830 J. GETKIE ON THE GLACIAL PHENOMENA 



the strike is W. 35° N. and E. 35° S, and the dip north-east, 

 usually at high angles. In the neighbourhood of Roinebhal, Loch 

 Langabhat, and the rocky district to the north-east the strike is 

 approximately the same and the beds vertical ; but stratification is 

 frequently obscure. These dips show that there is at least one main 

 anticlinal between the south-west mountain-district of Lewis and 

 North Harris ; and they likewise indicate the presence of one main 

 synclinal axis traversing the island from Borgh Bay to Pionnsbhag 

 (Pinnsbay). The main dips are shown by black arrows on the 

 accompanying map. 



3. Glaciation. — Mr. J. P. Campbell describes* the hills of Harris 

 as being " much glaciated, but weathered ; " and he adds, " So far 

 as I could make out, the ice came from N.N.W. through a gorge 

 at Tarbert." It needs but a glance to assure one that glacier-ice 

 has modified almost every part of the surface of Harris. The hill- 

 sides are everywhere mamillated and rounded, and crowded with 

 roches moutonnees, while the tops of most of even the highest hills 

 are smoothed off. A closer and more detailed examination convinced 

 my companion and myself that not only are the marks of glaciation 

 general over all Harris, but also that the direction in which the 

 abrading agent flowed has been from south-east to north-west, or in 

 approximately the same line as the general or average strike of the 

 gneiss. In certain of the higher valleys, however, there are distinct 

 traces of a later local glaciation, to which reference will be made in 

 the sequel. Meanwhile, some details of the main glaciation fall to 

 be given here. 



Perhaps one of the best displays of an ice-worn surface occurs in 

 the immediate vicinity of the Tarbert. All the hill-slopes in that 

 neighbourhood are finely glaciated. This is particularly the case 

 with the hill called Gilebhal-ghlas (1556 feet), which presents a 

 broad uudulating surface to the south, thickly set with dome-shaped 

 and finely mamillated rocks. Upon not a few of these rounded 

 masses, glacial striae are still preserved (in most cases they are faintly 

 marked), all pointing persistently towards north-west, and indica- 

 ting the ice-flow to have been from the south-east. Striae occur 

 also at various places near the shore and close to the road leading 

 from Tarbert along the base of Gilebhal-ghlas. The hill-slopes on 

 the opposite coast of West Loch Tarbert are also highly glaciated in 

 the same direction. 



Above the village of Airdasaig the road to Stornoway passes the 

 base of a steep cliff that faces the north-west, and forms the westerly 

 termination of Gilebhal-ghlas. Had the land been glaciated from 

 the Atlantic, this cliff-face must have been highly abraded and ice- 

 worn ; for it would lie right in the path of any ice advancing from 

 the sea. It shows, however, very little trace of rubbing; and this is 

 just what we should expect, for it occupies the Lee-seite, and has 

 thus escaped the action of the glacier ice that so polished the flanks 

 of the mountains in its neighbourhood. 



The direction of the glaciation is also well seen upon the moun- 

 * Quart. Journ. Geol. Soc. vol. xxix. p. 545. 



