86
The East Anglian Earthquake.
Langenhoe ...... Not less than 20 seconds.
Wivenhoe ... ... 6 to 7 seconds.
,, (On river) About 5 seconds.
Chelmsford ... ... ,, ,,
Bocking ... ... Under 3 seconds.
Chigwell Row...... About 15 seconds.
Dedham ...... 10 to 12
Great Wakering ... 5 to 7 ,,
Halstead ...... About 10 seconds.
,, ... ... 2 seconds.
Stebbing ... ... 15 to 30 seconds.
Thorington ...... About 3 ,,
West Ham ... ... About 5 ,,
Faulkbourne Rectory... 6 to 8 seconds.
Barham ... ... 6 to 8 ,,
Ipswich ... ... 3 to 10 „
,, ... ... About 3 seconds.
Norwich ... ... Not exceeding 10 seconds.
Ashby Parva ... ... 5 seconds.
Southall ...... 10 to 15 seconds.
After considering all the records purporting to give the
number of shocks felt at various stations, and as the result
of conversations on this point with many of the observers, I
am forced to conclude that within the area of structural
damage but few of the statements made are precise enough
to be admitted as strict scientific evidence. Much confusion
appears to have arisen owing to the observers attaching quite
different meanings to the statement " number of shocks."
In many cases where the building in which the observation
was made performed several distinct vibrations these were
considered as so many " shocks," but it will be readily
understood that such movements may have been the result of
a series of vibrations which, being communicated to the
building, would cause the latter to swing, especially if " top-
heavy," with a motion analogous to that of an inverted
pendulum, the amplitude finally being sufficient to produce
the impression of a shock or series of shocks which might
bear no direct relationship to the originating impulse. The
same result could in fact be produced by a single initial dis-
turbance, for if we imagine a building suddenly displaced
from the vertical through an angle of several degrees, it