THE SOUTH-EASTERN COALFIELD 381 



they plunge beneath the newer beds ; the Mendip hills are 

 simply a covering of newer rocks laid down over this ridge. 

 The Upper Greensand Inlier at Kingsclere and the Weald 

 Clay Inlier at Maidstone are, to the geological eye, due to its 

 influence, and the high ground of the chalk escarpment, along 

 the edge of the North Downs, betrays its presence : this new 

 ridge of the North Downs is cut open by that geological ditch 

 the English Channel, and it requires little imagination to 

 realise from the cliffs of Folkestone the physical continuity of 

 the chalk Downs of Kent with the white cliffs of Grisnez on the 

 French coast opposite. In France the old rocks are rising near 

 the surface. The hills of Artois are but a thin sheet of chalk 

 over the old Devonian rocks beneath, and these are sometimes 

 even struck by quarrymen near Clarence and Lievin. 



Now from what has gone before it is evident that the tracing 

 of this line is a most valuable achievement. It shows us where 

 not to look for coal. But we might reasonably hope to find it 

 at some distance to the north or to the south of the anticline. 

 It should be remembered that the general opinion of geologists 

 at that time was that the Mesozoic rocks extended in complete 

 succession in the south-east of England down to a great depth, 

 and Godwin-Austin's views met with considerable scepticism. 

 Murchison refused to the last to believe in the existence of the 

 old palaeozoic rocks at an accessible depth in this district. 

 But before his paper was printed, a boring at Kentish Town 

 struck the old palaeozoic floor immediately beneath the Gault, 

 and a little later a black slaty rock, of apparently Primary age, 

 was struck at Harwich, also beneath the Gault. 



The Lower Greensand crops out with such regularity all 

 round the London basin that few were prepared for any break 

 in the succession ; but all open-minded geologists were bound 

 to accept the evidence of these borings, and Prestwich did not 

 hesitate to set the example. Shortly afterwards another boring, 

 at Meux's brewery in Tottenham Court Road, struck the 

 Devonian rocks at a depth of about 1,000 ft., beneath 64 ft. of 

 Lower Greensand. 



II. Faith 



These discoveries aroused so much interest, that there was 

 great speculation as to the depth at which the palaeozoic floor 

 would be met with beneath the Weald. 



