GEOLOGY 
and other terrigenous deposits from the land. If, further, this con- 
ception can be still more extended by realizing that the various deposits 
laid down under any given set of conditions formed a series of crescents 
one within another, in which the inner crescents are made of coarse 
materials transported from the land, and the outer ones of organico- 
chemical deposits laid down in the clear water of the sea, the reader 
may obtain a good generalized view of the sequence of events that arose 
during Carboniferous times in Cumberland. 
It has already been stated that, while purely marine conditions pre- 
vailed in Cumberland and in the areas to the south-east, those not farther 
off than the south of Scotland were more or less of an estuarine nature. 
Furthermore, no traces of any kind of volcanic action occur in these 
rocks in Cumberland, although there is abundant and perfectly clear 
evidence of the existence of numerous small volcanoes in the northern 
area referred to. To put this statement into a more definite form : 
While a deep-sea limestone was in process of formation, say at Greystoke, 
deposits of fine mud were being laid down in the Bewcastle area, and 
volcanoes were in full activity in Dumfries and Roxburgh. Further 
north still, at the same period, there was land, upon which flourished a 
luxuriant vegetation, whose remains being drifted seaward, and becoming 
entombed in the terrigenous sediments, gave rise to much carbonaceous 
matter, which in extreme cases took the form of seams of oil-shale and 
beds of coal. Itis the presence in deposits of the same age as that of the 
limestones of Greystoke Park of an abundance of these carbonaceous 
materials that has given rise to the name Carboniferous Limestone, which 
is applied to the rocks now under consideration. Around the head 
waters of the River Eden the aggregate thickness of this subdivision 
attains to fully 3,500 feet; but as these rocks are traced towards the 
Solway, or in other words as they are traced from an area where they 
were found under deep-water conditions towards the part where the 
conditions on the whole were shallower, the limestones gradually be- 
come thinner, and are more and more divided by beds of shale and 
sandstone, until in the northern part of the county the aggregate thick- 
ness of the beds of limestone is barely one-tenth as much near the mouth 
of the Eden as it is near its source. 
(c) The Carboniferous Limestone Series is locally divisible into a 
lower subdivision, to which the term Mountain Limestone is usually 
restricted, and an upper, the Yoredale Rocks. These two subdivisions, 
bracketed with the Lower Limestone Shales, form the Lower Carboni- 
ferous Rocks of geologists. In Cumberland the Carboniferous Limestone 
Series may be said to present three types. Of these we may take as 
one type that found in south-east Cumberland, which is much the same 
as that occurring throughout most of Westmorland and north - west 
Yorkshire. In its fullest development this consists of an almost undivided 
mass of pure grey marine limestone, locally exceeding 2,000 feet 
in thickness. Above this come the Yoredale Rocks, which consist 
essentially of a great mass of shale with interbedded sandstones and flag- 
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