440 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
1 he Fife coast-section from wliicli these details are taken supplies almost 
endless instances of the varjdng characters of the pyroclastic materials of 
the puy-eruptions. The very same cliff, bank or reef will show at one point 
an accumulation of excessively coarse volcanic debris and at another thin 
laminic of the finest dust and lapilli. These rapid gradations are illus- 
trated in Fig. 162, which is taken from the east end of the Kingswood 
Craig. The lower part of the declivity is a coarse agglomerate which passes 
upward into finer tuff. 
Besides the thin partings and thicker layers of tuff which, intercalated 
among the sedimentary strata of the Carboniferous system, mark a compara- 
tively feeble and intermittent volcanic activity, we meet in some localities 
with examples where the puys have piled up much thicker accumulations of 
fragmentary material without any intercalated streams of lava, or inter- 
stratified sandstone, shale or limestone. Thus the widespread Houston 
marls above described reach a thickness of some 200 feet. The vents of 
the Saline Hills in Fife covered the sea-floor with volcanic ashes to a depth 
of several hundred feet. In the, north of Ayrshire the first eruptions of the 
puys have formed a continuous band of fine tuff traceable for some 1 5 miles, 
and in places at least 200 feet thick. 
Where volcanic energy reached its highest intensity during the time of 
the puys, not only tuffs but sheets of lava were emitted, which, gathering 
round the vents, formed cones or long, connected banks and ridges. Of 
these there are four conspicuous examples in Scotland — the hills of 
the Burntisland district, the Bathgate Hills, the ground between Hairy and 
Galston in north Ayrshire, and a broken tract in Liddesdale. Howhere 
in the volcanic history of this country have even the minutest details of 
that history been more admirably preserved tlian among the materials 
erupted from puys in these respective districts. 
Lava-cones, answering to solitary tuff-cones among the fragmental 
eruptions, do not appear to liave existed, or, like some of those in the great 
lava-fields of Northern Iceland and AVestern America, must have beeu mere 
small heaps of slag and cinders at the top of the lava-column, which were 
washed down and effaced during the subsidence and entombment of the 
volcanic materials. The lavas never occur without traces of fragmentary 
discharges. Two successive streams of basalt may indeed be found at a 
given locality without any visible intercalation of tuff, Imt proofs of the 
eruption of fragmental material will generally be observed to occur some- 
where in the neighbourhood, associated with one or both of them, or with 
other lavas above or below them. 
Where the phenomena of the puys have beeu most typically developed, 
lavas and tuffs succeed each other in rapid succession, with numerous or oc- 
casional iuterstratiflcations of ordinary sediment. Perhaps the most complete 
and interesting example of this association is to be found on the coast between 
Burntisland and Kirkcaldy, where, out of a total thickness of rock which 
may be computed to be between 1500 and 2000 feet, it will probably be a 
fail estimate to say that the igneous materials constitute four-fifths, or from 
