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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

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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 36 of 38)
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the candle flame at A, diverging to different points on the

Fig. 239.




lens, are converged to a focus at a. The point B, in like
manner, sends forth rays that find a focus at I ; the foci
of rays from other points of the flame will fall in their
proper places between a and #, and the image represents
the true shape of the flame.

1486. Iij this case the image is smaller than the object^ but it
will be sufficiently evident upon reflection, from the method by
which the image is produced, that if a bright object were placed at
a b, a large inverted image would be formed at A B. These rela-
tive positions of image and object are easily found for any good lens
by experiment.

Fig. 230.




1487. The diminishing effect of a concave lens is illus-



MECHANICS.



435



Explain trated by Fig. 230. The rays of light from top
Fig. 230. an( j bottom of the vase A I>, when passing through
the lens, are rendered less convergent, and appear when
reaching the eye to proceed from a much smaller object,
as a b. This lens cannot be made to form an image on a
screen.



Explain
Fig. 231.



1488. The use of the convex lens of the eye is
in Fig. 231. The rays from A B, after



Fig. 221.




233.



passing through the aqueous humor, the crystalline lens
and vitreous humor form a small but wonderfully accurate
image (a ~b) on the retina.

Explain the 1489. In some eyes the convex lens is too

defect in near- far from the retina, and consequently the
image formed is very indistinct. For such
cases spectacles of con-
cave lenses are needed
to check the too rapid
convergence of the ray:.
People needing such
aids to distinct vision
are said to be near-
sighted. Fig. 232 represents the position of the crystalline
lens in such cases.




436



MECHANICS.



Ffc. 233.



Explain 1490. Fig. 233 represents the opposite condi-
Fig.23'3. tion ; here no distinct image is formed, because

the crystalline lens is
too near the retina.
Tho rays require to
be converged more
rapidly. Spectacles
of convex lenses are
therefore required.
People needing them to see distinctly are called far-
sighted'.

Fig. 234.





Explain the 1491. The Prism, whose construction and
Prism. properties is explained on page 252, has be-

come of late one of the most important optical instruments.



MECHANICS. 43?

When a beam of light falls upon the prism, as repre-
sented in Fig. 234, the slowest waves are deflected from
their course mucli less than the more rapid ones ; hence
what would be a bright spot on the wall, if the prism were
removed, becomes by the different amount of refraction of
different waves an elongated band cf several colors, called
the spectrum. The red ray is refracted least, and the
violet most of the visible rays. Experiment shows that
other waves pass through the prism, and are refracted some
less than the red, and others more than the violet. The
waves below the red are heat waves, and may be detected
by the thermometer ; while those beyond the violet pro-
duce chemical effects, and are detected by such sensitive
preparations as the photographer uses.

1493. If the aperture admitting the light be exceedingly narrow,
and parallel to the direction of the prism, dark ' lines are seen
across the spectrum lying between the bands of color. These have
long been known as the Fraunhofer lines, and are accounted for as
follows, viz. : Different gases and vapors intercept certain of the
waves of light, and permit others to pass. When such waves are
wanting in the spectrum, the places where they would fall, not
being illuminated through the slit, are left dark.

The instrument used in the study of these lines is called the
Spectroscope. The spectrum in this instrument, instead of falling
upon a screen, is directed by means of lenses to the eye. The
lenses serve to magnify the lines and the spaces between them, so
that a far greater number are seen. In the forms of the spectro-
scope designed for the higher scientific uses, several prisms are em-
ployed, and also measuring scales to determine the exact relative
position.of the lines.

On what facts 1493. The following facts form the foun-
^ectr U ^e k0 dation of spectroscopic analysis :
founded? (i) Every gas or vapor possesses the property

of intercepting certain waves of light while permitting others to
pass freely through.

(2) Each gas or vapor has this property in a degree peculiar to
itself, so that the dark lines of the spectrum afford a means for its
detection.

(3) Solid or liquid luminous bodies give spectra without dark
lines (continuous spectra) when no gas or vapor is in the path of
the light.



