Front matter
x 0c i<.
N V ^ c^ <y
V
Chap. I. — General Properties of Matter 15
Sec. 1. Gravitation 17
Div. 1. Centre of Gravity, 19; Div. 2. Specific Gravity and
Density 21
Sec. 2. General Laws of Motion 21
Sec. 3. Compound Motion 22
Div. 1. Curvilinear Motion, 24; Div. 2. Centrifugal and
Centripetal Forces 26
II. — Angular Measurement 27
Part Ii.— Descriptive Astronomy
Chap. I. — Solar System •. 29
II.— The Sun 30
III. — Interior Planets 34
Sec. 1. Mercury 35
Sec. 2. Venus 37
IV.— The Earth 42
V. — Exterior Planets 51
Sec. 1. Mars 53
Sec. 2. Asteroids 56
Sec. 3. Jupiter 58
Sec. 4. Saturn 61
Sec. 5. Uranus 63
Sec. 6. Neptune 63
VI.— Satellites 65
Sec. 1. The Moon 66
/Sec. 2. Jupiter's Satellites 87
Sec. 3. Rings and Moons of Saturn 90
Sec. 4. Moons of Uranus 93
Sec. 5. Moons of Neptune 94
VII.— Motion of the Earth 96
Sec. 1. Diurnal Motions of the Earth 96
Sec. 2. Annual Motion of the Earth 100
Sec. 3. Seasons 102
VIIL— Time 108
IX. — Ecliptic and Zodiac 114
X.— Tides 117
XL— Eclipses 123
Sec. 1. Solar Eclipses 125
Sec. 2. Lunar Eclipses 131
See. 3. Transits 134
Div. 1. Transits of Mercury, 136 ; Div. 2. Transits of Venus 136
Sec. 4. Occultations 138
XII.— Comets 140
XIII. — Systems of Astronomy 155
Sec. 1. Ptolemaic System 155
Sec. 2. Egyptian System 156
Sec. 3. Tychonic System 156
Sec. 4. Copernican System 157
Part Iii.— Sidereal Astronomy
Chap. I.— Fixed Stars 159
Sec. 1. Apparent Motions and Positions of the Stars 161
Div. 1. Precession, 164 ; Div. 2. Nutation, 165 ; Div. 3. Refraction, 166 ; Div. 4. Aberration, 169 ; Div. 5. Proper Motion, 172; Div. 6. Parallax 174
