Copyright
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 17 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 17 of 38)
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depend f

the sound produced by wind instruments de-

pends upon their size, their length, and their internal diameter.

680. When music is made by the use of strings, the air is struck
by the body, and the sound is caused by the vibrations ; when it is
made by pipes, the body is struck by the air ; but as action and re-
action are equal, the effect is the same in both cases.

681. Long and large strings, when loose, produce the lowest



NATURAL PHILOSOPHY

tones but differet-t tones may be produced from the saii.e string,
according to -the degree of tension. Large wind instruments, also,
produce the lowest tones ; but different tones may be produced
from the same instrument, according to the distance of the aperture
for the escape of the wind from the aperture where it enters.

How does the 682- Tb. e qu dity of the sound of all musical

temperature of ,

the weather of- instruments is anected by the changes in the

feet the tone of temperature and specific gravity of the atmos-
a musical in- ,
ttrument? P nere '

683. As heat expands and cold contracts the materials of which
the instrument is made, it follows that the strings will have a
greater degree of tension, and that pipes and other wind instru-
ments will be contracted, or shortened, in cold weather. For this
reason, most musical instruments are higher in tone (or sharper)
in cold weather, and lower in tone (or more flat) in warm weather

On what is the ^^' ^ ne sc i ence of harmony is founded on
science of har- the relation which the vibrations of sonorous
many founded? bodieg have to each other>

685. Thus, when the vibrations of one string are double those ol
another, the chord of an octave is produced. If the vibrations of
two strings be as two to three, the chord of a fifth is produced.
When the vibrations of two strings frequently coincide, they pro-
duce a musical chord ; and when the coincidence of the vibrations
is unfrequent, discord is produced.

686. A simple instrument, called a monochord, contrived for the
purpose of showing the length and degree of tension of a string tft
produce the various musical tones, and to show their relations, may
thus be made. A single string of catgut or wire, attached at one
end to a fixed point, is carried over a pulley, and a weight is sus-
pended to the other end of the string. The string rests on two
bridges, between the fixed point and the pulley, one of which is
fixed, the other movable. A scale is placed beneath the string by
which the length of the vibrating part between the two bridges
may be measured. By means of this simple instrument, the respect-
ive lengths required to produce the seven successive notes of the
gamut will be as follows : it being premised that the longer the
gtring the slower will be its vibrations.

637. Let the length of the string required to produce the note
called C be 1 ; the length of the string to produce the successive
aotes will be

CDEFGA B C

J I t J I A -4-



ACOUSTICS.



183



688. Hence, the octave will require
only lialf of the length of the fundamen-
tal 'note, and the vibrations that produce
it will be as two to one. The vibrations
of the string in producing the successive
notes of the scale will be as follows :



C D E F O A

1 * t I i"f



That is, to produce the note D nine vibra-
tions will be made in the same time that
eight are made by C, five of E to four of
0, four of F to three of C, three of G
to two of C, five of A to three of C,
fifteen of B to eight of C, and two of
the octave C to one ol the fundamen-
tal C.

689. The same relations exist in each
successive octave throughout the whole

nusical scale.

690. As harmony depends upon the
coincidence of vibrations, it follows that
the octave produces the most perfect har-
mony ; next in order is the fifth, as
every third vibration of the fifth corre-
sponds with every second vibration of the
fundamental. Next to the fifth in the
order of harmony follows the fourth, and
after the fourth the third.

691. The following scale, containing
three octaves, exhibits the proportions
which exist between the fundamental and
all the other notes within that compass.

692. In the lowest line of this scale
the numbers show the intervals. The
figures above express the number of

'ibrations of the fundamental or tonic,
and the upper line of figures represents
the proportionate vibrations of each suc-
cessive interval.

693. It is found in practice that when
two sounds are caused by vibrations
which are in some simple numerical pro-
portion to each other, such as 1 to 2, or
<2 to 3, or 3 to 4, &c., they are pleasing
to the ear ; and the whole science of har-
oiony is founded on such relations.

694 The principal harmonies are the
Kituvc, fifth, fourth, major third, and



- !



| ORB



~f1



-



iffl



INI s
lljTj -
ilWIi s



184 NATURAL PHILOSOPHY.

minor third ; and the relations between them and the fundamental
or tunic are as follows :

Octave, 2 to 1.

Fifth, 3 " 2.

Fourth. 4 " 3.

