DISLOCATIONS OF THE OLD RED SANDSTONE. 



189 



the numerous bold escarpments, deep ravines, and fine natural sections with which the 

 country abounds, we have inferred that the system contains no mineral ores worthy of 

 economical attention. The presence of these copper veins in the Old Red is curious, 

 as presenting an analogy to similar veins described as the chief mineral ore in the 

 New Red Sandstone. If it be worthy of remark that these two Systems, so dif- 

 ferent in age, yet agreeing so much in their predominant colour and component parts, 

 should contain the same metallic ores, we shall hereafter have occasion to see the phe- 

 nomenon repeated a third and fourth time in sandstones of the Silurian and Cambrian 

 Systems, the rocks in such cases being of the same red and green colours as in the 

 New and Old Red Systems. 



Shall we suppose that these coincidences are purely accidental, or that they have 

 originated in a general cause? Although I have never reflected on them without 

 being led to speculate on the hypothesis, that some portion of the matrix, common 

 to all these red deposits, had been so operated on by heat, galvanic agency, or other 

 cause of mineralization, that copper ores have been the result ; still, as I am not aware 

 that any chemist will yet venture to establish a theory founded on such data, and as 

 we know that similar ores occur in other countries throughout strata of grey and other 

 colours, as well as those of red and green, we must, I fear, remain contented with the 

 simple announcement of the fact, until the chemical philosopher shall more particularly 

 direct his powers to the subject. 



As there are no metallic veins, so is there no coal in the Old Red Sandstone of this 

 region. I have, indeed, previously shown, that there are not the smallest hopes of ever 

 discovering a workable seam of coal within the area occupied by this system, because 

 it never contains the vestiges of any quantity of vegetable matter out of which that 

 mineral may have been formed 1 . 



Dislocations. — Some of the most prominent dislocations of the Old Red Sandstone, 

 are those which appear on the northern and western edges of the south Welsh coal-field, 

 and in the Clee Hills ; in short, in the elevated tracts already described in the eighth 

 and thirteenth chapters, where the Old Red Sandstone is seen supporting the carboni- 

 ferous limestone and overlying coal-fields. One of the most powerful of these dislo- 

 cations is probably that of the Caermarthenshire Fans, described p. 164, being an upcast 

 of at least eight hundred feet. It has also been shown that the elevated coal tracts 

 which lie in basins, have been fashioned into those forms by violent dislocations which 

 have necessarily upturned the surrounding ledges of Old Red Sandstone, in common 

 with the superposed carboniferous masses. The geologist will readily understand, that 

 as such dislocations are generally transverse to the circular or elliptical edges of the 

 coal-fields, the course of the faults must vary with every change of the strike, and 



1 On the borders of England and Scotland, principally on the northern banks of the Tweed, coal seams re- 

 occur at intervals, not only through the whole of the carboniferous system, including the mountain limestone, 

 but also partially beneath that formation, in the upper member of the Old Red System. 



2 A 



