Ixxxiv PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



condition in the superjacent shale, caused a rupture or breach of 

 continuity, and allowed the subjacent plutonic rocks to be pushed 

 through them ; and such appears to be JNIr. Moore's opinion, as he 

 considers the intrusion to have been subsequent to the folding of the 

 strata, and to have even modified its usual E.N.E. strike. The next 

 object of Mr. Moore is to determine the relative age of the graptolitic 

 schists of Wigtownshire, as regards the conglomerate beds observed 

 in the Loch Ryan Section, and at Corswall Point, &c. In Professor 

 Harkness's paper the position of certain graptolitic and anthracitic 

 beds associated together was shown to be above other fossiliferous 

 schists also containing graptolites which lie close to the base of the Silu- 

 rians ; the object of this paper is to show that the equivalents of these 

 graptolitic beds or the graptolitic schists of Wigtownshire are really 

 geologically below certain conglomerate beds, though apparently stra- 

 tigraphically above them. After a careful examination, Mr. Moore 

 concludes, that the folds of the Silurian strata have thrown them 

 over and caused them to appear as if deposited upon the conglomerate 

 beds and limestone of the south of Ayr, which he considers the equi- 

 valent of the Wrae limestone and its associated conglomerates. The 

 latter, Professor Nicol has shown to be superior to the graptolitic 

 schists, and their apparently contradictory position in Wigtownshire 

 and Ayrshire Mr. Moore ascribes to one of those great inversions or 

 flexures so remarkable in the Ardennes, Eifel, and Appalachian Alps. 

 Another paper on Scotch geology was contributed by Professor 

 Nicol, who describes the results of his careful examination of the 

 Red Sandstones and Quartzites of the north-west of Scotland, over a 

 district extending in a N.N.E. and S.S.W. direction, from Cape 

 Wrath and Durness to Sleat, the southern portion of the Isle of 

 Skye, containing an area of 100 miles in length by a breadth of 

 from 15 to 30 miles. The immense difficulties which must ever 

 attend the examination of so wild a district, independent of its 

 magnitude, are fully recognized by Professor Nicol, and we must re- 

 member, as explanatory of the possibility of effectually examining it 

 in a short time, that he had before gone over much of it with Sir R. 

 Murchison, and that he had had before him the results of the labours 

 of MacCulloch, Sedgwick, Murchison, and others. One of the most 

 remarkable features in this paper is the recognition of two bands of 

 gneiss, the one below, both as respects its position and the dip of its 

 beds, the series of sedimentary rocks described, and the other appa- 

 rently above them, as shown by the dip of the strata. In the Loch 

 Broom, southern section, the lower gneiss appears underlying the Red 

 Sandstone, and the series is lower gneiss in vertical beds, sandstone 

 in very gently sloping beds, quartzite resting unconformably at a 

 higher dip on the sandstone, a bed of porphyry or serpentine, upper 

 gneiss, dipping at an angle of 23°, or nearly parallel to those of the 

 quartzite. In all the other sections a siliceous limestone occurs be- 

 tween the quartzite and the upper gneiss, being in stratification 

 conformable to both. The maximum thickness of the Red Sand- 

 stone with its conglomerates is considered to be about 3000 feet, 

 thinning off to the eastward, and that of the quartzite, with its sili- 



