CHAP. XXXVII 
THE PLATEAU OF MULL 
209 
(1873 feet) in Morven, and others further north, prove that its volcanic 
sheets once spread into the interior of Argyleshire (Fig. 266). On the 
south, its tine range of lofty cliffs, with their horizontal bars of basalt, bear 
witness to the diminution which it has undergone on that side ; while, on 
the north, similar sea-walls tell the same tale. Not only has it suffered 
by waste along its margin, it has also been deeply trenched by the excava- 
tion of glens and arms of the sea. The Sound of Mull cuts it in two, and 
the mainland portion is further bisected by Loch S unart, and again by Loch 
Aline. The island of Mull is so penetrated by sea-lochs and divided by 
deep valleys that a comparatively slight depression would turn it into a 
group of islands. But, besides its enormous denudation, this plateau has 
been subjected to disruption, and perhaps also to subsidence, from sub- 
Fig. 266 . — Basalt-capping on top of Beinn. Iadain, Morveu. 
The hummocky ground to the right consists of the Highland schists against which the basalts are 
brought by lines of dislocation ^ 1 
terranean movements. I 11 the southern portion of the island of Mull it has 
been broken up by the intrusion of large bosses and sheets of gabbro, and by 
masses as well as innumerable veins of various granitoid and felsitic rocks. In 
Ardnamurchan, it has suffered so much disturbance from the same cause that 
its original structure has been almost obliterated over a considerable area. 
Moreover, it has been dislocated by many faults, by which different portions 
have been greatly shifted in level. The most important of these breaks is one 
noticed by Professor Judd, and visible to every tourist who sails up the 
Sound of Mull. It traverses the cliffs on the Morven side, opposite Craignure, 
bringing the basalts against the crystalline schists, and strikes thence 
inland, wheeling round into the long valley in which Lochs Arienas and 
Teacus lie. On its western side, the base of the basalt-series is almost at 
the sea-level ; on its eastern side, that platform rises high into the outliers 
of Beinn na h-Uamha (1521 feet) and Beinn Iadain. The amount of dis- 
1 There are 110 fewer than three faults in the basalt-capping on the summit of Beinn Iadain. 
By bringing the basalts and schists into juxtaposition, they have given rise to topographical 
features that can be seen even from a distance. 
VOL. II 
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