438



MECHANICS.



(4) Luminous gases never give continuous
spectra ; they yield only bright lines or bands
exactly in those places where dark lines appear
Vv-heii the gases are permitted to intercept the
light from a luminous solid or liquid body.

1494. The inference drawn from these facts
respecting sunlight is, that the sun itself is a
Bell-luminous solid or liquid body, and that it is
surrounded with numerous vapors, which we
recognize for the most part as familiar sub-
stances. Well-known metals, when vaporized
by intense heat, can be made to produce the
lines we find in the solar spectrum.

1495. Fraunhofer discovered and mapped five
hundred or six hundred of these lines in 1814.
As many as six thousand are now observed and
so located by philosophers as to be recognized.
A portion of these lines as they appear in the
solar spectrum, with the letters by which Fraun-
hofer designated the larger ones, is represented
in Fig. 235.



&$ s^rswjffi2*?fcS

new metals not previously known. The knowl-
edge of the existence in the sun of substances
familiar to us as forming essential portions of
the earth. That the fixed stars are similar to
our sun in constitution. That many of the neb-
ulas are only gaseous bodies.

1497. In addition to these it forms by far the
most delicate method in the laboratory for the
detection of the chemical elements.

The problems at which philosophers are now
engaged with this wonderful instrument are the
determination of the source of the light in the
Zodiacal light, the Aurora Borealis, and the
Solar Corona, all of which afford one or two
lines not familiar, among substances of the
earth.

Comets hereafter will be objects of the
closest scrutiny ; and when bright enough to
afford a spectrum, the question of their consti-
tution will probably be satisfactorily settled.



Why are red,



Colors ?



1498. The spectrum is
S enerall y Considered to be
made up of seven different





VIOLET.



MECHANICS.



430



colors, each forming a separate band. It is found, how-
ever, that having pigments of red, yellow, and blue colors
only, all other colors may be formed by mixing these in
proper proportions. These three have consequently been
called the Primary Colors, and many have supposed that
the remaining colors of the spectrum were caused simply
by the overlapping of the bands of these three colors.

What is said 1499. On the other hand, it is found that

of Secondary the so -called Secondary Colors orange,

Colors ? , . , . j -i i i

green, and violet cannot be decomposed

by the prism, as they should be if composed only of mixed
light.

Explain 1500. A green band from a spectrum being
Fig.23Q. p asS8( j through a second prism, gives the same



Fur. 230.




Explain the
Eainlow.



color again. (See Fig. 236.) The same result is obtained
with each of the colors of the spectrum.

1501. The Rainbow is formed by the re-
fraction and reflection of sunlight in the
rain-drops each drop acting as a prism to decompose the
white light.

The inner or primary bow is the brightest, being formed
by two refractions and one reflection, while the secondary
bow is formed by two refractions and two reflections. As
some light is lost at each reflection, the secondary bow is
not so bright as the primary.



440



MECHANICS.



The Fig. 237 represents the courses of the rays in form-
ing both rainbows.

Fig. 237.




What are 1502. Colors are said to be complementary

Complementary to each other when, taken together, they
contain all the constituents of white light.
This recognizes the theory of three primary colors. Red
and green are complementary, because green may be com-
posed of yellow and blue. Yellow and purple are comple-
mentary to each other ; also blue and orange.

Why are they 1503. Complementary colors are also called
called Contrast- . , , , . ,

ing Colors f contrasting colors, because, when seen side

by side, each heightens the effect of the other.

Explain 1504. Fig. 238 exhibits the pairs of contrasting
Fig. 238. co lors. The primary colors are joined to the cen-
tre by heavy lines ; midway between these are the second-
ary colors, so placed that each lies between the primaries
that compose it.

Each color about the circle is complementary to the
color that is exactly opposite. The colors about the circle



MECHANICS.



441



Fig. 238.
GREEN



ELLOWISH GREEN




VIOLET



ORANGE



RED



having double names, as yellowish-green, reddish-orange,
etc., are supposed to be
composed of equal parts
of the colors that lie ad-
jacent.

