G. P. (George Payn) Quackenbos.

A natural philosphy: embracing the most recent discoveries in the various branches of physics .. online

. (page 2 of 42)
Online LibraryG. P. (George Payn) QuackenbosA natural philosphy: embracing the most recent discoveries in the various branches of physics .. → online text (page 2 of 42)
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erty which renders a body incapable of being destroyed.

Matter may be made to assume a new form and new
properties, but it can not cease to exist. The quantity of
matter now in the world is precisely the same as when it
was first called into being, and it will continue undimin-
ished till the end of time. The Deity alone created, and it
is only He that can destroy.

15. To this universal law we have some apparent exceptions; but, when
closely examined, it will be found that they are exceptions in appearance
only. Water, for instance, exposed to the air in a shallow dish, will at length
disappear by evaporation ; but it is not destroyed. Assuming the form of
vapor, it ascends, becomes incorporated with clouds, is condensed into rain,
and falls, to go through the same process again. The oil in a burning lamp
gradually gets lower and lower till at last it is all gone, and we say it is
burned up ; but the process of combustion, or burning, only changes it, into
invisible gases, not one particle of its substance is lost. In like manner,
when fuel of any kind is consumed, there is only a change of form, not a de-
struction of the least portion of matter.

Such changes are constantly going on in the operations of nature. One
body perishes, and of the materials that composed it another is formed. Our
own frames may contain particles that were in the bodies of Adam, Noah, or
Socrates ; or, if they do not now, may do so to-morrow, for they are constant-
ly parting with portions of their substance, the place of which is as con-
stantly supplied by new matter. It is supposed that the whole body, in-
cluding even the innermost parts of its hardest bones, is completely renewed
every seven years. Yet, amid all the countless transitions of nature, not a
single particle of matter is destroyed or lost.

16. It was by a knowledge of the indestructibility of matter that Sir Wal-
ter Raleigh is said to have won a wager of Queen Elizabeth. Having weighed
out a sufficient quantity of tobacco to fill his pipe, he came into the queen's
presence, and as the wreaths of smoke curled up offered to bet her Majesty
that he could tell their weight. Elizabeth accepted the bet, and Sir Walter
quietly finished his pipe ; then, having shaken out the ashes, he weighed
them, and, subtracting the amount from that of the tobacco originally put



flow. 14. What is Indestructibility? What can be done to matter, and what not?
15. What is said of the apparent exceptions to this law ? What becomes of water
exposed to the air ? What becomes of the oil in a burning lamp ? W hat is said of
the changes of nature ? What is said of the changes in the human body ? 16. How
did Sir Walter Ealeigh teach Queen Elizabeth that matter is indestructible ? 17. What



INERTIA. 15

in, told the queen the exact weight of the smoke. Elizabeth paid the wager,
and thus learned to her cost that matter is indestructible.

1 7. INERTIA. Inertia is that property which renders a
body incapable of putting itself in motion when at? rest, or
coming to rest Avhen in motion.

When a stationary body begins to move, or a moving
body comes to rest, it is not through any power of its own,
but because it is acted on by some external agency, which
we call a Force.

That no inanimate body can put itself in motion, is evident from our daily
experience. The rocks that we saw on the earth's surface ten years ago are
to-day in precisely the same place as they then were, and there they will re-
main forever unless some force removes them.

It is equally true, though not so obvious, that a body once in motion can
not of itself cease to move. The earth revolves on its axis, the heavenly
bodies move in their orbits, just as they did at the time of the Creation ; they
have no power to stop. It is true that on the surface of the earth a moving
body gradually comes to rest, when the force which put it in motion ceases
to act ; but this is owing to the resistance of the air and a force which draws
it towards the centre of the earth not to any agency of its own. Remove
all external forces, and its inertia would keep it moving on in a straight line
forever.

IS. Familiar Examples. It is in consequence of inertia that a horse has to
strain hard at first to move a load, which, when it is once in motion, he can
draw with ease. A car, through its inertia, continues moving after the loco-
motive is detached. Through inertia, a person standing erect in a stationary
boat or wagon is thrown backward if it suddenly starts : his feet, touching
the bottom, are carried forward with it, while his body by its inertia does not
partake of the onward motion and falls backward. So, a person standing
erect in a boat or wagon that is moving rap- -p.^

idly, is thrown forward if it suddenly stops ;
his feet ce.ase to move at once, while his body
continues in motion in consequence of its iner-
tia, and falls forward.

