312 THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 
4“ 
through the intervention of the air and the supports, and, on the other hand, 
from the vessel also receiving through the supports the slight vibrations due to 
external sounds communicated by the ground. It is only by withdrawing the 
vessel, by means of certain expedients, from these two influences that the vein 
assumes the aspect proper to it. 
7. But all the phenomena enumerated under the first five of the preceding 
numbers become much more decided and regular when, by help of an instru- 
ment, we produce, in the vicinity of the apparatus, a sound in consonance with 
that which would result from the shock of the discontinuous part of the vein 
against a stretched membrane. ‘I'he continuous part is then considerably short- 
ened; the diameter of the limpid portion is increased, the dilatations, being still 
further massed upon themselves, grow larger, so that the nodes which separate 
them are more elongated, and appear of smaller diameter. 
8. Besides the above unison, other sounds, produced by an instrument in the 
neighborhood of the apparatus, act upon the vein in an analogous manner, but 
with much less energy. ‘There are also sounds which exert no influence. 
9. In the particular case where the instrument varies very little from unison, 
the continuous part of the vein is lengthened and shortened alternately, and the 
ear is sensible of beats which coincide with those variations of length. 
10. When the discontinuous part of the vein is received on a body which 
can render only a determinate sound, it frequently happens that the vibrations 
of that body modify the sound proper to the vein; but this appears impossible 
unless the interval between the latter sound and that which agrees with the 
body impinged upon does not exceed a minor third. When the sound of the 
vein is thus modified by a foreign sound, it frequently requires only, in order 
to cause a return to the tone which pertains to it, a slight blow on the apparatus 
or a change of position in the body impinged upon, and it is always by abrupt 
starts that the return is effected. If the interval between the two sounds be 
very slight, they may make themselves heard periodically or even simultaneously. 
11. ‘The modifications which the vein experiences under the influence of the 
vibratory movements still increase and acquire a perfect regularity when the 
sonorous instrument, (7,) instead of being at a certain distance from the appara- 
tus, is placed in contact with the walls of the vessel and renders a very intense 
sound exactly in unison with that which is proper to the vein. ‘The continu- 
ous part is then so much abridged that the upper extremity of the first dilata- 
tion almost touches the orifice, and, further, the superposition of the expansions 
formed by the individual masses (4) is exact, so that no appearance of films is 
longer perceptible. 
12. This extreme regularity enables us clearly to distinguish the apparent 
figure produced by the passage of the spherules interposed between the masses, 
a figure which occupies the axis of the vein from the extremity of the continu- 
ous part; here also may be observed expansions and nodes, but shorter than 
those which are due to the passage of the masses. 
13. By means of an instrument thus placed in contact with the walls of the 
vessel, almost all sounds can produce effects analagous to those of unison with 
the tone proper to the vein; but these effects are less decided in proportion as 
the sound of the instrument varies more from the unison in question. 
14. Further, under this condition, when the sound which is natural to the 
vein is not in accord with that of the instrument, it may be brought to be so, 
even when the variance between the numbers of vibrations is sufficiently great 
to constitute an interval of a fifth above or more than an octave below the 
sound proper to the vein. 
15. If the vein, instead of flowing vertically from above downwards, is pro- 
jected horizontally, and is left to the ordinary circumstances, or, in other words, 
is not under the influence of a sonorous instrument, but is allowed to strike the 
liquid of the vessel which receives it, the discontinuous part presents expan- 
