CHAP. XLVI 
METAMORPHISM OF THE BASALTS 
387 
base of that hill. Another of larger size forms a prominent knob about 
three-quarters of a mile further west, and is prolonged into the huge dark 
excrescence of Creagan Dubha, which rises in such striking contrast to the 
smooth red declivities of the granophyre cones around it. This prominence 
at its eastern and northern parts consists of highly indurated splintery 
basalt in distinct beds, some of which are strongly amygdaloidal. The 
bedding is nearly vertical, hut with an inclination inwards to the hill, 
towards the south-west end a thin hand of basalt- breccia makes its 
appearance between two beds of basalt. Its thickness rapidly increases 
southward until it is the only rock adhering to the granophyre. Beyond 
the foot ol the hill, limestone and quartzite occupy for some distance the 
bottom of Strath Beg, much invaded by masses of quartz-porphyry. At the 
summit of Creagan Dubha abundant veins run into the basic rocks from the 
granophyre, which is here finer grained towards the margin; and there 
are likewise veins of quartz-porphyry which, though their actual connection 
with the main mass of granophyre cannot be seen, are no doubt apophyses 
from it. “ 
This outlier of altered basalt and breccia appears to me to be a fragment 
of the plateau-basalts which once overlay the Cambrian and Jurassic rocks 
of Strath Beg, and were disrupted by the uprise of the granophyre. It 
continues to adhere to the wall of the eruptive mass that broke up and 
baked its rocks. Its breccia, passing southward into a coarse agglomerate, 
may be a product of the same vent or group of vents that discharged the 
great agglomerate mass above Kilbride and Kilchrist. I have already 
(p- 282 ) referred to what appears to be another outlier of the basalts on the 
south side of Beinn Dearg. 
On the northern and southern flanks of Beinn 11a Cro, similar evidence 
oiay be observed of the posteriority of the granophyre to the basic rocks, 
bound the northern base of the hill a continuous tract of plateau-basalts, 
dolerites and gabbros forms the ridge between Strathmore and Strathbeg! 
There is an admirable section of the relation of the two groups of rock on 
the eastern side of the western glen. Along the lower part of the declivity, 
coarsely-crystalline gabbros, like some of those in the Cuillin Hills, are 
succeeded by sheets of dolerite and basalt, the whole forming an ascending 
succession of beds to the summit of the ridge. The edges of these beds are 
obliquely truncated by the body of granophyre, which slants up the hill 
Across them and sends veins into them. They are further traversed by 
’Usalt dykes, which here, as almost everywhere, abound (Fig. 349 ). On the 
Sl, uth side of Beinn 11a Cro, highly indurated black and grey Lias shales and 
sandstones have been tilted up steeply and indurated by the eruptive rock 
°| tbe hill ; and at one place some 800 feet above the sea, a little patch of 
a tered basalt, lying on the shale, but close up against the steep declivity of 
granophyre, forms a conspicuous prominence on the otherwise featureless 
slope. 
lteferenee has already been made to the mass of fine-grained hornblende- 
granite which runs for several miles at the base of the volcanic series on 
