Shepherdstown register. [volume] (Shepherdstown, Va. [W. Va.]) 1849-1955, 1914-02-26
Water Pressure.

IIOHi ~ "OAiS
seem that there is no limit TO the depths
to which diver or submarine boat
might 60. Such, however, is not the
case. What prevents diving TO great
depths is the enormously increasing pres
sure of water. No diver without suit
can 90 over $50 feet, because the pres
sure on the body is then about five tons
to the square foot on his body. Eardrums
would be STAYED in, and other fearful dif-
ficulties would result.
To remedy this the diving suit was in
vented, but there is limit also TO its depth
At depth OF one mile the pressure due
TO the water alone is l65 tons TO the square
foot Even il a diving suit Was devised
to Withstand this enormous pressure
trouble would be found in getting pipe
line that long and withstanding the pres
sure that would not break OF its own
weight.
In the case of a submarine boat il is
slightly different. Here only the strength
OF the boat is the necessary thing. But
to be strong the walls have to be thick
ened, and this adds to the weight, conSe-
quently adding to the load to be pulled
through the water, and so at last the limit
OF the engine propelIiug the boat is reach
ed. If a larger engine is procured il itself
weighs more, larger quarters are needed
for 1t, etc. So there is well defined
limit to a marine boats diving.
Let us take the extreme depth OF the
sea so far found, that of five miles, and
find the pressure TO the square loot on
the bottom. AS water is comparatively
incompressibe, cubic foot OF il weighs
practically the same on the surface as at
the bottom of the sea. In the case OF
fresh water this is slxty-two and half
pounds. Salt water weighs slightly more.
So all one has TO do to find the pressure
due TO the water al any depth is to multi
ply the depth IN feet by slxty-two and
a-half, and the answer is apparent at once
in pounds.
AT depth of live miles, the number OF
feet being 26, 400, we have that number
OF cuolc feet TO multiply by sixty-two and
a-half. The answer is $50, 600 pounds,
or 825 tons, to the square loot pressure.
No known hollow vessel can Withstand
this.
While on the subject OF increasing wa
ter pressure number OF interesting OBJ
servaiions can be made in connection
with air compressioility. Air is very
compressible, the volume decreasing as
the pressure increases. If bottle is
tightly corked it will contain air at ordi-
nary pressure Of fifteen pounds to the
square inch, and that is the pressure il ex-
erts. Then lie weight TO the bottle
and let il down in the sea by means OF
string. On bringing it TO the top again
twill be found that the stopper has been
forced into The bottle by the water preSS
sure. If the bottle is filled with water
and stoppered and let down no such thing
takes place, showing that water is not
compressible to any great extent.
II by any means some dir could be
placed at the bottom OF sea five miles
deep it would not rise to the top, for IT
would be denser-that is, would weigh
more to the cubic foot than water-and
the water would have TO float on the ali
hence no man knows if the bottom Of our
seas is wet or not.
There is only one thing that would
prevent the air from becoming this dense,
and that is if It was cold enough il would
liquefy However, it IS almost impossi-
ble-is, in fact, impossibe-for anything
at the bottom OF the sea to be colder than
a degrees C., for if it got colder the wa
ter around it would become colder and
larger and consequently lighter and Use.
and its place would be taken by degree
water, which would bring the object TO
that temperature. SO we have no argu-
ment against the suggestion, for the tenn
perature at or below which air liquefies
is between 100 and 200 degrees below
zero c.
Some people seem 10 think that stone
thrown into The sea can sink only 10 a
certain depth and is there held suspended
on account OF the pressure OF water. A
body immersed in fluid is byoyed up only
by the weight OF the fluid displaced.
We have found that water is practically
incompressible, so if the stone displaces
a cubic foot OF water that wafer weighs
the same, or practically so, at the top or
at the bottom of the sea. So the stone
would be buoyed up only by that con-
slant force and would be carried down by
its weight. Thus the difference in The
forces would be always downward, and
the stone would sink to the bottom.
In fact, if the stone is at all compressi-
BILE the tendency is foy il to get heavier
per unit volume as il goes down, for we
have the same weight in smaller space.
Il will be remembered that this is what
happens to the air il we take it in rub
Der bag under the surface Of the sea.
The volume gets less and less, conSe-
quently weighing more and more per
unit volume and displaciug less and less
water and being buoyed up less and less
until at last place is reached where the
air weighs more volume for volume than
does the water and it will not rise.