GEOLOGY 
succeeded the period of maximum development of the volcano, for the 
structure of the rocks was highly complicated to begin with, and the 
complexity has been considerably increased by later events. But a broad 
review of the facts, by the light obtained from the structure of similar 
rocks of the same age which occur elsewhere, seems to point to there 
having ensued a period during which the volcano was apparently extinct, 
and the earth movements may have been taking the form of upheaval 
over the entire area. During this period of quiescence the whole sur- 
face underwent much of that waste which invariably arises from pro- 
longed exposure of rocks above the level of the sea. To the present 
author the facts appear to suggest that in the area now represented by 
northern Cumberland the remnants of the older volcano were exposed 
long enough to be wasted away entirely, and, with these remnants, were 
also removed much of the older rock which underlay the volcano. 
Subsequently, another group of volcanoes, different in character 
from the first, and in form and arrangement more like the ‘ puys’ of 
central France, broke out here and there over the whole area, and their 
lava streams and tuffs were spread out across the wasted surface of those 
older rocks to which reference has just been made. Then subsidence 
again set in, and some bands of sediment and one or two bands of lime- 
stone were deposited on the sea floor both on and amongst the rocks 
of volcanic origin. On the southern flanks of Roman Fell, in West- 
morland, there is displayed a fine series of alternating sedimentary and 
volcanic rocks, which mark this phase in the history of Cumberland ; 
and it is just possible that the same kind of rocks may occur in still 
greater development in the Caldbeck Fells and near Melmerby in north 
Cumberland. The character of the fossils which occur in the sedi- 
mentary rocks associated with these latter volcanic rocks indicates that 
their formation commenced in Lower Bala times, and was continued until 
late on in the Upper Bala period. The rocks in question are con- 
temporaneous with a vast thickness of strata of the same kind which 
occur in Wales. In Cumberland at least they appear to lie unconform- 
ably upon the older rocks beneath: in other words, an upper volcanic 
series there lies discordantly upon a lower. 
It may be well to state at this point that the older group of rocks 
heretofore noticed, including the upper part of the Skiddaw Slate, the 
Milburn Rocks, and the older volcanic rocks of the Lake district (the 
Borrowdale Series) are comprehended in the Lower Ordovician group ; 
while the latter series, including the associated limestone, shales, and 
other sedimentary rocks, are here ranked as Upper Ordovician : that is 
to say, in Cumberland the Bala Rocks are unconformable to those of 
Llandeilo and Arenig age. 
Neither of these volcanic episodes appears to have extended far to 
the north, as in the southern uplands of Scotland the rocks formed during 
this period are mainly fine-grained muds, slowly formed on the floor of 
the ocean at a great depth below the surface, rocks of volcanic origin 
being almost unrepresented. 
II 
