Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1918-08-29
BY Garrett p. Seryiss


sion which has arouse quite an in
terest in our company? The questions
are. First is the water at the bot
tom of the ocean denser than that
at the surface? Second, Can a. sub
marine remain suspended between
the surface and bottom without
moving forward or backward by its
motive power, and if it can, is it due
to density or pressureH Third. Can
water be compressed, or can the air
be pressed out of water, and what
per cent will ordinary water COM
press by pressing the air out? C.
B., Camp Colt, Gettysburg"
1. Yes, the water at the bottom
of the ocean is denser than that at
the surface. both because of the
greater pressure upon it, and because
of its lower temperature. When it
is saltier than the surface water
(Which is not everywhere the case),
1t is denser on that account also.
You should, however, read what is
said in answer to your third ques-
ton, in connection with the subject
of the effect of pressure in the
depths of the ocean.
. Yes, a submarine can, theo-
retically. remain suspended between
the surface and the bottom, without
motion. It's ability to do so depends
upon a balance between it's total
weight and the weight of equal vol
ume of the water in which it is
;e oh hxr
trolling the amount of air and of
ballast in the chambers and reser-
voirs. The principle employed is
the same as that which governs the
floating of balloon.
When the weight of the ballon,
together with it's burden, equals the
weight of a quantity of air having
the same aggregate volume, l. e., fill
ling the same absolut space, the bal
Ion will neither rise nor decend.
But if increase of heat expands
the gas in the balloon faster than
expands the surrounding air, the
balloon will rise; whereas if the sur
rounding air increases in tempera-
ture faster than the gas does, the
balloon will descend because now the
equilibrium between it and the air
is destroyed by the latter becom-
ing, bulk for bulk. the lighter. On
the other hand, if the gas should
suddenly be chilled, as by a cloud
shadow, the balloon would drop un-
til the equilibrium was restored in
the denser air lower down.
This reference to the conduct of
a balloon is made because changes
of density in the air occur rapidly
and, on a relatively large scale
while the density of water at CIV
en- depth does not perceptibly vary,
and even at widely different depths
the variation of density is small, so
that the underlying principle is
more readily illustrated by the ball
Ion than by the submarine.
The principle, or law, concerned
is that known under the name of
buoyancy. When a body is INNER
sed in either air or water, it dis
places a quantity of air or water
equal to its own bulk, and the
weight of that quantity of air or
water represents the vertical pres
sure, or buoyance effect, of the fluid
upon the immersed body. If the
buoyant uplift equals the total
downward pressure, the body will
float at the point where it then is
without either rising or sinking
Both pressure and density are con-
cerned in the matter since the pres
sure, which is the immediate active
agent. varies with the density
3-Water can be compressed. but
it requires an enormous force to
produce a noticeable degree of COM
preston. A given volume of water
at ordinary temperatures can Ne
compressed to the extent of only
one-fifty- -millionth of it's bulk by
doubling the atmospheric pressure
upon it! At the greatest depth of
the ocean the pressure' produced by
the weight of superintendent water
must amount to at least 500 times
the ordinary atmospheric pressure at
the surface, or say four tons to the
square inch.
Now under such a pressure as
that, to quote a striking comparison
by II. r. Mill, I'll, 900 cubic feet of
air would be squeezed into 22 cubic
feet, but 1000 cubic feet of water
would only be reduced to about
10000 cubic feet, the density being
only slightly increased" This shows
the immense difference between the
compressibility of air and water.
and yet they obey the same law of
buoyancy. But slight as the re-
bulk of the ocean is so great that
it has been caculated that if the
sea water should suddenly cease to
be compressible and should assume
the volume that it would have If it
did not yield at all to compression
the ocean would rise at least 116
feet above their present level and
inundate about 100000 square
miles of now dry land, including all
the great ports of the world.
Some calculations. base on diff
ferent data concerning the mean
depth of the ocean, put the rise of
sea level. in the case supposed at
200 feet As to the air contained in
water, the way to get 1t out would
not be by pressure but by boiling.
Some air is mechanically inclosed
in water, as may be seen in pools
at the foot of waterfalls where it
escapes in bubbles.