16 M. J. Plateau on Jets of Liquid under the 
duced, however, not being great, the modifications of the jet can- 
not acquire all that development of which they are susceptible ; 
besides, as the vibrations under consideration are not very regular, 
and are accompanied by other smaller and still more irregular 
ones proceeding from external noises, the phenomena must be 
affected by such irregularities ; in fact, it was under these cir- 
cumstances that Savart described the appearance of the waves 
within the ventral segments. 
With respect to jets issuing under these circumstances from 
two different orifices, and under different charges, Savart mea- 
sured, approximatively, the lengths and the diameters of the ven- 
tral segments as well as the diameters of the nodes. It may be 
of use to reproduce here the results of these measurements, in 
which the centimetre is assumed as unit. 
| Diameter of Length of the|Length of the) Diameter of | piameter of 
| ‘the orifice. Charge. continuous | ventralseg- | the ventral | the nodes. | 
part. ments. segments. | 
| —_—_—— —— I Sane 
0-6 45 40 25 he O90: 0:70 
Keine 12 59 30 | 100 | 0-75 
he 27 82 39 ~| 110 0:80 
wee 47 112 60 1:20 0:90 
Lins 45 16 78 050 | 028 
12 | 25 9 052 | 0:32 
27 41 13 055 | 0:36 
47 55 16 | 0°60 0:40 
We may here remark, that as the length of a ventral segment 
coincides with the space described by a mass during one of its 
oscillations of form, and as the period of such an oscillation is 
constant for one and the same jet, the ventral segments of the 
latter ought to increase in length from the first downwards on 
account of the acceleration in the descent. It is somewhat sin- 
gular, therefore, that Savart, who in another part of his memoir 
mentions this augmentation in reference to a particular experi- 
ment, has nevertheless in the above Table given the lengths in 
question as if they were absolute ; it is to be presumed that they 
refer to the first ventral segment of each jet. In fact, the expe- 
riment in which Savart observed the augmentation of the lengths 
of the ventral segments must have rendered the effect more than 
ordinarily apparent, since the first ventral segment was generated 
very near the orifice. 
§ 11. If, whilst the jet is falling freely into the vessel placed 
to receive it, a note in unison with its own is produced on an 
instrument in its neighbourhood, as we have hitherto sup- 
posed, then under the action of these more intense and perfectly 
regular vibrations the modifications of the jet will necessarily be 
