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POPULAR SCIENCE REVIEW. 
orifice be not circular, the section of the jet undergoes remarkable transfor- 
mations, the peculiarities of the orifice being inverted and exaggerated in 
the jet. With an elliptical orifice of which the major axis is horizontal, 
the jet becomes circular at 30 lines, the vertical axis then increasing till the 
vein spreads into a flat vertical sheet which preserves its continuity to 6 feet 
from the orifice. An orifice shaped as an equilateral triangle furnishes a jet 
composed of three flat sheets disposed symmetrically round the axis, their 
planes being perpendicular to the sides of the orifice. A vein issuing from 
a regular polygon of any number of sides resolves itself into an equal num- 
ber of thin sheets, with planes perpendicular to the sides of the polygon. This 
extension of the sheets has, however, a limit, and sections taken at greater dis- 
tances show gradual shortening, ending in a return to the form of the first con- 
traction. Beyond this point sheets are again thrown out, again to return to the 
original figure. The explanation of the phenomenon seems to depend on capil- 
lary force. The fluid behaves as if enclosed in an envelope of constant tension, 
the recurrent forms of the jet being due to vibrations of the fluid column 
about the circular figure of equilibrium, superposed upon the general pro- 
gressive motion. The distance between consecutive corresponding points of 
the recurrent figure, or as it may be called the wave-length of the figure, is 
directly proportional to the velocity of the jet, i.e. to the square root of the 
head of water. But little variation in the magnitudes of successive wave- 
lengths is to be noticed, even in the case of jets falling vertically with small 
initial velocity. In the experiments described, the jets issued horizontally 
from orifices in thin plates adapted to a large cistern. 
Tables of seven sets of experiments follow, giving the observed wave- 
length and square root of pressure for different heads of water. At the 
higher pressures the observed wave-lengths have a marked tendency to in- 
crease more rapidly than the velocity of the jet. The orifices were rectan- 
gular, elliptical, triangular, and square. It was found that the value of 
A depends on the nature of the fluid ; methylated alcohol, for instance, gave 
a wave-length twice that of water. If a jet of mercury discharging into 
dilute sulphuric acid be polarized by an electric current, the change in the 
capillary constant, discovered by Lippmann, shows itself by alterations in 
the length of the wave. A mathematical investigation of the above facts 
follows. The flow of a vein from circular orifices is next adverted to, and 
its resolution from a cylinder into drops. This phenomenon is much in- 
fluenced by vibration of the orifice under the impact of the jet, and when 
the disintegration of the jet establishes itself with complete regularity, it is 
attended by a musical note. The pitch of this, due to a jet of given 
diameter, issuing under a given head, enables the wave-length of the nascent 
divisions to be at once deduced. The most certain method of obtaining 
complete regularity of resolution is to bring the reservoir under the influence 
of an external vibrator, the pitch of which is approximately the same as that 
proper to the jet. Savart found that the note might be a fifth above, and 
more than an octave below that proper to the jet. An electrically main- 
tained timing-fork is perhaps the best apparatus for the purpose. In conse- 
quence of the rapid motion, some optical device is necessary to render 
apparent the phenomena attending the disintegration of the jet. The shadow 
of the jet thrown on a ground glass screen from the electric spark illumina- 