1505. The principles gov-
erning the use of contrasting
colors are of great import-
ance to decorators and all
who employ colors in per-
manent ornamentation. Har-
monies and discords are rec- tfioiET^
ognized in color compositions
as well as in music ; but we
have at present no nomen-
clature of colors which will
enable us to identify by name

any but the simplest. The rules to be observed in the use of colors
cannot, therefore, be given, until names are devised by which, they
can be recognized.

1506. Color Blindness is simply inability
distinguish between colors, and does not
imply any imperfection in the eye, so far as seeing form is
concerned. To a person entirely color-blind, all objects
appear either black or white or gray.

1507. People partially color-blind usually distinguish yellow
without difficulty, although they may be unable to see any differ-
ence between red and green. In an examination of over three hun-
dred persons by Dr. Wilson, of Edinburgh, one in every fifty-five
was color-blind to this extent. A slight approach to color-blindness
is manifested in an inability to see the slight purple tint in com-
binations of purple and blue. This is very common indeed. All
attempts to cure this defect in the eye by training have failed.

Describe the 1508. TELESCOPES. The achromatic tele-

a^hromatic' sc P e descri bed in P ar - 90 ? is represented in
lens. section in Fig. 239.

It will be observed that the object-glass is composed of
two different lenses, and of different forms ; the halves of
the lenses, as, for instance, the parts between M and D,
appear in the section like two prisms. If either were em-



What is Color
Blindness?



442



MECHANICS.



ployed alone, it would act like a prism, and refract the
colors to the eye somewhat separated. An indistinct view

Fig. 239.




is the result of such action. But when two prisms are em-
ployed, and so used that one corrects the color separation
of the other, the opposite surfaces will be parallel, and the
rays leave the prisms with the same direction in whicli
they come to it, provided the prisms are of the same den-
sity ; otherwise the denser prism may be the thinnest one.

Fig. 240.



vr




Describe 1509. This is shown in Fig. 240. The ray I,
Fig.24Q. under the action of the prism C, alone would
form a spectrum whose violet color would be at v, and red
at r ; by interposing a thinner prism of material having
higher dispersive power, the ray is directed to v r, and the
colors are combined.

1510. In the case of the object-glass of the telescope, the
compound lens thus formed is thickest in the middle
hence belongs to the class that magnify. The rays of light
from the distant object form an image a I c which is
viewed with the eye-lens P Q.



MECHANICS.



443



1511. The above is the Astronomical Telescope. The
arrangement of lenses in the Terrestrial Telescope is shown
in Fig. 241.

Fig. 241.




The first image is formed at n m, but if viewed through
the lens CD would appear as through the astronomical
telescope, inverted ; hence the rays are allowed to cross
each other at L, and form another image at m' n', which
being seen through the" eye-piece C H, is in the desired
position.

1512. The Galilean Telescope employs only one object-
glass and one eye-glass to see objects erect. This arrange-
ment forms the common "opera glass" and the "mariner's

Fig. 242.




glass." The magnifying power is low, but the amount of
light it collects and brings to the eye adapts it for use at
night.

1513. It will be seen by the figure that the rays, after
passing through the object-glass, converge in such a man-
ner as would form an image at m n ; but the concave eye-
19



444 MECHANICS.

piece checks this convergence, and brings the rays to the
eye nearly parallel.

1514. The Beflecting Telescope, represented in section
in Fig. 141, is sometimes constructed so as to be used by
looking in at the side. This is accomplished by setting
the reflector, represented at C in Fig. 141, at such an
angle that the collected rays are directed into the eye-piece
in the side of the tube.

1515. The largest Reflecting Telescope ever constructed is that
of the Earl of Rosse. The great speculum is six feet in diameter,
and the tube is sixty feet long.

The largest Refracting Telescopes yet completed have object-
glasses of only twenty-three inches diameter.



