Murchisoris Silurian System. 



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the hills are fissured. The workmen, however, have to contend with 

 rather an unusual natural obstacle to mining, in the winds which blow 

 with great force against this lofty and unprotected district, and which 

 not only render the labour at the pit's mouth difficult, but, without 

 certain precautions, would, at times, entirely stop the works. The 

 most violent winds are from the west and south-west, and during their 

 prevalence the galleries are filled with powerful gusts, accompanied 

 with much noise. This furious ventilation prevents, of course, the 

 collection of any fire damp, so that the Brown Clee miner is compen- 

 sated for working in these cold and noisy chambers by the absence of 

 all noxious gases. 



The coal measures of these hills are intersected by a vast number of 

 small faults, one set of which trend from north to south, the other from 

 east to west. In the Abdon Barf there are four principal faults, two of 

 which have north and south direction, the other two from east to west, 

 cutting the former at right angles. The north and south faults range 

 along the coal measures on the eastern slope of the hills, where no 

 basalt overlies them, one near the junction of the coal with the old red 

 sandstone, the other passing within two or three hundred paces of the 

 cap of basalt. The two transverse faults (termed facing faults) are 

 about eleven yards in width, and affect all the measures and faults up 

 to the edge of the basalt, and are therefore of the most recent date. 

 The north and south faults are upcasts towards the basaltic summit ; 

 the principal or lower south and north fault being an upcast of twenty- 

 six yards. The upper north and south fault is only an upcast of about 

 six yards, and neither of the east and west faults exceeds that amount 

 of dislocation. Besides these, there are innumerable minor north and 

 south faults, which are all upcasts, reckoning from the old red sandstone 

 of the surrounding low country as a base line. 



In the Clee Barf the faults are not large, and unlike the Abdon 

 Barf the coal has been proved, if not worked out, under every part of 

 it. In this hill most of the faults are more or less from east to west, 

 producing small and trifling upcasts to the south. The fissures result- 

 ing from these dislocations are filled with an indurated breccia of coal 

 measures (clods, shale, sandstone, &c), the miners persisting that no 

 fragment of jewstone or basalt was ever found in them. 



The most extensive of the east and west faults are those by which a 

 large mass of the old red sandstone has been heaved up to the same 

 level as a portion of the coal, so as to occupy the depression between 

 the two basaltic summits, and thus to separate the coal measures into 

 the two small tracts described. 



The bare recital of these various dislocations may have caused my 



