132 COAL-FIELD OF CLACKMANNANSHIRE. 



passed under these mountains, as is the case with 

 the Old Red Sandstone on the eastern part of the 

 range; whereas, in place of passing under the 

 Ochills, it rises with the coal and other accompany- 

 ing strata at a short distance to the north of where 

 the coal is seen, and lies in a conforming situation 

 with the, face of the mountains, at a great angle 

 with the horizon, exactly similar to the coal strata 

 adjoining the Woodhill of Alva, as represented in 

 the section. This blush-coloured sandstone fre- 

 quently contains masses of sandstone of a deep red 

 colour, with mica : and sometimes these darker co- 

 loured portions, found in the soft sandstone, are of 

 adamantine hardness, and are perforated by the 

 miner with the greatest difficulty. The hardness is so 

 great, that I have seen twenty-seven steel boring 

 chisels blunted, in boring a shot-hole 20 inches in 

 depth. This is a fact worthy of remark. The same 

 case occurs in the white and yellow coloured sand- 

 stone. These hard portions found in beds of sand- 

 stone, are named by the miners, Tongues or Yolks, 

 according to their shape, as represented Fig. III. 

 Plate VI. Granite and greenstone compared with 

 these Yolks, are very soft. 



With regard to the great slips which dislocate 

 the strata, these lie in the direction of the line of 

 bearing of the strata, and are nearly parallel with 

 the Ochill Mountains. The great north slip dislo- 

 cates or throws down the strata 700 feet ; and the 

 great south slip dislocates or throws down the strata 



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