A grammar of astronomy, with problems on the globes: to which are added, a glossary of terms, and questions for examination: designed for the use of schools and academies

I. .72

Southern District of New-YorJc,$$.

BE IT REMEMBERED, That on the fifteenth day of August, A. D 1825, in the fiftieth year of the Independence of the United States of America, J. Towle, of the said district, hath deposited in this office the title of a book, the right whereof he claims as author, in the words following, to wit :

" A Grammar of Astronomy, with Problems on the Globes : to which are added a Glossary of Terms, and Questions for Examination : designed for the use of schools and academies. By J, Toxvle"

In conformity to the act of congress of the United States, entitled " An Act for the encouragement of learning, by securiug the copies of Maps, Charts, and Books, to the Authors and Proprietors of such copies, during the time therein mentioned." And also to an act, entitled " an act supplementary to an act, entitled an act for the encouragement of learning, by securing the Copies of Maps, Charts, and Books, to the authors and proprietors of such copies, during the times therein mentioned, and extending the benefits thereof to the arts of designing, engraving. a.nd etching historical and other. prints."

JAUDON'S EXPOSITOR.

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Have lately published a new stereotype edition, on fine paper and handsome perspicuous type, of the English Orthogiiaphical Expositor : being 1 a Compendious Selection of the most useful words in the English language, alphabetically arranged, divided and explained, according to the most approved modern authorities: also, a list of more than eight hundred words, similar, or nearly similar, in sound, but of different spelling and import. By Daniel Jaudon, Thomas Watson, i*nd Stephen Addington.

They also have in press, a new edition of the Youth's Arithmetical Guide, Improved, with additional Questions in Federal Money, &c. by Daniel Jaudon. This work will contain all the rules requisite to be taught to younger pupils, and especially adapted to Female Academies.

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PREFACE-

On the subjects of Astronomy and the Globes, though several valuable but expensive treatises are already before the public, the compiler of the following pages has experienced no little inconvenience for want of a concise work adapted to the business of teaching, and to the comprehension of beginners.

The astronomical part of this little treatise is intended to prepare the learner to solve the problems understandingly.

] It is unnecessary to burden the reader with preliminary observations. The intelligent can better judge of the merits of a work by a candid perusal, than by all the arguments that can be offered in its favour.

THE AUTHOR.

New-Yorh 1825.

COmTBTSTB

Explanation of Plates . . . . •! .- ?

History of Astronomy 9

Solar System . . 12

Sun 14

Mercury . . 16

Yenus 17

Earth 13

Mars .21

Asteroids, or minor Planets .... 22

Jupiter 24

Saturn 2G

Herschel 27

Tabular view of the Solar System . . . 27

Secondary Planets . . . . . . 3!

Satellites of Jupiter 32

Satellites of Saturn 33

Satellites of Herschel ..... 34

Fixed Stars ....... 36

Constellations . . . . . . 38

Table of Eclipses 47

Tides 48

Atmosphere 50

Table showing the velocity of Winds, &c. . 53

Table showing the breadth of the several climates, &c. 54

Aurora Borealis 56

Galaxy 57

Zodiacal light . . . . . . 57

VI CONTENTS.

Time 57

Definitions on the Globes .... 60

Problems performed by the terrestrial Globe . 65

Concluding remarks on the terrestrial Globe . 108

Celestial Globe 113

Alphabetical list of constellations . . . 115

Problems performed by the celestial Globe . 118

Promiscuous exercises on the Globes . . 146

Glossary of terms 1 50

Questions for examination . . . 16f>

EXPLANATION OF PLATES.

PLATE I.

A view of the Solar System.

PLATE II.

Geometrical Diagrams.

Pig. 1. Right line.

2. Curved line.

3. Parallel right lines.

4. Parallel curved lines.

5. An Angle.

6. A right angle.

7. An obtuse angle.

8. An acute angle.

9. A Triangle.

10. A Circle.

A. Diameter.

B. Radius.

11. An Ellipsis.

D. The centre.

E. One of the foci.

H. Excentricity.

12. Comparative magnitudes and distances of the

primary planets. [See Rev. S. Brown's Ura~ nescope.]

13. Circles of the sphere.

AB. Ecliptic.

AC. Tropic of Cancer.

BD. Tropic of Capricorn.

EQ. Equator.

FG. Arctic Circle.

HO. Horizon.

Viii EXPLANATION OF PLATES.

