32 MONOGRAPH OF DURA DEN. 



ill the dip of the strata on the one side ; a few black lines 

 interspersed among stripes of white on the other side ; and 

 this is the simple lithograph by which nature tells of energies 

 whose products are mountains and valleys, new teeming lands 

 of forest wealth, seas swarming with the moving things that 

 have life, and mineral treasures enclosed for man's use which 

 time only can exhaust. 



The northern line of the Carboniferous system — the lip of 

 the great coal-basin in Scotland — lies within the valley of Dura 

 Den. It is distinguished by three or four thin seams of coal, 

 with alternating bands of whitish sandstone, and all much 

 broken, indurated, and upheaved by an outburst of greenstone 

 trap. At the point of junction {p x) the sandstone is converted 

 into chert, and in several places so welded to the igneous rock 

 as scarcely to be disjoined by the stroke of the hammer. In 

 the more southern part of the Den, the trap repeatedly alter- 

 nates with the sandstone, which is there of great thickness, 

 and thin bands of ironstone, shale, coal, and limestone begin to 

 appear as the harbingers of the true coal series in the Ceres 

 basin. There the beds of coal are of great thickness, the main 

 seam being sixteen feet ; and the limestone is equally remark- 

 able for its vast profusion of animal remains, some of the 

 bands at Teases, Craighall, and Drumcarro being an aggrega- 

 tion of encrinites, producti, and other molluscs. The Mytilus 

 alone forms a band of shale of several feet thick, extending 

 from the West Lomond to the Witch Lake at St. Andrews, in 

 nearly one continuous mass of dark-coloured sliells. 



The mountain limestone defines throughout the district 

 the limits and outcrop of the true series of coal-metals. 

 All the beds beneath are of little value as combustibles, and 

 unremunerative in the working ; those above this calcareous 

 mass are extremely rich in qualit}^ and amount upon an 

 average to fifteen workable seams of coal, while in the Dysart 

 basin they are thirty-three in number, and some of them of 



