File:The Quarterly journal of the Geological Society of London (12512122313).jpg

362
PROCEEDINGS OF THE GEOLOGICAL SOCIETY.
varied and cliffy aspect ; partly due to the
escarpment side of the mica-slates, and
partly to the frequent alternations of
these with intrusive masses of a close-
grained porphyritic granite.
It is the relative position which these
two rocks occupy with reference to each
other, and the manner in which they are
associated, that constitutes the great pe- •
culiarity of this district.
We have seen that in the ridges be-
tween the Clyde and Loch Fyne, where
there is a great anticlinal effected from
some cause or another, there is no ap-
pearance of any intrusive rock ; and we
shall now find, that between Loch Fyne
and Loch x\we, where there is a perfect
conformity in the dip of the stratified
slates, there the intrusive rocks are ne-
vertheless developed in great force.
The summit ridge of this district (see
fig. 1) is a ridge of mica-slate. It falls
rapidly into the basin of Loch Awe, the
dip of the strata being steeper along the
line of greatest elevation, which runs far
back from Loch Fyne, and much nearer
to Loch Awe. The intervening space
between this summit ridge and Loch Fyne
is occupied by a series of lower ridges, in
general diminishing in height as they
approach the Loch. The tops of these
ridges are granite ; but the tops only.
Both at their back and on their front, the
stratified rocks ascend generally to more
than half their height, as well as occupy
the whole of the intervening hollows. In
short, these granite tops may be said to
be intei'stratijied on a gigantic scale with
the mica-rslates ; the latter always pre-
senting the same dip and the same general
direction. At many spots the line of
junction is easily accessible ; and the ig-
neous and stratified rocks may be seen,
surface to surface, in undisturbing con-
tact with each other.
The general character of this peculiar
association of the granite with the mica-
slates will be best understood by an ideal
section of the district (fig. 2).
Before venturing upon any suggestion
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