OF THE OUTEK HEBKIDES. 829 



faces to the north-east, a feature which is wanting in the southern 

 districts. 



The general outline of the high grounds, as viewed from east and 

 south-east, is hummock y, rounded, and somewhat monotonous. 

 This character prevails over all Harris. There is a singular absence 

 of peaks and serrated ridges, the only appearance of such occurring 

 at the highest elevations, as in the Langa and the Cliseam. Seen 

 from the south-west of Lewis the Harris hills assume a much wilder 

 and more rugged aspect; and even from any eminence in Harris 

 itself the rounded and flowing outline of the ground, which appears 

 so conspicuous when the observer looks towards north-west, becomes 

 much less striking when his face is turned in the opposite direction. 



There are a number of deep glens in Harris ; but, as might have 

 been expected, the streams are of little importance. In many of these 

 valleys lakes occur, the most notable being Loch Lacasdail (Laxdail). 

 Like most mountain-lakes they are long and narrow, and relatively 

 deep. Besides these mountain-lakes there are numerous small lakes 

 or tarns, that lie in rocky hollows. These are specially abundant in 

 the rugged rocky low country of South Harris that slopes down to 

 the shores of the Minch. The largest of the lakes is Loch Langa- 

 bhat, which is two miles long by about half a mile in breadth. Most 

 of the others are much more insignificant. 



2. Geological Structure. — To Macculloch's account of the petrology 

 of Harris I have little to add. There is, as usual throughout these 

 islands, much sameness in the rocks, which consist almost exclu- 

 sively of gneiss and its varieties. There are, however, certain of 

 these varieties which appear to be confined to special localities ; thus 

 the beautiful granatiferous gneiss of Roinebhal seems to be peculiar 

 in Harris to that mountain, although somewhat similar granatiferous 

 rocks are met with in some of the islands further south. Numerous 

 dykes and veins of basalt traverse the country, the larger dykes 

 having a tendency to keep along the strike of the gneiss. The basalt 

 is generally dark grey or blue, with a texture varying from gra- 

 nular to crypto-crystalline and compact. It generally weathers 

 with a brown ferruginous crust, and here and there splits up into 

 rough flags which have often a minute fissile structure, so much so 

 as in places to assume quite the aspect of a decomposed ferruginous 

 shale. 



The strike of the gneiss throughout Harris is approximately north- 

 west and south-east, with occasional local deflections. In North 

 Harris the average strike is "W. 15° 1ST. to E. 15° S., with a somewhat 

 constant dip towards the south-west ; and hence all the great es- 

 carpments face the north-east. The same dip and strike continue 

 into South Harris as far south as Borgh. In the neighbourhood of 

 Miabhag (Forest of Harris) very low dips are found (10° to 15°); 

 but the inclination increases in the area between Airdasaig and Loch 

 Seaforth to 35°, 50°, and upwards, the beds not unfrequently becoming 

 vertical. In the north part of South Harris the strike swings round 

 to W. 30° N. and E. 30° S., the dip being, as before, south-westerly, 

 at angles that vary from 20° up to nearly vertical. South of Borgh 



