BOOK V 
THE VOLCANOES OF DEVONIAN AND OLD EED 
SANDSTONE TIME 
CHAPTER XV 
THE DEVONIAN VOLCANOES 
TiiROuaiioUT the whole region of the British Isles, whei'ever the uppermost 
strata of the Silurian system can be seen to graduate into any later series of 
sedimentary deposits, they are found to pass up conformably into an 
enormous accumulation of red sandstones, marls, cornstones, and con- 
glomerates, which have long been grouped together under the name of 
“ Old Eed Sandstone.” In England and Wales, in Scotland and in Ireland, 
this upward succes.sion is so well shown that at first British geologists 
were naturally disposed to believe it to represent the normal order of the 
geological record. When, however, Sedgwick and Murchison demonstrated 
that in the counties of Devon and Cornwall a very different group of strata 
contained an abundant assemblage of organic remains, including types which 
Lonsdale showed to be intermediate between those of the Silurian and the 
Carboniferous systems ; when, moreover, this pahTeontological facies of the 
south-west of England, termed by its discoverers “ Devonian,” was found to 
be abundantly developed on the Continent, and to be there indeed the 
prevalent strati graphical type of the formations intervening between Silurian 
and Carboniferous, geologists began to perceive that the Old Eed Sandstone 
must be regarded as the record of peculiar local conditions of sedimentation, 
while the Devonian type was evidently the more usual development of the 
same geological period. 
From the remote Shetland Isles, across the whole of Scotland and 
England, down to the northern shores of the Bristol Channel, the Old Eed 
Sandstone maintains its general characters. Nowhere, indeed, are these 
characters more typically developed than in Soutli Wales, where many 
thousands of feet of red sediments, almost entirely devoid of organic 
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