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 2 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 2 of 38)
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can we conceive of anything so small that it is not made up of two
halves or four quarters. It is indeed true that our senses are quite
limited in their operation, and that we cannot perceive or take
cognizance, by means of our senses, of many objects of the existence
of which we are convinced without their immediate and direct

39. Sir Isaac Newton has shown that the thickest part of a soap-
bubble does not exceed the two-millionth part of an inch.

40. The microscopic observations of Ehrcnberg have proved that
there are many species of little creatures, called Infusoria, so small
tnat millions of them collected into a single mass would not exceed
the bulk of a grain of sand, and thousands of them might swim
side by side through the eye of a small needle.

41. In the slate formations in Bohemia these little creatures aro
found in a fossil state, so small that it would require a hundred and
eighty-seven millions of them to weigh a single grain.

42. A single thread of the spider's web has been found to be
tornposed of six thousand filaments.

43. A single grain of gold may be hammered by a 'gold-beater
until it will cover fifty square inches ; each square inch may bo
divided into two hundred strips ; and each strip into two hundred
rarts. One of these parts is only OIK two-millionth part of a graiw
:f gold, and yet it may be seen with the naked eye


44. The particles which escape from odoriferous objects also
aflbrd instances of extreme divisibility.

\Vhat is

l nde . 45. INDESTRUCTIBILITY. By the Indestructi-

siructi- bility of matter is meant that it cannot be destroyed.

46. A body may be indefinitely divided or altered in its form,
color, and other unessential properties, but it can never be destroyed
by man. It must continue to exist in some form, with all its
essential properties, through all its changes of external appearance.
HE alone " who can create can destroy."'

47. When water disappears, either by boiling ove* a fire or by
evaporation under the heat of the sun, it is not destroyed, but
merely changed from a liquid to a fluid form, and becomes steam or
vapor. Some of its unessential properties are altered, but its essential
properties remain the same, under all the changes which it under-
goes. In the form of water it has no elasticity * and but a limited
degree of compr-*^ bility.* But when "it dries up" (as it is
called) it rises in the form of steam or vapor, and expands to such a
degree as to become invisible. It then assumes other properties,
not possessed before (sucb as elasticity and expansibility), it ascends
In the air and forms clouds ; these clouds, affected by the temperature
of the air and other agents, again fall to the earth in the form of
rain, hail, snow or sleet, and form springs, fountains, rivers, &c
The water on or in the earth, therefore, is constantly changing its
shape or situation, but no particle of it is ever actually destroyed.

48. Substances used as fuel, whether in the form of wood, coal,
or other materials, in like manner undergo many changes by the
process of combustion. Parts of them rise in the form of smoke,
part ascends in vapor, while the remainder is reduced to the form
of ashes ; but no part is absolutely destroyed. Combustion merely
disunites the simple substances of which the burning materials ar
composed, forming them into new combinations ; but every part still
continues in existence, and retains all the essential] properties of

What is 49. INERTIA. Inertia J is the resistance of
Inertia ? matter to a change of state, whether of motion or
of rest.

* Late writers assert that water has a slight degree both of elasticity and

t The reader wil] bo careful to carry in his mind what is meant by the
terra an essential property. It is explained in the note to No. 31, page 21

} The lite-rid meaning of inertia is inactivity, and implies inability tc
change a ttat* of rest or of motion. A clear and distinct understanding 0)
this property of all matter is essential in all the departments cf material
philosophy. All matter, mec. v mically considered, must be in a state either


50 A body at rest cannot put itself in motion, nor can a
in motion stop itself This incapacity to change its state from rest
to motion, or from motion to a state of rest, is what is implied by
the term inertia.

51. It follows, therefore, from what has Just been stated, that
when a body is in motion its inertia will cause it to continue to ino-ve
until its motion is destroyed by some other force.

