216 Mr. BuDDLE on the Great Fault called the Horse 



the seam of coal, to a considerable distance on both 

 sides of it, undulates and is irregular, causing the seam 

 to vary in thickness, while the pavement nearly pre- 

 serves its ordinary regularity. The depressions of the 

 roof, as shown in the Section, are called " Lows " by 

 the colliers. 



The pavement is composed of the ordinary argil- 

 laceous deposit which accompanies the seam all 

 through the Forest Basin, and the roof is formed of 

 the strong sandstone which usually reposes upon the 

 Coleford High Delf seam, with the occasional interpo- 

 sition between it and the coal of a thin layer of a 

 black slaty substance. 



The coal under the depressions of the roof or lows 

 is generally deteriorated in quality by being inter- 

 mingled with particles of the sandstone of the roof; 

 but it is not mixed with boulders, angular fragments, 

 and gravel, as has been erroneously imagined. What 

 have been understood to be boulders and gravel are 

 nodules of highly indurated, ferruginous sandstone of 

 various sizes, some very large, scattered irregularly 

 through the thick stratum of sandstone, forming the 

 roof of the Coleford High Delf seam. These nodules 

 are generally of a spherical form, but some of them 

 are kidney-shaped, and others are only sections or 

 parts of spheres. The latter cannot be detached from 

 the surrounding sandstone rock, but form part of it, 

 and generally occur in the middle of the " pannels " 

 of the rock, in the solid part between the beds and 

 partings or backs. 



The more perfectly formed nodules, called Yolks by 

 the miners, lie in a mould formed in the rock to which 

 they are attached by their ferruginous coating, but 

 the surrounding and immediately adjoining parts of 

 the stone are much indurated, and radiating cracks 

 generally proceed from the sides of the cavities. These 

 yolks occur in all parts, sometimes in the middle of 

 the pannels and sometimes near the joints. 



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