﻿1851 .J MURCHISON SILURIAN ROCKS OF SCOTLAND. 163 



In reference to details, however, Mr. Harkness maintains that the 

 three bands of anthracitic and alum shale with courses of Grapto- 

 Utes — in many parts a complete alum shale, owing to the quantity 

 of decomposed pyrites it contains — are repetitions of the same band. 

 It might, however, be possible, I think, to explain their repetition 

 by great curvatures, the upper parts of which had been denuded, as 

 well as by the occurrence of a series of parallel faults of great magni- 

 tude to which that author refers them*. His own sections show, 

 indeed, a great parallelism between the strata on either side of these 

 supposed faults. 



Difficult as it may be in such a covered and broken region, to un- 

 ravel the physical contortions to which it has been subjected, the 

 task will doubtless be accomplished at some future day ; and when 

 this is done, I have no doubt that, gigantically thick as they may 

 appear on a superficial survey, the older rocks of Dumfriesshire, 

 like those of parts of the South of Scotland where we have been able 

 to explore closely, will be reduced to reasonable dimensions. In the 

 mean time, if the point be substantiated, we shall be much indebted 

 to Mr. Harkness for labours, which lead us to believe that, whatever 

 be their precise place in the Silurian series, the graptolite-schists of 

 Dumfries are simply repetitions of one band — an important step in 

 limiting the thickness of the strataf . 



* Quart. Journ. Geol. Soc. vol. vii. pp. 51, 52. 



f Although this is not the place to offer many observations on other rock-for- 

 mations of this tract, I may state, in passing, that I am not yet satisfied that the 

 Red Sandstone of Dumfries and Corn Cockle Muir is of the age of the Trias as 

 suggested by Mr. Harkness (Quart. Journ. Geol. Soc. vol. vi. p. 389 et seg.). In 

 the upper recesses of the valleys, and notably east of Moffat, this formation is a 

 coarse shingly and quasi-angular conglomerate, made up of the debris of the Si- 

 lurian greywacke on which it rests, and is there associated with deep-red sandstone. 

 In its range southwards, I have not seen this same red sandstone also overlapping 

 ^conformably the edges of the carboniferous deposits. If those red rocks were 

 really of the age of the " Bunter sandstein," they would surely (seeing their wide 

 spread in Dumfriesshire) be somewhere seen in overlying and contrasted positions 

 to the carboniferous rocks which were formed at a period so long anterior to them. 

 My scepticism on this point acquires some strength from the recollection I have of 

 red sandstones in Arran, which Professor Sedgwick and myself (even when we 

 were introducing reforms into Scottish geology) classed as New Red, and which 

 we now regard as Carboniferous. The truth is, so many of the Scottish sandstones 

 from the Old Red upwards are of a red colour, that much discrimination will be 

 required in separating those which are of Devonian from some which are of 

 carboniferous, and from others which may probably be of Permian age. If I 

 were to judge from the aspect of the rocks, their flag-like and hard character, 

 and the great dislocations they have undergone (almost as great as those of the car- 

 boniferous limestone), I should prefer classing the Red Sandstone of Dumfries 

 with the Permian. At present, as far as I know, geologists, guided exclusively 

 by the footmarks, consider the impressions left by Reptiles at Corn Cockle Muir 

 to belong to species whose footprints are found in the, so called, New Red of 

 England. (See the forthcoming Ichnology of Annandale, by Sir W. Jardine, Bart.) 

 But this is as yet doubtful evidence ; for, with the exception of the Keuper sand- 

 stone, we really at present scarcely know what amount of rock beneath it ought 

 to be classed with the Trias or Mew Red, or how high the Permian system, or 

 summit of the palaeozoic rocks (in which Reptiles also occur), should ascend 

 in the English scale. A reference to section fig. 1, accompanying Mr. Harkness's 

 paper (Quart. Journ. Geol. Soc. vol. vii. p. 52), will indicate the difficulty of sharply 



