166 Prof. Magnus's Hydraulic Researches. 



even when the note sounded is not the same as, nor a harmonic 

 of, the note belonging to the vessel. If the tuning-fork (§ 126) 

 be fastened to a large sounding-box, and, after being struck, be 

 approached to the stream, swellings are produced even by a much 

 greater water-pressure than when the fork is used without the 

 box. 



132. If the pressure under which the water flows out be so 

 chosen that the tuning-fork without the sounding-box produces 

 no swellings when held at some distance below the orifice whence 

 the water flows, when the fork is then approached quite close to 

 the opening, without of course touching it, swellings immediately 

 appear. 



This is an additional proof that the vibrations of the sonorous 

 body are not communicated to the stream directly through the 

 air ; for if such were the case, the swellings must occur indififer- 

 ently, whether the sounding body be approached to the upper or 

 lower portion of the jet. 



133. In order to prove the effect of the vessel, and especially 

 of its bottom, the following experiment was made : — Into the 

 bottom of the vessel a plate was introduced provided with a 

 casing projecting downwards of 3 centimetres diameter, having 

 an orifice of the same width. A second casing furnished with a 

 plate, cd (fig. 4), in which the exit-orifice for the water was 

 situated, was fastened to the first case by means of a caoutchouc 

 tube, a b, of the same diameter and 8 centimetres long. In this 

 manner the hole for the flow of water was only connected with 

 the reservoir by the caoutchouc tube. On allowing the water to 

 flow out of the apparatus so arranged, the caoutchouc tube 

 became elongated, and the plate with the efflux-orifice began to 

 vibrate in such a manner as to render an examination of the 

 jet impossible. To avoid this, the plate c d was made 15 cen- 

 timetres in diameter, and was supported upon two cushions, x x, 

 of soft wooUen cloth. The cushions themselves rested on a firm 

 support, that is, upon a board, /"^, provided with a hole 6 cen- 

 timetres in diameter, through which the jet fell. This board, 

 fg^ was also separated from the stand P P Q Q by means of 

 woollen cushions, zz. 



134. After the vessel had been so arranged, if Neef's hammer 

 was screwed upon the foot P Q of the stand P P Q Q and set in 

 vibration, no swelHngs were formed. But on connecting the 

 plate c 6? by means of any solid body with the bottom A B of the 

 vessel, as by slipping a piece of wood between A B and c d, 

 swellings were formed of full size and distinctness. 



The action of the wood or of the solid substance introduced, 

 consists in its comnmnicating io cd the same vibrations as occur 

 in the bottom of the vessel. In the absence of this solid substance. 



