A new system of astronomy, in question and answer. For the use of schools and academies

Front matter

EW SYSTEM

ASTRONOM Y,

QUESTION AND ANSWER.

Preface

The following system of Astronomy was written some time since, for the use of those by whom I was employed as private instructer, and for the use of Miss Desabye's Boarding School, in which I am engaged to superintend the English department. Knowing, therefore, from experience, that their acquisition of the knowledge of the elements of Astronomy has been facilitated by this work, more than by any other which I could place before them, I am induced to publish it, believing that, while it relieved me from the laborious duty of copying it for every student, it would serve to introduce into our Schools and Academies, the study of this useful and important science.

The study of Astronomy has been too much neglected in the system of education. This has probably arisen from the want of some astronomical work, which could be introduced into schools at a small expense and which would render this science intelligible tc youth. These objects, it is believed, will be effected by the following work, which is now published for the use of those who find it necessary to complete their education at Schools and Academies without enjoying the advantages of a liberal education at college, where the science of Astronomy would be embraced in their course of studies.

When I have conversed with teachers on the propriety of making Astronomy a branch of elementary education, they have observed that the usual works on that science were too expensive, and were likewise accompanied by many geometrical and algebraical explanations, which the young student could not comprehend, and of which a knowledge could not be acquired in the short period allotted to elementary education. This objection, supported by fact, has influenced me to avoid, in the definitions and explanations, too frequent use of technical terms, and to omit some things which are not practically useful, and can be understood by those only who are acquainted with the higher branches of geometry and mathematics.

To obtain an accurate knowledge of the following work, it will be necessary for the teacher to require the student to explain, as far as possible, every definition and problem upon the globes. No impressions are so clear and impressive as those presented to the eye. The reasons for this I need not now enumerate. Experience, the infallible test of every theory, fully confirms this assertion.

Though the general importance and utility of the study of Astronomy has never been denied, yet I have often heard it observed, that it is entirely useless in the system of female education. All the reasons which can be given in support of this position are equally forcible against the benefit of any science to the female mind. The science of Astronomy explains and illustrates the phenomena of the natural World, and exhibits, in the system of the universe, that harmony and order, which bespeak the creative power and wisdom cf the Deity. It enlarges the faculties, and strengthens the energies of the mind. If such a study must be rejected from the system of female education^ •where, I ask, will retrenchment end ?

> If the objection arise from the opinion, that the female mind is not competent to the investigation cf the Elements of Astronomy, I leave it to the contempt 't so justly deserves, only asking the objector on what authority he attributes to the female sex, that inferiority of intellect which his objection supposeo ?

I have for some time past, been exclusively engaged in the business of instruction : and my own experience, and the opinion of those teachers in whom I place the highest confidence, have convinced me, that the method of instruction by "question and answer," is, in many branches of education, highly beneficial ; provided the questions are so constructed, that the answers to them will necessarily involve all the important principles of the science to which they are adapted.

When the lesson in this form is placed before students, they know what will be required of them in the recitation, and are sure that nothing, which will be required, has escaped their attention. Such a course of study inspires them with confidence, and dissipates that uncertainty, which perplexes and confuses the mind, and destroys all that pleasure which is to be derived from the pursuit of literature.

These views have influenced me to adopt, as far as possible, the catechetical mode of instruction. I shall be cautious not to carry it too far; but to adopt it to that extent, which, while it diminishes the labour of the teacher, will promote the assiduity, advancement, and satisfaction of the student.

That teachers and the public concur with me in this respect, I have sufficient evidence, in the unexpected and rapid sale of a work which I lately published, entitled, "Questions adapted to the study of Tytler's Elements of History." And in the approbation given to a similar work, entitled, "Questions to Blair's Rhetoric," published by A. Bixby, principal of John-street School.

Should the encouragement given to those works he extended to this, I shall publish some others, calculated to introduce into the schools of this country, some salutary branches of literature, which have been hitherto excluded from the attention of youth either by extending the volumes which contain them, to an unnecessary expense, or by treating of them in a manner not suited to the general use of schools and academies.

I confidently trust, that the experience of other teachers will convince them of the utility of this method of instruction ; since it is one. which makes their own duties less laborious, and consults the welfare of students, by making them confident of their ability to acquire a knowledge of those sciences, whose obscurity, or difficulty, has hitherto checked their progress, and discouraged their application.