8 CONTENTS.
PAGE
Chap. II. — Distances of the Fixed Stars 177 III.— Milky Way 180
IV.— Magnitude of the Stars '. 182
V. — Appearance of the Stars 184
Sec. 1. Variable and Periodic Stars 184
Sec. 2. Temporary Stars 185
Sec. 3. Compound Stars.... 187
Div. 1. Double Stars, 187 ; Div. 2. Multiple Stars 189
Sec. 4. Clusters and Nebulae 190
Div. 1. Double Nebulae, 193 ; Div. 2. Nubeculae or Magellanic Clouds 194
VI.— Meteors 195
Sec. 1. Meteorites 196
Sec. 2. Zodiacal Light 198
VII.— Constellations 198
Sec. 1. Zodiacal Constellations 200
Sec. 2. Northern Constellations 212
Sec. 3. Southern Constellations 240
Part Iv.— Practical Astronomy
Chap. I. — General Properties of Light 260
Sec. 1. Refraction of Light 261
Sec. 2. Reflection of Light .' 264
II.— The Observatory 267
III.— Telescopes 268
Sec. 1. Refracting Telescopes 268
Sec. 2. Achromatic Telescopes 269
Sec. 3. Equatorial Telescopes 270
Sec. 4. Transit Instruments 270
IV. — Micrometer 274
V. — Instrumental Adjustments 275
Sec. 1. The Vernier 275
Sec. 2. The Level 276
Sec. 3. Plumb-Line 277
Sec. 4. Artificial Horizon 277
Sec. 5. Collimator 278
Sec. 6. Transit Clock 279
VI.— Graduated Circles 281
Sec. 1. Mural Circle 281
Sec. 2. Transit Circle 284
Sec. 3. Altitude and Azimuth Instrument 287
Part V.— Treatise On The Globes
Chap. I. — Problems on the Terrestrial Globe 287
II. — Problems on the Celestial Globe 307
Part Vi.— History Of Astronomy
Chap. I. — Sec. 1. From the Earliest Times to the Christian Era 320
Sec. 2. Astronomical Instruments in use from the Earliest Times to the
Christian Era 327
II.— Sec. 1. From the Christian Era to the year 1600 329
Sec. 2. Astronomical Instruments invented from the Christian Era to
the year 1600 335
III. — jSec. 1. From the beginning of the Seventeenth to the end of the
Eighteenth Century 336
Sec. 2. Astronomical Instruments in use from the beginning of the
Seventeenth to the end of the Eighteenth Century 341
IV. — History of Astronomy from the beginning to the middle of the Nineteenth Century 343
Itttrjfouctifltt*
Q. What is Astronomy ?
A. The science which treats of the heavenly bodies, describes their appearances, and the laws by which their motions are governed.
Q. Into how many parts may the science of Astronomy be divided?
A. Into four parts. Physical, Descriptive, Sidereal, and Practical Astronomy.
Q. What is Physical Astronomy ?
A. Physical Astronomy treats of the motions of the heavenly bodies, and the laws which operate to produce them.
Q. What is Descriptive Astronomy ?
A. Descriptive Astronomy is a relation or description of the appearances of the heavenly bodies belonging to the solar system.
Q. What is Sidereal Astronomy ?
A. Sidereal Astronomy treats of the Fixed Stars, Nebula? , &c. ; or those bodies which do not belong to the solar system.
Q. What is Practical Astronomy ?
A. Practical Astronomy treats of astronomical instruments, and their application.
The following definitions are inserted for the benefit of those who have never studied spherical Geometry ; a knowledge of the circles of the sphere being of the utmost importance to the right understanding of the principles of Astronomy.
A circle is a figure contained by a uniform curved line, called its circumference, which is everywhere equidistant from a point within, called its centre.
Fig. l.
An Arc of a circle is any part of the circumference ; consequently, in fig. 1, the dotted line, and also the black one, are arcs of the circle, because neither of them constitutes the whole circumference, but only a part.
LO
BOUVIER S FAMILIAR ASTRONOMY.
Fig. 3.
Fig. 4.
The Diameter of a circle is a line drawn through B the centre and terminating at the circumference.
A B is the diameter of the circle.
The Radius of a circle is a line drawn from D the centre to the circumference. C D is the radius of the circle in fig. 3.
A Semicircle is half the circle, or a segment cut off by a diameter. A C B is a semicircle. A half circumference is sometimes called a semicircle. It contains 180°.
A Quadrant is half a semicircle^ or one-fourth part of a whole circle. A quarter of a circumference is sometimes called a quadrant. B E C and C E A {fig. 4) are quadrants, all of which contain 90°.
A Ghreat circle of a sphere is one whose plane B passes through the centre of the sphere, as A B,
{fig- s.)
A Lesser or Small circle of the sphere is that whose plane does not pass through the centre of the sphere, but divides it into two unequal parts ; asee, in fig. 5.
The Axis of the earth, or of a heavenly body, is that diameter about which it performs its diurnal revolution. In fig. 5, P C P represents the axis of the earth.
The Poles of a sphere are the extremities of its axis. P P [fig. 5) represent the poles of a sphere.
The Equator is an imaginary circle on the surface of the earth equidistant from the poles. In fig. 5, A B represents the equator.
Introduction
The Equator of the heavens, or Equinoctial, is the terrestrial equator extended to the surface of the starry sphere.
Fig. 6.
The Tropics are two lesser circles of the sphere, situated at the distance of 23° 28' north and south from the equator. The tropic (c c, fig. 6) north of the equator is the tropic of Cancer ; the tropic (N N) south of the equator is the tropic of Capricorn.
The Polar circles are two lesser circles situated at the distance of 23° 28' from each pole. The north polar, or Arctic circle, is marked a a, (fig. 6,) and the south polar, or Antarctic circle, is marked S S.
Fig. 7.
Concentric circles are circles of different diameters drawn round a common centre.
A Sphere is a solid figure, every part of whose surface is equally distant from a point within, called its centre.
Fig. 8.
