Richard Green Parker.

A school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of online

. (page 11 of 38)
Online LibraryRichard Green ParkerA school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of → online text (page 11 of 38)
Font size
QR-code for this ebook

been sunk to great depths in the sea will have its pores so filled with
water, and its specific gravity so increased, that it will no longer float.

f " Experiments at Sea We are indebted to a friend, who has just arrived
from Europe, says the Baltimore Gazette, for the fol'owing experiments
made on board the Charlemagne :

- 26th of September, 1836, tko weather being calm, I corked an cuiptj



437. Questions for Solution.

(1.) What pressure is sustained by the body of a fi**h having a surface of
i> square feet at the depth of 150 feet 1 -4ns. 8-4136.32 Ib.

(2.) What is the pressure on a square yard of the banks of a canal, at the
depth of four feet \ . Ana. ii243.tis52 tt>.

(3.) What pressure is exerted on the body of a man, at the depth of
30 feet, supposing the surface of his body to be 2j sq. yd.1 Ans. 4206S.1<5#>.

(4.) Suppose a whale to be at the depth of 200 feet, and that his body
.presents a surface of 150 yards. What is the pressure ? Ans. 16827264 Ib.

(5.) How deep may a glass vessel containing 18 inches of square surface
be sunk without being broken, supposing it capable of resisting an equal
pressure of 1500 lbs.1 Ans. 192.54/5. +

(6.) What is the pressure sustained on the sides of a cubical water-tight
box at the depth of 150 feet below the surface, supposing the box to rest on
'he bed of the sea, and each side to be 8 feet square? An*. 299151.36/6.

(7.) How deep can a glass vessel be sunk without breaking, srjpposing
that it be capable of resisting a pressure of 200 pounds on a square inch \

Ans. 462.1 /t +

438. The lateral pressure of a fluid proceeds

14 hat causes the en tirely from the pressure downwards, or. in
lateral pressure , . _

of fluids ? other words, from the weight or the liquid

above ; consequently, the lower an orifice is
made in a vessel containing water or any other liquid, the
greater will be the force and velocity with which the liquid will
rush out.

wine-bottle, and tied a piece of linen over the cork ; 1 then sank it intf
the sea six hundred feet ; when drawn immediately up again, the cork waf
inside, the linen lemained as it was placed, and the bottle was filled with

*' I next made a noose of strong twine around the bottom of the cork,
which I forced into the empty bottle, lashed the twine securely to the necb
i)l' the bottle, and sank the bottle six hundred feet. Upon drawing it up
immediately, the cork was found inside, having forced its way by the twine,
and in so doing had broken itself in two pieces ; the bottle was filled with

" I then made a stopper of white pine, long enough to reach to the bot-
tom of the bottle; after forcing this stopper into the bottle, I cut it ofif about
half an inch above the top of the bottle, and drove two wedges, of the same
wood, into the stopper. I sank it six hundred feet, and upon drawing it
up immediately the stopper remained as I place'd it, and there was about
a gill of water in the bottle, which remained unbroken. The water must
have forced its way through the pores of the wooden stopper, although
wedged as aforesaid ; and had the bottle remained sunk long enough, there
is no doubt that it would have been filled with water." [See also note on
page 109.]

It is the opinion of some philosophers that the pressure at very great
depths of the sea is so great that the water is condensed into a solid state j
*nd that at or near the centre of the earth, if the fluid could extend so
deeply, this pressure would convert the whole into a solid mass of firo.



Fig. 64.

489 Fig. 64 represents a vessel of water, with ori
fices at the side at different dis-
tances from the surface. The
different curves in the figure, described by
the liquid in running out of the vessel, show
the action of gravity, and the effects pro-
duced by the force of the pressure on the
liquid at different depths. At A the press-
ure is the least, because there is less weight of fluid abo\e.
At B and C the fluid is driven outwards by the weight of that
portion above, and the force will be strongest at C.

440. As the lateral pressure arises solely
from the downward pressure, it is not affected
by the width nor the length of the vessel in

What effect has
the length and
the width of a
body of fluid

upon its lateral which it is contained, but merely by its depth ;
pressure ? ^ ag everv p ar ti c le acts independently of the

rest, it is only the column of particles above the orifice that cap
weigh upon and press out the water.