52. There are two forces constantly exerted around us which
tend to destroy motion, namely, gravity and the resistance of the air.
All motion caused by animal or mechanical power is affected by
these two forces. Gravity (which will presently be explained)
eausf* all bodies, whether in motion or at rest, to tend towards the
ceutn of the earth, and the air presents a resistance to all bodiea
moving in it. Could these and all other direct Fig. 2.
obstaJes to motion be set aside, a body when

once put in motion would always remain in *\ M. r*HJ
motion, and a body at rest, unaffected by any **"*-
external force, would always remain at rest.*

53. Experiment to illustrate Inertia.
Fig. 2 represents the simple apparatus
employed for illustrating the inertia of a
body. A card is placed on the top of a

stand, and a ball is balanced on the card. A quick motion

of motion o/ rest ; and, in whatever state H may be, it must remain in that
state until a change is effected by some r flicient cause, independent of the
body itself. A body placed upon another body in motion partakes of the
motion of the body on which it is placid. But, if that body be suddenly
stopped, the superincumbent body will not stop at the same time, unless it
be securely fastened. Thus, if a hors" moving at a rapid rate be suddenly
stopped, the rider will be thrown fofyard, on account of this inertia of his
body, unless by extra exertion he secures himself on the saddle by bracing
his feet on the stirrups. On the contrary, if the horse, from a state of rest,
start suddenly forward, the rider will be thrown backwards. For the same
reason, when a person jumps from a vehfcle in motion to the ground, his
body, partaking of the motion of the vehicle, cannot be suddenly brought
to a state of rest by his feet resting on the ground, but will be throwr
forward in the direction of the motion which it has acquired from the
vehicle. This is the reason that bo many accidents happen from leaping
from a vehicle in motion.

* In the absence of all positive proof from the things around us ol
the statement just made, we may find from the truths which astronomy
teaches that inertia is one of the necessary properties of all matter. Th*
heavenly bodies, launched by the hand of their Creator into the fields of,
infinite space, with no opposing forca but gravity alone, have performed
their stated revolutions in perfect consistency with the character which
'.his property gives them ; and all the calculations which have been made
with respect to them, verified as they Lave repeatedly been by v - '"-ration,
havo been predicated on their possess ; on of this necessary piv, .-> of iJI


is then given to the card by means of a spring, and the
card flies off, leaying the ball on the top of the stand.*

54. Nature seems to have engrafted some knowledge of mechan-
ical laws on the instinct of animals. When an animal, and especially
a large animal, is in rapid motion, he cannot (on account of the
inertia of his body) suddenly stop his motion, or change its direction ;
and the larger the animal the more difficult does a sudden stoppage
become. The hare pursued by the hound often escapes, when the
dog is nearly upon him, by a sudden turn, or changing the direction
of its flight, thus gaining time upon his pursuer, whose inertia is not
so readily overcome, and who is thus impelled forward beyo^V the
spot where the hare turned.

55. Children at play are in the same manner enabled " ti ^oitge^
their elder playmates, and the activity of a boy will often enable
him to escape the pursuit of a man.

56. It is the effect of inertia to render us sensible to mention. A
person in motion would be quite unconscious of that state, were it
aot for the obstacles which have a tendency to impede his progress.
In a boat on smooth water, motion is perceptible only by the
apparent change in the position of surrounding objects ; but, if the
course of the boat be interrupted by running aground, or striking
against a rock, the person in the boat would feel the shock caused
by the sudden change from a state of motion to a state of rest, and,
unless secured to his seat in the boat, he would be precipitated

What is At- 57. ATTRACTION. Attraction is the tendency
traction? which different bodies or portions of matter
have to approach or to adhere to each other.

What is the ^' Every portion of matter is attracted by everj
MW of At- other portion of matter, and this attraction is the
ractwn . g t r0 nger in proportion to the quantity and the dis-
tance. The larger the quantity and the less the distance, thw
stronger is the attraction.!

* The ball remains on the pillar in this case not solely from its tncrtif
but because sufficient motion is not communicated to the bll by the fi Lo-
tion of the card to counteract the effect of gravity on the ball. If ihe
bail, therefore, be not accurately balanced on the card, the experiment vilJ
not be successful, because the card cannot move without communicating at
least a portion of its motion to the ball.

f [N. B. This subject will be more fully treated under the head of
7rawfy See page 33.]


7 . , 59. There are two kinds of attraction
How many kinds

of Attraction namely, the Attraction of Gravitation and
are there ? the Attraction of Cohesion. (See par. 1388.)