A Spheroid is a figure nearly spherical. It may be prolate or oblate. A lemon is in the form of a prolate spheroid, and an orange is in the form of an oblate spheroid. The earth is an oblate speroid, though much less compressed than the figure.
Zenith, that point in the heavens directly overhead.
Nadir is that point in the heavens directly under the feet of the observer. The zenith and nadir are the poles of the horizon.
Vertical circles of the sphere are great circles passing through the zenith and nadir.
The prime vertical is a circle perpendicular to the meridian, which passes through the east and west points of the horizon.
A Hemisphere is the half of a globe or sphere.
Meridians are imaginary circles drawn through the poles, and cutting the equator at right angles.
The celestial sphere is the concave surface of the heavens surrounding the earth in all directions.
BOUVIER S FAMILIAR ASTRONOMY.
Axis of the heavens is the axis of the earth extended to the concave surface of the celestial sphere.
Fig. 9.
An Angle is the opening of two straight lines having different directions and meeting in a point.
A line is perpendicular to another when it inclines no more on one side than on the other, making the angles on both sides of it equal.
Fiff. li.
An Acute angle "is less than a right angle ; that is, less than 90°.
ABC (Jig. 10) is an acute angle.
A Bight angle is that which is made by one line perpendicular to another; or, when the angles on each side of a perpendicular are equal to one another. In jig. 11, D B is perpendicular to F C, and the angles C B D and DBF are right angles, and equal to each other.
An Obtuse angle is greater than a right angle ; that is, it contains more than 90°. C B E and A B F are obtuse angles.
Fie. 12
A Triangle is a figure bounded by three sides.
A Parallelogram is a figure which has its opposite sides equal and parallel.
Fig. u.
Parallel lines are always at the same perpendicular distance from each other; they never meet, though indefinitely produced.
INTRODUCTION.
An Ellipse is an oblong plane figure, having two points, called its foci, around which the figure is described.
The transverse axis of an ellipse is the longer one A B, fig. 14.
The conjugate axis is the shorter one, marked C D.
Latitude on the earth is the distance of a place north or south of the equator, measured on the meridian.
Latitude of a heavenly body is its distance north or south of the ecliptic.
Longitude of a place on the earth is its distance east or west from any given meridian.
Longitude of a heavenly body is its distance from the first point of Aries, reckoned eastward on the ecliptic.
Declination of a heavenly body is its distance north or south of the equinoctial, measured on the meridian.
Right ascension. — The distance of any celestial body eastward from the point Aries, reckoned on the equinoctial.
The Ecliptic is that great circle in which the sun appears to move, but which is the real path of the earth. The poles of the equator are the poles of the earth ; but the poles of the ecliptic do not correspond with those of the equator, but are 23° 28' distant from it ; therefore the ecliptic must be inclined 23° 28' to the equator. If two rings be placed one within the other so that their circumferences shall not coincide, they will be inclined to each other, unless they be so placed as to cross each other at right angles, in which case they will be perpendicular to each other.
The Equinoxes, or Equinoctial points, are the points where the ecliptic and equator intersect each other. The vernal equinox is that point of the ecliptic in which the sun appears about the 21st of March ; the autumnal equinox is his apparent place about the 22d of September. At both these points the sun is vertical to all inhabitants of the earth living at the equator.
The Solstices, or Solstitial points, are those points of the ecliptic most distant from the equator. The solstices are situated 90° from the equinoxes. The summer solstice occurs about the 21st of June, and the whiter solstice about the 22d of December.
BOUVIER S FAMILIAR ASTRONOMY.
Fig. 16. A Sine of any arc is the straight line drawn
from one extremity of the arc perpendicular to the radius drawn to the other extremity. Thus A B is the sine of the arc A C, because it is drawn from A, which is at one extremity of the arc A C, and is perpendicular to the radius, which is half the diameter C D. Therefore, the radius meets the other extremity C of the arc A C. For the same reason A B is the sine of the arc A D, for it is drawn from A, which is one extremity of the arc A D, and is perpendicular to the radius, which, being one-half the diameter C D, meets the other extremity D of the arc A D. Therefore every sine is equal to two arcs, which together form a semicircle.
A Tangent is a straight line which touches but does not cut a curve. A B is a tangent to the circle C D.
A Chord is a straight line connecting the two
extremities of an arc. A B is a chord common
the two arcs ADB and A E B, which together constitute the whole circumference.
