CHAP. XLIII 
THE GABBROS OF SKYE 
34i 
area of the Cuillin Hills. The first impression of the geologist who visits 
that wild district is that the main mass of rock is as thoroughly amorphous 
as a core of granite. Yet a little further examination will reveal to him 
many varieties of texture, sometimes graduating into, sometimes sharply 
marked off from, each other, and suggesting that the rock is not the 
product of one single protrusion. He will notice further indications of 
successive discharges or extravasations of crystalline material during prob- 
ably a protracted period of time, and in the intricate network of veins 
crossing each other and the general body of the rock in every direction, as 
well as in the system of basalt-dykes that traverse all the other rocks, he 
Fig. 334. — Section across the Coire Uaigneich, Skye. 
a, b, Jurassic sandstones and shales ; r c, bedded basalts and dolerites ; cl d, gabbros and dolerites with indurated 
basalts ; e, line-grained hornblende-granite sending veins into surrounding rocks ; ff basalt-dykes running 
through all the other rocks. 
will recognize the completion of the evidence of repeated renewals of sub- 
terranean energy. 
But the observer will he struck with the absence of the more usual 
proofs of volcanic activity in such forms as vesicular lavas and abundant 
masses of slag, bombs and tuffs, which are commonly associated with the 
idea of the centre of a volcanic orifice, though he will meet with isolated 
masses of coarse volcanic agglomerate within the gabbro area and along 
some parts of its junction with the granophyre. The general characters of 
the rocks around him suggest that he' stands, as it were, far beneath that 
upper part of the earth’s crust which is familiar to us in the phenomena of 
modern volcanoes ; that he has been admitted into the heart of one of the 
deeper layers, where he can study the operations that go on at the very 
roots of an active vent. 
When the geologist begins a more leisurely and systematic examination 
of the interior of the gabbro area of Skye he soon sees reason to modify the 
impression he may at first have received that this rugged region presents 
the characters of one single eruptive mass. The more he climbs among 
the hills the more will he meet with evidence of long-continued and oft- 
repeated extravasation, one portion having solidified before another broke 