INDEX



Aberration of light 384

" spherical . . 247

\ccidental colors ... . 252, 442

, Achromatic . 247

Acid, carbonic 21

Acid, sulphuric, effects of on

water 187

Acoustic paradox 177

Acoustics 173

" definition of . 18

Acoustic tubes 179

Action 45

Action and reaction, illustration

of 46

Action, suspension of 85

Actynolite ... 21

Aeriform, definition of . ... 19

fluids 138

Aeriform fluids compressed and

expanded without limit . . . 139
Aoriform fluids have no cohesive

attraction 139

Aeriform fluids have all the prop-
erties of liquids 140

Aeriform fluids have weight. . . 139
Aeronaut, how he descends from

a balloon 38

Aerolites 387

A flinity, chemical 19,27

Agents 18

" imponderable 18

" ponderable 18

Air 140, 426

Air, a bad conductor of heat . . 191

Air, as an element 19

Air-bladder of fishes ....... 47

Air-chamber 163, 42C

Air, component parts of the . . 140
281 note

Air, compression of, caused by
gravity 39



Air, compressibility of the . 162

Air, condensation of at srrface of
the earth 140

Air, condensed, experiments with 103

Air contained in wood and water,
experiments to show ..... 161

Air diminishes upwards in dens-
ity 14C

Air, elasticity of the ... 142, 102

Air, elasticity of the, experiments
showing 160

Air, effect of gravity on density of 38

Air essential to animal life, ex-
periment to prove 16fc>

Air essential to combustion, ex-
periments to prove lOf

Air, fluidity of 142

Air, fluidity of, experiments show-
ing 1'io

Air, gravity of the, experiments
illustrating .... ... 1^7

Air-gun 164

Air, how a mechanical agent . . 142
" impenetrability of ... 22, 141
inertia of 28, 143

Air, inertia of, experiments show-
ing 1C5

Air, lightness of the 162

" materiality of the 162

Air miscellaneous experiments
Wl th . . . 166

Air necessary to animal life and
to combustion 140

Air, of wnat composed 20

Air, pressure of the as the depth 102
** pressure of in all directions 162

Air, pressure of the on a barom-
eter HO

Air, pressure of the on a square
inch Hi

Air, pressure of the on the body 141

Air, pressure of the preserves the
liquid form of some bodies . . 19



446



INDEX.



Air, pressure of the retards ebul-
lition 168

Air-pump 154

Air-pump, experiments performed

by the 157

Air-pump of steam-engine . . . 201

Air-pump, the double 156

Air, resistance of the . . . .25,38
Air, resistance of the to a cannon-
ball 62

Mr, scales for weighing . . . .160
Air, two principles, properties of 139

'* when heaviest 140

Air, when the best conductor of

sound 176

Air, why not visible 140

Albite 20

Alison, extract from 70

All's well," how far heard . . 176

Alumina 21

Aluminum 20

Ampere's discoveries in electro-
magnetism 309

Ampere's electro-magnetic appa-
ratus 314

Analysis of the motion of a fall-
ing body 52

Angle 48

Angles, how measured 48

Angle of vision 219

Angles of incidence and of reflec-
tion 48, 4 ( .i, 216

Angles, right, obtuse and acute . 48

Animal electricity 282

Animals, sagacity of 92

Annealing 31

Antimony 20

" not malleable 31

Aphelion 349

Apogee 349

Apparatus for illustrating the
tendency of a body to revolve
around its shorter axis .... 61
Apparition, circle of, perpetual . 385

Apparitions, deceptive 225

Aqueous humor 237, 239

Arago's experiments on velocity

of sound 176

Arbor 81

Archimedes' boast to Hiero . . 95
Archimedes, burning mirrors of. 228
Archimedes discovers the method
of ascertaining the specific grav-
ity of bodies 127 note

Archimedes, screw of 132

Arc of a peiilulun 101

4rctur\i . . . 309



Aristotle's opinion of the verity

of a falling body 53

Arsenic 20

" not malleable 3?

