THE CARBONIFEROUS VOLCANOES 
BOOK VI 
360 
Lower OH Eecl Sandstone were distrilnited, yet they were scattered 
across the larger part ot the site of the British Isles. From the vents 
of Fife to those of Limerick is a distance of above 300 miles; from the 
latter eastward to those of Devonshire is an interval of 250 miles; while 
the space between the Devonslure volcanoes and those of Fife is about 
400 miles. In this triangular space Amlcanic action manifested itself at 
each of the apices, to a slight extent along the centre of the eastern side, 
but with much the greatest vigour throughout the nortlieru part of the 
area. 
Since the volcanic phenomena of Carboniferous time are exhibited on a 
much more extensive scale in Scotland than in any other region of the 
world yet studied, it will Ije desirable to describe that area in considerable 
detail. The other tracts in Britain where -^-olcanic rocks of the same age 
occur need not be so fully treated, except where they help to a hettm- 
comprehension of the general volcanic history. 
It is ill the southern hall of Scotland that the Carl ion iferous system is 
developed (Map lY.). A line drawn from Machrihanish Bay, near the Mull 
of Cantyre, north-eastward across Arran and Bute to the south end of Loch 
Lomond, and thence eastward by Bridge of Allan, Kinross and Cupar to St. 
Andrews Bay, forms tlie northern limit of this system. South of that line 
Carboniferous volcanic intercalations are to he met with in nearly every 
county across into the borders of Korthumberland. 
d'hat we may follow intelligently the remarkably varied volcanic history 
of this region, it is desirable to begin by taking note of the nature and 
sequence of the sedimentary formations among which the volcanic rocks are 
intercalated, lor these serve to bring before us the general conditions of 
the geography of the period. The subjoined table exhibits the subdivisions 
into whicli the Carboniferous system in Scotland has Ijeen grouped : 
g Ypper Eed Sandstone groiqj, nearly devoid of coal-seam.s. 
J i I'Coal-bearing, white, yellow and grey sandstones, dark shales and ironstones (Upper 
g I Coal series). 
j-Thick white and reddish sandstones and grits. 
c 
Sandstones, shales, fireclays, coal-seams, ironstones and three seams of marine 
limestone, of which the uppermost is known as the Oastlecary seam, the 
second as the Calmy or Arden, and the lowest as the Index (Lo\ver Coal series). 
Bands of marine limestone intercalated caniong sandstones, shales and some coal- 
seams. A thick band of limestone lying at or near the liottom of the group, 
traceable all over Central Scotland, is known as the Hurlet or Wain Limestone'. 
Some higher and thinner seams are called Hosie’s (see Fig. 150 ). 