ASTRONOMY.

FART I.

SECTION I. Definitions

'What is Astronomy ?

It is the science which treats of the heavenly bodies.

What do we learn by it 7

We learn the figure, dimensions, motion, and relative distances of the heavenly bodies.

What is an Angle 7

It is the space contained between two lines meeting at a point.

What is a Right Angle ?

It is an angle formed by one line falling perpendicularly upon another, thus :

A B C is a right angle, or contains^, ninety .degrees.

What is an Acute Angle ?

It is less than a right angle, or contains less than ninety degrees. JK

What is an Obtuse Angle? &

It is greater than a right angle, or contains more than ninety degrees.

1"

"iT

A is a figure bounded by three

What is a Triangle 7 Iti rides.

bZ ^e

What are Parallel Lines 7

Those which never approach — —

each other. — — —

What is a Circle 7

It is a plain figure bounded by a curve line, every part of which is equally distant from a point called the centre.

1. The Circumference is the curve line that bounds

2. The Radius is a straight line drawn from the centre to the circumference, as AC or CB — all radii are equal.

3. The Diameter is a line drawn through tlie centre, terminated both ways by the circumference, as AB.

4. An Arc is any part of the circumference, as DF.

5. The circumference is divided into 360 degrees ; each degree into 60 minutes, and each minute into 60 seconds.

What is a Sphere 7

A sphere is properly a globe ; but in Astronomy, tAe celestial sphere means the apparently concave orb of the heavens, in which all the heavenly bodies appear to be placed.

What is the Axis of a heavenly body ?

It is an imaginary line, round which it performs its daily motion.

To what is it equal ?

It is equal to a diameter.

What is the Axis of the Artificial Globe 7

It is a line which passes through its centre from one pole to the other.

What are the Poles of a Great Circle 7

They are two points equally distant from every part of its circumference.

What are the Poles of the Earth 7

They are the extremities of the axis; and are called the north or arctic pole, and the south or antarctic pole.

What are the Celestial Poles 7

They are the extremities of the earth's axis produced to the heavens.

What is the Diameter of a sphere ?

It is a straight line which passes through the centre, and is terminated both ways by the surface of the sphere.

What is the Circumference of the sphere ?

It is any great circle drawn on its surface. . 4

How are the circles of the sphere divided 1 v \

In two kinds — Great and Small.

What is a Great Circle 7

It is that whose plane divides the sphere into two ?qual parts, called hemispheres.

What is a Hemisphere 7

It is half a globe.

How many hemispheres are there ?

The number is innnite 5 as any great circle divide?

the g>obe into two hemispheres. Those most frequently used are six :

1. The Northern and Southern, formed by the equator.

2. Tne Eastern and Western, formed by ameridian.

3. The Upper and Lower, formed by the rational horizon.

Mention the principal great circles.

There are four : Equator, Ecliptic, Meridian, and Horizon.

Can two great circles be parallel ? No.

What is a S?nall Circle ?

It is that whose plane divides the globe into two unequal parts.

Mention the principal small circles.

They are four : the two Tropics and two Polar Circles.

What are the Parallels of Latitude

They are all those small circles parallel to the equator.

Are all small circles parallel to the equator ?

They may be parallel to the ecliptic, horizon, meridian, or any other great circle.

What are parallels of latitude on the celestial globe?

They are small circles parallel to the ecliptic ?

What are Parallels of Declination ?

They are small circles parallel to the equator, and are the same as parallels of latitude on the earth.

What are Parallels of Altitude ?

They are small circles parallel to the horizon.

What are Concentric Circles ?

They are circles drawn round the t same centre.

What are Cardinal Points 7

They are certain fixed points that , never change, and to which all calculations are referred.

SECTION II. Of the Equator

What is the Equator 7

It is a great circle whose plane divides the earth into northern and southern hemispheres.

How far distant is it from the poles 7 Every part of it is ninety degrees distant. What is it called when referred to the heavens ? The Equinoctial.

What is it called by mariners 7 The Line.

What are reckoned on it 7 Longitude, right ascension, &c.

