GEOLOGY 



PALAEOZOIC ROCKS 



The question whether productive Coal Measures are likely to occur 

 at a workable depth beneath Essex is one which has aroused keen interest 

 of late years. So long ago as 1858 a boring at Harwich proved the 

 occurrence of a dark slaty rock beneath the Gault, at a depth of 1,029 ^ eet 

 from the surface. 1 It was then thought that this rock, which was pene- 

 trated to a depth of 69 feet, was of Lower Carboniferous age owing to 

 the supposed occurrence in it of the fossil mollusc Posidonomya. The 

 specimen was however re-examined in 1896 by Prof. W. W. Watts, and 

 he came to the conclusion that, while the rock itself was not at all like 

 that of any known British Carboniferous rock, the supposed fossil was an 

 inorganic structure. 1 



A somewhat similar dark slaty rock was touched at a depth of 994 

 feet in a trial boring in Suffolk, at Stutton on the northern side of the 

 Stour estuary ; and again in a further trial in Essex, at Weeley between 

 Colchester and Walton-on-the-Naze, where the old rock was reached at 

 a depth of 1,094 feet. 8 



These two trials in search of Coal Measures were made after due 

 deliberation with the highest geological authorities. That they were 

 unsuccessful is an indication, not that the chances of obtaining coal 

 beneath Essex are hopeless, but that scientific knowledge is insufficient 

 to tell precisely where concealed coal-basins occur. Nevertheless en- 

 terprise need not be damped. There is always a possibility of finding 

 coal where the strata at the surface are newer than the Coal Measures ; 

 but as the older rocks were bent and fractured and largely eroded before 

 the Secondary and Tertiary strata were spread over them, it is evident 

 how speculative must be the search for Coal Measures under these 

 circumstances. Were the exposed coalfields to be covered up with a 

 mantle of Chalk, we should have no certain guide from one successful 

 boring as to the nature of the deep-seated rocks at a distance of a few 

 miles, because there is no regularity in the preservation of coal-basins. 

 Again if rocks much older are proved in a boring, it is quite possible 

 that Coal Measures may exist near by, because in south Staffordshire, 

 Leicestershire and Warwickshire the older Palaeozoic rocks occur in 

 juxtaposition with productive Coal Measures. 



It has lately been suggested by Prof. W. J. Sollas that Enfield Lock, 

 just across the Lea on the Hertfordshire side, is a likely place for a 

 successful trial. It may be so, but there is no information that would 

 prove that it is a more promising site than any other unproved locality 

 in Essex or Hertfordshire. 4 



In Essex several deep borings have been made in search of water. 

 Thus at Wickham Bishop a boring was carried to a depth of 1,180 feet, 



1 Prestwich, Quart. Journ. Geol. Sot., vol. xiv. p. 252. 



* Ann. Report of Geol. Survey for 1896, p. 5. Whitaker, Ref. Brit. Ante, for 1895. 



4 For further information on the underground rocks see Whitaker, Geology of LenJen, vol. i. p. 10. 

 (In this work full references are made to the suggestions of Godwin-Austen, Prestwich and others on 

 the older deep-seated rocks.) 



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