Asteroids 33S

Astnea 339

Astronomy, definition of . 17, 18, 33
Astronomers, distinguished . . . 330

Astronomy, father of 336

Atmosphere, weight of the . . .141

Atmospheric telegraph 331

Attraction . 25, 26, 33

capillary Ill

chemical 27

kinds of 27

law of falling bodies . 51

mutual 34

of all bodies 34

of cohesion '27

of gravitation .... 27

" of the earth 33

" on what dependent . . 34

Attwood's machine 52

Augite 21

Austral polarity 30 2

Axes of the planets, inclination

of 3->0

Axis, exact sense of 81

Axis, longer, a body revolving

around . . . t'l

Axis of motion 59

Axis of the earth, effects of its

inclination 334

Axis of the earth, geological the-
ory of 62

Axis, what bodies revolve around

an 59

Axle. . . .' 81

Azote 20, 140



B.



Babbit's metal 99

Bain's telegraph 326

Baker, the Connecticut 191

Balance-wheel 104

Balance 75, 411

Ballistic pendulum 63

.balloon, how to descend from . . "58
" the pneumatic .... 161
Ball, thrown in a horizontal di

rcction ........... 64

BailH, force of, how estimated . 63
Bands with one and two centres

of motion 83

Banks, Sir Joseph ,190

Barber'? Grammar of Elocution 180



INDEX.



44?



Barium 20

Barometer ..... 144 ind note
Barometer, the aneroid or porta-
ble 145

Barometer, the diagonal . . . 145
Barometer, of the different states

01 the 148

Barometer, greatest depression of

the 147

barometer, its importance 146 note
* rules of the . . . . . 147

" the mercurial . . . .145

Base of a body 67

Batteries, thermo-electric . . . 335

" galvanic 287

Battering ram 105

Battering ram, force of, how es-
timated 105

Battery, electrical 264

Battery, Grove's 293

" how discharged silently 2G5
Battery of the electro-magnetic

telegraph 321

Battery, protected sulphate of

copper 293

Battery, Sraee's 290

" sulphate of copper . . 292

Beam of light . 213

Belgrade, battle of, and the cornet 380
Bellows, hydrostatic, how con-
structed 119

Boll, the diver's or the diving . 150

Bevelled wheels 85

Birds, bodies of 123

how they fly 47

* muscular power of .... 47

Bismuth 20

not malleable . ... 31

Bissextile, meaning of 396

Black 252

Black lead, uses of in overcom-
ing friction 99

Bladder-glass 159

Bladder, inflated, why compress-
ed in water 115

Boats, how propelled 47

Boats, on what principle they

float 123

Boats, motion in, why impercep-
tible 26

Bode's law 342

Bodies 18

" attraction of 33

Bodies of drowned persons, why

they sink and afterwards rise . 123

Bodies, what are easily overset . 69

" what stand most firmly . 68



Bodies, what will rise aud what

will fall in air 4C

Body acted upon by three or more

forces 57

Body, parts of which move with

greatest velocity 60

Bodies, what ones will float and

what sink in water 123

Body, when it will fall 66

Bohemia slate, formations of . . 23

Bolt-head, and jar 167

Bomine M 370

Bones of a man's arm, levers of

third kind 77

Borax . 20

Boreal polarity 302

Bottle, effect of pressure of the

sea upon 115

Boyle 144

Boynton's, Dr., chart of materi-
als which form granite .... 21
Bramah's hydrostatic press . . 121
Brass, how made brittle .... 30

Breadth 23

Breaoc-wheel 8 '2, 83

Brittleness 27, 30

Brittleness, how acquired by iron,

steel, copper and brass .... 30

Bromine 2(.

Brooks, how formed 124

Buckets of water-wheels .... 82
Buckets of water, why heavier

when lifted from the well . . 12fc
Bulk of a body, how ascertained

from its weight 125

Burdens, how made unequal . . 77
Burning-glasses 228, 23-'



C.



