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. 15. _Birds made to sing, and be silent alternately by flowing Water._ The construction is after this manner. Let A (fig. 15) be a stream perpetually running. Underneath place an air-tight vessel, B C D E, provided with an inclosed diabetes or bent siphon F G, and having inserted in it a funnel, H K, between the extremity of the tube of which and the bottom of the vessel a passage is left for the water. Let the funnel be provided with several smaller pipes, as described before, at L. It will be found that, while B C D E is being filled with water, the air that is driven out will produce the notes of birds; and as the water is being drawn off through the siphon F G after the vessel is filled, the birds will be mute. [Illustration: Diagram of apparatus as described in text]