CHAP. XLIII 
THE GAB BROS OF SKYE 
339 
at the outside into coarse gabbros further towards the central mass, and 
that this intrusion has been accompanied by a certain amount of induration 
of the older rocks. 
On the eastern side, the same structure can be even more distinctly 
seen, for it is not only exposed in gullies and steep declivities, but can be 
traced outward into the basalt-plateau. In the promontory of Strathaird, 
Jurassic sandstones and shales, which form the coast-line and lower 
grounds, are surmounted by the bedded basalts. Denudation has cut 
the plateau into two parts. The smaller of these makes the outlier that 
rises into Ben Meabost (1128 feet). The larger stretches continuously 
trom Glen Scaladal and Strathaird House northward into Blath Blieinn. 
Hence from the ordinary terraced basalts, with their amygdaloids, thin tuffs, 
red partings, and seams of lignite, every step can be followed into the huge 
gabbro mountain. Starting from the black Jurassic shales on which the 
lowest basalt lies, we walk over the successive terraces up into the projecting 
ridge of An da Bheinn. But as we ascend, sheets of dolerite and gabbro 
make their appearance between the basalts, which gradually assume the 
altered aspect already noticed. The dip of the whole series is at a low 
angle northwards, and the beds can be followed round the head of the Glen 
nan Leac into the southern slopes of Blath Bheinn. Seen from the eastern 
side of this valley, the bedded character of that mountain is remarkably 
distinct, but it becomes less marked towards the upper part of the ridge 
where the gabbros preponderate. One of the most striking features of the 
locality is the number and persistence of the dykes, which strike across 
from the ordinary unaltered basalts of the plateau up into the highest 
gabbros of the range. Where less durable than the intractable gabbro, they 
have weathered out on the face of the precipices, thereby causing the vertical 
rifts and gashes and the deep notches on the crest that form so marked a 
feature in the scenery. On the other hand, they are often less destructible 
than the plateau-basalts, and hence in the Glen nan Leac they may be seen 
projecting as low dams across the stream which throws itself over them in 
picturesque waterfalls. The youngest dykes in the Blath Bheinn group of 
hills, have been found by Mr. Harker to have a north-easterly trend, and 
a north-westerly hade of about 40°, and to give a stratified appearance to 
the gabbro when viewed from a distance. 
The deep dark hollow of the Coire Uaigneich has been cut out of the 
very core of Blath Bheinn, and lays bare the structure of the east part of 
the mountain in the most impressive as well as instructive way (Fig. 334). 
By ascending into this recess from Loch Slapin, we pass over the whole 
series of rocks, and can examine them in an almost continuous section in 
the bed of the stream and on the bare rocky slopes on either side. Sand- 
stones and shales of the Jurassic series extend up the Allt na Dunaiche for 
nearly a mile, much veined with basalt and quartz-porphyry, by which the 
sandstones are locally indurated into quartzite. At last these strata are 
overlapped by the basalts of the Strathaird plateau, which with a marked 
inclination to N.N.W., here dip towards the mountains. But by the time 
