358 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
and Silurian formations ; while over wide tracts, where their volcanic 
chapters are fullest and most interesting, they lie at the surface, and can 
thus be subjected to the closest scrutiny. Hence the remains of the 
volcanic phenomena of the later Paheozoie periods present a curiously 
modern aspect, when contrasted with the fragmentary and antique look of 
those of older date. 
The history of volcanic action during the Carboniferous period in Britain 
is almost wholly comprised in the records of the earlier half of that period, 
that is, during the long interval represented by the Carboniferous Limestone 
series and the ilillstone Grit. It w’as chiefly in the northern part of the 
region that volcanic activity manifested itself. In Scotland there is the 
onicle of a lon,^ succession of eruptions across the district of the central 
and southern counties, from the very beginning of Carboniferous time down 
to the epoch when the Coal-measures began to be accumulated. In England, 
on the other hand, the traces of Carboniferous volcanoes are confined within 
a limited range in the Carboniferous Limestone, while in Ireland they appear 
to be likewise restricted to the same lower division of the system. During 
the whole of the vast interval represented by the Coal-measures volcanic 
energy, so far as at present known, was entirely dormant over the region of 
the British Isles. 
These general statements will be more clearly grasped from the accom- 
panying table, which shows the various sections into which the Carboniferous 
system of Britain has been divided, and also, by black vertical lines, the 
range of volcanic intercalations in each of the three kingdoms. 
England. 
O 
« t- 
Upper Red Sandstones witli Sjnr- \ 
orfeis-liniestone. j 
Middle or chief coal - bearing I 
measures. 
Gannister group. 
Grits, flagstones and shales with 
thin coals. 
Yoredale group of shales and grits 
with limestones. 
Thick (Scaur or Main) Limestone 
of England, with sandstones 
and coals in Scotland. 
Lower Limestone Shale (Calci- 
ferous Sandstones of Scotland) 
Scotland. 
Ireland. 
Such being the general range in time of the Carboniferous volcanic 
phenomena, it may be convenient, in this preliminary survey, to take note of 
the general distribution of the volcanic districts over the British Isles, as in 
this way we may best realise the extent and grouping of the eruptions, 
which will then be considered in further detail (see Map L). 