PART I. IPJjgsital %ztxauam%
"Enrich, me with the knowledge of Thy -works !
Snatch rne to Heaven; Thy rolling -wonders there.
World "beyond world in infinite extent, Profusely scattered o'er the blue immense, Show me. Their Motions, Periods, and their Laws, Give me to scan. Through the disclosing deep Light my blind way."
Q. Are the laws -which govern the heavenly bodies similar to those observed on the earth ?
A. They are; many of the same laws which are observed on the earth may be traced to the most distant parts of the universe.
Chapter I
Q. What is matter ?
A. Matter is any thing which is the object of our senses.
Q. Is every thing which we can see, taste, or feel, composed of matter ?
A. Yes; also whatever is the object of the senses of smelling or hearing.
Q. How can the objects of the senses of smelling or hearing be composed of matter ?
A. The odoriferous particles which emanate from bodies are material, as also the air, the concussion of which produces sound.
Q. What are the general properties of matter ?
A. The principal qualities of matter are magnitude, impenetrability, divisibility, compressibility, dilatability , and inertia. Q. What is magnitude ?
A. It means size or bulk.
Q. Have all bodies magnitude ?
A. All bodies occupy space, therefore they must have magnitude.
Q. What is meant by the impenetrability of matter ?
A. It cannot be penetrated without disturbing its component
parts.
Q. What is the result if a gimlet penetrate a board, or an oar penetrate the water ?
A. In the first instance the component parts of the board are displaced by the gimlet; and in the second, the particles of water are displaced by the oar.
Q. What is understood by the divisibility of matter ? A. Its capability of being separated or divided.
Q. Are all bodies divisible ?
A. All matter is divisible, however minute it may be. (See Note 1.)
"Animalcules have been discovered so minute that thousands of them do not equal a grain of sand in bulk, yet, as these creatures have life and the power of motion, they may be supposed to be possessed of the functions of living beings. How exceedingly minute must be their heart, lungs, nerves, &c. ! Yet the particles of light are infinitely more minute than these."
According to Ehrenberg, a cubic inch of water may contain more than 800,000,000,000 of animalcule; and a single drop placed under the microscope will be seen to hold 500,000,000; an amount, perhaps, nearly equal to the whole number of human beings on the globe !
"In thousand species of the insect kind, Lost to the naked eye, so wondrous small, Were millions joined, one grain of sand would cover all ; Yet each within its little bulk contains A heart, which drives the torrent through its veins ; Muscles to move its limbs aright ; a brain, And nerves disposed for pleasure, and for pain; Eyes to distinguish, sense, whereby to know What's good, or bad, is, or is not, its foe."
Q. What is meant by the compressibility of matter?
A. The diminishing its bulk or size, without destroying its
component parts.
Q. Suppose a goblet to be inverted over a basin of water just so as to permit its rim to touch the surface of the water, what will the goblet contain ?
A. The goblet will be filled with air.
Q. What would be the effect if the goblet should be forced down into the water, without permitting the air to escape ?
A. The water would rise some distance inside of the goblet, thereby proving the compressibility of the air.
Q. How does this prove the compressibility of the air ?
A. The air in the goblet was compressed by forcing the goblet down into the water without permitting the air to escape, causing it to occupy less space than before.
Q. What other property of air does this experiment prove ?
A. It proves the impenetrability of air; for it prevented the water from penetrating into its mass.
Q. Some bodies after being compressed return to their former dimensions ; what is this property called ?
A. It is known by the name of elasticity.
Q. Are all elastic bodies compressible ?
A. Yes ; but all compressible bodies are not elastic, that is, they will not return to their original forms after being compressed.
India rubber is an elastic body.
Q. What is meant by the dilatability of matter ?
A. Its capability of extension without increasing its mass.
Take a bladder, the mouth of which is tied, so as to prevent the escape of the air from the inside, and place it under the receiver of an air-pump. Exhaust the air in the receiver, and the bladder will be observed to swell. This is owing to the external pressure of the surrounding air having been removed, which permits that in the bladder to dilate or expand.
