CARBONIFEROUS VOLCANIC ROCKS OF THE FIRTH OF FORTH BASIN. 467 
_ rapidly disappear in the tuff, one of them ascending tortuously to near the top 
of the cliff. They at once recall the appearance of the well-known dykes in 
the great crater wall of Somma, 
e 
Fig. 10.—Columnar basalt in vent at Kincraig, Fife. 
That many of these dykes served as lines of escape for the basalt to the 
outer slopes of the cone is highly probable, though denudation has usually 
oyed the proofs of such an outflow. In some of the Fife necks a distinct 
tion of the dykes from the centre of the neck is still traceable. This 
acture is most marked on the south cone of Largo Law, where a number of 
d ribs of basalt project from the slopes of the hill. Their general trend is 
h that if prolonged they would meet somewhere in the centre of the cone. 
the south-east side of the hill a minor eminence, termed the Craig Rock, 
nds out prominently. It is oblong in shape, and like the dykes, points 
towards the centre of the cone. It consists of a compact columnar basalt, the 
| columns converging from the sides towards the top of the ridge. It looks like 
| the fragment of a lava-current which flowed down a gully on the outer slope of 
the cone. (B/ in fig. 13.) 
; The veins of basalt are not confined to the necks, but may be seen running 
| across the surrounding rocks. The shore at St Monans furnishes some 