Major Third, 5 " 4.

Minor Third, 6 " 5.

695. Tht following Rules may serve as the basts of interesting
calculations.

(1.) Strings of the same diameter and equal tension vibrate in
times in an inverse proportion to their lengths.

(2.) The vibrations of strings of equal length and tension are in
an inverse proportion to their diameters.

(3.) The vibrations of strings of the same length and diameter
are as the square roots of the weights causing their tension.

(4.) The vibrations of cylindric tubes closed at one end are in an
inverse proportion to their length.

(5.) The sound of tubes open at both ends is the same with that
of tubes of half the length closed at one end.

[The limits of this work will not admit the further consideration
of the subject of Harmony. It constitutes of itself a science, in-
volving principles which require deep study and investigation ; and
they who would pursue it advantageously will scarcely expect, in
the pages of an elementary work of this kind, that their wants will
be supplied.]

696. Questions for Solution.

(1.) A rocket was seen to explode, and in two seconds the sound of the
explosion was heard ; how far off was the rocket 1 Ann. 2240 ft.

(2.) The flash from a cloud was seen, and in five seconds the thunder was
heard ; what was the distance of the cloud 1 Arts. 5600./Z.

(3.) A musical string four feet long gave a certain tone; what must be
the length of a string of similar size and tension to produce the note of a
fifth 7 Ans. 2ft. 8 in.

(4.) A certain string vibrates 100 times in a second ; how many times
must a string of the same kind vibrate to produce the octave 1 the fifth 1
the minor third 1 the major third 1 Am. 200; 150; 120; 125.

(5.) Supposing that two sounds, with all their attending circumstances
similar, reach an ear situated at the point of interference of the undula-
tions, what will be the consequence 1 [See Nos. 653 and 054.]

(6.) The length of a string being 36, what will be length of its octave !
fifth 'J fourth 1 major and minor thirds ] Ans. 18; 24; 27; 28.8; 30.

(7.) A stone, being dropped into a pit, is heard to strike the bottom in
7 seconds ; how deep was the pit 1 Ans. By Algebra, 600,/i.

[N. B. In estimating the velocity of sound, it is generally reckoned in
practice as only at 1090 feet per second, supposing the thermometer at the
freezing point ; and one foot per second is added for every degree of tem
perature above the freezing point, or 32. The average rate of 1120 fetyj
Kaa been assumed in the text.]



PYRONOMICS. 185

(8.) Suppose the length of a music-string to be five feet ; what will bo
the length of the 15th, all other circumstances being equal ? Ans. 4 in.

(9.) The length of the fifth being four, what will be the length of the
fundamental, or tonic ? Ans. 6.

(10.) What must be the length of a pipe of an open diapason to produce
the same tone with four foot C of the stopped diapason ? Ans. ^ft.

[N. B. The open diapason consists of pipes open at both ends ; the
stopped diapason has its pipes closed at one end. [See No. 695 (5).]

(11.) In what proportion are the vibrations of two strings of equal
length and diameter one stretched with a weight of twenty-five pounds,
the other with a weight of fifty pounds ? [See No. 695 (3).] Ans. 1 to 1.41 +

(12.) In what proportion are the vibrations of two strings of equal
length and tension, but having diameters in the proportion of 3 to 5 ?

Ans. 5 to 3.

What is 697. PYRONOMICS, OK THE LAWS OF

Pyronomicsf J EAT . Pyronomics is the science which
treats of the laws, the properties and operations of heat.

What is 698. Heat is now known to be a motion of the
Heat? minutest particles (or molecules) of a body. The
molecules of all known bodies are continually in motion. This
motion may be transmitted from one body to another.

What is 699. Cold is therefore only an absence or partial
Cold ? absence of this motion of the molecules. We say a
body is cold when the motion of its molecules is less than usual,
or less than that of surrounding bodies.

What effect has 700. When a body is heated to a high tem-
heat on bodies ? perature, the motion of the molecules becomes
greater and greater, and the whole body becomes larger. Heat
and the attraction of cohesion constantly act in opposition to
each other ; hefice, the more a body is heated, the more its par-
ticles will be separated. (See par. 1463.)

