﻿part 2] 



THE I SLAT ANTICLINE. 



161 



Society in 1891. No one has since questioned the fa r 

 being separate limestones, and it is doubtful whether ti ive is now 

 a single modern official Survey publication in which the Loch lay 

 Limestone is not taken to be below the Quartzite. Had ; 

 facts been published at the' time, the remarkable discuss 

 the Quartzite being at the top of the Series could not h; 

 place — it is an obvious absurdity. 



Thus on the eastern side of Islay the top and the basi- 1 if tht 

 Quartzite occur : the latter (as usual) is the coarser, the top I 

 finer, often very fine and often remarkably white ; this fine n 

 occurs on the side next the Blair Athol Limestone, and there 

 be in the Highlands altogether many hundred outcrops of tins 

 white margin, though, except by the speaker, they are ran if 

 ever mentioned. The usual erosion Occurs" below the 'limes 

 and, being in a folded area, it causes the outcrop of the bee to 

 approach and recede from the margin of the Quartzite in the usual 

 characteristic manner seen on most modern maps. When the 

 limestone is followed round, it is seen that the Quartzite is all one 

 quartzite; and this- is confirmed by the' frequent occurrence of 

 the typical white margiil in the area some distance west of Loch 

 Finlagg'an. It is now' seen that the Boulder Bed (Portaskaig 

 Conglomerate) of this area has exactly the same relations with the 

 limestone and quartzite as at Schiehallion, placing the identity , of 

 the various beds beyond serious' doubt ; the limestone is the Blair 

 Athol Limestone. (The speaker here placed on the table the 

 Geological Survey 1-inch maps, Sheets 27 & 55, so that the 

 Fellows might satisfy themselves as to this identity.) 



In view of what has been stated, the theory advanced by the 

 ■ Author that the ground 1 between the two outcrops of quartzite is 

 an anticline seems impossible : if, as shown, the lirriestone is above 

 the fine margin of the Quartzite, it must be a tilted syncline, the 

 structure being identical with that at Portsoy in the East of 

 Scotland. The white margin is well seen on the ground, where 

 . the so-called ' Fucoid Beds ' are shown to terminate on the map ; 

 the speaker found no trade of Fucoid Beds at the places indicated. 

 The statement that the Author disagreed with the view that the 

 Portaskaig Conglomerate was not the Scarba Conglomerate is not 

 well put : the ground was mapped by Mr. Wilkinson, who held no 

 .such view, but his opinion was ignored ; further, Mr. Wilkinson 

 had no doubt that the two conglomerates are on opposite sides of 

 the Quartzite, but he doubted whether the side on which the 

 limestone occurs was the fop. 



. Turning now to the sandstone south-west of the so-called ' Loch 

 Skerrols Thrust,' the speaker thought these crucially important; 

 he doubted the existence of the thrust at all, and believed that these 

 sandstones are brought on by pitching of the folded Quartzite, and 

 that small patches cross the so-called thrust and are infolded with 

 the margin of the Quartzite. These beds, as also their relation to 

 the limestone and Quartzite, are better seen in the Bowmore area. 

 One now sees that these sandstones have the persistent flaggy habit 

 and the curious persistent dip in one direction, due to singularly 



