412 C. CALLAWAY ON THE NEWEK GNEISSIC 



1. The Caledonian was laid down unconformably upon the He- 

 bridean. 



2. The Caledonian was faulted down to the east along a S.S.W. 

 line, and was subsequently denuded from the upcast side. 



3. The Assynt series was deposited on the Hebridean ; and being 

 derived from land to the west, it thinned out eastwards, only the 

 attenuated extension of its strata passing beyond the fault to the 

 Caledonian. 



4. The motion of the Caledonian was reversed, and it was up- 

 heaved along the old line of fault, breaking off the overlying quartzite 

 and dolomite along the same line, parallel faults being formed near 

 it to the west. By powerful lateral thrust from the east, the 

 Caledonian was forced up beyond the fault, so as to double back 

 the Assynt rocks and to overlie them for some distance. At the 

 same time a parallel slice of Hebridean lying to the west was, in 

 like manner, thrown over onto the quartzite and dolomite. 



5. The Assynt rocks east of the great fault were denuded, leaving 

 only a few scanty patches of quartzite. 



VI. Reply to Objections. 



Perhaps the most serious difficulty is found in the fact that when 

 the Assynt series reaches the Caledonian, the former suddenly dis- 

 appears, except in the insignificant patches east of Loch Emboli. 

 These, if true outliers, of which I entertain no doubt, at once fix 

 the superior antiquity of the gneiss, even in the absence of all other 

 proof ; but I think it can be shown that, irrespective of these out- 

 liers, the difficulty indicated is not so great as may at first appear. 



I may point out that an adherent of the Murchisonian school 

 making this objection would expose himself to an effective tu quoque 

 retort. If the Eastern Gneiss once overlay the Durness and Assynt 

 limestones, why are there no outliers of the gneiss upon the lime- 

 stone ? If so tough and enduring a rock as the quartzose schist of 

 the gneiss series once extended for miles to the west over the lime- 

 stone, it is incredible that every scrap should have been swept out 

 of their synclinal folds. Some of these folds were closely pressed 

 together at probably the close of the Ordovician epoch ; yet they 

 do not enclose the merest fragment of the immense thickness of 

 gneiss which ex hypothesi conformably overlay. 



The objection suggested may be mitigated by the following con- 

 siderations : — 



(1) The Assynt series thins out towards the east. The Torridon 

 Sandstone rarely reaches as far as the Caledonian ; in some places, 

 as on Loch Glen Coul, it disappears at two or three miles west of 

 it. The upper members of the series are also attenuated in the 

 same direction. In Glen Coul, the quartzite, flags, and dolomite 

 do not exceed 250 feet. Even if the thinness of the dolomite be 

 due to faulting, this cause cannot account for the insignificance of 

 the flags, which are conformably interbedded between the quartzite 

 and the dolomite. In Ben More of Assynt and Ben Arnaboll, the 



