Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1874-12-09
Scientific.

VIBRATIONS OF LIQUID SURFACES
Barthelemy has subjected to investiga-
tion the undulations which are pro-
duced upon liquid surfaces when these
are thrown into vibration. The best
results were obtained when the vessel
of liquid was placed upon the resonant
case of tuning fork. Similar results
were also obtained upon the sounding
/ board of piano. In this way the sur
face of the liquid assumed fixed con-
dition of elevation and depression. the
result of uniform vibration over its
entire area. Rectangular vessels give
two sets of brilliant lines parallel to
each side, formed by the ridges of the
waves. Between these are less luminous
lines produced by the hollows. Bright
points are formed at the intersections
of both. As the movement dies away,
the lines parallel to the shorter sides
disappear first. leaving those parallel
to the longer though sometimes COM
ponents of both are left, forming zig
zsgs diagonally across the surface.
From his experiments Barthelemy de-
duces the following laws: LIST, the
breadth of the undulations is inversely
as the number of vibrations and I'd,
the distance between two lines pro-
duced by the same fork is Independent
of the density of the liquid. The figures
given by circular masses of liquid con-
sist of equidistant circular lines inter-
sected by radii equally equidistant,
thus giving trapezoidal forms with
curyilinear bases. If the fork touches
q nf
appears, corresponding to the modal
lines of this vessel, AS the vibration
ceases, two opposite sectors disappear
and the two alternate ones remain. BY
placing sand on the surface of the
mercury and then covering it with
water, circular lines are formed and
also the cross OF no vibration, the sand
gathering in heaps at the vibrating
parts. Triangular vessels give lines
perpendicular to the sides, forming
brilliant hexagons, the centres of which
are the angles of fainter heXsgons,
having the radii of the first set for
sides. As the motion lessons, only one
set Of lines persists, and the surface is
covered with rectilInear waves perpen-
dicular to one of the bases. Elliptical
vessels give figures of exceeding beauty
the lines having reference to the two
axes of the elhpse. The author calls
attention TO the general character of
these wave surfaces. In the basin of a
fountain, in the waves of the sea, these
forms are recognized. Even in the
sand on the sea bottom they can be
traced. Certain lines thus made gave
on measurement 2'6 vibrations per
second. They may be seen 800 feet
from the beach and and at a depth of
- or 30 feet. So, out of the water, the
sand on the beach was found to have
taken these forms, thus suggesting that
the air itself was capable of similar
vibration. So also clouds are arranged
often in parallel bands, being then con-
sidered precursor of fine weather.
Even in geology, the author thinks
certain regular and equidistant fold
ings of stratified rocks evidence of
analogous vibrations. The ventral
segments of liquid vein, NJ. Barthe-
lemy thinks, are produced by the vibra
tion of the liquid mass upon which it
falls reacting upon it. And he makes
an ingenious application of these facts
to account for the phenomena of strait
fication produced by electric discharges
IN rarefied media.