THE PHYSICAL GEOGRAPHY OF THE PAST. 
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great streams, is shown by the absence of any material 
incoming of sedimentary strata as the southern shore is 
approached. This southern land was in fact an island bounded 
by a rocky coast. Of this island the northern portion of the 
Charnwood area was part, and there is not much difficulty by 
the aid of natural exposures, and by the results of borings, in 
determining approximately its extent and shape. It must 
have been long, narrow, and rocky, and extended from what 
is now the east coast of Ireland, through the Central 
Midlands, to an indeterminate point eastward. 
The proof of this is afforded by the following facts:—At 
Coaibrook Dale, in Shropshire, we find an attenuated repre¬ 
sentative of the Mountain Limestone, very similar to that of 
Grace Dien, of the same earthy character, and having about 
the same thickness. This must also have been a shore deposit, 
and a line drawn through these two places, which are fifty 
miles apart, cannot deviate far on either side from the old 
coast line, which must have had a general trend a little south 
of west. South of this line lies the Coalfield of South 
Staffordshire, in which the Coal Measures rest directly upon 
the older Palaeozoic rocks, with the intervention of the 
Mountain Limestone, so that we are quite sure that the sea 
in which this latter was deposited did not extend so far south. 
From the neighbourhood of Coaibrook Dale the old coast 
bent round somewhat to the north, for it must have run to 
the east of the tract occupied by the Shrewsbury Coalfield, 
where, just as in South Staffordshire, the Mountain Limestone 
is absent under the Coal Measures. Mantling round the 
hilly district of North Wales are undoubted beach deposits 
of Lower Carboniferous age, and by means of these we can 
trace, with close approximation to accuracy, the old shore 
line in its course northward and westward between Anglesea 
and the mountains of Snowdonia to the margin of the Irish 
Sea. 
The western limit of the old island was doubtless where 
are now the mountains of Wicklow in Ireland, and its 
southern coast is clearlv marked for some distance across 
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South Wales. 
On its southern side, in what is now South Shropshire, 
was a deeply cut little inlet or bay, the existence of which 
is indicated by the small outlying representatives of the 
Carboniferous Limestone in the Clee Hills. That there was 
land on the eastern side of these hills is shown by the Coal 
Measures of the Forest of Wyre resting on the older rocks, 
without the intervention of any members of the Lower 
Carboniferous. From this point to Northampton, almost due 
