﻿1851.] MURCHISON SILURIAN ROCKS OF SCOTLAND. 



157 



B. Schistose Rocks ranging through Wigtonshire and 

 Galloway to Kircudbright. 



It would be presumptuous in any one who, like myself, merely 

 made one transverse section of them, to pretend to define the precise 

 relative age of the schists of Wigtonshire which succeed on the south 

 to those of Ayrshire. Mr. J. Carrick Moore and Mr. Salter have 

 already described some of their Graptolites* , and Professor Sedg- 

 wick has visited the localities and is better acquainted with them than 

 myself. 



Referring, however, to the opinion already expressed, that the 

 limestones and associated strata of the Stinchar are the oldest rocks 

 of the tract, and also that the portion of them in which any stratifi- 

 cation is visible dips southward, it might be suggested, that the schists 

 of Wigtonshire, in which the Graptolites occur, may possibly lie above 

 them ; but I have formed no decisive opinion on this point. 



To the south of Ballantrae all sequence of the stratified masses is 

 again cut off by a large development of igneous rocks, which form the 

 chief eastern headland of the mouth of Loch Ryan. We have thus 

 ample space for another great axis and repetition of shelly sandstones, 

 &c. Mr. J. Carrick Moore has, indeed, it seems to me, done much 

 to indicate an equivalent of such by having found, as he has recently 

 informed me, masses of vertical conglomerate very similar to those 

 of Kennedy's Pass at the point of the headland of Finnart and to the 

 south of all the trappean cliffs. This conglomerate, therefore, when 

 prolonged upon the strike, lies in an intermediate position ; the great 

 trappean and limestone region being on the north, the Wigtonshire 

 schists on the south. Little evidence is obtained on the sides of the 

 high road which passes inland by Glenap Lodgef, and owing to in- 

 trusive bosses of trap the strata are in great disturbance and undu- 

 lation. As soon as we pass over undulations of worthless greywacke- 

 sandstone, which is exhibited in a rude anticlinal, this tract is seen 

 to consist almost exclusively of schists, on the whole much re- 

 sembling the *rotch' and mudstone of S. Wales. In a rough, rocky 

 glen, which leads down to the valley of the Finnart, the rocks pre- 

 sent all that irregularity or confusion of stratification so prevalent in 

 the schists and ' rotch ' of S. Wales, with numerous imperfect clea- 

 vages ; but after some rude undulations, acquiring more of a flagstone 

 character, the beds pitch southwards at a high angle, and thus con- 

 duct the observer to the well-known slate-quarries of Cairn Ryan. 

 There, as Mr. J. Carrick Moore has shown, Graptolites both folia- 

 ceous and simple abound. There are no slates (at least none that 

 Professor Sedgwick would admit to be such) in the quarries of Cairn 

 Ryan ; but those used for roofing are simply finely laminated flag- 

 stones. The surfaces of the beds have here and there a most re- 

 markable polish, and are farther remarkable in exposing Graptolites 

 spread along the laminae of deposit. Some of the surfaces of the beds 

 have even a slightly rippled surface, and curvatures occur here and 

 there. 



* Loc. cit. p. 15, 16, PL 1, 



f The seat of the Earl of Orkney, 



