1856.] MOORE — SILURIAN ROCKS OF WIGTOWNSHIRE. 365 



pressure by the folding, and so has preserved no vestiges of strati- 

 fication. 



The beds then decline to a low angle, becoming almost horizontal, 

 still showing red shales covered by thick-bedded grit, until at the 

 north side of Port Naughan Bay they resume their south dip at an 

 angle of about 15°. At the south side of Garvillan Bay the red flags 

 dip S.E. at an angle of 60°, and a little farther north, the rock under- 

 lying these red flags loses all traces of bedding ; — again suggesting 

 that we have arrived at an anticlinal folding. Accordingly a little 

 farther north, near the Genock Rocks, vertical red flags are seen, with 

 thick-bedded grit to the north of them. These continue to a point 

 a little south of the Ox, where the first bed of coarse conglomerate 

 occurs, and from thence to the Corswall Lighthouse the rocks con- 

 sist of repetitions of red flags, grit, and conglomerate, all vertical or 

 nearly so. Where the conglomerate first occurs, it is almost in- 

 distinguishable from the grit : it is, in fact, a grit of the same kind 

 of sand, but containing here and there a block of granite or felspar- 

 porphyry from 1 to 2 feet in diameter. 



Farther north, near the Lighthouse, the rock is mainly composed 

 of these blocks, some of them of very large dimensions. I have 

 measured one of 6^ feet in its greatest diameter. 



If we take the section along the eastern shore of Loch Ryan, and 

 examine it carefullv, we shall come to the same results. The coarse 

 conglomerate is found on the Ayrshire shore near the Finn art Point, 

 and from thence to the Cairn the Graptolitic schists appear to lean 

 against it : but I believe the following to be the true interpretation. At 

 the Cairn the schists are vertical ; a quarter of a mile to the north they 

 are seen dipping at an angle of about 30° to the south ; from thence 

 to Glen App they are bent into three or four folds which all dip 

 south : at the south side of Glen App they are still seen, containing 

 the Graptolites and dipping south at an angle of about 45°. From 

 thence to the north side of the bay all rock has been washed away : 

 but at the north side the slates are seen again vertical, and some 

 highly contorted flaggy beds immediately to the north of them. I 

 infer therefore that Glen App is the site of an anticlinal arch, and 

 that the valley has been scooped out along a line where the fracturing 

 of the rocks has facilitated their removal by denudation. From 

 thence to the conglomerate at Finnart Point the Graptolitic schists 

 never re-appear ; but the rocks consist of flaggy beds similar to those 

 which intervene between the conglomerate and schists first described 

 along the Irish Sea. From both of these sections, therefore, I con- 

 clude that the coarse conglomerate is superior to the schists with 

 Graptolites. 



With respect to the rocks from thence to the Mull of Galloway, I 

 would only state briefly that the red and buif shales near the Mull 

 of Galloway are lithologically very like those next to the coarse con- 

 glomerate at the Corswall Point ; that the bluish slates of the Gren- 

 nan, and perhaps also the dark anthracitic shales of Morroch Bay, 

 containing Graptolites, are probably repetitions of the blue flags of 

 the Cairn ; and lastly, that certain dark gritty beds, consisting of 



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