844 J. GEIKIE ON THE GLACIAL PHENOMENA 



Lacasdail, and as may have been the case also with the local ice in 

 the lower reaches of the hollow now occupied by Loch Seaforth. It 

 is quite possible, however, that the depression in the bottom of that 

 sea-loch may owe its origin in some degree to the action of the 

 great mer de glace itself, which streamed through this hollow into 

 the low grounds of Lewis, and which must have been subjected to 

 great compression and strangulation in the very place where the 

 depression or excavation now exists. 



The sea-lochs that enter the island from the west contain no 

 rock-basins ; and this is evidently due to the absence of any con- 

 siderable local glaciation. The local glaciers in that part of the 

 island seem to have occupied themselves chiefly in the excavation of 

 those small rock-basins in mountain-valleys that now hold fresh- 

 water lakes. From the configuration of the ground, indeed, it is 

 obvious that no large local glacier could ever have entered Loch 

 Eoag. Nor could Loch Resort in late glacial times ever have 

 received the same quantity of local ice as seems to have streamed 

 into Loch Seaforth. 



IV. Islands in the Sound op Harris. 



The Sound of Harris is very shallow, and studded with countless 

 rocks and sandy shoals. Indeed there is only one narrow track for 

 vessels through this dangerous channel, and in some places the track 

 has not more than 5 or 6 fathoms of water. We did not land upon 

 any of the little islands, but boated round them and about them. 

 They all afford strong evidence of having been abraded by glacial 

 action. Papeidh has quite the rounded glaciated outline, and so 

 have the hills in Bearnareidh. The islands of Einseidh and Ceile- 

 greidh are flat ; but they also show roches moutonnees, and well- 

 rounded rocks are likewise conspicuous in the Grotheidh group of 

 islets. In Giliseidh and Lingeidh the gneiss dips north-east at an 

 angle varying from 50° to 65°, and on the former islet are some 

 perched blocks. The same dip is found in the Harmatreidh group, 

 and there seems to be some till on the island of Harmatreidh itself. 

 The glaciation on all these islands has the same trend as that of 

 Harris ; it coincides in direction with the Sound. 



Y. North Uist. 



1. Physical Features. — North Uist (14 miles from north to south, 

 and 15 to 17 from west to east) exhibits much the same kind of 

 scenery as portions of Lewis and Harris. A ridge of very rugged 

 hills runs along the east coast, and attains a height in Beinn Ebhal 

 of 1133 feet. The central portion of the island might aptly be 

 described as a -wide peat-bog, interspersed with innumerable irre- 

 gular peaty lakes, which are apparently quite shallow. Prom this 

 flat central area the land rises towards the west, forming a rolling 

 hilly tract in which there are but few lakes. Along the north-west, 

 west, and south-west coasts the ground is low and level, and shelves 

 gently into the sea, so much so that at low tide very extensive tracts 

 of sand are exposed, and the adjoining island of Benbecula may then 