Q. What is meant by inertia ?
A. That quality of matter which implies indifference to either rest or motion — passiveness.
Q. What would be the effect if a person be riding on horseback at a rapid pace, and the horse stop suddenly ?
A. He would be thrown over the horse's head.
Q. Why would he be thrown over the horse's head ?
A. Because by reason of his inertia he would continue in the motion first imparted to him by the horse.
SECTION I. (Urabtianxm
"That very law which moulds a tear, And "bids it trickle from its source, That law preserves the earth, a sphere, And guides the planets in their course."
Q. What is meant by gravitation ?
A. That power which impels bodies towards each other.
Q. Why does a stone, when dropped from the hand, fall to the earth ?
A. Because the powerful attraction of the earth's greater mass impels the smaller body to move towards it.
Q. What would be the effect if the earth and the stone were of equal mass ?
A. They would fall towards each other, and meet half way.
Q. If a stone were abandoned to itself at a great distance from the earth's surface, would it fall towards the earth ?
A. Yes ; if the stone were several thousand miles distant it would as certainly fall to the earth as it does when dropped at the distance of a few feet.
Q. Would a stone, a thousand miles from the earth, weigh as much as it would at the earth's surface ?
A. No ; the power of gravitation decreases above the earth's surface, in proportion as the square of the distance from the earth's centre increases.
Q. Explain this.
A. A body which, at the surface of the earth weighs one pound, would at 4000 miles above the surface, that is, at double the distance of the surface from the centre, only weigh a quarter of a pound.
As the moon is about 2-40,000 miles from the earth, the attraction of the earth at that distance must he equal to the square of 240,000 divided by the square of -4000, the distance of the centre from the surface of the earth. Br this method it is found that a body weighing one pound at the surface of the earth, would weigh the tj-^j jj of a pound at the distance of the moon.
Q. With what velocity do bodies fall, which are situated near the surface of the earth ?
A. Bodies near the earth's surface fall sixteen feet in the first second, three times sixteen in the next second, five times sixteen in the third second, and so on, continually increasing, according to the odd numbers 1, 3, 5, 7, 9, &c.
Q. What is the law of falling bodies ?
A. The space through which a body falls increases in proportion to the square of the time it occupies in falling.
Q. Illustrate this law.
A. If a stone require four seconds to reach the ground from a high tower, the tower will be two hundred and fifty -six feet high. Because the stone would fall 16 feet in the first second, 3 times 16 in the next, 5 times 16 in the third, and 7 times 16 in the fourth, which, added together, make the sum of 256 feet.
Q. Is there a shorter method of obtaining the same result ?
A. Yes; by squaring the number of seconds, and multiplying the result by 16 ; thus 4 X 4 X 16 = 256.
Q. Does the attraction of gravitation act on all bodies ?
A. It does ; without any regard to their figure or size.
Q. Does it act more powerfully on some bodies than on others ? A. It acts in proportion to the quantity of matter which they contain.
. Q. Would a greater force of gravity be exerted on a body weighing ten pounds, than on one weighing one pound ?
A. A ten times greater force would be exerted on the body weighing ten pounds.
Q. Would two bodies of unequal weight fall to the earth in the same space of time?
A. Yes; they would fall to the earth with equal velocities. {See Note 2.)
Q. If, by the attraction of gravitation, all bodies are drawn to each other, why do they tend to the earth ?
A. The earth being so much more vast than any body on or near its surface, the effect of this attraction between smaller bodies is not perceptible. (See Note 3.)
GENERAL PROPERTIES OF MATTER.
DIVISION I. — CENTRE OF GRAVITY.
Q. What is the centre of gravity ?
A. It is that point of a body upon which, if it he freely suspended, it will rest. The centre of gravity is no other than the centre of parallel and equal forces.
Q. Have all bodies a centre of gravity ?
A. Yes ; there is a point in every body, of whatever form it may be, in which the forces of gravity may be considered as united.
Q. In what direction does a body, when not supported, endeavour to fall?
A. In a line drawn from its centre of gravity towards the centre of the earth.
Q. What is that line called along which every body when unsupported endeavours to fall ?
A. It is called the line of direction.
Q. Why does a body sometimes stand and at other times fall ?
A. If the line of direction fall ivithin the base, it will stand : but if it fall without the base, it will fall.
There is a tower in Pisa, in Italy, which leans so much as to appear as if it would fall; but its line of direction falls within the base, so that it will be likely to stand in its present position until its materials fall into decay.