Cadmium 20

Calcium 20

Calliope 339

Caloric 187,427

Calorimotor 297

Camera obscura 219, 240

Camera obscura, portable, how

made 21y

Cannon-ball, greatest velocity

that can be given to 03

Cannon-ball, force of the resist-
ance of the air to 62

Cannon, how far heard 17<!

Caoutchouc, or India-rubber . . bU
" balls, elasticity of . 47

Capillary attraction Ill

" cause of . .111



448



INDEX,



CapUlarj tubes Ill |

Capstan , .80

Capstan and windlass, diffeionoe

between . . 80

Carbon 20

Carbonate of lime 21

Carbonate of magnesia 21

Carbonic acid . . ! 21

Carriages, high, why dangerous . 68

Carronades 63

Cartesian devil 162

Cask, how burst by hydrostatic

pressure 1'20 note

Cassegranian telescope .... 250
Castors, why applied to legs of

tables, <tc 85

Catoptrics 215

Celestial bodies, true place of . 384
Celsius' thermometer ..... 149

Central forces 59

Centre of gravity . . 57, 58, 59, 66
Centre of gravity, illustrations

of 66 note, 409

Centre of magnitude . . 58, 59, 66
Centre of motion . . . . 58, 5y, 71

Centre of sphericity 37

Centre, what bodies revolve

around a 59

Centres 58

Centrifugal force 59

Centrifugal force, eifect of on a

body revolving around its longer

axis 61

Centrifugal force, to what propor-
tioned 60

Centrifugal force, where greatest 103
" meaning of .... 59

Centripetal force 59

" meaning of .... 59

Ceres 339

Cerium 20

Chain-pump 131

Chaises, tops of, toggle-joint . 97

Chamfered 91

Chantrey, the sculptor ..... 191

Charged, meaning of 261

" Charlemagne," experiment on

board of the ........ 115

Charles V. and the comet . . . 379
Charles' wain or wagon .... 398

Chart of materials forming the

crust of the earth 20

Chemical affinity 19, 27

Chemical attraction 27 j

Chemical effects of light . . 256, 257

Chemical electricity 259

Chemistry 19, 110



Chimneys, glass, Low preserved

from cracking > -.?

Chisels, on what principle coii

structed 91

Chlorine 20

Chlorite 21

Chord, musical, how produced . 182

Choroid 237, 240

Chromatics 251, 436

Chromium 20

Circle 48

Circle of perpetual apparition . 385

Circies 59

Circles, circumference of, how di-
vided 48, 365

Circular motion 5S*

Circular motion changed to rec-
tilinear by cranks 81

Circular motion, how caused . . 58



Clai



21



Climates, cause of 354

Clock, before and after the sun . 397

" how regulated 102

" moving power of .... 104
Clock, periods when it agrees with

the sun 397

Clocks, why they go fastest in

winter 103

Clock, what it is 102

" wheels of, their use ... 102
Clothing, cause of warmth of . . 189
Clouds 24

" of what composed .... 186
Cobalt 20, 298

" not malleable 31

Coffee-pots, why with wooden han-
dles .............. 190

Cogs 83, 84

Cohesion, attraction of 27

Cohesion, attraction of, its effects

on watery particles 186

Cold 185, 192

Cold, its effects on the density of

bodies 192

Colors 254

" accidental 252

Columbium 20

Comets 372

" density of 379

Comet, Halloy's, as seen by Sir

John Herschel, and by Struve.

377,378,379
Comet, Halley's, periodical time

of 371

Comets, how regarded former y . 373
Comets in the' solar system, num-

br of . .379



INDEX.



449



Comets, Kepler's opinion of their ,

number 380 ;

Comets, number of ...... 373 j

Comet of 1080 375 I

" " 1744 376 !

" " 1811 373

Comet of 1853, Mr. Hind's ac-
count of the . 381

Comet of 1856 379

Comets, orbits of .374

Comets, return of, first predicted
by Halley, Encke, and liiela . 377

Cornets, tails of 374



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 36 of 38)