182 The East Anglian Earthquake.
lying harder rocks. Keeping to the analogy of a basin, it
may be said that the effects were spread to the rim by virtue
of the superior conductivity of the material composing the
basin. The Palaeozoic rocks are thus not to be regarded as
being necessarily concerned in the production of the earth-
quake. It has not been possible to discriminate between
the effects transmitted by the Palaeozoics and the Lower
Secondaries—all that it is necessary to consider is that these
two series are harder and more elastic than the Cretaceous
and supra-Cretaceous formations.
It will be instructive, in concluding, to present the general
results in another way. If we imagine the newer formations
of East Anglia to be extended eastwards across the German
Ocean to the same distance as Street or Bristol in the west,
the older rocks remaining at their present depth below the
Chalk at Harwich, the disturbance probably would not have
had an eastward extension equal to its present westward
extension. In the present case, for instance, no records have
been received from Holland. If, again, we imagine the seat
of the disturbance to be transferred to the west,—say, near
Bristol,—it is improbable that the effects would have been
felt as far eastwards as those of the present shock extended
towards the west. In fact, the majority of the earthquakes
in this country which are reported to have been spread over
a very wide area appear to have originated towards or at the
eastern parts of England. As an instance may be mentioned
the eastern earthquake of 1185, by which Lincoln Cathedral
was "rent from top to bottom," and which, according to
Holinshed, was felt "through all the parts of this land."
The 1480 earthquake, again, which caused structural damage
at Norwich, extended widely throughout the country. On
the other hand, the western earthquake of 1248, which
wrecked the Cathedrals of Wells and St. David's, and which
appears to have been of equal or greater intensity than the
present one, did not extend to any great distance eastwards.
In the light of the evidence furnished by the present earth-
quake, these and similar facts respecting the distribution of
British earthquakes may perhaps be explained by the greater