The former belongs to all matter, whatever its form, th<?
latter appears to belong principally to solid bodies.

What is thi 60. The Attraction of Gravitation is the
n/Gravi^ reciprocal attraction of separate portions of
tation * matter.

What is the 1. The Attraction of Cohesion is that whicn
Attraction causes the particles of a bodv to cohere together.
of Cohesion? r w jVo. 31.]

62. The attraction of cohesion appears to exist but in & very
slight degree, if at all, in liquids and fluids.


the two kinds 63. The attraction of gravitation causes a body,

of Attrac- when unsupp orted, to fall to the ground. The

tion ; name- . ,

ly, Gravity attraction of cohesion holds together the particles

and Cohesive O f a b O( jy an( j causes them to unite in masses.*

Attraction f J

64. Having described the essential properties of bodies, we
come now to the consideration of other properties belonging respect-
ively to different kinds of matter ; such as Porosity, Density, Rarity,
Compressibility, Expansibility, Mobility, Elasticity, Brittleness,
RltxibiKty, Malleability, Ductility, Tenacity.

65. It has already been stated that matter consists of minute
particles or atoms, unixed by different degrees of cohesive attraction.
These atoms are probably of different shapes in different bodies, and
the different degrees of compactness with which they unite give
rise to certain qualities, which differ greatly in different substances
These qualities or properties are described under the names of
Porosity, Density and Rarity, which will presently be described.

* Besides those two kinds of attraction, there seem to be other kinds
ot attractive force, active in vegetation and in animal life, known by the
names of Endosmose and Exosmose, terms applied to the transmission of
gaseous matter or vapors through membranous substances. See note to
Capillaiy Attraction, under the head of Hydrostatics, on page 112.

Other kinds of attraction, called Electrical and Magnetical Attraction,
will hereafter be considered under their appropriate head. The subject of
Chemical Attraction or Affinity belongs distinctly to the subject of Chemistry
ind will not, therefore, be cuusidei od in this work


66. Besides the property of attraction possessed by u ne particles
or atoms of which a body is composed, there seems to be another
property, of a nature directly opposite to attraction, which exerts
.tself with a repulsive force, to prevent a closer approximation of
the particles than that which by the law of their nature they assume.
This property is called repulsion. This repulsion prevents the par-
ticles or atoms from coming into perfect contact, so that there must
he small spaces between them, where they do not absolutely touch
one another. [See Figure 1st.] These spaces are called pores, and
where they exist give rise to that prop^rtj- or quality described
under the name of Porosity.

What is M- POROSITY. Porosity implies, therefore, that

Porosity? there are spaces, or pores, between the particles or
atoms which form the mass of a body.

68. DENSITY. "When the pores are few, so that a large number
of particles unite in a small mass, the body is called a dense body.

What is 69. Density, therefore, implies the closeness or

Density? compactness of the particles which compose any

70. RARITY. When the pores in any substance are numerous,
so that the particles which form it touch one another hi only a few
points, the body is called a rare body.

What is 71. Rarity, therefore, is the reverse of density,
Rarity 1 an( j i m pli e s extension of bulk without increase in
the quantity of matter.

72. From what has now been stated it appears [See No. 67] that
the particles of a body are connected together by a system of attrac-
tions and repulsions which give rise to distinctions which have
already been described. It remains to be stated that these attractions
and repulsions differ much in degree in different substances, and this
difference gives rise to other properties, which will now be explained,
under their appropriate names.

73. COMPRESSIBILITY. When the repulsion of the particles of any
lubstance can be overcome and the mass can be reduced within
narrower limits of extension, it is said to possess the property of
Compressibility *

* Compressibility differs from Contractibility rather in cause than hi
effect. Contractibility implies a change of bulk caused by change of
imperature, or any other agency not mechanical. Compressibility implies
Jlmt the diminution of bull" is caused by some external mechanical force


What ^' Compressibility, therefore, may be defined, tha
Comprey susceptibility of a reduction of the limits of ex-

