406 Mr. Macgillivray’s Account of the Outer Hebrides. 
same substance, running across a protuberance of gneiss. This 
limestone is large—granular, and, when nearly pure, of a purplish- 
grey colour. It contains hornblende, sahlite, coccolite, mica, chlorite, 
diallage, serpentine, and other substances, generally in such quan- 
tity as to give the fragments the appearance of granite or syenite. 
The weathered surfaces are singularly rough, owing to the decom- 
position of the carbonate of lime, while the other substances have 
withstood the action of the atmosphere. 
Ben-Capval, or Toe Head, is remarkable for a large granite 
vein, upwards of a mile in length, which runs obliquely across its 
eastern and southern sides, and is conspicuous at a distance of many 
miles. At its north-western extremity, facing the Atlantic, is a 
precipice upwards of 500 feet high, on which there is generally an 
eagle’s nest, and of which the base is perforated by numerous ca- 
vities or caverns. In a projecting part of the hill near this rock is 
the largest cave in Harris, and probably in the Outer Hebrides. 
A large portion of this mountain consists of a granular rock, having 
no appearance of stratification. The other hills are of the more or- 
dinary form of gneiss, until we reach the valley running across 
the country, the bottom of which is in part occupied by Loch Lan- 
gavat. 
From this to Tarbert, the rock, which is in many places granitic, 
has generally a more compact character, and is much less covered 
with soil, in so much that the most striking difference is perceptible 
between the hills on each side of the valley of Loch Langavat in 
respect to their vegetation. At the southern extremity of this lake 
is an eminence of a reddish colour, and for that reason conspicuous 
at a distance, which exhibits so singular an aggregation of mine- 
rals, as to deserve a more minute investigation than it has hitherte 
received. Chlorite-slate containing small grains of magnetic iron- 
ore, talc-slate, hornblende-slate, actynolite-rock, asbestus in vari- 
ous forms, and a black variety of serpentine containing anthophyl- 
lite, are found intermixed in an inextricable manner. Veins of 
actynolite run across the gneiss in the neighbourhood, and have 
been traced by me to the sea shore, in the neighbourhood of Fins- 
bay and Ardsleav. The same formation makes its appearance 
along the eastern shore of Loch Langavat, at irregular intervals, . 
and from thence extends to the shore of Borve. Various remark- 
able protuberances appear at the surface in the course of this irre- 
gular deposit or vein, of which that cf the Dun of Borve is the 
most remarkable. It consists of a mass of black substance, inter- 
mediate in appearance between basalt and serpentine, and contains 
numerous plates of pale and dark-green mica, approaching to chlo- 
rite, tegether with abundance of anthophyllite and asbestus. Enor- 
mous masses of the latter occur at the northern extremity of Loch 
Langavat, and exhibit rocks of great beauty, having a stellular 
fibrous structure. | 
From this place to Tarbert nothing of great interest occurs ex~ 
. eepting a vein of greenstone which runs across the country frony 