To what is the 441. The lateral pressure on one side of a
lateral pressure cu bical vessel will be equal only to half of the
pressure downwards ; for every particle at the
bottom of a vessel is pressed upon by a column of the whole depth
of the fluid, while the lateral pressure diminishes from the bottom
upwards to the surface, where the particles have no pressure.
What causes the 442. The upward pressure of fluids, althougl
upward pressure apparently in opposition to the principles of
gravity, is but a necessary consequence of the
operation of that principle ; or, in other words, the pressure
upwards, as well as the pressure downwards, is caused by gravity.

443. When water is poured into a vessel with a
8 P out (like a tea -P ot > f r instance), the water rises in
the spout to a level with that in the body of the ves-
sel. The particles of water at the bottom of the vessel are
pressed upon by the particles above them, and to tins pressure
they will yield, if there is any mode of making way for the


particles above them. As they cannot descend R

through the bottom of the vessel, they will
change their direction and rise in the spout.
Fig. 65 represents a tea-pot, and the columns
of balls represent the particles of water magni-
fied. From an inspection of the figure, it appears that the par-
tide numbered 1, at the bottom, will be pressed laterally by the
particle numbered 2, and by this pressure forced into the spout,
where, meeting with the particle 3, it presses it upwards, ana
this pressure will be continued from 3 to 4, from 4 to 5, and so
on, till the water in the spout has risen to a level with that in
the body of the vessel. If water be poured into the spout, the
water will rise in the same manner in the body of the vessel ,
from which it appears that the force of pressure
de P ends entirely on the height, and not on the
ture. length or breadth, of the column of fluid. [Sen

No. 434.]

444, Any quantity of fluid, however small,

What is the m j^ ma( j e ^ k a l ance an y other quantity
Hydrostatic * J ^ J

Paradox ? however large. This is what is called the Hy-
drostatic Paradox.*

Explain 445. The principle of what is called the hydro-
Fig. 66. static paradox is illustrated by the hydrostatic bellows
represented in Fig. 66 A B is a long tube, one inch square
C D EF are the bellows, consisting of two boards, eight inches
square, connected by broad pieces of leather, or india-rubber
ploth in the manner of a pair of common bellows. One pound

* A paradox is something which is seemingly absurd, but true in fact. But
in what is called the Hydrostatic Paradox there is in reality no paradox at
all. It is true that a small quantity of fluid will balance any quantity,
however large, but it is on the same principle as that with which the longer
arm of the lever acts. In order to raise the larger quantity of fluid, the
smaller quantity must be elevated to a height in proportion as the bulk of
the larger quantity exceeds the smaller. Thus, to raise 500 Ibs of watei
by the descending force of one pound, the latter must descend 500 inohes
while the former is rising one inch ; and hence, what is called the hydro-
rtatic paradox is in strict conformity with the fundamental principle of Me
p'lauics, that what is gained in power is lost iu time, or hi space



of wator pour ,<1 iiito the tube will raise sixty- Pig. 66

four pounds on the bellows. If a smaller.

tube be used, the same quantity of water will

fill it higher, and, consequently, will raise a

greater weight ; but, if a larger tube be used,

it will, of course, not fill it so high, and, con-

sequently, will not raise so great a weight,

because it is the height, not the quantity, which

causes the pressure.

The hydrostatic bellows may be constructed
in a variety of forms, the simplest of which
consists, as in the figure, of two boards connected together bj
broad pieces of leather, or india-rubber cloth, in such a manner
as to allow the upper board to rise and fall like the common
bellows. A perpendicular tube is so adjusted to this apparatus
that water poured into the tube, passing between the boards,
will separate them by its upward pressure, even although the
upper board is loaded with a considerable weight.

[N. B. A small quantity of water may be poured into the "bellows to separate
the surfaces before they are loaded with the weight.]

How is the force 446. The force of pressure exerted on

lettoics estimated f tube is estimated by the comparative size
of the tube and the bellows. Thus, if the tube be one inch
square, and the top of the bellows twelve inches, thus con-
taining 144 square inches, a pound of water poured into
the tube will exert a pressure of 144 pounds on the bellows.
Now it will be clearly perceived that this pressure is caused
~by the height of the column of water in the tube. A pound,
or a pint, of water will fill the tube 144 times as high as the
same quantity would fill the bellows. To raise a weight of
144 pounds on the bellows to the height of one inch, it will
be necessary to pour into the tube as much 'water as would
What f undo- fill the tube were it 144 inches long. It will
mental law of tlms be perceived that the fundamental prin-



Fig. 67.

