436 M. J. Plateau on Jets of Liquid under the 
thread becomes transformed, the small contractions there pro- 
duced also become changed into more attenuated threads, each 
of which becomes ruptured at two points, and thus furnishes by 
its middle portion a very small spherule*. The latter spherules 
are often thrown out of the axis of the jet, being carried away, 
no doubt, by currents of air; but as their mode of generation is 
the same as that of the larger spherules above considered, they 
ought also to perform oscillations of form. Savart, indeed, says 
that this takes place, though he does not indicate by what means 
he established the fact. The parabolic trajectory, described by 
those of the spherules which are thrown outside the jet, probably 
presents to the eye a trace sufficiently distinct to admit of the 
recognition of ventral segments and nodes therein ; perhaps, too, 
the apparent figure resulting from the passage of those which 
remain in the axis may be distinguished. 
§ 20. The sonorous instrument being still placed im contact 
with the sides of the vessel in order to impart greater energy to 
the action of the vibrations, let us now suppose that a note dif- 
ferent in pitch from that of the jet is again produced. By 
No. 13 of paragraph 38, it will be seen that in this case the three 
last conclusions of paragraph 12 are exactly in accordance with 
Savart’s observations. ‘There is, it is true, some vagueness in 
the words almost all tones; though they cannot mean that the 
notes of both kinds, effective and ineffective, alternate with each 
other. For let us assume for a moment that certain intermediate 
notes are ineffective, and let us conccive the interval between the 
notes of the instrument and the jet to increase continuously ; 
then on leaving one of these ineffective notes, one of two things 
must take place: either the action upon the jet will gradually 
increase from zero up to a certain point, or it will become sud- 
denly developed. But the first of these deductions is contrary 
to the statement in the cited No., according to which the action 
diminishes as the interval between the two notes increases, and 
the second is scarcely admissible. It is very probable, there- 
fore, that the notion of ineffective notes, involved in the words 
almost all notes, refers simply to those which are too distant from 
that of the jet, and which, in virtue of the statement in question, 
ought only to produce an insensible action. 
§ 21. In paragraph 15 we have stated, that, within certain 
limits, vibrations differing in period from those of the note 
natural to the jet may predominate over the forces of figure in 
the generation of expansions and contractions; that the trans- 
formation thus commenced is then completed according to the 
new mode, and hence that the note of the jet is brought into 
unison with that of the instrument. Now the most favourable 
* Second Series, § 62. 