IK. Antarctic circle.

MN. Meridian.

PR. Axis.

P. North pole.

R. South pole.

PLATE III. -

Fig. 1. Laws of motion. .

2. The apparent retrograde motion ot interior planets.

PLATE nM

Fr». 1. The umbra and penumbra of a planet's shadow.

2. A total Solar Eclipse.

3. A total Lunar Eclipse. ]

4. Diurnal Parallax.

5. Spring Tides.

6. Neap Tides.

7. Positions and phases of the Moon.

PLATE V.

Fig. 1. The Seasons.

2. Vertical and oblique rays. \

PLATE VI.

A Planetarium.

J*

TLATE1.

rff*

Libra,

V

*

^Kaji&

I

V

IP*

PLATE II .

I b c d e. fghi

PLATE Ml.

c b B

PLATE IV.

* ffffh

Tig.%

Tig.Z

FJ.JLTJE.V.

Grvvmmav tf MstvQwmg*

Astronomy is a mixed mathematical science, which explains the shapes, magnitudes, movements., distances, periods, and various phenomena, of the celestial luminaries.

The celestial luminaries are the sun, planets, stars, and comets.

CHAPTER X.

Of the History of Astronomy,

1 Astronomy was cultivated, at an early period, by the Chaldeans, Eg}'ptians, Phoenicians, Greeks, Arabians, and Chinese.

2. It was studied, in a particular manner, in Chaldea; thence it passed into Egypt; and soon after into Phoenicia, where it was applied to the uses of navigation, which enabled this people to excel others in commerce.

3. The particular object of their observations, was the north polar star.

4. These observations were at length brought into Greece by Thales, who taught the theory of the motion of the sun, which accounted for the difference in the length of days, the number of days in a solar year, the theory of eclipses, and the art of foretelling them.

B

5. To Anaximander, the disciple of Thaies, Pliny and Diogenes Laertius ascribed the invention of the terrestrial globe, or according to Strabo, geographical maps.

6. By these instructions, the Greeks were enabled to make considerable voyages, and to plant colonies in different countries. They much improved their knowledge, by an intercourse with the Pythagorean philosophers of Italy, the Druids, and the Egyptians; Alexandria being, for a long time, the seat of astronomical literature.

7. The Romans encouraged Astronomy, and endeavoured to carry it nearer to a state of perfection.

8. The x\rabian princes made some exertions to promote its cultivation ; and it was at length brought to its present state of perfection, by the laudable exertions of modern Europeans.

9. Among the ancient astronomers, Pythagoras and Ptolemy were the most noted. Pythagoras flourished about 590 years before Christ. In his system of the universe, the sun was placed in the centre, around which the planets were supposed to move. The planets then known, were Mercury, Venus, the Earth, Mars, Jupiter, and Saturn.

10. Ptolemy, the Egyptian astronomer, flourished 130 years after Christ. He supposed the earth to be at rest in the centre, around which moved the sun and planets, once a day, in circular orbits, in the following order; viz., the Moon, Mercury, Venus, the Sun, Jupiter, and Saturn ; beyond these were placed the fixed stars.

11. From that time, Astronomy was much neglected, until near the close of the 13th century, when Alphonsus, king of Castile, formed more accurate tables than had been before known.

12. In the l6th century, this science began to assume a rational appearance, by the system of Copernicus, which was afterwards perfected by Kepler and Galileo.

13. Nicholas Copernicus, a native of Poland, revived the ancient Pythagorean system, A. D, 1530. His work was published in 1543; a copy of which was handed him a few hours before his death.

14. This system met with much opposition ; and Galileo was thrown into the prison of the Inquisition for supporting it ; nor was he able to regain his liberty, without first rejecting these opinions.

15. These bigots were not Ms only adversaries : for even Tycho Brahe, the great Danish astronomer, was so prejudiced as to reject this discovery. From the experiment, that a stone being dropped from a lofty tower, fell perpendicularly to its base, he inferred that the earth is at rest ; forgetting that a stone, being dropped from the top of a ship's mast while she is under sail, will fall directly to its foot.

16. Tycho projected another system, in the centre of which he placed the Earth, and supposed the sun, moon, and stars, to move around it ; after which, he made Mercury, Veaus, Mars, Jupiter, and Saturn, revolve around the Sun.

17. These monstrous absurdities died with their projector; but we. must still do him the credit to say, that his other calculations were far more accurate than any that preceded them.

