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voleanic intrusions penetrating the overlying strata (see ‘‘ Geology 
of England and Wales” by H. B. Woodward, p. 587.) 
Messrs. Woodward and Teall, and many other writers, are very 
decided as to the geological date of the formation of Coal basins. 
But the mere term of ‘‘crumpling,” used by those authors, does 
not appear to do justice to the great phenomena so marvelously 
developed in our neighbourhood. What the nature of the effect 
of the igneous intrusion on the stratified or unstratified rocks 
which lie so deep in the earth’s crust could have been, must ever 
be a matter of speculation, since its operation must have been 
located probably three thousand yards below the surface. Whether 
that effect was simply to cause dislocation followed by depression 
of the upper strata, or, whether, at that great depth, fusion 
may be the result on a much larger scale than anything of the 
kind we have discovered at the surface, is a matter of speculation. 
We will take the Radstock Coal basin as typical of all other coal 
deposits in England and Wales. All, more or less, lie in similar 
basin-like depressions, and are split up with faults and dislocations ; 
they are all accompanied with igneous protrusions usually 
situated in the upturned strata which invariably forms the margin 
of the basin. To examine more particularly the example we have 
chosen ; the surface assumes an elongated oval shape, bounded on 
all sides by the upturned edges of the strata which form the base 
of the centre at a depth of probably two miles, each succeeding 
deposit cropping out at the surface, the most recent forming the 
centre. 
It is a remarkable fact that the deepest part of the basin, and 
its greatest dislocations, are either on the side towards the igneous 
_ dyke on Mendip, or they present indisputable evidence that the 
connection between the two, is a case of cause and result ; although 
the cause as it appears at the surface may itself be the result of 
deeply seated igneous action in the crust of the earth (see British 
Petrography by J. J. Harris Teall, M.A., F.G.S., p. 391.) 
_ We learn from this that the dyke is a consolidated vent 