Mechanics ciple of the laws of motion is here also in full
'hwirostatfc * f orce namely, that what is gained in power
pressure ? is lost either in time or in space j for while
the water in the bellows is rising to the height of one inch,
that in the tube passes over 144 inches.
Explain 447. Another form of apparatus, by means of
Fig. 67. which it can be proved that fluids press in proportion
to their perpendicular height, and not their quantity, is seen in
Fig. 67. This apparatus unites simplicity with convenience.
Instead of two boards, connected with leather, an india-rubber
bag is placed between two boards, connected by crossed bars
with a board below, loaded with weights, and the upper boards
are made to rise or fall as the water runs into or out of the
bag. It is an apparatus easily repaired, and the bag may also
be used for gas, or for experiments in Pneumatics

A and B are two vessels of unequal size, but of the same
length. These may suc-
cessively be screwed to
the apparatus, and filled
with water. Weights
may then be added to
the suspended scale until
the pressure is counter-
balanced. It will then
be perceived that, al-
though A is ten times
larger than B, the water
will stand at the same
height in both, because
they are of the same
length. If C be used
instead of A or B, the
apparatus may be used as the hydrostatic bellows.

If a cask be filled with water and a long pipe be fitted to
it, water poured into the pipe will exert so great hydro
static pressure as to burst the cork.






ployed as a

MECHANICAL POWER. If water be confined
* u an ^ vesse ^ an( * a pressure to any amount
be exerted on a square inch of that water, a
pressure to an equal amount will be trans-
mitted to every square inch of the surface of
the vessel in which the water is confined.

449. This property of fluids seems to invest us with a power of
increasing the intensity of a pressure exerted by a comparatively
small force, without any other limit than that of the strength of
the materials of which the engine itself is constructed. It also
enables us with great -facility to transmit the motion and force of
one machine to another, in cases where local circumstances pre-
clude the possibility of instituting any ordinary mechanical con-
nexion between the two machines. Thus, merely by means of
water-pipes, very great pressures may be transmitted to any dis-
tance, and over inequalities of ground, or through any other ob-
structions. (See par. 1423.)

On what prin- ^ ^ * s on ^ e P r i n ip le OI> hydrostatic press-
cipJe is Bra- ure that Bramah's hydrostatic press, represented

in Fi ~ gg j g cons t ruc ted. The main features of

. ,

this apparatus are as iollows : a is a narrow, and

mah's hydro-
static press

Explain Fig. A a large metallic cylinder, having communi-
cation one with the other. Water stands in both
the cylinders. The
piston S carries a
strong head P, which
works in a frame op-
posite to a similar
plate R. Between
the two plates trie
substance W to be
compressed is placed.
In the narrow tube,
z is a piston p,
worked by a lever
cf)d, its short arm


j& driving the piston, while the power is applied at d. The
pressure exerted by the small piston p on the water at a is
transmitted with equal force throughout the entire mass of the
fluid, while the surface at A presses up the piston S with a
force proportioned to its area. For instance, if the cylinder ,
of the force-pump has an area of half an inch, while the greal
cylinder has an area of 200 inches, then the pressure of the
water in the latter on the piston S will be equal to 400 times
that on p

Next, suppose the arms of the lever to be to each other as
1 to 50, and that at d, the extremity of the longer arm, a man
works with a force of 50 pounds, the piston p will consequently
descend on the water with a force of 2500 pounds. Deducting
one-fourth for the loss of power caused by the different impedi-
ments to motion, and one man would still be able to exert a
force of three-quarters of a million of pounds by means of this
machine. This press is used in pressing paper, cloth, hay, gun-
powder, &c. ; also in uprooting trees, testing ths strength of
ropes, &c. (See pars. 1425, 1426.)

When will one

fluid float on 451. A fluid specifically lighter than another

the surface of fl u id w {\\ fl oat Up0 n its surface>

another fluid?

