CHAPTER LI 
SUMMARY AND GENERAL DEDUCTIONS 
The foregoing chapters comprise a connected narrative of the history of 
volcanic action in the area of the British Isles during the vast succession of 
ages from the early Archaean dawn down to the latest eruptions of Tertiary 
time. In this final chapter I propose to present a brief summary of the 
facts of largest import and widest interest which this protracted history has 
placed before us, together with a statement of deductions which may he 
drawn from them regarding the nature and progress of volcanism in the 
evolution of the globe. 
1. Among the broad features which soonest arrest attention in such a 
survey is the geographical position of the theatre of this volcanic activity. 
In the distribution of volcanoes at the present time we are familiar with 
their tendency to range themselves along continental borders or in oceanic 
islands. The volcanic energy so conspicuous in the geological history of 
Britain has shown itself along the western or Atlantic margin of the 
European continent. When the eruptions have not been actually on the 
land itself, they have taken place within the shallow tracts near the land, 
where the lavas and tuffs have been interstratified with sediments derived 
from the adjacent coasts. 
Moreover the volcanic rocks in Britain are ranged along the greatest 
length of the group of islands, in a general north and south line, from the 
south of Devonshire to the far Shetlands. It is on the western side of the 
country that they occur. East of a line drawn from Berwick by Leicester 
to Exeter, although the geological formations, ranging from the Carboniferous 
Limestone to the latest Pleistocene deposits, are there abundantly exposed 
to view, they include no contemporaneous volcanic rocks. 
2. A second and still more remarkable feature in the geological history 
of Western Europe is the persistence of volcanic activity along the site ol 
the British Isles. Evidence has been brought forward in these volumes 
that from the primeval time vaguely termed Archaean, onward to that of the 
older Tertiary clays and sands of the south-east of England — that is to say, 
through by far the largest part of geological history, as chronicled in the 
stratified crust of the globe — this long strip of territory continued to be 
intermittently a theatre of volcanic action. Every great division of Palaeozoic 