Q. In what part of a globe is the centre of gravity placed ?
A. In the centre.
Q. The earth is an oblate spheroid ; in what part of the earth is its centre of gravity?
A. In its centre.
Q. In irregularly formed bodies where is the centre of gravity situated ?
A. It is always situated near the largest portion of the mass.
BOUVIER S FAMILIAR ASTRONOMY.
Fig. 20. In order to find the centre of gravity of
the triangle ABC, {fig. 20.) draw a line from the point A to D, situated at the middle of the base. This line A D equally divides all those lines which may be drawn parallel to B C : the centre of gravity will be found on the line A D. From the point C to the middle of the opposite side A B, draw the line C E : the centre of gravity will be found on this line also ; and as it lies somewhere on the line A D, it must be at their intersection at F. Now draw the line ED; and as A : D E : : A F : F D ; but A C is double D E ; then A F must also be double F D, and consequently the centre of gravity of a triangle is situated on a line drawn from the highest point, and at two-thirds of its length from its base. Q. In what part of a cone is the centre of gravity situated ?
A. At a point about one-fourth of its height from its base.
Q. Why will a cone stand more firmly than a cylinder ?
A. Because in the cone the centre of gravity is situated near the base, while that of the cylinder is midway between its extremities.
Q. If persons were to be overtaken by a squall of wind while in a small boat, in what position should they place themselves ?
A. They would incur less risk by sitting in the bottom of the boat.
Q. Why would that be the safest position ?
A. Because by sitting in the bottom of the boat they lower their centre of gravity.
Q. Why does a man stand with his feet apart when driving a cart ?
A. Because by increasing his base he lowers his centre of gravity.
The broader the base, the nearer is the line of direction to the middle of it. Q. Why are all spherical bodies more easily moved than bodies of any other form ?
A. Because the base is a mere point, and consequently the line of direction is easily moved beyond the base.
Q. Suppose two balls of equal size be united by a stiff wire, where would the centre of gravity be situated ?
A. At a point in the wire equidistant from each of them.
Q. Suppose one of the balls to be three times heavier than the other, where would the centre of gravity be situated ?
A. It would be three times nearer to the large ball than to the small one. {See Note 4.)
The sun is so much larger than the earth and all the planets put together, that the centre of gravity of the solar system is situated within the globe of the sun.
DIVISION II. SPECIFIC GRAVITY AND DENSITY.
Q. "What is understood by specific gravity ?
A. It denotes the weight of a body, as compared with the weight of an equal bulk of some other body taken as a standard.
Q. What other body is commonly used as a standard of unity !
A. The standard commonly used is distilled water, at the temperature of 60° Fahrenheit ; but any other substance would answer as well as water.
Q. What is meant by density ?
A. By the density of a body is meant its mass, or quantity of matter, compared with that of an equal volume of water, or some other body taken as a standard.
The density of a body is the relation of its weight to its volume. Q. Would a cubic inch of water and a cubic inch of steel hold each other in
EQUILIBRIUM ?
A. No ; although their masses measure the same, the steel is nearly eight times more dense than the water.
Q. How many cubic inches of water would be required to balance the cubic inch of steel ?
A. It would require nearly eight cubic inches of water to balance one of steel.
The specific gravity of steel is nearly eight times that of water. Thus, we say ice is less dense than water, and water less dense than gold, silver, steel, &c.
Section II
Q. What is motion ?
A. Motion means change of position; the act of moving.
Q. When is a body said to be in motion ?
A. When it successively occupies different positions at different times.
Q. How is motion classified, or divided ?
A. It is classified into three kinds, viz. Absolute motion, Relative motion, and Apparent motion.
Q. What is absolute motion?
A. Absolute motion is a change of position with regard to a stationary point.
Q. What is relative motion ?
A. Relative motion is a change of position in a body, with respect to another body also in motion.
Q. What is apparent motion ?
A. Apparent motion is due to a. change of place in the observer, which produces a change in the lines of vision between certain fixed objects and himself.
Q. When is a body said to be in a state of rest ?
The opening of the book is shown; the full text loads in the reader.
Loading the full text…
The end
You’ve reached the end of Familiar astronomy; or, An introduction to the study of the heavens.