The Earthquake in relation to Geological Structure. 177
South-eastern area. Shock felt at—
1. Sulhampstead, Berkshire.—Lower Eocene, near out-
crop of Cretaceous.
2. Portsmouth.—Eocene, near Cretaceous.
3—5. E. Cowes, Ryde and Freshwater, Isle of Wight.—
Eocene.
In the foregoing lists the superficial deposits have for
the sake of simplicity been ignored and the deep formations
only taken into consideration. This mode of treatment is
justified by the fact that the greatest thicknesses of Drift
formations overlie the country included within the circle.
The six extra-radial Lincolnshire stations have been
omitted, because their position does not admit of their being
fairly comprised within either area, and it is moreover
possible that at some of these places the shock was felt on
account of their marginal situation.
The records are thus 27 from the N.W. area as compared
with 5 from the S.E. area, and of the latter every place but
Sulhampstead is on the coast, and may have therefore
experienced marginal effects. The complete absence of
records from the great Cretaceous and Eocene areas of the
south-west of England is certainly remarkable, when com-
pared with the numerous records from the north-west. This
absence of observations from the south-west cannot be
ascribed to the want of large towns, since Winchester,
Dorchester, Salisbury, Andover, Southampton, Chichester,
&c, are all within this area.
The facts of the distribution of the shock appear to us
therefore to favour the view that the disturbance spread more
readily along the older (geological) portions of this country,
and it will now be advisable, before proceeding to consider
the special effects of the Palaeozoic rocks, to anticipate
certain objections which may fairly be raised against the
present mode of treatment.
In the first place it may be objected that the 86-mile
radius is quite arbitrary, and that some other circle might
have been equally well taken as a boundary. In so far as it
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