SECTION III. Of the Meridian

What are Meridians 7

They are great circles, whose planes divide the globe into eastern and western hemispheres.

What is their direction 7

They all pass through the poles, and cut the equator at right angles.

How many meridians are there 7

Their number is unlimited ; there may be as many as there can be taken points on the equator

Why are they called Hour Circles 7

Because as they are drawn on most globes, the sun masses from one to another of them every hour 7

What supplies their places as hour circles 7

The hour circle and its index.

What is the Hour Circle 7

It is a small circle of brass fixed to the north pole, vith the hours of the day marked on it.

What is the First Meridian 7

It is that from which geographers begin to count the longitude.

What first meridian is most frequently used 7

The meridian of London.

What is the Brazen Meridian ?

It is that in which the artificial globe turns.

How are the degrees numbered on it ?

On the upper semicircle from the equator towards the poles — on the lower semicircle from the poles to the equator.

What is Longitude ?

It is distance east or west from the first meridian reckoned on the equator.

What is the greatest longitude a place can have ?

One hundred and eighty degrees either east or west from the meridian.

What is Latitude ?

It is distance either north or south from the equator, reckoned on a meridian.

What is the Greatest Latitude a place can have ?

Ninety degrees either way from the equator.

What is Declination, on the celestial globe ?

It is the distance north or south from the equinoctial, and corresponds to latitude on the earth.

How is latitude reckoned on the celestial globe ?

Ninety degrees each way from the ecliptic.

What is longitude in the heavens ?

It is distance on the ecliptic, reckoned eastward from the first degree of the sign Aries.

What is the greatest longitude of a heavenly body ?

Three hundred and sixty degrees, beginning at the first degree of Aries, and reckoning on the ecliptic eastward quite round the globe.

What is the greatest latitude of the sun, a planet and star.

1. The sun being always in the ecliptic, has no latitude.

2. A planet can have only eight degrees of latitude, because it never leaves the zodiac^ which is eight degrees wide on each side of the ecliptic*

3. A star may have ninety degrees of latitude. What is the greatest declination of the sun, a planet,

or star?

1. The greatest declination of the sun is about twenty-three degrees and a half.

2. That of a planet about thirty-one degrees and a half to the limit of the zodiac.

3. That of a star 90 degrees.

What are the Geocentric latitudes and longitudes of the planets ?

Their latitudes and longitudes as seen from the earth.

What are their Heliocentric latitudes and longitudes ?

Their latitudes and longitudes as seen from the sun.

What is the Rigid Ascension of a heavenly body?

It is that degree of the equinoctial, which rises with the body in a right sphere ; and is reckoned from the first degree of Aries eastward round the globe.

What is Oblique Ascension 7

It is that degree of the equinoctial, which rises with the body in an oblique sphere, and is reckoned in the same way.

What is Oblique Descension ?

It is that degree of the equinoctial which sets with the body in an oblique sphere. .

How many positions has the sphere ?

Three ; Right, Oblique, and Parallel.

What is a Right Sphere ?

It is that in which all the circles of daily motion lise directly above and descend directly below the horizon.

How is it represented ?

By placing both poles in the horizon

What is an Oblique Sphere ?

It is that in which all the circles of daily motion are Oblique to the horizon.

How is it represented 1

By raising one pole a little, and depressing the other.

What is a Parallel Sphere ?

It is that in which the equator coincides with the horizon, and all the circles of daily motion are parallel to the horizon.

How is it represented 1

By elevating one pole to the zenith, and depressing the other to the nadir.

What places have each of these spheres ?

Those directly under the equator have a right sphere, those between the equator and poles have an oblique sphere, and those directly under the poles have a parallel sphere.

SECTION IV. Of the Ecliptic

What is the Ecliptic 7

It is a great circle which intersects the equinoctial at an angle of about twenty-three degrees and a half.

Of what is it the path ?

It is the orbit in which the earth revolves round the sun once a 3rear.

What are the Equinoctial Points ?

They are the points where the ecliptic and equmoclial intersect each other.

When does the sun pass these points

It passes Aries twenty.-first of March, called the vernal equinox, and Libra twenty-third of September, called the autumnal equinox.

"When are the day and night every where equal ?

When the sun is in the equinoxes.

What are the Solstitial Points ?

