498 Proceedings of the Royal Society 
Upper Old Red Sandstone shows traces of contemporaneous 
volcanic activity in Berwickshire. During the early half of the 
Carboniferous period the volcanic forces were amazingly busy all 
over central Scotland. To that time must be referred the hills of 
the south of Arran and of Bute, the north of Ayrshire, Renfrew- 
shire, the Campsie Fells, and most of the craggy hills which 
roughen the basin of the Forth from Stirling to the May Island 
and the Bass Rock. Then come the Permian volcanic rocks of the 
south-western counties. And lastly, we have those strange per- 
sistent dolerite dykes, which cross all the other rocks and even 
large faults, and which range from south-east to north-west, or from 
east to west towards the great mass of dolerites and basalts stretch- 
ing from the south of Antrim along the western seaboard of 
Scotland. Those dykes I have formerly shown to the Society to be 
probably of miocene age.* 
Several areas of metamorphic rocks have been mapped. The 
gradual passage of ordinary sedimentary rocks into crystalline com- 
pounds, and thence into various porphyries, syenites, and granites 
has been traced, particularly by Mr James G-eikie, both among the 
Lower Siluran and Lower Old Red Sandstone series of Ayrshire. 
The details which have been gathered in the course of these inves- 
tigations will, it is hoped, throw considerable light upon the 
metamorphism of rock-masses. 
While the structure of the rocks underneath is thus delineated 
on the maps, attention at the same time is directed to the superfi- 
cial deposits, which are all mapped out in the same detail. The 
various divisions of the Drift series are traced, and as the work 
advances the movements of the ice of the glacial period become 
from month to month more clear. We are now at work among the 
uplands of Galloway, and I anticipate thence a large accession of 
information regarding the history of the Ice Age in Scotland. 
It is impossible that, while these various investigations are in 
progress, attention should not often be called to the relation between 
the structure of the rocks underneath and the form that they as- 
sume above ground. The nature of our work necessitates frequent 
reflection upon this subject, and implies the accumulation of a 
* See Proceed, vol. vi. ; and Address as President of the Geological Section 
of British Association, 1867. 
