436 
THE TERTIARY VOLCANOES 
BOOK VIII 
This granophyre sheet presents a further point of interest inasmuch as 
it appears to have preserved one of the dyke-like masses which may mark 
channels of escape from the general body of the acid magma below. Hear 
the Manse the section represented in Fig. 373 may be observed. Owing to 
great denudation, the massive sheet of granophyre has been cut into isolated 
Manse Tur Ruagh Millstream 
Fig. 373. — Section to show the connection of a sill of Granophyre with its probable funnel of supply, 
Kaasay. 
a a, Jurassic sandstones ; b, granophyre. 
outliers which cap the low hills, and the rock may be seen descending 
through the Jurassic sandstones, which in places are much indurated. It is 
observable that the amount of contact-metamorphism induced by the grano- 
phyre sills upon the rocks between which they have been injected is, in 
general, comparatively trifling. It is for the most part a mere induration, 
sometimes accompanied with distortion and fracture. 
Although the intrusion of the granophyre sills has been subsequent to^ 
that of the basalt-sheets with which they are so generally associated, we may 
expect that as there is a series of post-granophyre basic dykes, so there may 
be some basic sills later than the injections of the acid sheets. The Eaasay 
granophyre appears to 
\\ yl \ furnish an example of 
such a later basic in- 
trusion. At the Point 
of Suisnish on that 
island I have observed 
the relations shown in 
Fig. 374. There the 
dark shales of the 
Lower Lias ( a a) are 
immediately overlain 
by the granophyre sill 
(&), and are cut by a 
basalt-dyke which, 
when it rises to the base of the granophyre, turns abruptly to one side, and 
then pursues its course as a sill (c) between the granophyre and the shales. 
There can be little doubt that this intrusion is later than the granophyre. 
Here a basic sill is interposed at the bottom of the acid sheet; and is 
Fig. 374. — Granophyre sill resting on Lower Lias shales with a dyke of 
basalt passing laterally into a sill, Suisnish Point, Isle of Raasay. 
