172 The East Anglian Earthquake.
north coast of Norfolk to Brighton, and through the following
known earthquake and volcanic districts :—
Spain ; Guadiana mouths.
France ; mouth of Loire, St. Malo, Cherbourg Promontory.
Norway ; valley of the River Tanie (volcanic).
Amur River, mouths.
Sagalin Islands; Jesso Island.
Solomon and Santa Cruz Islands; passes between these
islands (volcanic).
New Caledonia (volcanic).
New Ulster (volcanic).
South Shetland (volcanic).
According to Mallet79 the British Islands are not connected
as a seismic region with Norway and Sweden, but the mean
horizontal direction of our earthquakes " appears to be one
from south to north, veering more or less to the east or west,
but having on the whole a direction passing through the
probable focus of the Lisbon earthquakes and of the Canary
Islands." This direction corresponds rather with Professor
O'Reilly's great circle passing through Kilkenny, the islands
of Mull and Skye, and the eastern group of the Faroe Islands.
In concluding this portion of the geological report it must
be pointed out that, as far as we have been able to ascertain,
the earthquake has produced no perceptible alteration of level
in the district most affected. Although no measurements
have been undertaken with the object of taking the levels by
the bench-marks, it is almost certain that any change of
level, if only to a slight extent, would have been detected
along the coast, which is intersected by numerous creeks,
and is frequented by a maritime population accustomed to
watch every movement of the tides.
Propagation of the Shock along the Older Rocks.
The velocity of propagation of earthquake movement
depends, as has already been shown (p. 89), upon the
elasticity of the rock material, and on the occasion of the
79 Brit. Assoc. Esp. Leeds, 1858, pp. 3 and 6.