75. This property is possessed by all known substances, Nut in
very different degrees, some substances requiring but little force
to compress them, others resisting very great forces ; but it is not
known that there is any substance unsusceptible of compression . if
a sufficient force be applied *

76. Liquids in general are less easily compressed than solid
bodies ; so much so, indeed, that in practical science they are gen-
erally considered as incompressible. Under a very considerable
mechanical force, a siight degree of compression has been observed. \

77. EXPANSIBILITY. The system of attractions and repulsions
among the particles of a body are sometimes so equally balanced
that they exist, as it were, in an equilibrium. In other cases the
repulsive energy is so great as to predominate when the attractive
force is unaided. When the repulsive energy is permitted to act
without restraint, it forces the particles asunder and increases the
limits of extension, giving rise to another property of matter
possessed by many bodies, but in an eminent degree by matter in a
gaseous form. This property is called Expansibility.

What is 78. Expansibility, t therefore, may be defined
Expansi- as that property of matter by which it is enabled
1 ^ to increase its limits of extension.

79. ELASTICITY. When the atoms or particles which constitute
a body are so balanced by a system of attractions and repulsions
thf.t they resist any force which tends to change the figure of the

* Sir Isaac Newton conjectured that if the earth were so compressed
as to be absolutely without pores, its dimensions might not exceed a cubio

f Under a pressure of fifteen pounds on a square inch, water has been
diminished in bulk only by about forty-nine parts in a million. Under a
pressure of fifteen thousand pounds on a square inch, it was compreased
by about one-twentieth of its volume. The experiment was tried in a cannon,
and the cannon was burst.

^ Expansibility and Dilatability are but different names for the same
property ; but expansion implies an augmentation of the bulk or volume,
dependent on mecnanical agency, while dilatation expresses the same
condition produced by some physical cause not properly falling under the
denomination of mechanical force. Thus heat dilates most substances,
while cold contracts them. It is on this principle that the thermometer is
constructed. [See page 149, No. 546.]

All gaseous bodies are invested with the property of dilatability to an
unlimited degree, by means of which, when unrestrained, they will expand
spontaneously, and that without the application of any external agency *<*
a degree to which there is no known limit.


Dody, they will possess another property, known by the name ol

What is 80. Elasticity, therefore is the property which
Elastic- causes a body to resume its shape after it has been
compressed or expanded.*

81. Thus, when a bow or a steel spring is bent, its elasticity
causes it to resume its shape.

82. India rubber (or caoutchouc) possesses the property of
elasticity in a remarkable degree, but steam and other bodies in
a gaseous form in a still greater.!

83. Ivory is endowed with the property of elasticity in a remark
able degree, but exhibits it not so much by the mere force of pressure,
out it requires the force of impact to produce change of form. J

What is 84. BRITTLENESS. Brittleness implies aptness

Brittle- , ,

ness? to break.

* This property is possessed, in at least some small degree, by all sub-
stances ; or, at least, it cannot be said that any substance is wholly
destitute of elasticity. Even water and other liquids, which yield with
difficulty to compression, recover their volume with a force apparently
equal to the compressing force. But, for most practical purposes, many
substances, such as putty, wet paste, moist paper, clay, and similar bodies,
afford examples of substances possessing the property of elasticity in so
slight a degree that they are treated as non-elastic bodies.

t The gases or aeriform bodies afford the most remarkable instances
of elasticity. When water is converted into steam it occupies a space
seventeen hundred times greater than the water from which it is formed, and
its elasticity causes it to expand to still larger dimensions on the application
of heat. It is this peculiar property of steam, modified, as will be explained
in a future part of this work, which is the foundation of its application in
the movement of machinery. All gaseous bodies are equally elastic.

^ The metals which are best adapted to produce sound are those
which are most highly elastic. It sometimes happens that two metals,
neither of which have any great degree of hardness or elasticity, when
combined in certain proportions, will acquire both of these properties.
Thus tin and copper, neither of which in a pure state is hard or elastic,
when mixed in a certain proportion, produce a compound so hard and
elastic that it is eminent for its sonorous property, and is used for making
bells, Ac

Brittleness and hardness are properties which frequently accom-
pany each other, and brittleness is not inconsistent with elasticity. Thu
glass, for instance, which is the most brittle of all known substances, i
hignly elastic. The same body may acquire or be divested of its brittle-
aeA3 according to the treatment which it receives. Thus iron, and somo
Dther metals, when hezteJ and suddenly plunged into eold water, become
brittle; but i?J in a tested state, they are burled in hot sand, and thus o


What is 85. FLEXIBILITY. Flexibility implies a dis-
position to yield without breaking when bent.

