10 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



Hill of Harripool. It differs from the preceding in so far as it 

 shows the effect of the fault along the eastern side of Beinn Shuar- 

 dail, and the reappearance of the breccia in the Heast stream at b'. 

 In Section IV. MS. a small knob of red sandstone is seen projecting 

 through the limestone on the west side of Beinn Shuardail. I think 

 it highly probable that this and another similar patch half a mile 

 north are prominences of the underlying rock from which the over- 

 lying limestone has been torn away, so that the breccia, though in- 

 visible, may flank their base, as shown in the section. As corrobo- 

 rative of this conjecture, I may remark that at Sithean, where the 

 sandstone, divested of its calcareous covering, descends almost to 

 the level of the road, the breccia is found resting above it ; but where 

 the limestones begin to creep up the hill-side to the south, the 

 breccia gets covered over, together with the sandstone below. 



I am thus particular in the details of this sandstone-ridge and its 

 casing of breccia, because the appearances described appear to me 

 indisputably to prove that the period of the Lower Lias of Skye 

 was marked by movements of upheaval and depression. Whilst 

 limestones and shales were alternately accumulating at the bottom 

 of the old liassic sea, a long low reef was thrown up, raising with it 

 the calcareous and muddy deposits that had formed the ocean-bed. 

 Exposed to the beating of the surf, these strata were broken up, their 

 fragments dispersed along the slopes of the reef, and the red sand- 

 stone once more laid bare. At length the ridge began to suffer a 

 downward movement, and, as it slowly sank, fresh accumulations of 

 limestone gathered around and over it, in a sea swarming with 

 Ammonites, Pinnce, and Pectines. 



There is another point of interest in this sandstone-ridge which I 

 am unwilling to omit. The remarkable parallelism of the mountain- 

 ranges and glens of Scotland long ago drew the attention of geolo- 

 gists, and the progress of investigation has shown that what is so 

 marked in the north can be no less distinctly traced in the general 

 structure of the British Islands. The great faults traced on the maps 

 of the Geological Survey have generally a parallel strike from south- 

 west to north-east, corresponding with the direction of the Highland 

 glens and straths. With regard to the relative ages of these upheavals 

 and depressions mere parallelism can prove nothing, for there is strong 

 reason to believe that at least most of the great disturbing move- 

 ments which have taken place within the area of the British Islands, 

 from the earliest eras whereof we have any cognizance, have been 

 along a north-east strike. Now, the sandstone-ridge of Strath pre- 

 serves the same direction, and, though invaded by the syenite of 

 Beinn an Dubhaich and shattered by the fault of Glen Kilchrist and 

 Glen Shuardail, it is still tolerably perfect for nearly five miles. Of 

 its age there can be no doubt ; it was formed towards the close of the 

 lower horizon of the Lower Lias, and had begun to sink when the 

 limestones of the upper horizon of that division were deposited. 

 Many a long year had rolled away, and its site was well nigh effaced, 

 when the Pabba-shales, belonging to the lower and middle horizons 



