strong, and is succeeded by a faint palpitation, repeating the sound
at the rate of twenty-eight times in five seconds, and which therefore
corresponds to a distance of 184 feet, or very nearly the double
interval from the road-way to the water. Thus it appears, that in the
repercussion between the water and road-way, that from the latter
only affects the ear, the line drawn from the auditor to the water
being too oblique for the sound to diverge sufficiently in that
direction.--Another peculiarity deserves especial notice, namely, that
the echo from the opposite pier is best heard when the auditor stands
precisely opposite to the middle of the breadth of the pier, and strikes
just on that point. As it deviates to one or the other side, the return
is proportionably fainter, and is scarcely heard by him when his station
is a little beyond the extreme edge of the pier, though another person,
stationed (on the same side of the water) at an equal distance from the
central point, so as to have the pier between them, hears it well."

In treating the important subject of echoes in churches and public
buildings, Mr. Herschell has exposed several prevailing errors, and laid
down several useful principles, which merit the particular attention of
the architect. In small buildings the echo is not distinguishable from
the principal sound, and therefore serves only to strengthen it; but
in very large buildings, where the original sound and its echo are
distinctly separated, the effect is highly disagreeable. In cathedrals,
this bad effect is diminished by reading the service in a monotonous
chant, in consequence of which the voice is blended in the same sound
with its echo. In musical performances, however, this resource is not
available. When _ten_ notes are executed in a single second, as in
many pieces of modern music, the echo, in the direction of the length of
a room fifty-five feet long, will exactly throw the second reverberation
of each note on the principal sound of the following note, wherever the