The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1912-02-15
A ROPE OF water.
Berthelot's Test That Showed Its
Tensile Strength.
THE COHESION OF MATTER.


Brought Into Contact Will Adhere to
One Another as Though They Were
Glued Together.
1t is well known that liquids are
among the least compressib!e 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
tepths of its volume under ordinary
conditions would require a pressure
of no less than 5000 atmospheres. or
5000 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 filling leaden shell
with it 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 Tue water " pCAV'oeS NAS -
mute pores of the lead and exude In
drops like perspiration on the outer
surface of the shell The same effect
was found for silver shell.
But. while it is familiar fact that
liauids 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 so
readily dipped from pail or poured
from one vessel to another how can
it be capable of withstanding tension!
If. however. we prevent change of
form we find that pure water is capa-
bic Of bearing fifty atmospheres of ten
sion. or $50 pounds to the square inrh
If it was possible. then. to utilize this
property by making rope" Of water
we should find it capable Of sustaining
a good fraction of the weight that
could be borne by an ordinary rope OF
the same size. But it must be admit
ted that the task Of making rope out
of such material would be rather diff
licult, to say the least. Notwithstanding
the fact that it possesses this desirable
property of tensile strength. Recause
of its inability to resist deformlng
force it would have to be inclosed in
tube: but, while it would here be In
condition to Withstand compression. as
from a piston in the tube. any attempt
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 filled nearly full Of wa
ter and then closed The tube was then
| cautiously heated until the water had
expanded and completely filed it. 1t
was then slowly and carefully cooled
| back to It's original temperature. when
it was found that the water had not
contracted. but still filed the tube.
It is almost universal law that a
small extension in volume Of body
requires the same magnitude Of force
to produce it as to cause Il similar
amount of compression. the forces. how
over, being tension in one case and
compression in the other. With this
law in mind it is readily seen that the
water that now fills the tube must br
under tension. since previously at the
same temperature 1t did not quite III
the tube-that is, it has actually been
stretched or expanded beyond its nor
NAL volume for this temperature. am
from our knowledge Of tho forces thai
would be required to produce the cor
responding compression we can figure
out what this tension must be.
The ultimate particles or molecule:
gether by powerful forces. known va
riously as cohesion or adhesion. bu
being in any case forces of attraction
and these forces tend to prevent an.
) expansion of the matter, be it solid o
liquid 1t might be thought that thes
! forces would cause two bodies In con
tact to adhere to each other. but par
. ticles have to be so near together t
be acted upon by them that 1t Is Dill
ficult to bring bodies into such clos
contact that an appreciable area
one is within this distance OF th~othel
However. two clean pieces OF lea
! can readily be pressed so closely t
gether that they will adhere. and
+ set of copper cubes was once mad
! with such true faces that when do
/ en- of them were piled one on top
! the other the series adhered togethe
so we'll that the whole could be lifte
s from the top one. But the best e!
ample is furnished by pieces OF o.
tical glass whose surfaces have bee
worked so plane that when pressed t
pether they will as readily break
some other spot as at this plane,
Perhaps it is unfortunate that the!
d useful forces. which hold AL matt
together and keep il from col!apsir
2 into impalpable dust are confined
Y their action to such limited rang
1 If this were not so. break OF al
It sort could be fixed by merely brin
VI ing together the broken ends Gil
IL of any kind would be unnecessary.
IN But even this state of affairs won
b have it's drawbacks \ book laid
Q q table would have to he pried OF wi
wedge. and the same insfrume
ID would be required 70 open It
ID erything would stick to everythi
a else. and the pleasure Of walki
[it would be lost in the tedious process
s. prying first one foot and then the o
.ir er from the viselikr grin Of the II
walk or the door. Boston Post.