produced by a Jet of Water. 235 



vestigation " On the notes formed by a jet of air." A current of 

 air issuing from an aperture in a thin plate gave no independent 

 note, but began to sound when a suitable note (according to the 

 data the number of vibrations appears proportional to the velocity 

 of efflux) was sounded in the vicinity. But an independent note 

 was produced if, at some little distance above the aperture, a 

 plate was held with an aperture of about the same size ; and the 

 result was obtained that the number of vibrations of the note 

 was directly as the velocity with which the air issued, and 

 inversely as the distance of the plate. The notes are formed even 

 with as low a pressure as 55 millims., if the plate is more than 

 1 millim. from the aperture. It may be shown, by means of 

 tobacco-smoke, that the emergent current only forms a continuous 

 column for about an inch from the aperture; and M. Sondhauss 

 thinks that this column of air acts like a solid rod, which by 

 friction against the edges of the two apertures forms sonorous 

 vibrations. Apertures in a thick plate, at the end of wide cy- 

 lindrical tubes, gave notes which were influenced by the note of 

 the tube. 



M. Sondhauss has made analogous experiments on the pores 

 of a water-jet. 



A closed iron-plate cylinder A, 3 inches in diameter, and 3 J 

 in height, had a circular aperture at the top, over which plates 

 and other apparatus could be suitably fixed. This could be fed 

 with water from a reservoir, at a height' of 4 feet, by means of an 

 indiarubber tube provided with a Bunsen's clamp. In order that 

 water might issue either into air or into water, the wall of the 

 cylinders was prolonged to a height of 2| inches above the top, 

 so as to form a sort of cistern ; and in order to regulate the 

 height of the water in this, there was a tubulure in its side, 

 just above the top of the cylinder, in which was fitted, by 

 means of a cork, a glass tube bent twice at right angles, which 

 could thus be easily raised or lowered. With the interior 

 of the vessel a manometer was connected for measuring the 

 pressure of the water, the supply of which from the reservoir 

 could be regulated by means of the clamp. The vessel was also 

 provided with a vertical scale, the vernier of which was furnished 

 with a bent rod, on which could be fixed the plates with different- 

 sized apertures which were to be held against the jet. 



Besides this cylinder, a larger vessel, B, was used, consisting 

 of an upright wine-cask ; in an aperture on the top of this a 

 cylinder open at the bottom could be fitted. The water was 

 supplied from the higher reservoir through the bung-hole, by 

 means of a caoutchouc tube with a clamp. 



When the water flows, under a small pressure, from an 

 aperture in the top of the cylinder, a small elevation only is 



