36 MONOGRAPH OF DUE A DEN. 



and among all classes of rocks, from the oldest 2;)rinmry to the 

 newest tertiary, they are obviously designed to subserve some 

 grand purpose in the plan of creation. 



The coal measures are likewise intersected by faults or 

 fractures, the fissures occasioned by which are usually filled 

 with clay and debris of the surrounding rocks. They may be 

 considered as so many excellent mechanical contrivances, by 

 means of which the useful mineral has been rendered accessible 

 to man. Had they not existed, the pits must have speedily 

 filled with water, or the w^ater have accumulated in such quan- 

 tities as to have exceeded all power of machinery in effecting 

 the drainage of a mine ; whereas, by the natural arrangement 

 of a system of faults, the continuous beds of shale and sand- 

 stone, alternating with the coal, are broken up into limited 

 sections, and the water percolates in limited quantities. The 

 component strata are thus divided into insulated masses, rising- 

 one above another in the form of a stair, and inclined at a 

 considerable angle to the horizon ; so that, while each section 

 is separated from the adjacent beds by a mass of clay imper- 

 vious to water, the limited extent which it occupies, and the 

 inclined position into which it has been thrown, serve to render 

 the operations of the miner comparatively easy, as well as 

 greatly to diminish the expenses of excavating the mineral. 



The first appearance of the coal deposit in Dura Den fur- 

 nishes a beautiful example of these remarkable phenomena in 

 the action of both dykes and faults. Three beds of coal, with 

 their enclosing shales and sandstones, are severally lifted from 

 their original horizontal position, elevated to an angle of forty- 

 two degrees— some of them to the pei-pendicular — are again 

 shifted downwards, and finally replaced in the most perfect 

 horizontality towards the upper part of the Den. There are 

 several repetitions of similar dislocations, upheavals, and de- 

 pressions, as the coal metals rise southwards to Largo-ward, 

 there attaining an elevation of 600 feet above the level of Dura 

 Den, and even higlier in the coal basin of Rires on the slo[>ing 