701. Heat causes most substances to dilate or expand, while
cold (which is merely the absence of heat) causes them to contract.*
Since there is a continual change in the temperature of all bodies
on the surface of the earth, it necessarily follows that there will be
a constant corresponding change in their magnitude as they are
affected by heat and cold. They expand their bulk in a warm day,
and contract it in a cold one. In warm weather the flesh -swells,

* Two exceptions to this remark are water and clay. Water expand*
when it freezes ; clay contracts when heated.



1 86 NJ TURAL PHILOSOPHY.

{he blocl vessels are well filled, the hands arid the feet, as will an
othei parts of the body, expand or acquire a degree of plumpness
,md the skin is distended ; while, on the contrary, in cold weathei
the flesh appears to contract, the vessels shrink, and the skin
Appears shrivelled. Hence a glove or a shoe which is too tight in
the summer will often be found to be easy in cold weather.

702. The effect of heat in separating the particles of different
Kinds of substances is seen in the melting of solids, such as metals,
wax, butter, &o. The heat insinuates itself between the particles,
;md forces them asunder. These particieo thn are removed from
that degree of proximity to each other within which coxitsive attrac
ii(n exists, and the body is reduced to a fluid form. When the
heat is removed the bodies return to their former solid state.



147. t k' d f ^^' -^ eat P asses through some bodies with
'at lies arrest diore difficulty than through others, but there is

'he progress no kind of matter which can completely arrest its
v,f hf.at ?

progress. (See par. 1465.)

What is 704. Of all the effects of heat, that produced upou
fteam? ,oter is, perhaps, the most familiar. The particles
are totally separated, and converted into steam or vapor, and
{heir extension is wonderfully increased. The steam wlrch
arises from boiling water is nothing more than portions of the
water heated. The heat insinuates itself between the par-
ticles of the water, and forces them asunder. When deprived
of the heat, the particles will unite in the form of drops of
A r ater.

This fact can be seen by holding a cold plate over boiling water.
The steam rising from t ho water will be condensed into drops on
the bottom of the plate. The air which we breathe generally con
tains a considerable portion of moisture. On a cold day this
moisture condenses on the glass in the windows, and becomes
visible. We see it also collected into drops on the outside of a
tumbler or other vessel containing cold water in warm weathor.
Heat also produces most remarkable effects upon air, causing it to
expand to a wonderful extent, while the absence of heat causes it
r.'j "shrink or contract into very small dimensions.

705. The attraction of cohesion causes the

How is 'M' small watery particles which compose mist or

vapor to unite together in the form of drops of

water. It is thus that rain is produced. The clouds consist of



PYKO^OMICS. 187

mist or vapor expanded by heat. They rise to the cold regions
of the skies, where the particles of vapor lose their heat, and
then, uniting in drops, fall to the earth. But so long as they
retain their heat the attraction of cohesion can have no influence
upon them and they will continue to exist in the form of steam,
vapor or mist.

706. The thermometer, an instrument designed to measure degrees
of heat, has already been described,, in connexion with the barom-
eter, under the head of Pneumatics. Heat, under the name of
caloric, is properly a subject of consideration in the science of
Chemistry. It exists in two states, called, respectively, free heat
and latent heat. Free heat, or free caloric, is that which is per-
ceptible to the senses, as the heat of a fire, the heat of the sun, &c.
Latent heat is that which exists in most kinds of substances, but is
not perceptible to the senses until it is brought out by mechanical
or chemical action. Thus, when a piece of cold iron is hammered
upon an anvil, it becomes intensely heated ; and when a small
portion of sulphuric acid, or vitriol, is poured into a vial of cold
water, the vial and the liquid immediately become hot. A further
illustration of the existence of latent or concealed heat is given at
the fireside every day. A portion of cold fuel is placed upon the
grate or hearth, and a spark is applied to kindle the fire which
warms us. It is evident that the heat given out by the fuel, when
ignited, does not all proceed from the spark, noi can we perceive it
in the fuel ; it must, therefore, have existed somewhere in a latent
state. It is, however, the effects of free heat, or free caloric, which
are embraced in the science of Pyronomics. The subject of latent
heat belongs more properly to the science of Chemistry. (See par.
1470.)

707. The terms heat and cold, as they are generally used, are
merely relative terms ; for a substance which in one person would
excite the sensation of heat might, at the same time, seem cold to
another. Thus, also, to the same individual the same thing may be
made to appear, relatively, both warm and cold. If, for instance, a
person were to hold one hand near to a warm fire, and the other on
a cold stone, or marble slab, and then plunge both into a basin of
lukewarm water, the liquid would appear cold to the warm hand
and warm to the cold one.