1 S. By the help of Tycho's labours, John Kepler, a German astronomer, confirmed the true sys*-" tern of the universe, and discovered the laws wfei regulate motion.

GRAMMAR OF ASTRONOMY.

19- Galileo of Florence, is said to have been the first who made use of the telescope, and by its assistance, discovered many new phenomena; as the different phases of Saturn, the satellites of Jupiter, their motion, the uneven surface and mountains of the moon, the spots of the sun, and its revolution about its axis.

20. We owe much to the labours of the indefatigable Mr. Flamstead, to Dr. Hally, Olbers, Piazzi, Harding, and others ; but, perhaps, more to the great Sir Isaac Newton and Dr. Herschel, than to all their predecessors together.

CHAPTER IS.

Of the Solar System.

1. The system of the celestial bodies, now universally received as the true one, is called the Solar, or Copernican System. As we have before stated, it was first taught by Pythagoras, 590 years before the Christian era ; but it was afterwards rejected, until the sixteenth century, when it was revived by Copernicus, from whom it received its name.

2. It comprises the sun, eleven primary, and eighteen secondary planets ; besides a number of comets.

3. The primary planets are those which revolve around the Sun as a centre ; viz., 1. Mercury £ , 2. Venus 9 , 3. Earth , 4. Mars g , 5. Vesta ft , 6. Juno § , 7. Ceres 9 , 8. Pallas £ , 9. Jupiter if, 10. Saturn £ , 11. Herschel ig.

4. Four of the primary planets, namely, Vesta, Juno, Ceres, and Pallas, are called asteroi They are but minor planets.

GRAMMAR OF ASTRONOMY.

5* The secondary planets are those which revolve round the primary planets. The earth has 1, called the moon; Jupiter has 4; Saturn, 7; and Herschel, 6.

6. Comets are wandering bodies, which revolve round the sun, in very eccentric orbits ; and are only seen when in that part of their orbit nearest the sun. *

7. The Sun is the centre of the system ; around which all the primary planets move, in their respective orbits, from west to east, attended by their secondaries or moons.

8. The orbit of a celestial body, is the line which it describes in performing its revolution round the sun, or its primary planet. The orbits of the planets are elliptical. [See Ellipsis, Glossary.]

9. The time which a planet takes to revolve round the sun, is called its year; and the time which it takes to revolve on its axis, its day.

10. The axis of a planet, is an imaginary line passing through its centre, on which it is supposed to revolve.

11. The sun and all the planets are of a globular form, though not perfect globes.

12. A globe, or sphere, is a body perfectly round , having every part of its surface exactly the same distance from the centre.

13. The sun and planets are known to be of a globular form, because they bear that appearance to the naked eye ; and from the circumstance of their casting a circular shadow, during the time of an eclipse.

14. Several things combine to prove that the form of the earth is globular. 1. Navigators by steering their course directly westward, arrive at

B 2 the same place whence they departed* 2. The north polar star becomes more elevated as you travel north. 3. The mast of an approaching ship is visible before the hull; wh:ch proves the convexity of the sea.

15. The Zodiac is that part of the heavens, comprising the paths in which the planets move. It is divided into 12 equal parts, called signs; viz., Aries T» Taurus y , Gemini n? Cancer 55? Leo^, Virgo trg, Libra =s=, Scorpio rri, Sagittarius $ , Capricornus VC?? Aquarius £?, and Pisces 3£. — These are 12 constellations of stars, through which the planets appear to pass.

16. The Ecliptic is the orbit of the earth around the sun. All the planets are supposed to cross the ecliptic, in two opposite points, called nodes

CHAPTER XXI.

Of the Sun, ©.

1. This grand luminary is a spherical body, situated in the centre of the planetary system. Its diameter is 883,246 miles. It performs a revolution about its axis in 25 days 14 hours 8 minutes; and dispenses light and heat to all the planets, in proportion to their distances.

2. The sun is nearer to the earth in the winter season, than in the summer.

3. The sun's diameter forming different angles with us, at different times, is a proof that the earth moves round the sun, in an elliptical orbit ; and the reason that it is notter in summer than in winter, is because the sun's rays fall more obliquely on us in winter than they do in summer.

4-. "it is supposed that an atmosphere environs the sun, and that its light and heat are occasioned by a gaseous combustion of a phosphoric nature? which takes place in the surrounding atmosphere. •

5. The atmosphere by which the sun is surrounded, is supposed to extend about 2000 miles from its surface; and its density to be at least eighty times greater than that which environs the earth.

