Geology. 149 



Geology. — Gneiss is the predominating rock in Harris. All 

 the inhabited islands consist of it. In the Forest there are nu- 

 merous beds and irregular masses of hornblende rock, horn- 

 blende mixed with black mica, and scaly mica. At Marig, on 

 Loch Seaforth, there is a deposit of hypersthene rock, ofconsi- 

 derable extent ; and in the island of Scalpay, close to the light- 

 house, a bed of serpentine and potstone, with veins of green talc 

 and 'flexible asbestus. The northern part of the second division 

 is gneiss, the greater part of the middle portion granite, and the 

 southern part chiefly gneiss, with masses of syenite and garnet 

 rock. At the junction of the granite with the gneiss, along 

 the north side of Loch Langavat, there commences between 

 Finsbay and the eastern extremity of that lake, an irregu- 

 lar bed of indurated talc, with talc slate and asbestous ac- 

 tynolite. Close to the eastern extremity of the lake, it forms 

 a considerable eminence named Scaire-ruadh, and, proceed- 

 ing westwards, appears, at long intervals, in the form of great 

 nodular masses, and terminates in the Dun of Borg, near 

 the west coast. It contains immense quantities of acty no- 

 lite of several varieties, hornblende, rigid asbestus, and dark- 

 green mica. The varieties of the gneiss ai'e endless. The prin- 

 cipal minerals which enter into its constitution are quartz, fel- 

 spar, hornblende, mica, and garnet. The most beautiful kinds 

 are those which contain garnets, of which fine examples are seen 

 in the Glen of Rodill, in the Corry of Ronaval, at Big Scarista, 

 and in Ben-Capval. In the northern part of the latter mountain, 

 a variety of garnet, much resembling cinnamon-stone, forms a 

 principal ingredient in the rock. The most remarkable geological 

 appearances are those presented by the veins, which are of two 

 kinds, greenstone and granite. Of the former, the finest is a great 

 vein, running from Shelibost, near the sand of Loskentir, to the 



observer is to the level of the sea, and in calm weather with sunshine, when 

 a sort of exhalation is expanded over the surface, in which rapid and minute 

 motions are presented, very much resembling the appearance produced when 

 .a quantity of alcohol is poured into water. The mirage is common on the 

 sands of the west coast, where it always presents the appearance of water, 

 ami, by distorting and amplifying the sand-banks, rocks, sea-birds, and other 

 bodies, produces fairy landscapes, in which lakes, trees, ruins, and £mtastic 

 dwellings, are mingled in strange disorder. 



