OF THE OUTER HEBRIDES. 849 



interior, reaching nearly to the west coast. Two thirds of the 

 island are mountainous, the remaining portion forming a narrow 

 belt of low ground that faces the Atlantic. With the exception of 

 this low-lying strip, which extends from north to south along the 

 whole length of the island, and does not average more than a mile 

 in breadth, and the moory district in the north, which is cut up by 

 Lochbi, Lochsgiport, and Lochcarnan, all the rest of the island is 

 mountainous. The dominant points are ranged, as in North Uist, 

 along the east coast, and form a broken and interrupted ridge which 

 rises to elevations of 2000 feet and more. These mountains have 

 precisely the same character as those of the islands already described ; 

 they present for the most part an undulating and rounded outline, 

 save in the cases of Hecla and Beinn-mhor, the tops of which are 

 somewhat sharp and peaked. The low grounds also find their exact 

 counterpart in the moory flats of Benbecula and Worth Uist. Ad- 

 joining the sandy shore are the delightful " machairs," with their 

 wealth of bright colour; while inland from the " machairs " stretch 

 the brown sombre peat and moorland, intersected in all directions, 

 as usual, with shallow freshwater lakes. The only streams of any 

 importance are those that flow from the knot of high ground in the 

 middle of the island. 



2. Geological Structure. — South Uist shows nothing remarkable in 

 its petrology, so far as we saw. The prevailing rock is gneiss, but 

 green slate and schist occur in the island of Staoleidh. Dykes of 

 basalt are also occasionally met with, some fine examples being 

 visible in the cliffs a little to the north of Staoleidh. In the north 

 of the island near Lochbi the strike of the gneiss is nearly north and 

 south, the beds dipping west at a high angle. Near Breimsdal the 

 strike runs a little east of north and west of south, the dip being to 

 the north of west. Prom Beinn-mhor south to Eirisgeidh Sound the 

 average strike is about W. 15° or 20° N. and E. 15° or 20° S., 

 sometimes more and sometimes less, the beds being generally 

 vertical. 



3. Glaciation. — South Uist affords every evidence of having been 

 subjected to intense abrasion, and next to Harris is perhaps the 

 island of the Outer Hebrides which has most interest for a glacialist. 

 Roches moutonnees, glacial strise, till, erratics, and perched blocks, 

 evidence of the general or primary and local or secondary glaciations 

 and of the maximum thickness attained by the old mer de glace, 

 may all be studied in South Uist. 



Striated rock-faces are of frequent occurrence. Without leaving 

 the road for any distance I took the bearings of about forty examples 

 between the South Eord and Pollachara, and in the neighbourhood 

 of Loch Baghasdail or Boisdale and Beinn-mhor I got also a con- 

 siderable number. Some are as fresh as if they had been recently 

 graven, others are weathered and faint, and some are so faded that 

 a good light is needed to bring them out. 



Close to the South Pord are strise pointing W. 15° N. ; and 

 further south than this, about a mile and a half from the Pord, at a 

 place called Iocar, there is a finely glaciated face, which Mr, 



Q.J.G.S. No. 136. 3l 