[N. B. This is but another way of stating the law mentioned in Nos 409
and 410.]

452. If an open bottle, filled with any fluid specifically lighter
than water, be' sunk in water, the lighter fluid will rise from the
oottle, and its place will be supplied with the heavier water.

j .,, 453. Any substance whose specific gravity is

body rise, sink greater than any fluid will sink to the bottom of
or float, in a that fluid, and a body of the same specific gravity
with a fluid will neither rise nor fall in the fluid
but will remain in whatever portion of the fluid it is placed

* The slaves in the West Indies, it is said, steal rum by inserting th
long neck of a bottle, full of water, through the top aperture of the rum
aask. The water falls out of the bottle i uto the cask, while the light*

rum ascends in ite stead


But a body whose specific gravity is less than that of a
fluid will float.

This is the reason why some bodies will sink and others
float, and still others neither sink nor float.* (See par. 1427.)

How deep will 454 - A bod y specifically lighter than a fluid
a body sink in will sink in the fluid until it has displaced a por-
a fluid? tion of the fluid eual in we ih t to

455. If a piece of cork is placed in a vessel of water, about one-
third part of the cork will sink below, and the remainder will stand
above, the surface of the water ; thereby displacing a portion of
water equal in bulk to about a third part of the cork, and this
quantity of water is equal in weight to 'the whole of the cork
because the specific gravity of water is about three times as great
as that of cork.

456. It is on the same principle that boats, ships, &c., although
composed of materials heavier than water, are made to float. From
their peculiar shape, they are made to rest lightly on the water.
The extent of the surface presented to the water counterbalances
the weight of the materials, and the vessel sinks to such a depth as
will cause it to displace a portion of water equal in weight to the
whole weight of the vessel. From a knowledge of the specific
gravity of water, and the materials of which a vessel is composed,
rules have been formed by which to estimate the tonnage of vessels ;
that is to say, the weight which the vessel will sustain without

standard for ^"' ^ e standard which has been adopted to

estimating the estimate the specific gravity of bodies is rain or

specific grav- distilled water at tho temperature of 60.t
ity of bodies ?

* The bodies of birds that frequent the water, or that live in the water,
are generally much lighter than the fluid in which they move. The
feathers and down of water-fowl contribute much to their buoyancy, but
fishes have the power of dilating and contracting their bodies by means of
an internal air-vessel, which they can contract or expand at pleasure.

The reason that the bodies of persons who have been drowned first sink,
and, after a number of days, will float, is, that when first drowned the air
being expelled from the lungs, makes the body specifically heavier than
water, and it will of course sink ; but, after decomposition has taken place.
the gases generated within the body distend it, and render it lighter thaa
water, and they will cause it to rise to the surface.

t As heat expands and cold condenses all metals, their specific gravity
cannot be the same in summer that it is in winter. For this reason, the}
will not serve as a standard to estimate the specific gravity of other bodies
The reason that distilled water is used is, that spring, wel', or river water u
eldom perfectly pure, aud the various substances -mixed with it affect itf


This is found to be a very convenient standard, because a
cubic foot of water at that temperature weighs exactly one
thousand ounces

458. Taking a certain quantity of rain or distilled water, we find
that a quantity of gold, equal in bulk, will weigh nearly twenty
times as much as the water ; of lead, nearly twelve times as much ;
while oil, spirit, cork, &c., will weigh less than water.*

weight. The cause of the ascent of steam or vapor may be found in its
specific gravity. It may here be stated that rain, snow and hail, are formed
by the condensation of the particles of vapor in the upper regions of the
atmosphere. Fine, watery particles, coming within the sphere of each
aiher's attraction, unite in the form of a drop, which, being heavier than
the air, falls to the earth. Snow and hail differ from rain only in the
different degrees of temperature at which the particles unite. When rain,
snow, or hail falls, part of it reascends in the form of vapor and forma
clouds, part is absorbed by the roots of vegetables, and part descends into
the earth and forms springs. The springs form brooks, rivulets, rivers,
<fco., and descend to the ocean, where, being again heated by the sun, the
water, rising in the form of papor, again forms clouds, and again descends
in rain, snow, hail, <fec. The specific gravity of the watery particles which
constitute vapor is less than that of the air near the surface of che earth ;
they will, therefore, ascend until they reach a portion of the atmosphere of
the same specific gravity with themselves. But the constant accession of
fresh vapor from the earth, and the loss of heat, cause several particles to
come within the sphere of each other's attraction, as has been stated above,
and they unite in the form of a drop, the specific gravity of which being
greater than that of the atmosphere, it will fall in the form of rain. Water,
as it descends in rain, snow or hail, is perfectly pure ; but, when it has
fallen to the earth, it mixes with the various substances through which it
s, which gives it a species of flavor, without affecting its transparency.

