DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 173 



Skulamus. It may be found again on the west side of the ridge of Beinn Suardal and 

 on the moors above Corry till it reaches the shore at the Rudh' an Eireannich 

 (Irishman's Point). It skirts the west side of Scarpa Island, and runs for some miles 

 through Kaasay. 



Over a large part of its course, the rocks of this belt rest as a great overlying sheet 

 upon the Jurassic strata, which may almost everywhere be seen dipping under them. 

 From the analogy of other districts, we may, I think, infer that their position indicates 

 the intrusion of these sills at the base of the plateau-basalts which have since been 

 removed from almost the whole tract. Fortunately, a portion of the basalts remains in 

 Raasay, and enables us to connect that island with the great plateau of Skye of which it 

 once formed a part. There can be no doubt that the amygdaloidal basalt-beds of the 

 Dun Caan ridge once extended westwards across the band of granophyre which now 

 forms most of the surface between that ridge and the Sound of Raasay. A thin sheet of 

 quartz-porphyry, interposed among the Oolitic strata, may be seen a little inland from 

 the top of the great eastern cliff and below the position of the bedded basalts. 



The great sheet, or rather series of sheets, which stretches north-eastwards from 

 Suisnish consists of a rock which for the most part may readily be distinguished in the 

 field from the granitoid material of the bosses. It appears to the naked eye to be a 

 rather close-grained or finely crystalline-granular quartz-porphyry, with scattered blebs or 

 bi-pyramidal crystals of quartz and crystals of orthoclase. At the contact with adjacent 

 rocks, the texture becomes more felsitic, sometimes distinctly spherulitic (W. side of 

 Carn Nathragh, next Lias shale). Under the microscope the rock is seen to be a fine- 

 grained granophyric porphyry or porphyritic granophyre. It caps Carn Dearg (636 feet) 

 above Suisnish, where it covers a space of nearly a square mile, and reaches at its eastern 

 extremity (Beinn Bhuidhe), a height of 908 feet above the sea (fig. 14). This rock rests 

 upon a sill of dolerite, and is apparently split up by it. But, as I have already stated, 

 the basic rock is probably the older of the two, and the granophyre seems to have wedged 

 itself between two earlier doleritic sheets. To the north-west of Carn Dearg, above 

 the northern end of the crofts of Suisnish, the same sill, or one occupying a similar 

 position, crops out between masses of granophyre, and is intersected by narrow veins from 

 that rock. 



Though severed by denudation, the large sheets of granophyre to the east of Beinn 

 Bhuidhe are no doubt continuations of the Carn Dearg mass, or at least occupy a similar 

 position. That they are completely unconformable to the Jurassic rock is shown by the 

 fact, that while at Suisnish they lie on sandstones which must be fully 1000 feet above the 

 bottom of the Lias, only two miles to the east they are found resting on the very basement 

 limestones within a few yards from the underlying quartzite and Cambrian sandstone. 

 I do not think that this transgression can be accounted for by intrusion obliquely across 

 the stratification. I regard it as arising from the eruptive rock having forced its way 

 between the bottom of the now vanished basalt-plateau and the denuded surface of 

 Jurassic rocks, over which the basalts were poured. The platform underneath these 



VOL. XXXV. PAKT 2. Z 