6. The appearance of the sun's rising in the east, and setting in the west, is occasioned by the rotation of the earth on its axis.

7. When the sun is on the meridian of any place, it is noon at that place ; and at the opposite meridian it is midnight.

8. The period in which the sun revolves on its axis, has been ascertained by means of several dark spots viewed through a telescope. In the same manner have the rotary periods of Mars, Venus, and Jupiter, been ascertained ; hence it is supposed that all the planets have the same motion,

Obs. Sir Isaac Newton observes of the sun, 1. That its heat is seven times greater in Mercury, than with us ; and that water there would be carried off in steam : 2. That the quantity of matter in the sun, is to that in Jupiter, as 1 100 is to 1 : and that the distance of Jupiter from the sun, is in the same ratio of the sun's diameter; consequently the centre of gravity of the sun and Jupiter, is nearly in the superficies of the former: 3. That the quantity of matter in the sun, is to that in Saturn, as 2360 to 1 ; and the distance of Saturn from the sun, is in a ratio little less than that of the sun's semidiameter ; whence the common centre of gravity of Saturn and the sun, is a little within the latter: therefore the common centre of gravity of all the planets, cannot be more than the length of the solar diameter from the centre of the sun: 4. The sun's diameter is equal to 100 diameters of the earth, and the whole bodv exceeds that of the earth a million of times : 5. If 360 degrees be divided by the quantity of the solar year, it gives 59' J", and the horary motion" is 2' 27".

CHAPTER. IV.

Of Mercury, g .

1. Mercury is the nearest planet to the sun, his mean distance being about 37,000,000 of miles. He has a bright bluish appearance.

2. The diameter of Mercury is 3,224 miles.

3. His revolution is performed in 87 days 23 hours ; which is the length of his year.

4. Mercury revolves on his axis in about 24 hours, or nearty the same time in which the earth revolves : this makes his day about the same length as ours.

5. In his orbit, Mercury crosses the plane of the ecliptic in Taurus 15°, and in Scorpio, 15°: thus his ascending node is in 15° of Taurus, and his descending node in 15° of Scorpio. His greatest elongation is 28°.

6. The velocity of this planet in its orbit, is at the mean rate of J 09,500 miles an hour. Its eccentricity is 7,000,000 of miles.

7. By eccentricity is understood the distance between the centre of an ellipsis and either of its foci.

8. When viewed through a good telescope, Mercury assumes the different phases, or changes of the moon.

9. When Mercury passes exactly between the earth and the sun, lie appears on the sun's disk like a small dark spot, or speck. This is called a transit. Only three transits of Mercury have been observed.

10. By the sun's disk, is meant the round face of the sun, which, from its distance, appears flat;

0H4?nsE ir.

Of Vc?ius, $ .

1. Venus is the second planet in the system. Her situation is immediately within the orbit of the earth. Her brilliancy is greater than that of any other planet ; and she frequently causes the objects on which she shines to cast a shadow. Venus may sometimes be seen at noonday.

2. The d'ameter of Venus is 7,687 miles; and her circumference about 24,200 miles.

3. Her mean distance from the sun is 63,000,000 of miles; her eccentricity, 473,100 miles; and she moves in her orbit at the mean rate of 89,000 miles an hour.

4. The annual revolution of Venus is performed in about 224 days; and her diurnal rotation, in about 23 hours 21 minutes.

5. Venus, like Mercury, has phases similar to those of the moon.

6. Transits of Venus sometimes happen, though but seldom. A transit over the sun's disk, was first observed Nov. 16, 1739.

7. Two transits of Venus will occur in the present century: the former, Dec. 8, 1874, and the latter, in 1882.

8. Venus is sometimes seen as an evening star, and sometimes as a morning star. When she is m the upper part of her orbit, and rises before fhe sun, she is a morning star ; and when she is in the lower part of her orbit, and sets after the sun, an evening star.

9. There have been observed bright and dark spots on the disk of Venus : there are also mountains ; some of which are supposed to be six times higher than any on the earth.

10. The orbit of Venus intersects the plane of the ecliptic in 15° of Gemini, and in 15° of Sagittarius. These are her ascending and descending nodes.

11. She is surrounded with atmosphere, which lias been calculated to be 50 miles in height.

CHAPTER VI.