What are the ' SOURCES OF HEAT. The four prin-

itrindpal cipal sources of the development of heat are
twras of the gunj Electricity, Chemical Action and Me-
chanical Action. The heat produced by fire
rvul flame is due to chemical action.



IH8 . NATURAL PHILCSuPHY.

I*T._, ,L 709. But, of all the sources from which heat

V\ hat is the

ource of the has been developed by human agency, that pro-
greatest degree duced by electrical action, and especially the
galvanic battery, is by far the most eminent in
its degree and in its effects. It can reduce the most refractory
substances to a fluid state, or convert them to their original
elements.

710. The heat generally ascri jeu to the sun is attended by
peculiar phenomena, but imperfectly understood. It may, perhaps.
De questioned whether there be any absolute heat in the rays of
that luminary, for we find that the heat is not in all cases propor-
tionate to his proximity. Thus, on the tops of high mountains,
and at great elevation, it is not found that the heat is increased,
but, on the contrary, diminished. But there are other phenomena
which lead to the conclusion that his rays are accompanied by the
development of heat, if they are not the cause and the source of it.

711. All mechanical operations are attended by heat. Friction,
sudden compression, violent extension, are all attended by heat.
The savage makes his fire by the friction of two pieces of dry wood.
Air, suddenly and violently compressed, ignites dry substances ; *
and India-rubber especially, whan suddenly extended, shows evident
signs of heat ; and an iron bar may be made red hot by beating it
quickly on an anvil. Even water, when strongly compressed, gives
out heat.

What are the 712 ' The P rinci P al effects of heat arft

principal ef- three, namely :
f-cts of heat i ^ Heat expan( is mos t substances -

(2.) It converts them from a solid to a liquid state.

(3.) It converts them from the liquid to the gaseous state.

713. There are many substances on which ordinary degiees of
heat, and, indeed, heat of great intensity, seems to produce no
sensible effects ; and they have, therefore, received the name of
incombustible bodies. Bodies usually called incombustible are
generally mineral substances, such as stones, the earths, &c. All
vegetable substances, and most animal substances, are highly com-
bustible. The metals also all yield to the electrical or galvanic
battery. But there is sufficient evidence that all bodies were once
in a fluid or gaseous state, and that the solid forms that they have
assumed are due to the loss of heat Could the same degree of

* Syringes have been constructed on this principle A solid piston
being forcibly driven downward or dry tinder, ignites it



PYKONOMICS. 189

> a tensity of heat be restored, it is presumed that they would resume
tktiir liquid or gaseous form.

What is the 714 Heat tends to diffuse itself equally through

fast law of . '

heat ? a ^ substances.

If a heated body be placed near a cold one, the temperature of
the former will be lowered, while that of the latter will be raised.
All substances contain a certain quantity of heat ; but, on account
of its tendency to diffuse itself equally, and the difference in the
power of different substances to conduct it, bodies of the same
absolute temperature appear to possess different degrees of heat.

Thus, if the hand be successively applied to a woollen garment, a
mahogany table, and a marble slab, all of which have been for some
time in the same room, the woollen garment will appear the warmest,
and the marble slab the coldest, of the three articles ; but, if a ther-
mometer be applied to each, no difference in the temperature will
be observed.

What is the ^'^' -^ rom tn is ^ appears that some substances

reason that conduct heat readily, and others with great dif-

wme sub- faculty. The reason that the marble slab seems

stances feel y i , .

warm and tae coldest is, that marble, being a good con-

others cold in ductor of heat, receives the heat from the hand
thesameroom? &Q rea dil y that the loss is instantly felt by the
hand ; while the woollen garment, being a bad conductor of
heat, receives the heat from the hand so slowly that the los^ is
imperceptible.

What is the 716. The different power of receiving and

difference in conducting heat, possessed by different substances,
the warmth of is the cause of the difference in the warmth of

different gar- various substances used for clothing.
ments ?



Why are 1^-1 ^^us, woollen garments are warm gar

woollen gar- ments, because they part slowly with the heat

[G}i they ac( l uire from the bod y> and ' cons -
quently, they do not readily convey the warmth

of the body to the air ; while, on the contrary, a linen garment
is a cool one, because it parts with its heat readily, and as read-
ily receives fresh heat from the body. It is, therefore, con-
>iantly receiving heat fron- the body arid throw : ng it out into



190 NATURAL PHILOSOPHY.

the air, while the woollen garment retains the heat which it re-
ceives, and thus encases the body with a warm covering.