19. An interesting experiment to illustrate
inertia may be performed with the apparatus
represented in Fig. 3. On the top of a short
pillar is placed a card, and on the card a brass
ball. Beside the pillar is fixed a steel spring,
with an apparatus for drawing it back. If the

is Inertia? What is a Force ? What evidences of the inertia of matter have we in
nature ? If inertia is one of the properties of matter, why does a moving body coma
to rest on the earth's surface ? 18. Give some familiar examples of inertia and its
Consequences. 19. Describe the experiment with the inertia apparatus. Describe




16



PROPERTIES OF MATTER.



spring is drawn back and then suddenly released, it will drive the card from
the top of the pillar, while the ball in consequence of its inertia will retain
its place.

Those who have not the above apparatus may balance a card with a penny
placed upfln it on the tip of one of the fingers of the left hand, and strike it



Fig. 4.




suddenly with the middle finger
of the right hand, as represented
in Fig. 4. If properly balanced
and evenly struck, the card will
fly away, and the penny will be
left on the finger.

In these cases, there is not
sufficient time for the card to
overcome the inertia of the ball
and the penny, and impart to
them its own motion. "NYhcn,
however, motion has once been communicated by one body to another rest-
ing on it, the inertia of the latter keeps it in motion. A person riding in a
cairiage partakes of its motion, and if he jumps from it runs the risk of being
thrown down, because his feet cease to move the instant they strike tlie
ground, while the inertia of his body carries it forward. The circus-rider
pj^ K takes advantage of this fact.

While his horse is going at
full speed, he jumps over a
rope extended across the
ring (see Fig. 5), and re-
gains his footing on the
saddle without difficulty.
To do this, he has only to
leap straight up as he comes
to the rope, for his inertia
bears him along in the same
direction as his horse.
A bullet thrown at a pane of glass breaks it into many pieces, but, fired
at it from a rifle, merely makes a circular hole. In the latter case, all the par-
ticles of glass, on account of their inertia, can not immediately acquire the
rapid motion of the bullet; and consequently only that portion which is
struck is carried onward. On the same principle, a thin stick resting on two
wine-glassea (see Fig. 6) may be broken by a quick blow with a poker in its
centre, without injury to its brittle supports.




the experiment with the card and penny. What is the effect of inertia, when motion
has once been communicated to a body? "Why is a person who jumps from a car-
riage in motion thrown down ? Explain the leap of the circus-rider. What is the
effect of throwing a bullet against a pane of glass, and what of firing it ? What, causes
the difference ? What experiment may be performed to illustrate this point ? 20. To



DIVISIBILITY.



17



Fig. 6.




20. The heavier a body is,
the greater is its inertia ; the
more strongly does it resist
forces that would set it in
motion, change its 'motion, or
stop its motion.

Instinct teaches this fact. A child,
when nearly overtaken by a man, will
suddenly turn, or " dodge" as he calls
it, thus gaining ground, inasmuch as
the greater weight and inertia of the man compel him to make a longer turn.
So a hare, in making for a cover, often escapes a hound by making a num-
ber of quick turns. The greater inertia of the
hound carries him too far, and thus obliges
him to pass over a gfeater space, as seen in
Fig. 7, in which the continuous line shows the
hare's path and the dotted line the hound's.

2 1 . DIVISIBILITY. Divisibility
is that property which renders a
body capable of being divided.

Atomic Theory. Practically, ^^
there is no limit to the divisibility
of matter. Most philosophers, how- =
ever, hold what is called the Atom-
ic Theory, that if we had more
acute senses and instruments sufficiently delicate, we would
at last, in dividing and subdividing matter, arrive at ex-
ceedingly small particles, incapable of further division.
Such particles they call ATOMS, a term derived from a
Greek word meaning indivisible.

According to this theory, diiferent kinds of matter are
made up of different kinds of atoms ; but in the same sub-
stance the atoms are always the same in shape and nature.
It must be remembered, however, that no particle has yet
been arrived at that can not be divided.

22. Instances of Divisibility. Matter has been divided into parts incredi-

what is a body's inertia proportioned ? How do children turn this fact to account ?
How does the hare apply this principle? 21. What is Divisibility? Is there any
limit to the divisibility of matter ? Give the chief points of the Atomic Theory.




