[Illustration: Diagram of apparatus as described in text]
By immersing a thyrsus in water to produce the sound either of a
pipe or of any bird. Let A B C D (fig. 48), be a thyrsus; and at the
extremity of its head, which must be hollow and shaped like a fir-cone,
let there be an orifice D. Close the shaft a little below the mouth by
the partition A E, and place near it a small pipe, F, just beneath the
mouth of the tube, and passing through an orifice in the partition.
If we insert the thyrsus in water and force it downwards, the air
contained in it being driven out by the water will produce a sound.
If there is nothing but the pipe we shall have a whistle only; but if
there is any quantity of water under the partition there will be a
gurgling sound.
49. _A Trumpet, in the Hands of an Automaton, sounded by compressed
Air._
[Illustration: Diagram of apparatus as described in text]
A figure stands upon a pedestal having a trumpet in its mouth: if it
be blown into, the trumpet shall sound. Let A B C D (fig. 49), be an
air-tight pedestal on which a figure stands, and within the pedestal
let there be a hollow hemisphere, E F G, covered over at the top and
having small holes in the bottom. From the hemisphere a tube, H F,
extends upwards into the figure in the direction of the trumpet, which
is provided with a mouthpiece. Pour liquid into the pedestal through a
hole which must be afterwards stopped again by means of [a valve or tap
called] a smerisma. Now, if we blow into the bell of the trumpet, the
air passing from us will force out through the holes the water in the
hemisphere, which will mount up into the pedestal: but when we withdraw
the breath, the water will enter the hemisphere again and force out the
air, which, passing out through the mouthpiece, will produce the sound
of a trumpet.