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MESSRS. KIRKBY AND DUFF ON THE 



an article of great demand, and the small coal or dross, which 

 had previously been a source of trouble and expense to the coal- 

 owner, now proved of almost as much value as the large coal, 

 which in such soft seams as the "Brockwell," certainly meant 

 an important change for the better. 



COAL MEASURES. 



The Coal Measures of this district differ little in general struc- 

 ture from the rest of the coal-field, being composed of alternating 

 strata of sandstone and shale, with seams of coal and their ac- 

 companying underclays, and more rarely bands of ironstone. 



The principal coal seam is the Brockwell, which ranges from 

 four and a half feet to six and a half feet thick : it is generally 

 of excellent quality, forming a good but rather soft household 

 coal, while for coking it is probably the best in the county. 

 Above it, from twelve to twenty fathoms, is another, called the 

 Five Quarter or Busty, of inferior quality to the first, and vary- 

 ing from three feet to five and a half feet thick. This is chiefly 

 wrought as a steam coal, but is also largely used for coking. 

 Occasionally on the dip side of the Butterknowle and Wiggles- 

 worth faults a third and even a fourth workable seam are brought 

 in. The first of these is named the Harvey or Yard Coal ; the 

 latter is very little known. The distribution of the last mentioned 

 coals is very limited, and the importance of the district as a coal 

 field has hitherto depended upon the two former, more particu- 

 larly upon the Brockwell. 



Below the Brockwell there is a considerable thickness of Mea- 

 sures containing a few thin coals which will be afterwards noticed 

 separately, as the Brockwell is taken as the base of the group of 

 strata containing all the important coal seams. 



The dip of the Coal Measures on the north side of the Butter- 

 knowle fault is usually to the east, at no great angle ; towards 

 the southern termination of the field, on the south side of the 

 great faults, the general inclination of the strata is northerly, 

 at a comparatively high angle. 



Fig. 1 is a generalised vertical section of the coal-field about 



