No. 43. Notes from a Bird produced at intervals by an
intermittent Stream of Water.
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.