Temperature about 40 J Fahrenheit.

Distilled Water,

Mercury, 13.596

Sulphuric Acid, 1.841

Nitric Acid, 1.220

Prussic Acid, .696

Alcohol (pure), .792

Ether, .715

Spirits of Turpentine .869

Essence of Cinnamon, 1.010

Sea Water, 1.026

Milk, 1.030

Wine, .993

Olive Oil, .915

Naphtha, .847

Iodine, 4.946

PUtinum, 22.050

Goli, 19.360

Silver, 10.500

Rhodium, 11.000

Palladium, 11.500

Iridiuin, 21,500

Copper, 8.850

Lead, 11.250

Bismuth, 9.8'22

Tellurium, 6.240

Antimony, 6.720

Chromium, 5.900

Tungsten; 17.500

Nickel, 8.270

Cobalt, 7.810

Tin, 7.293

Cadmium, 8687

Zinc, 7.190

Steel, 7.820

Iron, 7.788

Cast-iron, 7.200

Manga ns, 8.012

Sodium, 975


Hou is tk. 459. The specific gravity of bodies that will

specific gravity ^ j water is "ascertained by weighing them

of a body as- J

certamed when first in water, and then out of the water, and

it is greater dividing the weight out of the water by tb loss

than that of n . , , .

water ? ^ weight in water. (See par.










White Lead,

Plaster of Paris,

Nitrate of Potash,







Bituminous Coal,


Pulverized Charcoal,

Woody Fibre,

Lignum Vitae,






Apple Tree,

Yellow Fir, .




Cork Tree,

Flint Glass,




Porcelain Clay,







Common Air,

Hydrogen Gas,

Living Men,




Carbonic Acid Gas,



























By means of this table the weight of any mass of matter can be ascer
tained, if we know its cubical contents. A cubic foot of water weighs
exactly 1000 ounces. If we multiply this by the number annexed tc *ny
substance in this table, the product will be the weight of a cubic foot of
that substance. Thus anthracite coal has a specific gravity of 1.800. A
thousand ounces, multiplied by this sum, produces 1800 ounces, which is
the weight of a cubic foot of anthracite coal.

The bulk of any given weight of a substance may also readily be ascer-
tained by dividing that weight in ounces by the number of ounces there ar
in a cubic foot. The result will be the number of cubic feet. The cube
root of the number of cubic feet will give the length, depth and breadth, of
the inside ol a square box that will contain it.

It is to be understood that all substances whose specific gravity is greater
than water will sink when immersed in it, and that all whose specific
gravity is less than that of water will float in it. Let us, then, tako a
quantity of water which will weigh exactly one pound ; a quantity of the
substances specified in the table, of the same bulk, will weigh as follows :

Fine Gold,




10.500 ioa
8.850 "



Describe tht.

460. Fig. 69 represents the scales for asce

teaks used for taining the specific gravity

finding the
specific grav-
ity of a body.

Fig. 69

of bodies. One scale is

shorter than the other, and

a hook is attached to the
bottom of the scale, to which substances
whose specific gravity is sought may be
attached and sunk in water.

461. Suppose a cubic inch of gold weighs nineteen ounces when
weighed out of the water, and but eighteen ounces * when weighed







Rain Water,



2.850 Ibs.
,793 "
.250 "

Living Men,


.003 "
.030 "
.320 "




.920 "
.865 "

Common Air,
Hydrogen Gas,

.820 fbs.

.891 "

.845 "

.852 "

.800 "

.. 7 "

.240 "


.000105 *

A cubic foot of water weighs one thousand avoirdupois ounces. By mu^

Online LibraryRichard Green ParkerA school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of → online text (page 11 of 38)