190 M. F. Savart on some Acoustic Phenomena 'produced by 



3. Influence of the height of Efflux Tube. 



The height of the efflux tube has a far greater influence on 

 the production of tones than on their nature when produced. 

 Thus, when the height of the efflux tube exceeds the double of 

 its diameter, the production of tones may be said to be almost 

 impossible, slight rustling noises are alone heard, and they, too, 

 only when the charge is feeble. Similarly, when the height of 

 the efflux tube is less than half its diameter, the efflux must be 

 regarded as taking place through a thiii plate, and consequently 

 tones are impossible. Hence it is evident that the necessary 

 vibratory motion can only occur within very narrow limits. 



A series of experiments were made with a reservoir tube 1"70 

 metre in height and 5 centims. in diameter, to which efflux 

 tubes, 5*4 millims. in diameter and of different heights, were 

 successively adapted. One of these had a height of 2-726 mil- 

 lims., or nearly equal to half the diameter, and the efflux took 

 place without a tone, as is always the case with thin plates. An- 

 other had a height of 10"9 millims., or nearly equal to double 

 its diameter, and with it no tone at all was obtained. Between 

 these extremes the results seemed to indicate, first, that the 

 number of ventral segments diminishes when the height of the 

 efflux tube is either greater or less than its diameter ; secondly, 

 that the charges corresponding to the first appearance of tone 

 are more and more feeble as the height of the efflux tube 

 becomes greater or less than its diameter; and lastly, that the 

 tones acquire their greatest intensity when the height is equal to 

 the diameter. 



^Yith regard to the influence of the height of the efflux tube 

 upon the number of vibrations, although no certain law could be 

 established, it was evident that the number was greater when 

 the efflux tube was shorter, and it appeared probable that this 

 number was inversely proportional to the height of the efflux 

 tube. 



By immersing the tube about 1 centimetre deep in water, and 

 causing the efflux to take place into this liquid instead of into 

 air, it was found that extremely short efflux tubes produced veiy 

 intense tones, and this continued to be the case until the height 

 was but one-fourth of the diameter. Indeed, tones continued 

 to be produced far beyond this limit, even when the height did 

 not exceed one-tenth of the diameter ; in short, it was only when 

 the efflux took place through orifices pierced through thin plates 

 that the production of tones was no longer possible, or rather 

 no longer perceptible by the ear ; for Savart has shown that even 

 then the efflux takes place with a velocity periodically variable. 



With efflux tubes whose height was gi-eater than their dia- 



