292 M. T. Plateau on the recent Theories of the Constitution of 



of his own for this kind of observations, affirms the same thing 

 in his memoir above cited. Hence if these protuberances, which 

 are carried by the translatory motion of the hquid, proceed from 

 the orifice itself, they there project very little. But, according 

 to Savart's experiments, they are more perceptible the further 

 they are observed from the orifice, until near the extremity of the 

 continuous part they become greatly developed, and finally at 

 the extremity they detach themselves successively as isolated 

 masses. Savart does not expressly mention the contractions 

 which alternate with these expansions, but it is evident that the 

 latter cannot become developed and acquire greater volume ex- 

 cept at the expense of the intermediate portions, so that these 

 parts must necessarily become hollower and thinner the more 

 the protuberances project. Now let us suppose for a moment 

 that the expansions and contractions are due to the pulsations at 

 the orifice, and that, as Savart thought, this vibratory motion 

 communicates itself to all the continuous part of the jet. Ac- 

 cording to this hypothesis, each portion of the liquid pressed 

 outwards, when leaving the orifice, by a compressing pulsation, 

 would during its transport soon become changed into a contrac- 

 tion by the opposite vibration which it would execute, then again 

 into an expansion, afterwards into a contraction, and so on; 

 whilst each portion originally contracted by a receding pulsation 

 would at the same time suffer inverse variations. But, accord- 

 ing to the above, these successive changes of each portion of 

 liquid, or the vibrations they perform during their movement of 

 translation, increase in amplitude from the orifice to the extre- 

 mity of the continuous part, and that in an enormous proportion; 

 for near the orifice the expansions and contractions are so minute, 

 that by the most delicate method of observation their commence- 

 ment cannot be ascertained. Now it is impossible to account 

 for this increase in the amplitude of the vibrations in the jet, 

 which increase, in fact, would constitute an efi^ect without a cause. 

 '^5 From this examination, we conclude that the hypothesis of 

 *piilsations at the orifice, engendered by the efflux itself, and 

 causing a vibratory motion in the jet, ought to be rejected, as 

 well as that of rupture produced by the acceleration in the velo- 

 city of translation of the liquid. ''' ': ' ' ' ifii/i./.h' 



In order to omit nothing, I ought to mention that Magnus 

 denies the existence of these expansions in a jet protected from 

 every external influence. But his only motive for doing so is 

 the aspect of the limpid portion of the jet, which appears per- 

 fectly white. " It has the appearance,'^ says he, " of a solid of 

 revolution formed of the whitest glass, for the least motion can- 

 not be perceived in it." Now Savart, when speaking of the lim- 

 pid portion of jets freely exposed to the small vibratory motions 