Of the Earth, ©.

1. The Earth, which we inhabit, is the third planet from the sun : it is situated between the orbits of Venus and Mars. In shape it is an oblate spheroid, elevated at the equator, and depressed at the poles.

2. The mean distance of the earth from the sun, is computed to be 95,000,000 of miles. It moves in its orbit at the rate of 68,000 miles an hour.

3. The equatorial diameter of the earth, is 7,924 miles; which exceeds the polar diameter by 37 miles. The eccentricity of its orbit is 1,618,000 miles.

4. The circumference of the earth, measured round the equator, is 24,904 miles, and through the poles, 24,773 miles.

5* The earth performs its sidereal revolution around the sun in 365 days 6 hours 9 minutes 12 seconds ; and its tropical, in 365 days 5 hours 48 minutes 49 seconds ; and revolves on its axis in 24 hours.

6. The sidereal revolution of the earth, is the time it occupies in passing from any fixed star, till it arrives at the same star again; and its tropical revolution is the time it takes in travelling through the fixed signs of the zodiac ; which is the length of the natural year.

7. In the movement of the earth in its orbit, the equinoctial points fall back, in a retrograde motion, from east to west, about 50i seconds of a degree, or 20 minutes 23 seconds of time every year : this retrograde motion is called the recession or precession of the equinoxes,

8. The length of the natural day is 24 hours, it being the time which elapses from the sun's appearing on any meridian, to the time in which it is seen on the same meridian again.

9. A meridian is a great circle of the sphere, which passes through the zenith and poles, perpendicular to the horizon.

10. The motions of the earth are three ; the annual, the diurnal, and the recession of the equinoxes.

11. The inclination of the earth's axis in its orbit, produces the variety in the seasons ; namely, Spring, Summer, Autumn, and Winter ; and its rotation on its axis produces the succession of day and night.

12. The ecliptic makes an angle of 23° 28' with a plane passing through the equator of the earth : this is called the obliquity of the ecliptic*

13. As the ecliptic is the apparent path of the sun, it will readily be perceived, that his greatest

JO GRAMMAR OF ASTRONOMY.

apparent declination from the equator, either north or south, can never exceed %3° 28'.

14. This apparent declination of the sun, is not occasioned by his own motion, but by the peculiar situation of the earth with respect to the sun.

15. When the sun is in his greatest apparent declination north, the days are longest in a northern, and shortest in a southern latitude; this happens on the 21st of June, at which time the sun shines 23° 28 over the north pole.

16. When the sun is in his greatest apparent declination south, the days are longest in a southern, and shortest in a northern latitude; this happens on the 21st of December. The sun then shines 23° 28' over the south pole.

17. The portions of the ecliptic in which the earth appears on those days, are called the solstitial points; these are the first degree of Cancer, and the first degree of Capricornus.

18. At the time of the equinoxes, that is, when the sun has no apparent declination, but shines equally on both poles, the days and nights are equal in length all over the earth. This happens twice a year, namely, on the 21st of March, and on the 21st of September.

19. When the earth is in that part of its orbit where both the north and the south pole receive the sun's rays at the same time, it is said to be in its equinox. This happens when the sun appears in the constellations of Aries and Libra, the first degrees of which are called the equinoctial points.

20. The declination is greatest at the solstices, and nothing in the equinoxes.

21. The earth is in 1° of Aries, on the 22d of September ; 1° of Taurus, on the 24th of Oc- + ober; 1° of Gemini, on the 23d of November:

IP of Cancer, on the 21st of December; 1° of Leo, on the 21st of January ; 1° of Virgo, on the 19th of February; 1° of Libra, on the 21st of March ; 1° of Scorpio, on the 21st of April ; 1° of Sagittarius, on the 21st of May; 1° of Capricornus, on the 21st of June; 1° of Aquarius, on the 24th of July ; and 1° of Pisces, on the 24th of August. The sun always appears in the opposite signs.

Obs. The ecliptic being inclined to an angle of 23 ■' 28' from the equator, the earth, in passing through it, must be at different distances from the plane. The nearest distance from this plane to the sun's vertical rays, is the earWs declination, f commonly called the sun-'s declination.

22. To the height of 45 or 50 miles, the earth is surrounded by a collection of vapours, called atmosphere, which is the support of animal life.

