Prof. MagQus'B Hydraulic Researches. 167 



the vibrations can only be communicated to the plate through 

 the water, and then no swellings are produced. At first I em- 

 ployed a tube of vulcanized caoutchouc. But in this case swell- 

 ings were formed even when no solid body existed between the 

 plate and the bottom ; and these swellings were not much in- 

 creased in strength when a piece of wood was introduced. The 

 commercial vulcanized tubes of 3 centimetres in diameter are, 

 however, rather stoutly made, and hence it happened that the 

 vibrations of the bottom were communicated through the caout- 

 chouc to the plate c d. On employing a tube of very thin non- 

 vulcanized caoutchouc, no such communication took place. 



135. Hence there appears to exist no doubt that the swellings 

 are produced by vibrations in the bottom plate. Inasmuch, 

 however, as this plate cannot vibrate without setting the mass 

 of water in the vessel in similar vibrations, and as, inversely, 

 the vibrations of the water set the bottom plate or the edge of 

 the egress-orifice in vibration, it follows that both exercise their 

 influence upon the formation of swellings. But it follows from 

 the experiments described in the preceding paragraph, that the 

 vibrations of the bottom plate, or of the edge of the egress-orifice, 

 are the immediate cause of the swellings. 



136. If, while the stream is flowing out, a soft body be held 

 below against the bottom plate A B, the swellings undergo an 

 appreciable but inconsiderable alteration. We must not, how- 

 ever, conclude from this that the bottom does not vibrate. For 

 if a body which is not too soft, such as a plate of cork, be pressed 

 by the hand against the bottom, the vibration is felt through 

 this plate as soon as the sounding tuning-fork is placed upon the 

 stand, or as soon as the battery is connected with the Neef's 

 hammer, which is screwed upon the stand. 



The swellings change ivith the strength of the note. 



1 37. The distance from the efflux-orifice at which the swellings 

 begin, changes with the strength of the note which causes them, 

 although the pitch of the latter remain the same. This distance 

 is smaller the stronger the note. 



If the tuning-fork be struck and placed upon the stand at P, 

 very strong swellings are immediately produced, the first of 

 which often lies quite close to the efflux-orifice. In proportion, 

 however, as the vibrations of the fork become weaker, the com- 

 mencement of the swellings is depressed, so that the swellings 

 often begin far down the jet. A similar effect is produced on 

 sounding a note on a violoncello. 



138. It is not only when the jet flows out of a hole in the 

 thin wall of the vessel that swellings are produced on placing 

 ♦he tuning-fork on the stand ; the same are formed when it flows 