18 PROPERTIES OF MATTER.

bly minute. With the proper instrument, ten thousand distinct parallel lines
can be drawn on a smooth surface an inch in width. So minute are these
lines that they can not be seen without a microscope, not even a scratch be-
ing visible to the naked eye.

A grain of musk will diffuse a perceptible odor through an apartenent for
twenty years. It does this by filling the air with particles of its substance ;
but so inconceivably minute are these particles, that, if the musk is weighed
at the end of the twenty years, no loss of weight can be detected.

A grain of copper dissolved in nitric acid will impart a blue color to three
pints of water. Each separable particle of water must contain a portion of
the grain of copper, which is thus, it has been computed, divided into no
less than 100,000,000 parts.

23. Nature affords many striking examples of the divisibility of matter.
The spider's web is so attenuated that a sufiicieut quantity of it to go around
the earth would weigh only eight ounces ; and yet this minute thread con-
sists of about a thousand separate filaments.

Blood is composed of small red globules floating in a colorless liquid. Of
these globules, every drop of human blood contains at least a million. Mi-
nute as they are, they may be divided into globules much more minute. As
we descend in the scale of creation, we come to animals whose whole bodies
are no larger than these little globules of human blood, yet possess all the
organs necessary to life. How inconceivably small are the vessels through
which the fluids of their bodies must circulate !

The microscope reveals to us wonders of animal life that are almost in-
credible. It shows us in duck-weed animalcules so small that it would take
ten thousand millions of them to equai the size of a hemp-seed. In a single
drop of ditch-water, it exhibits myriads of moving creatures. The mineral
called triroli is formed of these animalcules fossilized or turned into stone ;
and it has been shown that the fortieth part of a cubic inch of this mineral
contains the bodies of no less than a thousand million animalcules or more
than all the human beings on the globe.

24. POROSITY. "What shape the atoms of different
bodies are, we have no means of determining. By reason
of their shape, however, or from some other cause, they do
not everywhere touch each other, but are separated by in-
terstices, to which we give the name of Pores. Pores are
often visible to the naked eye, as in sponge and pumice-
stone ; in other cases, as in gold and granite, they are too
to be detected even with the microscope.



22. How has the divisibility of matter been illustrated with a smooth surface an inch
In width ? How does a grain of musk prove divisibility ? How, a grain of copper ?

23. What is said of the spider's web? Mention some examples of the divisibility of
matter afforded by nature. What does the microscope reveal to us ? Mention some
of these wonders. 24. What are Pores ? What is said of the difference in the size



POEOSITY. 19

25. Porosity is the property of having pores. It be-
longs to all bodies.

26. That water is porous, is proved by the fact that a vessel filled with it
will receive considerable quantities of salt and sugar without overflowing.
\Yhat can become of these substances, unless, as shown in Fig. 2, their par-
ticles lodge in the interstices between the particles of water ? It is on this
principle that hot water receives more salt and sugar without overflowing
than cold. Heat expands water, that is, forces its particles further apart,
and thus enables a greater quantity of salt and sugar to lodge between them.

That granite is porous, is shown by placing a piece of it in a vessel oj
water under the receiver of an air-pump (described on page 178), and remov-
ing the air. Little bubbles will soon be seen rising through the water. Theso
bubbles are the air contained in the invisible pores of the granite.

A piece of, iron is made smaller by hammering. This proves its porosity.
Its particles could not be brought into closer contact, if there were no inter-
stices between them.

27. An experiment performed some years ago at Florence, Italy, to ascer-
tain whether water could be compressed, proved that gold is porous. A vio-
lent pressure was brought to bear on a hollow sphere of gold filled with water.
The water made its way through the gold and appeared on the outside of the
sphere. Water will thus pass through pores not more than one half of the
millionth of an inch in diameter.

28. Density and Rarity. The fewer and smaller the
pores in a body, the more compact are its particles, and
the greater is the weight of a given bulk. Bodies whose
particles are close together are called Dense; those with
large or numerous pores are called Rare.

29. COMPRESSIBILITY AND EXPANSIBILITY. These two
properties are the opposites of each other. Compressibility
is that property which renders a body capable of being re-
duced in size. Expansibility is that property which renders
a body capable of being increased in size.

