388 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
Among the stones in this hand, pieces of the radiolariaii cherts of the Lower 
Silurian series of the Southern Uplands are conspicuous, likewise pieces of 
andesite which may have come from the neighbouring Pentland Hills. 
Above these strata lie the lavas of Corston Hill. These are highly 
vesicular in some parts, and include hands of tuff wdiich are well exposed 
further down the same stream, immediately above the railway bridge near 
the Mid-Calder oil works (Fig. 1 1 6). There the lavas, though much decomposed, 
show a highly vesicular structure with a rugged irpper surface, in the hollows 
and over the prominences of which fine flaky and sandy tuffs have been 
deposited, while thin seams of vesicular lava are intercalated among 
these strata. 
The upper part of the same plateau, as exposed in the course of the 
Murieston Water, contains evidence that the last eruptions consisted of 
tuff. The highly slaggy lava (1 in Fig. 117) is there surmounted by a 
thick mass of grey and greenish- white well-bedded granular tuff (2) in- 
Fio. 117. — Settioii of tlie top of tlie Miillotliiau Plateau in the Murieston Water. 
eluding occasional lumps of the basic lava, and passing up into black shale 
(3). But that the volcanic eruptions continued during the accumulation of 
the shale is proved by the intercalation of thin partings and thicker layers 
of tuff in the black sediment. A short way higher up the Burdiehouse 
Limestone comes in. 
The great lava -escarpment of the Kilpatrick Hills rests on a con- 
tinuous band of tuff which is thickest towards the west, near the group of 
vents above Dumbarton, while it thins away eastward and disappears in 
Strathblane, the lavas then forming the base of the volcanic series. But 
perhaps the most remarkable group of basal tuffs is that which underlies 
the lavas of the Garleton plateau, to which further reference will be im- 
mediately made. 
Extensive accumulations of tuft“ form in one or two localities a large 
proportion of the thickness of the whole volcanic series of a plateau. Thus 
in the north-eastern part of Ayrshire, between Eaglesham and the valley of 
the Irvine, the lavas die out for a space and give place to tuffs. During 
the discharge of the fragmentary materials over that ground no lava seems 
to have flowed out for a long period. Ordinary sediment, however, mingled 
with the volcanic detritus, and there were even pauses in the eruptions when 
layers of ironstone were deposited, together with thin impure limestone that 
inclosed shells of Froduclm giganteus? 
In some of the plateaux, particixlarly within the older part of the volcanic 
series, intercalations of ordinary sediment among the tuffs and lavas show 
that eruptions occurred only occasionally, and that during the long intervals 
’ Explanation of Sheet 22 Ceol. Sv.rv. Scoflmul, p. 12. 
