation of coal basins, is in some way closely connected with 
intrusions of granitic masses in a similar way as those of Devon 
and Cornwall, but in the case of Somersetshire the intrusion may 
have been situated in an horizon 5,000 feet below the level of 
those of the former counties. 
From all the evidence we can gleam of the general form of the 
Radstock coal basin, and the contour of the under or convex side, 
it certainly favours the opinion that it has gone down into a 
semi-fluid substratum. Whether that substratum be a molten 
magma protruded from the earth’s interior; or whether the 
lower palozozoic rocks have been reduced in a greater or less 
extent, to a like molten material, the result at the surface would 
be exactly as we find it; the centre has gone down, breaking 
away from the districts not affected. The molten material, 
escaping from the pressure of the centre, was forced to the 
points of least resistance, the up-lifted broken edges, forming 
the Mendip range, Wrington Warren, Clifton Down, &c. 
Having thus far given a brief outline of the forces which may 
have laid our Coal fields in their basin like form we will proceed 
to examine their effect on the interior. In this we have the 
