COAL MEASURES. 201 



deposition of the Secondary rocks. He showed that the main line 

 of disturbance had a general east and west direction, that part of it 

 formed the great anticlinal of the Ardennes, by which the Belgian 

 coal-field had been tilted up, and brought to the surface, and that 

 the Mendips with the Somerset coal-field were on the same line of 

 strike."' (See p. i6i.) This is but a brief outline of the general, 

 conclusions arrived at in the paper, which really deals with the 

 physical geography of the European area at many past epochs. 



The possible occurrence of productive Coal-measures beneath 

 the Cretaceous and Oolitic rocks of Norfolk has been pointed out 

 on many occasions by Mr. J. Gunn ; as yet, however, the matter 

 remains a purely speculative one, and, inasmuch as the rocks 

 exposed at the surface furnish no clue to the character or arrange- 

 ment of the Palaeozoic rocks beneath, the question can only be 

 settled by boring.* 



Several borings have been made which have reached Palceozoic 

 rocks in the area under consideration ; at present, however, the 

 rocks thus met with are all older than the Coal-measures ; and 

 these (jlder rocks are frequently so much disturbed, and sometimes 

 even inverted, that no accurate calculations can be made on the 

 probable position of the Coal-measures here or there, from the 

 facts at present made known by our deep borings. 



Thus at Harwich a dark bluish-grey slaty rock of Carboniferous age, probably 

 of an age immediately antecedent to the Coal-measures, was met with at a depth 

 of 1029 feet beneath the Eocene beds and Chalk. Under London, rocks classed 

 as Devonian have been reached at a depth of 1066 feet ; at Richmond and 

 Kentish Town red rocks have been proved at depths of 1240 and 11 14 

 feet (see p. 140) ; while at Ware in Hertfordshire, Silurian rocks (Wenlock 

 Shale) were touched at a depth of only 800 feet beneath the surface. Moreover, in 

 Belgium and the North of France, Coal-measures are found sometimes at depths of 

 only 300 to 400 feet beneath the Chalk and Tertiary strata ; and here they are 

 accompanied, seemingly in perfect conformity, by Devonian rocks, like those found 

 under London. (See also account of Well Sections.) Prof. Prestwich was 

 disposed to think that the slaty (Carboniferous) rock at Harwich lay on the 

 north side of a coal-basin, in which case the Lower Carboniferous and Devonian 

 beds would rise beyond it and pass under Suffolk. 



The accompanying diagram shows in a general way the 

 evidence made known, and the depth at which the older rocks 

 would be likely to occur.^ (See Fig. 31.) 



The evidence furnished by the Richmond boring is opposed to 

 the prospect of finding coal at workable depths under the southern 

 part of the London Basin. But Prof. Judd has noted the occurrence 

 in the junction-beds above and below the Great Oolite at Richmond, 

 of fragments of anthracite mingled with pebbles of Coal-measure 

 sandstone ; indicating that Coal-measures formed a part of the 

 Palaeozoic land at the time when the Jurassic strata were laid 



' Q. J. xxii. 38. See Prestwich, Report Royal Coal Commission, vol. i. 1871, 

 p. ^146. 



" See Geology of Country around Norwich, p. 168. 



^ Proc. Norwich Geol. Soc. i. I02 ; see also Whitaker, Guide to Geol. of 

 London, edit. 4, and Topley, Geol. of Weald, p. 242. 