23. The earth is attended by one secondary planet, or satellite, called the moon, which, in the sun's absence, dispenses light to the earth, though in a less degree than the sun.

Of Mars, $.

1. Mars, the fourth planet in order from the sun, is of a dusky red appearance, owing probably to the density of his atmosphere. Like Mercury and Venus, he is sometimes in conjunction with the sun, but never transits the sun's disk.

2. When viewed through a telescope, Mars sometimes appears full and round ; at other times gibbous, but never horned. His apparent motion

C

22 URAJYIMAR OF ASTRONOMY.

is sometimes direct, or from east to west; sometimes retrograde; and at others, he appears stationary.

3. Mars performs his annual revolution in about 687 days, at the mean distance of 144,000,000 of miles from the sun. The length of his diameter is computed to be 4,189 miles, and the eccentricity of his orbit, 13,463,000 miles. He moves at the mean rate of 55,000 miles an hour.

4. The diurnal rotation of Mars on his axis, is performed in about 24 hours, nearly the same time in which the earth performs its rotation.

5. The orbit of Mars makes an angle of 1° 52' with the plane of the ecliptic. The place of his ascending node is in 18° of Taurus.

6. When Mars rises before the sun, he is seen in the morning ; but when he sets after the sun, he is seen in the evening.

7. It is evident that the orbit of Mars is without that of the earth, as he is sometimes seen opposite to the meridian at noonday.

8. The earth would appear to the inhabitants of Mars, as Venus appears to us.

OHAPfEE VIIE.

Of the four Asteroids, or Minor Planets.

1. Vesta, one of the minor planets, was discovered by Dr. Gibers, of Bremen, in Lower Saxony, March 29, 1807. It is visible to the naked eye, only in very clear evenings. It shines with a pure white light, and appears like a star of the fifth magnitude.

2. The diameter of Vesta is computed to be 238 miles ; and its mean distance from the sun, 225,000,000 of miles. It revolves round the sun in about 3 years 60 davs, at the mean rate of 44,201 miles an hour. The eccentricity of its orbit is 30,000,000 of miles ; but the time which it takes to perform a revolution on its axis, is not known.

3. Juno was discovered by Mr. Harding, near Bremen, on the 1st of September, 1804. It is situated between the orbits of Vesta and Pallas, and shines with a brilliant light, owing probably to certain changes in the density of its atmosphere.

4. The diameter of Juno is computed, to be 1,425 miles; and its mean distance from the sun, 252,000,000 of miles. It performs its annual revolution in 4 years 128 days, at the rate of 41,170 miles an hour. Its eccentricity is 68,000,000 of miles.

5. Ceres, the next planet to Juno, was discovered by M. Piazzi of Palermo, in the island of Sicily, January 1, 1801. It exhibits a ruddy appearance, owing to the dense atmosphere by which it is surrounded ; and, to the naked eye, its size is that of a star of the sixth magnitude.

6. The diameter of Ceres is 1,024 miles; and its mean distance from the sun is about 263,000,000 of miles. It revolves around the sun in 1,681 days 12 hours 9 minutes, or about 4 years 221 days, at the mean rate of 40,930 miles an hour. The eccentricity of its orbit is computed to be 20,598,130 miles.

7. The height of its atmosphere, according to Shroeter, the German astronomer, is 676 miles.

8. Pallas was discovered bv Dr. Olbers of Bremen, March 28, 1802. Its appearance is not so ruddy as that of Ceres, by reason of the less extent of its atmosphere, which is computed to be 468 miles in height.

9. Shroeter estimates the diameter of Pallas at 2,099 miles ; and its distance from the sun, 265,000,000 of miles.

10. It performs its revolution round the sun in 1,703 days, at the rate of 40,930 miles an hour ; and its eccentricity is about 64,516,673 miles.

11. The orbit of Pallas crosses that of Ceres, in consequence of the great eccentricity of the former.

Obs. As the great space between the orbits of Mars and Jupiter, does not, without another planet, seem to agree with the harmony of proportionable distance in the solar system, the four minor planets are supposed, by some astronomers, to have been separated from one original planet, by some convulsion in nature, capable of destroying the mutual attraction of the fragments. It is evident that the smaller parts would, by the explosive force, be thrown to the greatest distance from the original orbit, while vthe greater fragments, on account of their gravity, deviate less from the original path of the primary body. Thus Pallas and Juno are supposed by some to be less than Ceres and Vesta, because of their greater eccentricity.