Compressibility and Expansibility follow from porosity.
Since the particles of bodies do not everywhere touch each
other, the application of a sufficient force will bring them
closer together, and the size of the bodies will thus be re-

of the pores ? 25. What is Porosity ? 26. How is water proved to be porous ? Why
does hot water receive more salt and sugar than cold ? How may it be proved that
granite is porous ? How is the porosity of iron proved ? 27. Give an account of the
experiment by which the porosity of gold was proved. How small pores will water
pass through ? 23. What bodies are called denx& f What bo.lies are called rare f
29. What is Compressibility ? What is Expansibility ? Show how these properties



20



PROPERTIES OF MATTER.



Fie. 8.




duccd. A sponge, for instance, by the simple pressure of the
hand, can be reduced to.one-tenth of its natural size. In like
manner, if the pores of a body are made larger by any agency
(as they are by heat), its size is proportionately increased.

SO. All bodies possess these properties. A rod of iron,
too large to enter a certain opening, may be so compressed by
hammering as to pass through it, and then so expanded by
heat as to render its entrance again impossible. Liquids,
which were long considered incompressible, are now known
to yield to a high degree of pressure ; their expansibility is
illustrated by the rise of mercury in the thermometer.

The compressibility and expansibility of air are shown
by the apparatus represented in Fig. 8. Let P be a piston,
fitted, air-tight, to the cylinder A B. As the piston is driven
down, the air, unable to escape, is compressed; ^is it is
drawn back, the air expands.

Aeriform bodies are more easily compressed and ex-
panded than any others.

31. MOBILITY. Mobility is that property which renders
a body capable of being moved.

Though the inertia of bodies prevents them from mov-
ing themselves, yet there is no body that can not be moved
by the application of a proper force.

32. GRAVITATION. Gravitation (or Gravity, as it is
called when acting at short distances) is the tendency

Fig. 9. which one body has to approach another, under
the influence of the latter's attraction. A can-
non ball dropped from the hand falls to the earth
by reason of its gravity. The earth at the same
time moves towards the cannon ball, but through
a space inconceivably small in consequence of its
vast superiority in size over the ball.

That the cannon ball is capable of attracting as well as be-
ing attracted, may be proved by suspending two balls close to
each other by very long cords. In consequence of the attrac-
tion of the balls, the cords will not hang parallel, but will
incline towards each other as they descend, as shown in

Fig - 9 -

follow from porosity. 30. How may compressibility and expansibility be illustrated
With an iron rod ? What is said of these properties in liqi'ids ? How may the com-
pressibility and expansibility of air be shown ? What bodies are most easily com-



COHESION.



21



Fig. 10.



We now proceed to the Accessory Properties, which
are confined to certain bodies.

33. COHESION. Cohesion is that property by which the
particles of a body cling to each other. As particles are
also called mol '-e-cules^ Cohesion has received from some
authors the name of Mo-lec'-u-lar Attraction.

Cohesion belongs particularly to solids, and is in fact the cause of their
solidity. In some it is stronger than in others, rendering them harder or
more tenacious. Liquids have so little cohesion that their weight alone over-
comes it, and causes a separation of particles. In aeriform fluids cohesion
is entirely wanting, its place being supplied by a Repulsive Force, which
tends to make their particles spread out from each other.

34. ADHESION. Adhesion is that property by which the
surfaces of two different bodies placed in contact cling to-
gether.

The bodies in question may
be of the same kind of mat-
ter. This is proved by an ex-
periment with two glass plates
ground perfectly even. Let
these be pressed together, and
it will be found, on attempt-
ing to pull them apart by their
handles^ that considerable
force will be required. The
larger the surfaces of the
plates, the harder it will be to
separate them. A pair of Ad-
hesion Plates is represented
in Fig. 10.

Adhesion also operates
between the surfaces of sol-
ids and liquids. Suspend a
piece of copper-plate from
one side of a pair of scales,
in such a way that its under
surface may be parallel to
the floor, and balance it with
weights placed in the scale
on the other side. Then,
without disturbing the cop-




ADIIESION PLATES.



Fig. 11.




pressed and expanded ? 31. What is Mobility ? 32. What is Gravitation ? How-
does it operate in the case of a cannon ball dropped from the hand to the earth ?
How does it operate in the case of two cannon-balls suspended close to each other?



