A HISTORY OF DURHAM 



here, and the Fell Top may well be taken as the obvious termination of 

 the Carboniferous Limestone or Bernician, the shaly beds immediately 

 following being grouped with the Millstone Grit. 



Perhaps the most striking point in connexion with the Bernician 

 Beds as developed in Durham is the marked disappearance of the coals 

 which characterize them further to the north. This disappearance is 

 not however complete. One seam (which sometimes is represented by 

 two) has already been mentioned as occurring beneath No. 145, another 

 is sometimes found beneath the Fell 'Top Limestone (No. 121), but of no 

 value; and one beneath the Scar Lhfiestone (No, 169). Indeed it is 

 clear that the many Bernician seams which crop out in west North- 

 umberland have a general tendency to thin away to the south-east, that 

 is towards Durham. It is, of course, possible that there may be a re- 

 crudescence of these seams beneath the Upper Carboniferous strata to 

 the east, but nothing but actual boring to very considerable depths can 

 prove whether this be so or not. Such rare borings bearing upon this 

 point as have been put down recently are decidedly in favour of a nega- 

 tive answer to this question. One at Sherburn, which went some way 

 beneath the Millstone Grit into the Upper Limestone horizons, struck 

 upon no seam approaching a workable thickness. The same result was 

 obtained by an extremely interesting and deeper boring put down in the 

 Chopwell Woods on the banks of the Derwent, and described by Mr. 

 J. B. Simpson in the ' Transactions of tiie North of England Institute ol 

 Mining and Mechanical Engineers in 1902.'* 



THE MILLSTONE GRIT AND COAL MEASURES 



The middle division of the Carboniferous Series is a very marked and 

 well individualized one in the midlands. On following it towards the north 

 it loses much of its individuality, and this loss of specialization is accom- 

 panied by very considerable thinning. The coarse grits which form the 

 fine bold escarpments or 'edges' of the Peak district of Derbyshire, or 

 the silicious scars of west Yorkshire, have not disappeared altogether in 

 Durliam, but they have sadly dwindled both in coarseness of texture and 

 in the relative importance which these beds bear to the rest of the strata 

 associated with them. In fact the grits of the Millstone Grit in this 

 county are scarcely in any way different from many of those of the 

 Limestone Series below or of the Coal Measures above them. It is true 

 that grits and sandstones are still the predominant rocks, and that the 

 quartz grains of the grits are often found to have been augmented in 

 size by the addition to each grain of crystallographically orientated 

 secondary quartz. On the other hand the shales which intervene be- 

 tween the grits are absolutely identical with those of the great forma- 

 tions above and below, and no fossils have so far been met with which 

 can be said to characterize the division pahcontologically. It may be 



' I'uWislicd in the Tianiacliotis of that Society in 1904. It .-ippcirs from this boring that several 

 limestone bcda which, in south NorlhumhcrlanJ, arc intercalated between the Great anil the Little 

 Limntonci, pcriist in north Durham, as indeed might well have been expected. 



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