What is 86. MALLEABILITY. Malleability implies thai
property by means of which a body may be ro-
d ucec i to the form of thin plates by means of the

kammer or the pressure of rollers

87. This property is possessed in an eminent degree by some of
the metals, especially gold, silver, iron and copper, and it is of vast
importance in the arts. A knowledge of the uses of iron, and of its
nalleability, is one of the first steps from a savage to a civilized state
jf life.

88. The most malleable of the metals is gold, which may be
hammered to such a degree of thinness as to require three hundred
and sixty thousand leaves to equal an inch in thickness.*

89. DUCTILITY. Some substances admit of being extended simul-
taneously both in length and breadth. Others can bo extended to
a greater degree in length alone ; and this property gives rise to
another name, called Ductility.

What is 90. DUCTILITY. Ductility is that property
Ductility? w hi cn renders a substance susceptible of being
Irawn out into wire.

91. The same metals are not always both ductile and malleable
to the same degree. Thus iron may be beaten into any form, when
heated, but not into very thin plates, but it can be drawn into
extremely fine wire. Tin and lead, on the contrary, cannot be drawn
out into small wire, but they are susceptible of being beaten into
ixtremoly thin leaves.

92. Gold and platinum have a high degree both of ductility and
malleability. Gold can be beaten (as has already been stated) into

permitted to cool very gradually, they will lose their brittleness art
icquire the opposite quality of flexibility. This process in the arts u
(ailed annealing,

* The malleability of the metals varies according to their temper-
iture. Iron is most malleable at a white heat. Zinc becomes malleable at
she temperature of 300 J or 400. Some of the metals, and especially anti-
mony, arsenic, bismuth and cobalt, possess scarcely any degree of this

The familiar process of welding is dependent on malleability The two
pieces of metal to be welded are first heated to that temperature at which
;hey are most malleable, and, the ends being placed together, the particles
ire driven into such intimate connexicn by the welding-tummer th-it tlujy
tubere Different metals may in some easss be thus weldeu tugetho-


leaves so thin that it would require many thousands 01 them to equaj
an inch in thickness. It has also been drawn into wiie so attenn
ated that one hundred and eighty yards of it would not weigh more
than a single grain. An ounce of such wire would t>e more thai
fifty miles in length. But platinum can be drawn oven to a fine
wire than this.

What is 93. TENACITY. Tenacity implies, the cohesion
Tenacity ? f t h e particles of a body.

94. Tenacity is one of the great elements of strength. It is th*
absence of tenacity which constitutes brittleness. Both implj
strength, but in different forms. Thus glass, the moct brittle of aL
substances, has a great degree of tenacity. A slender r'/d of glass,
which cannot resist the slightest lateral pressure, if suspended
vertically by one end will sustain a very considerable weight at the
other end.*

* A knowledge of the tenacity of different substances ic of great use in

the arts. The tenacity of metals and other substances has oeen ascertained

oy suspending weights from wires of the metals, or rc*8 and cords of

different materials.

The following table presents very nearly the weights sustained by wires

of different metals, each having the diameter of aDout one-twelfth of an


Lead, 27 pounds. Silver, 187 pounds.

Tin, 34 " Platinum, 274 "

Zinc, 109 " Copper, 302 "

Gold, 150 " Iron, 549 "

Cords of different materials, but of the same diametek, sustained the foi

lowing weights :

Common flax, 1175 pounds. New Zealand flax, 2380 pounds

Hemp, 1633 Silk, 3400 "

The following table presents a more extended list of materials. The

area of a transverse section of the rods on which the experiment was tried

iraa one square inch.

Pounds Avoirdupois. Pounds Avoirdupois

English Oak, 8,600 to 12,000 Tin, . 7,129

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 2 of 38)