22 PROPERTIES OP MATTER.

per, place a vessel beneath it, as in Fig. 11, and pour in water till the liquid
just reaches the plate. The adhesion between the solid and the liquid is now
so strong that additional weights (more or less, according to the extent of
surface) may be put in the scale on the other side without causing them to
separate.

35. HARDNESS. Hardness is that property by which a
body resists any foreign substance that attempts to force a
passage between its particles.

The hardness of a body depends on the degree of firm-
ness with which its particles cohere. It is therefore en-
tirely distinct from density, which depends on the number
of particles in a given bulk. Thus lead is dense, but not
hard.

Neither liquids nor aeriform fluids possess this property; and even in
some solids, for instance butter and wax, it is almost entirely wanting.

Of two bodies, that is the harder which will scratch the surface of the
other. By trying the experiment with different substances, it is found that
the precious stones are harder than any other class of bodies, the diamond
standing first, and the ruby, sapphire, topaz, and emerald following in order.
Rhodium and iridium are among the hardest metals, on which account they
are used for the tips of gold pens.

36. TENACITY. Tenacity is that property by which a
body resists a force that tends to pull it into pieces.

Both hardness and tenacity are the result of cohesion ;
but they must not be confounded. Of several rods equally
thick, that which will support the greatest weight without
breaking is the most tenacious that which it is most diffi-
cult to cut into, is the hardest.

The metals generally are remarkable for their tenacity. Some, however,
possess this property in a higher degree than others. This may be shown
by comparing the weights which different metallic wires of the same size
are capable of supporting. An iron wire one-tenth of an inch in diameter
will sustain nearly 550 pounds without breaking, while one of lead will be
broken by a weight of 23 pounds.

33. What is Cohesion? What other name has been given to cohesion? What
is said of cohesion in solids? In liquids? In aeriform fluids? 34. What is
Adhesion ? Describe the experiment with adhesion plates. Describe the exper-
iment which proves that adhesion operates between solids and liquids. 35. Wlrit
is Hardness? What is the difference between hardness and density? In what
is hardness wanting? How may it be determined which of two bodies is the
harder? What bodies are the hardest as a cluss? Mention the order in which.
they rank. TV hat two metals are distinguished for their hardness? 36. What
v* Tenacity? Of what are both hardness and tenacity the result? Show the differ-



TENACITY. 23

Iron is the most tenacious of the metals. A cable of this material, com-
posed of wires one-thirtieth of aa inch across, will support the enormous
weight of GO tons for each square inch in its transverse section. In conse-
quence of this great tenacity, such cables are used for the support of suspen-
sion bridges.

37. Tenacity of Different /Substances. It is important
in building and other arts to know the relative tenacity of
different woods and metals. To determine this, experi-
ments have been made. Their results do not precisely
agree, inasmuch as there are differences in different trees
of the same kind and different pieces of the same metal ;
yet we may take the following as the average weights that
can be supported by the several materials mentioned,
taking in each case a rod of given length with a transverse
section of a square inch.



POUNDS.

Metals. Cast Steel," 134,250

Swedish Iron, 72,000

English Iron, 55,800

Cast Iron, 19,000

Cast Copper, 19,000

Cast Tin, 4,700

Cast Lead, 1,825



POCJXD9.

Woods. Ash, 14,000

Teak, 13,000

Oak, 12,000

Fir, 11,000

Maple, 8,000

Rope, one inch around, 1,000

Rope, three inches around, 5,600



It is a curious fact that a composition of two metals may be more tenacious
than either of them separately. Thus brass, which is made of zinc and cop-
per, has more tenacity than either of those metals.

33. The liquids have comparatively little tenacity, yet there is a differ-
ence in them in this respect. Milk, for instance, is more tenacious than wa-
ter ; this makes it boil over more readily, inasmuch as its bubbles do not
break, but accumulate, climbing one upon another till they overtop the ves-
sel. In like manner, it is on account of their superior tenacity that soap-suds
will make a lather while pure water will not.

39. BRITTLEXESS. Brittleness is that property which
renders a body capable of being easily broken.



ence between them. What is said of the tenacity of the metals? How may their
relative tenacity be shown ? Compare iron and lead in this respect. What is said of
the tenacity of iron? 37. Explain the fact that experiments for determining the te-



Online LibraryG. P. (George Payn) QuackenbosA natural philosphy: embracing the most recent discoveries in the various branches of physics .. → online text (page 2 of 42)