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.