It must be evident
that this is chalk; naturally a soft calcareous earth, but which may be
also found consolidated in every different degree.
Through the middle of the Isle of Wight, there runs a ridge of hills of
indurated chalk. This ridge runs from the Isle of Wight directly west
into Dorsetshire, and goes by Corscastle towards Dorchester, perhaps
beyond that place. The sea has broke through this ridge at the west
end of the Isle of Wight, where columns of the indurated chalk remain,
called the Needles; the same appearance being found upon the opposite
shore in Dorsetshire.
In this field of chalk, we find every gradation of that soft earthy
substance to the most consolidated body of this indurated ridge, which
is not solid marble, but which has lost its chalky property, and has
acquired a kind of stony hardness.
We want only further to see this cretaceous substance in its most
indurated and consolidated state; and this we have in the north of
Ireland, not far from the Giants Causeway. I have examined cargoes of
this lime-stone brought to the west of Scotland, and find the most
perfect evidence of this body having been once a mass of chalk, which is
now a solid marble.
Pages:
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107