160 KAURIS. ALLUVIA. 



with an inert mass of this substance, is clothed with the Fes- 

 tucee, Airae, and other grasses which usually affect similar 

 situations. I have shown that in the southern islands this 

 often depends on the admixture of sand, but it is also 

 to be seen here as well as in Lewis, in situations where 

 no sand is found. While on this subject I may remark, that 

 there appear to be much greater accumulations of clay in 

 Harris than even in North Uist, producing in many places 

 an excellent soil capable of an almost constant system of 

 culture. This accumulation is very remarkable even on 

 the summits of the hills, where it often forms beds of a 

 foot or more in thickness, which, when unencumbered 

 with peat, produce excellent grasses, unless where ele- 

 vated into too high a region. This earth, like that of 

 North Uist, is extremely fine and soft, resembling porce- 

 lain earth when free from the black colour it sometimes 

 acquires from the peat, and evidently derived from the 

 decomposition of the felspar which abounds in the gneiss. 

 In many places it is so mixed with the decomposed peat 

 as to form a perfect black mould. 



I observed but few alluvial accumulations of greater note 

 than this ; no banks or beds of mixed stony and earthy mat- 

 ter, nor any of those deposits which mark the effects, either 

 of distant revolutions of the surface, or of the more recent 

 action of water. The want of recent accumulations may 

 be accounted for, as in the adjoining islands, partly by the 

 want of rivers and torrents, and partly by the extremely 

 durable and refractory nature of the rock. In this respect 

 Harris, as a mountainous country, presents a character 

 somewhat remarkable in Scotland. The deficiency of 

 running water is not the consequence of a want of rain, 

 since the climate is considerably more rainy than that 

 of any part of the Long Island, the mountains being 

 frequently involved in clouds for many days, when the 

 country both to the north and south is enjoying a serene 

 atmosphere. It appears to depend pnrtly on the mode 

 in which the mountains are grouped, and partly on the 



