LEWIS. ALLUVIA. 189 



occasional inclosure of the cattle in cases of alarm or 

 warfare. 



Of their relative antiquity to those much more singular 

 buildings, the vitrified works, it is impossible to conjecture. 



FRESH water lakes are found among the hollows of 

 the hills, and are scattered over the moory surface of the 

 level land, but they do not form the same characteristic 

 and distinguishing feature as in North and South Uist, 

 and in Benbecula. Compared with the rest of the Long 

 Island, Lewis may be said to possess rivers. These are 

 at least tolerably permanent, but in any other situation 

 they would attract little notice. The largest are at Loch 

 Stornoway, Loch Kenhulavig, and Loch Roig, the last 

 of which is somewhat distinguished by a salmon fishery. 

 The courses of these streams are attended by no alluvia 

 or other appearances deserving of notice in a geological 

 view. 



The alluvial land which is to be seen in Lewis is inde- 

 pendent of these, and however common a feature, is in 

 this situation remarkable, since it occurs no where else 

 in the whole chain of the Long Isle, with the slight 

 exception already mentioned in North Uist. It appears 

 to owe its origin to distant changes on which we have 

 no other conjectures to offer than such as have been 

 often produced to account for similar alluvia in various 

 parts of the globe. In one respect it presents a diffi- 

 culty, arising from the insular position of the land 

 which it occupies ; but even that difficulty is far from 

 solitary, since similar alluvia have been observed in 

 insular situations, and examples of them are described 

 in other parts of this work. If, here as elsewhere, it 

 is fruitless to inquire into the causes of these accumu- 

 lations, it is no less difficult to conjecture what the 

 circumstances were which limited the deposits to the 

 northern extremity of this long chain. This alluvial 



