[Illustration: Diagram of apparatus as described in text]
Vessels may be made such that, when water is poured into them, the note
of the black-cap, or a whistling sound, is produced. The following
is their construction. Let A B C D (fig. 14) be a hollow air-tight
pedestal: through the top, A D, let a funnel, E F, be introduced and
soldered into the surface, its tube approaching so near to the bottom
as only to leave a passage for the water. Let G H K be a small pipe,
such as will emit sound, communicating with the pedestal and likewise
soldered into A D. Its extremity, which is curved, must dip into water
contained in a small vessel placed near at L. If water be poured in
through the funnel E F, the result will be that the air, being driven
out, passes through the pipe G H K, and emits a sound. When the
extremity of the pipe dips into water a bubbling sound is heard, and
the note of the black-cap is produced: if no water is near, there will
be a whistling only.
These sounds are produced through pipes; but the quality of the sounds
will vary as the pipes are more or less fine, or longer, or shorter;
and as a larger or smaller portion of the pipe is immersed in the
water: so that by this means the distinct notes of many birds can be
produced. The figures of several different birds are arranged near a
fountain, or in a cave, or in any place where there is running water:
near them sits an owl, which, apparently of her own accord, turns at
one time towards the birds, and then again away from them; and when the
owl looks away the birds sing, when she looks at them they are mute:
and this may be repeated frequently.