The watchman and southron. [volume] (Sumter, S.C.) 1881-1930, 1911-09-30
A ROPE OF WATER.
eerthelot's Test That Showed Its
Tensile Strength.
THE COHESION OF MATTER.
Perfect Planes Of Metal or Glass When
Brought Into Contact Will Adhere to
One Another a. Though They Were
Glued roQether.

Brought Into Contact Will Adhere to
One Another a. Though They Were
Glued Together.
1t is we'll known that liquids are
among the least compressible Of sub.
stances: this In spite Of the fact that
they have the property Of conforming
to any shape Of vessel or Of yielding
to any forces. no matter how small,
which tend to change only their shape.
Thus, to squeeze water into nine
tenths Of It's volume under ordinary
conditions would require a pressure
OF no less than 5000 atmospheres. or
$4,000 pounds. to the square inch.
This property Of being almost incom-
pressible Is best illustrated perhaps
by an experiment tried centuries ago.
wherein an attempt was made to com.
press water by filing a leaden shell
with II and then. after closing. ham
mering and squeezing the shell. The
only effect Of the tremendous pres.
sures produced In this way was to
cause the water to penetrate the mi
mute pores of the lead and exude In
drops like perspiration on the outer
surface Of the shell. The same effect
was found for a silver shell.
But, while 1t Is q familiar fact that
liquids will resist an enormous force of
compression. the companion fact that
they are also capable Of withstanding
tension Is not so generally known. At
first sight this statement may appear
ridiculous. When water may be 80
readily dipped from a pail or poured
from one vessel to another. how can
Il be capable Of withstanding tension?
II. however. We prevent change Of
form we fnd that pure water is capa-
BILE If bearing fifty atmospheres Of ten.
sion. or 750 pounds to the square inch.
II It was possible. then. to utilize this
property by making a ''rope" Of water
we should nnd It capable Of sustaining
good fraction Of the weight that
could DO borne by an ordinary rope Of
the same size. But It must be admit
ted that the task Of making a rope out
Of such material would be rather DIFF.
ncult, to say the least Notwithstanding
the fact that It possesses this desirable
property Of tensile strength. Because
Of Its inability to resist a deforming
force II would have to be inclosed In a
tube; but. while It would here be In
condition to Withstand compression, as
from a piston In the tube, any attempv
at 'stretching' the liquid In this way
would simply result In pulling away
the piston from the water surface.
However. this tensile strength was
actually found by Berthelot in the fol.
lowing way: A strong glass tube sealed
at one end and drawn out very fine at
the other was filed nearly full Of wn.
ter and then closed. The tube was then
cautiously heated until the water had
expanded and completely filed II. 1t
was then slowly and carefully cooled
back to Its original temperature, when
IL was found that the water had not
contracted. but still filed the tube.
1t Is almost universal law that
small extension In volume Of q body
requires the same magnitude of force
to produce 1t as to cause a similar
amount Of compression. the forces. how.
ever, being tension in one case aud
compression In the other. With this
law in mind II Il readily seen that the
water that now fills the tube must be
under tension. since previously at the
same temperature II did not quite all
the tube-that Is, 1t has actually been
stretched or expanded beyond Its nor
NAL volume for this temperature. and
from our knowledge Of the forces that
would be required to produce the cor
responding compression We can figure
out what this tension must be.
The ultimate particles or molecules
Of matter we believe to be held to-
gether by powerful forces, known va
riously as cohesion or adhesion. uut
being In any case forces Of attraction.
and these forces tend to prevent any
expansion Of the matter. be It solid or
liquid. 1t might be thought that these
forces would cause two bodies In con-
tact to adhere to each other. but par
tcles have to be so near together TO
be acted upon by them that 1t Is diff.
hcult to bring bodies into such close
contact that an oppreciable area Of
one Is within this distance Of the other
However. two clean pieces Of lead
can readily be pressed so closely to-
gether that they will adhere. and
set OF copper cubes was once made
with such true faces that when q doz.
en- OF them were piled one on top Of
the other the series adhered together
SO well that the whole could be lifted
from the top one. But the best ex-
ample Is furnished by pieces OF op-
dcal glass whose surfaces have been
worked SO plane that when pressed to-
gether they will "a readily break Mt
some other spot as at this plane.
Perhaps II Is unfortunate that these
useful forces. which hold all matter
together and keep II from colapsing
Into impalpable dust, are confined I'm