It is, of course, quite possible that the first impulse towards these faults, the strain that produced the cracks, was communicated to them at the period when the great disturbances in the Carboniferous rocks took place generally through Britain; and that period seems certainly to have been previously to the existence of the New red sandstone. A further subsidence or elevation, or in other words a relative displacement, may have at some subsequent period, or even at several periods, taken place among these cracks, extending them into the more recently deposited beds of the Red marls and the Lias, and "throwing" those rocks up or down from their original level, as we see to be the case with the Red marls on both sides of the coal-field, and with the Lias south of Bromsgrove.
No one, I think, will now be able to look at a geological map of the centre of England without connecting in his mind's eye the Lias of Worcestershire and Warwickshire with that of Staffordshire and Cheshire, and being convinced that these outlying patches once formed one broad connected sheet, a level plain of Lias spreading over all the intervening districts, and sweeping up into the borders of Wales. Wherever a sufficient thickness of the upper Red marls has been left undenuded, to render it possible for beds of Lias to come in, there we find them; but for the denudation, therefore, we should have found Lias wherever we now find the Red marls. The same reasoning will apply to the several members of the New red sandstone, down to the base of that formation. Wherever, therefore, the New red sandstone spreads (in the Midland Counties, at all events), it was in all probability once covered by Lias.
At all events, it is clear from our previous descriptions, and from an inspection of the maps and sections, that before the production of the dislocations of the great boundary faults, the New red sandstone spread over the coal-field and whole district of South Staffordshire, and we can see no reason why it should not have had the whole of its beds everywhere, or why these beds should not have been everywhere covered by the Lias.
At some subsequent period great dislocations took place, and either the present coal-field was lifted up above the surrounding district, or it was left standing while the surrounding districts were depressed, and thus rising as a great protuberance, was of course subject to the more marked influence, and more complete action, of the denuding agencies which have worn and pared down all the country to its present surface. In this way the lower rocks have been stripped of their former covering in the district forming the present coal-field, while more or less of that covering, according to circumstances, has been left untouched in the surrounding country.
The practical bearing of these remarks is this, that wherever we find any of the upper parts of the New red sandstone, we shall there, in all probability, find all the inferior ones in their proper position below it. 'To commence sinking for coal, therefore, in any of the parts coloured as Red marl in the geological maps of the Midland Counties, would be only to throw away money; still
