TIIE IGNEOUS BOOKS OF THE BEREHAYEN DISTRICT. 159 
pact greenstone. Under the western light-house at Ardnakinna 
Point, there is a large felspathic trappean breccia, having a white fel- 
spathic base, enclosing pieces of altered slate, 
grit, &c., breaking into five or six dykes. At 
the western side there is a section (Fig.2) seen 
on the cliffs, where it seems to be conform¬ 
able ; but it is not so on the east side, though 
the dykes, if not contemporaneous, run along 
the beds, as seen by the coast section. To 
the east of the light-house, going along the 
coast, you find conformable felstones which 
run in an easterly direction with the bedding 
of the surrounding grits and slates, but are 
cut up in two or three places by the green¬ 
stone dykes. 
At the farthest south side of the island there are two large fel- 
stone beds, with greenstone dykes running across them, which are 
seen in the grits and slate, but do not appear through the felstone, 
whose resistance seems to have been too great for them, they being 
raised and twisted in the places where the dykes ought to be. 
There is a valley in the centre of the island due south of the 
Telegraph, which seems to have been the centre of action for the 
greenstones, as the felstones do not cross it, though they appear in 
the mountain that bounds it on the east. South-west of No. 4 Tower, 
in the valley, there is a large boss of greenstone, and innumerable 
small dykes, running mostly in a westerly direction. On the eastern 
side of the valley is a cliff full of small felstone traps, which seem 
to be conformable; also, one greenstone which begins at the cliff, as 
a hornblendic felstone; then changes into a beautiful porphyry, and 
then into a compact greenstone. All these beds die out or are lost 
in the drift. Due south of the valley there are principally felstones, 
with a few greenstones. To the west of that along the coast, the 
only place where the traps are seen, there are only felstones, a few 
of which are dykes; the rest are conformable,—some traps, others 
ash. The dykes run very small, none of them are over, and a few 
up to two feet in thickness; they are very compact, of a reddish hue, 
and sometimes very grit-like. Due south of the Telegraph along 
the coast are two masses of tabular, hornblendic felstone, with one 
or two greenstone dykes running through them. The felstone traps, 
all except a few of them, seem to have been contemporaneous with 
Fig. 2. 
a, Slates and grits. 
