Mineralogy of Sky. 1 9 



supplies the river running into Portree harbour appears to have had 

 some effect in filling up its southern branch which the ebb of the 

 loch has no tendency to remove. From below Portree to the nor- 

 thern point of the island, the coast consists of high cliffs of trap, 

 which exhibit the species of decomposition characteristic of these 

 rocks, in the vast slopes v;hich decline from them to the shore 

 wherever the action of the tide has not been sufficient to prevent 

 that accumulation. Continuing round the point of Ruhunish, 

 similar cliffs of trap resting on the secondary strata extend to the 

 bottom of Loch Snizort, at the end of which as well as of liOch Uig 

 the same appearances of encroachment are visible. The parish of 

 Kilmuir offers the only considerable tract of alluvial land in Sky, 

 from which its superior and long established fertility is probably to 

 be accounted for. I cannot speak positively of the shores which 

 form the point of Vaternish, having only seen them from a dis- 

 tance, but as they resemble both in aspect and composition the di- 

 vision of Trotternish just noticed, it is probable they possess no 

 great peculiarity in this respect. Neither does Dunvegan offer any 

 thing worthy of remark. 



The shores of Loch Bracadale exhibit when low, considerable 

 portions of clayey alluvial soil, characterised like those of Kilmuir 

 by extraordinary fertility. A similar alluvium may be observed at 

 the head of Loch Harpart, and the little valley of Talisker appears 

 to have been entirely gained from the sea at some distant period, 

 by a combination of the waste of the land with the counteracting 

 efforts of the western swell, which has thus formed a natural em- 

 bankment for its further protection. 



A remarkable difference is to be seen along the whole western 

 shore of the island from Dunvegan head to Loch Brittle, between 



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