200 The East Anglian Earthquake.
the swing of freely suspended objects are, however, applicable
with even greater force to the present class of observations,
and, when the general character of earthquake motion is
borne in mind, it can no longer be expected that these
observations would throw much light on the direction of
propagation. There is, in fact, no reason for believing that
the passage of an earth-wave, even supposing it to follow a
rectilinear path, would necessarily cause every building to
oscillate in the same plane, since the motion depends not
only upon the direction of propagation of the wave, but like-
wise upon the position of the centre of displacement of the
structure, to say nothing of the fact that the motion of the
ground at any particular place may bear no relation to the
general direction of propagation. Moreover, an observer
looking at a building could not give an accurate statement of
the direction in which it moved unless the plane of its
oscillation happened to be exactly at right angles to his line of
sight: if the plane of oscillation formed an angle with his
visual direction the component of the motion in his line of
view would either not be seen at all or else much under-
estimated. The only information of use would be furnished
by an observer who could command a general bird's-eye view
of a town or village, under which circumstances any pre-
vailing direction of movement might be detected. It is
stated, however, by a yacht captain at Wivenhoe, who hap-
pened to be high up on a ladder placed against the roof of
his house, that the houses appeared rocking in various
directions, "like a lot of boats during a gentle ground
swell."
Order of Succession of Phenomena.—Some few observations
have been given (pp. 61, 66, and 91), in which the direction
of the passage of the wave has been inferred from the sup-
posed order in which buildings were damaged, but such
statements must be dismissed as of but little importance,
since the experiences are not only in themselves contradictory,
but, from the nature of the conditions, could hardly be
expected to have been otherwise. Thus the actual time
during which chimneys, &c, are falling is so exceedingly