BOOK VI 
THE CAEBOmFEEOUS VOLCANOES 
CHAPTER XXIII 
THE CARBONIFEKOUS SYSTEM OF BRITAIN AND ITS VOLCANIC RECORDS 
Geography and Scenery of the Carboniferous Period — Range of Volcanic Eruptions during 
that time — I. The Carboniferous Volcanoes of Scotland — Distribution, Arrangement 
and Local Characters of the Carboniferous System in Scotland — Sketch of the Work 
of previous Observers in this Subject. 
Within the area of the British Isles, the geological record is compara- 
tively full and continuous from the base of the Upper Old Eed Sandstone 
to the top of the Coal-measures. AVe learn from it that the local basins of 
deposit in which the later portion of the Old Eed Sandstone was accumulated 
sank steadily in a wide general subsidence, that allowed the clear sea of the 
Carboniferous Limestone ultimately to spread for some 700 miles from the 
west coast of Ireland into AVestphalia. Over the centre of England this 
Carboniferous Mediterranean had a breadth of at least 150 miles, gradually 
shallowing northwards in the direction of land in Scotland and Northern 
Ireland. The gentle sinking of the floor of the basin continued until more 
than 6000 feet of sediment, chiefly composed of the remains of crinoids, 
corals and other marine organisms, had been piled up in the deeper parts. 
Traces of the southern margin of this sea, or at least of a long insular 
ridge that rose out of its waters, are to be seen in the protuberances 
of older rocks which appear at intervals from under the Coal-measures 
and later formations between the borders of AVales and the heart of 
Leicestershire, and of which the crags of Charnwood Forest are among the 
few peaks that still remain visible. To tlie south of this ridge, open sea 
extended far soutliward and westward over the site of the Mendip Hills and 
the uplands of South Wales. 
The Carboniferous period, as chronicled by its sedimentary deposits, was 
a time of slow submergence and quiet sedimentation, terrestrial and marine 
