SOUTH UIST. SOIL, SURFACE. 93 



EXCEPT the great tract of peat which I have described, 

 and the minor patches of sand found on the western shore, 

 there appears to be no alluvium in South Uist. The only 

 detached stones to be found, are fragments of the gneiss 

 of which the country consists, and these are rarely marked 

 by the signs of attrition which indicate either a distant 

 period of separation or a long-continued state of motion. 

 The western side of the island is, however, subject to 

 considerable alterations in its figure and dimensions from 

 the shifting of the sands of which it is principally formed. 

 This is a phenomenon common to almost the whole 

 western side of the Long Isle, from Barra Head to Loch 

 Tarbet in Harris. I have already mentioned its occur- 

 rence in Barra and the southern isles, but as I shall have 

 occasion to examine it hereafter when describing North 

 Uist, I forbear to dwell on it here. 



The lakes that occupy the flat soil on the western side 

 of the island, neither receive nor give exit to any streams. 

 They are generally shallow, often not exceeding two or 

 three feet in depth, and appear to be the mere repositories 

 of that drainage from the surface to which a country like 

 this must be subject. Their waters are invariably brown, 

 from a considerable solution of peat. The whole island 

 is indeed destitute of streams, since the ephemeral torrents, 

 of which a few can be traced flowing down some of the 

 declivities during a heavy fall of rain, scarcely deserve 

 that name. They vanish as they arose, since they are 

 not supplied by springs, not one of which has I believe 

 been observed. This want of springs must be attributed, 

 as in Barra, to the nature of the rock, which presents 

 neither receptacles for water nor fissures for its transmis- 

 sion. At the same time it must be remarked that the 

 climate is far from rainy, the clouds, which generally pass 

 the sea with rapidity, meeting no material obstacle until 

 they arrive at the continental land of Scotland. Hecla 

 indeed, and the mountains about Loch Eynort, are, in con- 



