WITHDRAWN FROM THE ACTION OF GRAVITY. 391 
nomena will be the less decided as the sound of the instrument deviates more 
from unison, so that the sounds which depart too much from that unison, 
whether above or below, will appear inoperative. 
We have supposed that extraneous action has been previously neutralized ; 
but this action tending of itself to occasion like effects, (§ 10,) it will be under- 
stood that if we allow it to subsist, it can scarcely but add to the intensity of 
the phenomena. We may here take notice that sounds, differing from unison, 
give rise at the same time to effects of another kind, effects which will, in gen- 
eral, be little apparent in veins directed vertically, but which are manifested, 
as will be seen, in those whose emission takes place under certain obliquities. 
These effects depend on the conflict between the vibrations and the configura- 
tive forces, and are consequently null in the case of unison; they cannot, 
therefore, like those we have been considering, go on decreasing from that 
point, but, on the contrary, it is with the departure from unison that they are 
developed. ’ 
§ 13. The first of the four conclusions above stated is clearly verified, in a 
particular case, by the fact of No. 9 of § 3. In effect, when the sound of the 
instrument is very nearly consonant, the duration of a vibration differs very 
little from that of a dilatation or a constriction, and consequently when a co- 
incidence shall occur, it will be almost complete; that is to say, the conflict 
will oceupy only extremely small portions of either the constriction or the two 
adjacent dilatations; for such a constriction, therefore, the effect will be nearly 
the same as if there were exact unison, whence it follows that at the moment 
of the rupture of this constriction the continuous part of the vein will have 
perceptibly the length which corresponds with unison; it will then acquire, 
progressively, greater lengths until that is reached which corresponds to the 
maximum of conflict; but on account of the approximate equality of the re- 
spective durations of a vibration and of the transit of a dilatation or a con- 
striction, it will evidently be only after a sensible space of time that this maxi- 
mum will present itself, so that the gradual elongation of the continuous part 
will be effected with sufficient slowness to be followed by the eye; and such 
will necessarily be the case with the next and the succeeding curtailments of 
length. As to the beats, it is plain that they result from the mutual reaction 
of the sound of the instrument and of that of the vein; for although Savart 
does not say so in express terms, we may conclude from the manner in which 
he states the fact in question, that the vein must fall on a stretched membrane. 
Except in this particular case of a very small interval between the sound of 
the instrument and that of the vein, Savart says nothing of periodical changes 
of the length of the continuous part, and not without reason, as we shall see. 
For intervals which do not meet the above condition, these changes are too 
rapid to allow their succession to be distinguished, insomuch that all the 
lengths must seem simultaneous as well as all the systems of expansions cor- 
responding to those lengths; each of the expansions of the vein, therefore, 
must, in these circumstances, appear to be formed of individual expansions not 
exactly superposed, and consequently present the aspect of an assemblage of 
films, (§ 8;) now, there was nothing new in this aspect for Savart, who had 
observed it (§ 10) in the expansions of veins not subjected to the influence of 
a sonorous instrument. 
§ 14. The three other conclusions of § 12 seem confirmed by No. 8 of § 3. 
Yet the manner in which Savart mentions the facts might cast some doubt on 
the entire exactness of that agreement; we shall therefore give verbatim the 
only passages which relate to the facts in question : 
‘* Sounds which form the grave octave and fifth, the minor third, the superfluous fourth, 
and the shrill octave of that rendered by the impact of the interrupted part against an 
auxiliary body, produce in the vein modifications analogous to those just described, [those, 
namely, produced by unison, ] but with much less energy; and there are sounds which do 
not act in any manner on its dimensions and the aspect it presents.” 
21s 
