Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1897-07-25

nv NHt'if We tfiIl stop inete motions
by increasing tho contamination on
siding the metal strip along the trough
and contracting the contaminated sur
race. IL the ring floating on this por-
ton of tho llduld is now loaded I'M II
sinks. we have the means OF knowing
tho diminution OF the surface tension re-
quired to stop tho motions Of the cam
phor
A LOWER TENSION.
III the ring Is placed near one end OF
the trough and the strip OF metal is sid
from the extreme OF the trough towards
the ring. but not near enough 10 II 10
cause such lowering Of surface tension
tnat the ring sinks. one will observe the
ring 10 move slightly away from the
moving strip. This is owing to the con-
taminatlon Of the surface being slightly
greater and the surface tension lower
near the side Of the strip toward the
rihS than II is al a distance from the
stflp near 10 and beyond the floating
ring. The consequence is that the sur
race him surrounding the ring and be-
yond II contracts and carries the ring
away from the strip. The strip now re-
naming stationary we have n lower
tension on the contaminated or ring side
OF the strip than on the other side, where
the surface OF the water is clean there
fore. on sliding the strip backwards with
gradually increasing velocity over this
clean surface. or on removing the strip
from the trough. the clean surface con-
tracts and keeps on contracting till 1t
has so stretched the contaminated sur
face that It covers uniformly the whole
= race OF the trough. The ring, hung In
this surface which is being stretched.
moves with 10. and is seen 70 go rapidly
towards the other end Of the trough.
III platinum, gold or silver wire Of 4-l0
millimetre in diameter Is formed into
ring. heated TO redness, and when cold
placed on water. Il sinks. II the ring Is
wiped dry and then placed on the water
1t sinks, but II wiped dry and exposed TO
the air for from ten to fifteen minutes II
will float. Also. ring of one of these
metals which las been heated TO redness.
and which has not been wetted, Will
float after having been exposed to the
air for about half an hour
Wires OF pla inum, gold. and Of silver
Of Ale millimetre in diameter, and wires
Of aluminium, copper. brass. and German
silver Of / millimetre in diameter fioated
when gently placed on the surface OF
water by means Of a fork made of fine
wire. These wires were five centimetres
long. All Of these wires sank after
having been passed slowly TO and fro
six times in the lower part Of "A spirit
fame, and recovered their property or
Rotation after they had remained from
two 10 five minutes In the air.
Glass rods of IL milllmetre diameter
and centimetres long behaved in similar
manner 10 the wires. II a sod Of glass
recently drawn out in a spirit flame and
just cold Is placed on water it sinks.
After a freshy-made glass rod has re-
manned exposed 10 the air for about fif-
teen minutes it will float. If recently
made glass rod which has just sunk In
water be Withdrawn. wiped dry, and ex-
posed 10 the air for from ten to fifteen
minutes, II will float. These floating
glass rods however, do not, as in the
case OF the wires. give straight lines OF
ifwarkatiOn between the surfaces of the
glass and the water. At some
places the water wets and covers
the glass; at others it does not
wet the glass, and the lines OF
oemarkation or the & ass and water are
Jagged This rod, placed vertically in
the water. shows an ascending meniscus
at the parts where it was wetted when
floating and q depressed meniscus at the
parts where it repealed the water. II a
glass rod is sunk and then brought 10
the surface of ne water and floated
and this operation repeated several
times the rod becomes more ana more
repcllant Of water and when depressed
I'm tie water-surface by fine wire the
lines OF separation Of the glass
and water become almost straight
and the rod acts like one Of clean metal
The rod can now be depressed. by fork
Of fine wire. to nearly three MILL
metres below the general level Of the
water. These experiments show how
soon the surface Of glass IS contami-
mated by exposure to water and ar,
this contamination reversing indeed, the
attractive property of clean glass To-
water.
The experiments on the metals show
that when their surfaces are freed OF
air they sink and that after the flm
of air has recondensed on their surfaces
they float. IN other words, in he nrs'
case the metals are wetted, ana in the
second they are not. II is evident That
the dry surface of the wire between the
two opposite depressed surfaces OF
wafer could not exist II the water wet
ted the wire as 1t would wet
ring made OF clean glass. At the same
time though the water does not wet me
wire as water vets glass, yet the water
ie attracted by the wire so that IL fu-
heres TO Il with such force that IL can
take the curvature required 10 WIN
stand the inward hydrostauc pressure
ON the Two depressed water surfaces
Another observation is of interest here
on observing the wire between the &c
--ressed sheets OF water through
microscope. one does not see me oppo-
site surfaces Of the water gradually anu
smoothly slide over the wire ana APP
proach one another as the wire goes
deeper and deeper In the depression pu,
.ho +ar,ninoI edges OF the depressed
- e,rfaces leave the wire 10 approach
one another in a series Of jumps. These
releases Of the two edges OF the water
.,~foces from the wire do not take
80 uniformly ard simultaneously
p aio,s, the whole OF these edges but take
rlace AT many points irregulaIy ulS'i
tP'..oa LONG the lines of demarkauon OF
the wire and water. - ,,o.,,.oo,, the
..1,he attraction existing between the
,,,,rc and the water is shown 10y ms
a boating ring above the genera, 49,
~ The water when the water auIiSi IN,
tho ring. and may be lifteo seNe,". - t,,o
ao+res II the ring be lifted quickly W.
' obtain a catenoid Of elevated
1-.tor-slyn apparently centlmeIe Vi
80 w height. When the elevated nm
lets n generally forms into drops
reenIlarly spaced around the rlhs' 49,
.Grbe Aim Of air on the surfaces OF 'nS nc
i've must be very thin, probably snai
tIne9 of the radius Of molecular ac-
.i..,,,. - however. the air be condensed
on the metals 10 the same degree Ina, enG'
Oh cen is occluded by platinum black.
tbe air-nlm may have the density OF
,rater. and IT'S attraction may De OF an
order approaching that OF me n'e,a 49,
IL for water. This condition, when
rnhablv exists. renders futile the deter
pi,y''tto, of the thickness Of the air-nm
by optical methods. Professor Wright
~ vale University suggested TO me 10
VI a, +otsl reflection took place