[Illustration: Diagram of apparatus as described in text]
There are vessels from which water is forced up by blowing into them.
Through the neck of the vessel (fig. 42), a tube is inserted, reaching
nearly to the bottom, and soldered in at its mouth. Stop this mouth
with the finger, and pour in some liquid through a hole: then, having
blown into the vessel through the same hole, close it by means of a
key, and set free the mouth of the tube; the liquid will be made to
spout up through the orifice by the compressed air which was blown in.
43. _Notes from a Bird produced at intervals by an intermittent Stream
of Water._
[Illustration: Diagram of apparatus as described in text]
The notes of birds are produced at intervals as follows. Take an
air-tight vessel (fig. 43), through which a funnel is inserted, the
tube being far enough from the bottom of the vessel to allow of the
passage of water. Above the funnel is placed a hollow vessel, turning
on pivots, and having a weight below, into which water is continually
carried. So long as the vessel on the pivots is empty it will be found
to remain upright, for a weight is attached to its bottom; but, when
the vessel is filled the water is overturned into the air-tight vessel,
and the air contained in the vessel being driven out through a small
pipe will produce the sound. The vessel is emptied of water by means
of a bent siphon, and, while it is being emptied, the vessel on pivots
is again filled and overturned. It will be requisite that the stream
of water should not fall into the centre of the vessel on pivots, that
when filled it may be inverted speedily.
44. _Notes produced from several Birds in succession, by a Stream of
Water._
[Illustration: Diagram of apparatus as described in text]
Sounds are produced at intervals in another way as follows. A vessel is
taken (fig. 44), provided with several transverse partitions. In the
chambers are placed siphons conducting into the chambers beneath, the
streams through them being unequal. In the lower compartment is placed
the pipe which produces the sound, and the stream of water falls into
the upper compartment. It will be found that when the upper chamber
is filled, the water passes through the siphon placed there into the
chamber below, until it has arrived at the lowest, and the vessel being
air-tight, the air in this chamber is driven out through the pipe and
produces the sound.