718. For a similar reason, ice in summer is wrapped in woollen
cloths. It is then protected from the heat of the air, and will not
melt.

How is Jieat 719. Heat is propagated in two ways namely,
propagated? by conduction and by radiation. Heat is "propa-
gated by conduction when it passes from one substance to another
in contact with it. Heat is propagated by radiation when it
passes through the air, or any other elastic fluid. (See par. 1469.)
720. Different bodies conduct heat with differ-
What are the en t degrees of facility. The metals are the best
orsofheat* conductors; and with regard to their conducting
power, stand in the following order, namely: Gold,
platinum, silver, copper, iron, zinc, tin, lead.

721. Any liquid, therefore, may he more readily heated in a
diver vessel than in any other of the same thickness, except one oJ
gold, or of platinum, on account of its great conducting power.

Why are the 722. Metals, on account of their conducting
handles of tea power, cannot be handled when raised to a tempe-

made'ofwoodi rature above 12 de g rees of Fahrenheit. For this
reason, the handles of metal tea-pots and coffee-
pots are commonly made of wood ; since, if they were made of
metal, they would become too hot to be grasped by the hand,
soon after the vessel is filled with heated fluid.

723. Wood conducts heat very imperfectly. For this reason,
wooden spoons and forks are preferred for ice. Indeed, so imper-
fect a conductor of heat is wood, that a stick of wood may be grasped
by the hand while one end of the stick is a burning coal. But an
iron bar, being a good conductor of heat, cannot be handled near
the heated end.

724. Animal and vegetable substances, of a loose texture, such
as fur, wool, cotton, &c., conduct heat very imperfectly , hence their
efficacv in preserving the warmth of the body. Water becomes
scalding hot at 150 degrees ; but air, heated far beyond the tempe-
rature of boiling water, may be applied to the skin without much
pain. Sir Joseph Banks, with several other gentlemen, remained
some time in a room when the heat was 52 D above the boiling
point ; but though they could bear the contact of the heated air
they could not touch any metallic substance, as their watch-chains



PYKOJNOMIOS. 1'Ji

money, <fcc. Eggs, placed on a tin frame, were roasted hard in
twenty minutes ; and a beef-steak was overdone in thirty-three
minutes.

725. Chantrey, the celebrated sculptor, had an oven which ne
used for drying his plaster cuts and moulds. The thermometer gen-
arally stood at 300 degrees in it, yet the workmen entered, and
remained in it some minutes without difficulty ; but a gentleman
rmce entering it with a pair of silver-mounted spectacles on, had his
face burnt where the metal came in contact with the skin.

726. The air, being a bad conductor, never radiates heat, nor is
it ever made hot by the direct rays of the sun The air which comes
in contact with the surface of the earth ascends, and warms the air
through which it passes in its ascent. Other air, heated in the
same way, also ascends, carrying heat, and this process is repeated
till all the air is made hot.

727. In like manner, in cold weather, the air resting on the earth
ts made cold by contact. This cold air makes the air above it cold,
and cold currents (or wind) agitate the mass together till a uniform
temperature is produced.

728. Heat is reflected by bright substances, and
How is heat . , n n .11 t

reflected? * ne an gi e of reflection will be equal to th* anglf

of incidence.

729. Advantage has been taken of this property of heat in the
construction of a simple apparatus for baking. It-is a bright tin
case, having a cover inclined towards the fire in such a manner as
to reflect the heat downwards. In this manner use is made botli ot
the direct heat of the fire, and the reflected heat, which would other-
wise pass into the room. The whole apparatus, thus connected with
the culinary department, is called, in New England, " The Connect-
icut baker."

730. This power of reflecting heat, possessed by bright sub-
stances, is the reason why andirons and other articles that are kept
bright, although standing very near the fire, u^ver become hot;
while other darker substances, further from the fire, become hot.
But, if they are not bright, heat will penetrate tLein.

731. The reflecting power of bright and light colovod substances
accounts also for the superior coolness of whi^e and light-colored
fabrics for clothing.

Whti are dark ^^' Black an( ^ dark-coloied surfaces absorb
garments heat. This is the reason why black and dark-



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 17 of 38)