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found that they will be thrown up again as much by one slip, as 

 they appear to have been thrown down by the other. It sometimes 

 happens that all the slips are down-slips, the strata seeming to have 

 sunk lower in each succeeding slip. These slips differ very much 

 in their width, as well as in the matter with which they appear to 

 have been filled. Some, which are wide, are filled with adventi- 

 tious and heterogeneous matters ; and others with soft argillaceous 

 substances. Other slips are seen, in which, although the strata are 

 thrown a great many fathoms off the ordinary level, the two sides 

 of the fissure are found, in some places, quite close together. In 

 these perpendicular fissures, or rake veins, as they are called by 

 miners, a confused mass of heterogeneous matter, solid whin-stone, 

 spar, ores, and metals, and particularly sulphurets of metals, are 

 frequently found ; very large ribs of spar, and of pyrites, being 

 very frequently thus disposed. A DYKE is a separation or chasm 

 in the coal and accompanying strata, which differs from the slip, 

 chiefly in bearing the marks of a mere fissure or separation ; the 

 coal seams and other strata being not thrown off their levels, as in 

 slips ; and the heterogeneous matters with which the chasm ' has 

 been filled, bearing more plainly the marks of having been brought 

 there by water. 



In slips the coal metals have a vise, which is the vestigia of the 

 coal, and which leads upwards, or downwards, to the separated 

 stratum of coal ; but in dykes there is no such vise leading through 

 to the other side. Sometimes the crack or chasm in the coal, and 

 in the accompanying strata, resembles the dyke in every respect, 

 except that the foreign matter is not indurated as in that of the 

 dyke, but always continues loose, and generally very wet. These 

 are called GALLS or GASHES. 



When the separation is not very considerable, and the strata on 

 each side the fissure maintain their original position, it is called 

 A HITCH. In some places, without any apparent cause, the coal 



