BARRA. SOIL, ALLUVIA. 79 



The deficiency of water arising from the want of springs 

 is, in an economical view, a source of much inconvenience, 

 not only to the inhabitants, but to the shipping which 

 frequent the harbours. None can be obtained in summer 

 except in the small cavities which the roughness of the 

 ground leaves in the winter water-courses, and this, being 

 the drainage water of the surface, is impregnated not 

 only with peat, but often with less innocent matters. In 

 a geological view some peculiarities seem to originate 

 from the same cause. No banks or deposits of 

 alluvial matter are to be observed in the flat parts 

 of the island or on the sea shores ; nor are there any 

 beds of clayey soil in situations where they might be 

 expected. There is indeed very little soil in the island, 

 if we except the hill above Kilbar. In general the peat 

 lies almost immediately on the bare rock in the higher 

 parts; while on the western side many feet in depth of 

 sand are accumulated by the incessant blowing up of 

 that which the sea rejects. The intermediate land offers 

 the best soil for agricultural purposes, being composed 

 of such a mixture of peat, earth, and sand, as might be 

 expected from its situation; the one or the other being 

 predominant in proportion to the vicinity of the sea or 

 of the mountain; or the greater or less facility with 

 which the sand drift is enabled to sweep it. The small 

 quantity of clay which enters into these soils is some- 

 corner of the area. The opposite angle contains a narrow tower, 

 which appears to have been the prison. The walls are embattled 

 on one side, and provided with a covered way and loop-holes. 

 A small circular flanking defence covers the dungeon tower ; the 

 remainder of the walls, as is most common, are suffered to rely for 

 protection on the goodness of their masonry. Near the entrance, 

 which is at one of the angles of the Keep, are the foundations 

 of a circular enclosure or basin, which was probably intended as a 

 place of security for the boats of the castle. In the centre of the area 

 is found the spring of fresh water alluded to, which, arising in the middle 

 of the sea, is an object of much wonder to the natives. It is secured 

 with masonry, and arched. 



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