A CHAPTER IN THE PHYSICAL GEOGRAPHY OF THE PAST, 55 
The proof of this is afforded by the following facts :—At 
Coalbrook Dale, in Shropshire, we find an attenuated representa- 
tive of the Mountain Limestone, very similar to that of Grace 
Dieu, 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 50 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 Paloeozoic rocks, without the inter- 
vention 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 Coalbrook 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 clearly marked for some distance across 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 Lime- 
stone 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 Zower Carboniferous. From this point to 
Northampton, almost due east, we have no direct evidence to 
guide us, but at or near the latter place a series of borings 
through a great thickness of the overlying Secondary Rocks has 
