h formed a continuous tube with only two bendings near its middle,
the lowest whisper at one end was distinctly heard at the other, through
a distance of 3,120 feet. A pistol fired at one end actually blew out
a candle at the other end, and drove out light substances with great
violence. Hence we see the operation of speaking tubes which pass from
one part of a building to another, and of the new kind of bell which is
formed of a wooden or tin tube, with a small piston at each end. By
pushing in one piston, the air in the tube conveys the effect to the
piston at the other end, which strikes against the bell--this piston
being, as it were, the clapper on the outside of the bell. The intensity
of confined sounds is finely exhibited at Carisbrook Castle, in the
Isle of Wight. There is here a well 210 feet deep, of twelve feet in
diameter, and lined with smooth masonry; and when a pin is dropped into
it, the sound of its striking the surface of the water is distinctly
heard.--_Ibid._

* * * * *

ECHOES.

Various remarkable echoes, and some not very credible, have been
described by different authors. Dr. Plott mentions an echo in Woodstock
Park, which repeats seventeen syllables by day and twenty by night.
The famous echo at the Marquess Simonetta's villa, near Milan, has been
described both by Addison and Keysler. According to the last of these
travellers, it is occasioned by the reflection of the voice between the
opposite parallel wings of the building, which are fifty-eight paces
from each other, without any windows or doors, and perpendicularly
to the main body of the building. The repetition of the sound dwells
chiefly on the last syllable. A man's voice is repeated about forty
times, and the report of a pistol about sixty times; but the repetitions
are so rapid, that it is difficult to number them, unless it be early in
the morning, or in a calm, still evening.

A curious example of an oblique echo, not heard by the person who emits
the sound, is described in the "Memoirs of the Academy of Sciences" as
existing at Genefay, near Rouen. A person singing hears only his own
direct voice, while those who listen hear only the echo, which sometimes
seems to approach, and at other times to recede from, the ear; one
person hears a single voice, another several voices; one hears the echo
on the right, and another on the left--the effect constantly changing
with the position of the observer.