FAULTY GROUND, 



lOT 



land or in Wales exceed from six to nine feet in thickness ; but a 

 difference in the quality may generally be observed in the upperj 

 lower, and middle parts of the same bed. 



A curious fact is stated by Mr, Keir respecting the main coal of 

 Staffordshire. In one situation the upper part of the bed separates 

 from the lower, and rises to the surface, or crops out. It is at first 

 divided by indurated clay called bind or clunch ; but as the distance 

 becomes wider, the intervening stone grows harder, and will strike 

 fire with flint. Similar separations sometimes take place in the beds 

 of coal in the mines of Northumberland and Durham. The largest 

 known bed of coal in the west riding of Yorkshire is near Barnsley : 

 it is ten feet thick, and is supposed to be formed by the meeting of 

 iwo or more seams, which soon separate again. The miners have 

 not been able to trace the same bed in situations where it might have 

 been found, had it preserved the same thickness, in other parts of its 

 course. 



Coal strata, beside the more common dislocations by faults, pre- 

 sent remarkable contortions, which it would be difficult to explain^ 

 except by admitting a lateral force, which has compressed them into 

 a zigzag form. To the same cause, or perhaps to a partial sinking 

 of the earth, we may attribute the origin of what is called faulty 

 ground^ which frequently occurs in coal-fields. In this, no actual 

 dyke. appears to have been formed; but the beds of coal, with all 

 the accompanying strata, are so broken and shattered, that no work- 

 ings can be carried on, till the miner has got through them into regu- 

 lar strata. These broken parts of the strata, called troubles and 

 faulty ground, occasion much more difficulty to the miner than com- 

 mon faults or dykes, and are sometimes of great extent. 



In some coal fields one part of a stratum is inclined, and the other 

 part vertical. A curious fact of this kind may be seen in a small coal 

 field near the town of Manchester.^ 



The position of coal strata in many coal fields may be represented 

 by a series of fresh water muscle shells, decreasing in size, laid with= 

 in each other but separated by a thin paste of clay. If one side of 

 the shell be raised, it will represent the general rise of the strata in 

 that direction ; and if the whole series be dislocated by partial cracks 

 rising one part a little and depressing the other, to represent faults in 

 the coal, it will give a better idea of the coal field than any descrip- 

 tion can convey. We are here to suppose that each shell represents 

 a stratum of coal, and the partitions of clay the earthy strata by 

 which they are separated » The outer shell represents the lowest 

 bed of coal, which may be many miles in extent. Now, if a much 

 larger shell be filled with sand, and the lowest shell be pressed into it 

 we may consider thelarge shell to represent limestone, and the sand 



* I have given a short account of this coal iickl m the second volume of tlw 

 Transactions of the GcoIoKicai Society 



