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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 28, 



pearance of violence or dislocation. It is true that a mass of granite 

 (Dunman) is intruded near that quarter, and that the bearing of that 

 granite towards the granite of Cairnsmuir in Kirkcudbrightshire is 

 nearly in the line of strike of the stratified rocks. But the granite of 

 Cairnsmuir is nearly thirty miles distant from that of Dunman ; and 

 this last does not occur at the point of change of dip, but about two 

 miles to the south of it. Moreover there are many reasons which 

 show that all the principal movements which these Silurian rocks have 

 undergone had been impressed upon them previously to the intru- 

 sion of the granites, which have deranged the E.N.E. strike of the 

 rocks — not occasioned it. Lastly, it seems to me that the intrusion 

 of a small wedge of rock, not two miles thick, is wholly inadequate 

 to account for a displacement which is felt for a distance of more 

 than thirty miles. 



II. I now come to the question of the relative ages of the Grapto- 

 litic schists of "Wigtownshire and of the coarse conglomerates of the 

 south of Ayrshire. 



There can be no doubt that the slate and anthracitic schists of 

 Selkirkshire and Peebleshire* are the equivalents of similar rocks 

 seen along the western coast of Wigtownshire ; and also that the 

 Wrae limestone with its associated conglomerates is the counterpart 

 of the limestones and conglomerates of the south of Ayrshire. And 

 as Prof. Nicol, in a section laid before the British Association in 

 1852, distinctly places the "Wrae limestone above the Graptolitic 

 slates of Grieston, the question may appear to be determined. Still, 

 as the two sections appear to be contradictory, the whole country for 

 many miles to the south of the Stinchar appearing, as above described, 

 to lean on that to the north, it may be worth while to attempt to 

 reconcile them. 



Beginning about three miles southof the CorswallLighthouse(fig. 4), 

 at the point marked * Burn-foot ' in the Ordnance Map, near Dally 

 Bay, we find thick-bedded grit overlying red shales and black shales, 

 which are in all respects similar to the shales of the Cairn on Loch 

 Ryan, and contain the same Gruptolitesi all these rocks dip south at 

 a high angle. As we proceed north, the thick-bedded grit is again 

 met with, traversed by a band of porphyry, and apparently forming 

 a sharp synclinal, with both legs dipping south. Next to them, to 

 the north, the red and black shales fill up all the space to the middle 

 of Dally Bay : they are vertical, or have a slight dip to the south. 

 The rock then becomes almost amorphous, with scarcely a trace of 

 bedding; but is of the same fine-grained material as the black 

 shales. This amorphous rock forms the north side of Dally Bay; still 

 further north the black shales, covered by red flags, and these last by 

 a thick-bedded grit, again appear, dipping north. It is clear that 

 we have passed an anticlinal, and the amorphous rock is doubtless 

 the dark shale, which, being in the centre, has suifered enormous 



* See Papers by Prof. Nicol, Prof. Harkness, and Sir R. Murchison : Quart. 

 Journ. Geol. Soc, vol. iv. p. 204 ; vol. vii. p. 46 & p. 139 ; vol. viii. p. 393 ; 

 voL xi. p. 468 ; and vol. xii. p. 238. 



