854 J. GEIKIE ON THE GLACIAL PHENOMENA 



tract between Beinn-mohr and Hecla, where a lake is represented 

 on the Admiralty chart as lying in the valley that conies down to 

 the bay called Bagh a Mhoile-deas. The sea-lochs are Lochcarnan, 

 Lochsgiport, Lochaoineart, and Loch Boisdale. None of these is 

 deep, the former two being studded with small rocky islets, and 

 having for the most part flat monotonous shores. The latter two 

 are bounded in their lower reaches by bold rocky hills ; but they 

 extend beyond the mountain- districts, Lochaoineart especially 

 stretching far into the peaty low grounds of the west. Their coast- 

 lines are quite as intricate as those of the freshwater lakes, and no 

 deep depressions or excavations, like that in Loch Seaforth (Harris), 

 are shown upon the Admiralty charts. 



VIII. Islands in the Sound oe Baeea. 



The Sound of Barra is very shallow, being studded with rocks and 

 broad shoals of sand. We did not land upon any of the islets, but 

 as we boated past them could see that each was more or less well 

 glaciated. Eirisgeidh, the largest of the number, shows bare, 

 highly moutonnee rock in the north and south. Lingeidh, Puideidh, 

 and Oroseidh are mere roches moutonnees. In Euideidh the gneiss 

 dips to the north-east. Gidheidh, Heiliseidh, and the adjoining 

 islets all show a bare moutonnee surface. Some of the islands, such 

 as Eirisgeidh and Euideidh, have much yellow sand blown in upon 

 them, chiefly along their western shores. 



IX. Baeea. 



1. Physical Features. — Barra (8 miles long by 3 broad) is one of 

 the most pleasing of these outer islands. Although almost wholly 

 mountainous, it appears comparatively well clothed with verdure 

 when we contrast it with the hilly districts of North and South 

 Uist. Yet the higher parts of the hills are almost as bare as those 

 of the latter islands. The dominant point is 1295 feet above the 

 sea, near the south end of Barra. The hills in the northern portion 

 do not attain a height of 700 feet. There are numerous small 

 streams ; but their fall is so rapid that they form no alluvial flats 

 along their course. The only low grounds occur here and there along 

 the west coast, where, as usual, there are considerable accumulations 

 of shelly sand. Otherwise the coast-line is bold and rocky. 



2. Geological Structure. — Barra, like the other islands, is com- 

 posed almost exclusively of gneiss, veined with granite in places. 

 In the northern part of the island the bedding is much confused, the 

 rocks dipping in many directions, and now and again lying ap- 

 proximately horizontal. In the south half of the island this con- 

 fusion disappears, and the strike runs persistently about N. 25° W. 

 Basalt-dykes are specially numerous, the larger ones running north- 

 west and south-east. But the smaller ones ramify in all directions, 

 penetrating the gneiss in long sinuous veins that branch again and 

 again, and split up sometimes into mere threads. The basalt of 

 these remarkable veins is a hard, fine-grained, sometimes compact 



