Miscellaneous Concluding Observations. 205
Locality. Plane of oscillation of pendulum.
London ..........N.—S. (nearly). Mr. E. Gellatly, p. 145.
,, ..........N.—S. Mr. A. Gerrard, p. 145.
,...........E— W. (2 clocks). Mr. J. Spiller, p. 146.
..........E.N.E.—W.S.W. Clapton ; Mr. Ogden, p. 146.
Lee..............E.—W. Burnt Ash Hill, p. 151.
Lewisham ........N.W.-S.E. Mr. B. M'Lachlan, p. 151.
Richmond........E.—W. Mrs. Hertslet, p. 152.
Wimbledon ......N.—S. Mr. L. J. Matow, p. 153.
Eastbourne ......N. 13° W.—S. 10° E. Mr. L. Dyer, p. 153.
Isle of Wight......N.—S. Freshwater. Hon. Hallam Tennyson, p. 154.
Careful analysis of the foregoing records has convinced us
that the data furnished by clock-stoppages are practically
useless in determining the general direction of propagation.
In but few cases do the perpendiculars to the planes of oscil-
lation of the pendulum lead to the origin as determined by
more trustworthy means. "We are disposed to conclude from
the evidence obtained that the stoppages of clocks are to be
attributed rather to the local direction of the movement at
the respective houses than to the general direction of propa-
gation. To this source of uncertainty must also be added
the different degrees of sensitiveness of the clocks according
to the weight and mode of suspension of the pendulum, as
well as the possibility of some clocks being even more readily
stopped by an impulse coinciding in direction with the swing
of their pendulums than by a movement perpendicular to
this plane.
Twists of Chimneys.—Some observers have expressed views
with reference to the general direction of propagation of an
earthquake wave based upon observations of the direction in
which chimneys, columns, &c, have been twisted by the
shock. As many such instances of rotation were observed
after the present earthquake, and have been recorded in the
descriptive report,107 it will be of interest to give in concluding
some general considerations on this subject.
The twists observed in broken chimneys, &c, give such a
strong impression of the displacement having been caused by
actual rotation that many writers, both with reference to the
present and to former earthquakes, have ascribed the
107 Fig. 7, p. 70, is an excellent example.