They are the points of the ecliptic farthest from the equinoctial, or where it touches the tropics.

How far from the equinoctial to the solstitial points ?

Ninety degrees, or a quarter of a circle.

When is the sun in the solstitial points ?

On the twenty-first of June, called the summer solstice, and on the twenty-second of December, called the winter solstice.

What are their signs ?

Cancer is the northern or summer solstice.

Capricorn the southern or winter solstice.

What is said of the day and night when the sun is in these signs ?

1. When the sun enters Cancer, all places in the northern hemisphere have their longest day. and those in the southern their shortest day.

2. When the sun enters Capricorn, all places in the southern hemisphere have their longest day, and those in the northern their shortest day.

3. When the sun enters Cancer, all places within the north polar circle have constant day, and all places within the southern constant night.

4. When the sun enters Capricorn, all places within the south polar circle have constant day, and all those within the northern constant night. The last two appearances continue for a short time only ; but it is to be observed,

5. That some places within the south polar circle, have continual night during the whole six months the sun is north of the equinoctial, and some places within the north polar circle have at the same time perpetual day ; and.

6. That during the six months the sun is south of the equinoctial, some places within the south polar circle have continual day, and some within the northern continual night.

NOTE. These six statements may be explained upon the globe. (See part 3, Problem 18.)

What is the Equinoctial Colure ?

It is that meridian which passes through the equinoctial points.

What is the Solstitial Colure 7

It is that meridian Which passes through the solstitial points.

How is the ecliptic divided ?

Into Twelve Signs, each containing thirty-degrees.

Mention the names of the signs, and the day on which the sun enters them.

T Aries twenty-first of March. )

b Taurus twentieth of April. \ Spring signs.

H Gemini twenty-first of May. \

52 Cancer twenty-first of June. )

SI Leo twenty-third of July. \ Summer signs.

i£ Virgo twenty-third of August. \

«2= Libra twenty-third of Sept. )

m Scorpio twenty-third of Oct. \ Autumnal signs.

J Sagittarius twenty-third Nov. )

V3 Capricornus twenty-second Dec. )

'- Aquarius twentieth January. V Winter signs.

H Pisces eighteenth February. )

What are the cardinal points of the ecliptic '?

They are the equinoctial and solstitial points.

What is the Zodiac ?

It is a space sixteen degrees wide, extending eight degrees on each side of the ecliptic : and contains tba orbits of the planets.

What is the Orbit of a planet }

It is the path in which it revolves round the sun.

What is the Figure of these orbits?

Elliptical, or longer one way than the other.

How do the planets revolve in them ?

From west to east round the sun.

What are the Apparent Motions of the planets ?

Three ; Direct, Stationary, and Retrograde.

1. A planet's motion is said to be Direct, when to a spectator on the earth, it appears to move forward in its orbit from west to east.

2. It is said to be Stationary, when it appears for some time in the same point of the heavens.

3. It is said to be Retrograde, when it appears to move backward in its orbit, from east to west, contrary to the order of the signs.

What are the Nodes 7

They are the two opposite points, where the orbit of the planet intersects the ecliptic.

What is Aspect 7

Aspect of the stars or planets is their situation and relative distances with respect to the sun and each other.

What is the Aphelion 7

It is that point of the orbit farthest from the sun.

What is Perihelion 7

It is that point of the orbit nearest the sun.

What is Elongation. 7

[t is the apparent distance of any body from the sun.

What is Apogee 7

It is that point in the orbit of the moon or any planet farthest from the earth.

What is Perigee7

It is that point in the orbit of the moon or planet nearest the earth.

The Apsis Line is that which joins the aphelion and perihelion, or which joins the apogee and perigee. These definitions are thus explained :

Let S be the Sun mid C the centre of the orbit; then A, the point nearest the Sun, is the perihelion ; and B, the point farthest from the sun, is the aphelion. As the sun is not exactly in the centre of the orbit, the distance from C, the centre of the orbit, to the centre of the sun, is called the Eccentricity

How do the planets move in their orbits ?

Variably ; sometimes faster and sometimes slower.

What is the Mean place of a planet 1

It is the place where it would be if it moved in its orbit with equal velocity at all times.

What is the True place ?

It is the place where it really is.

section v. Of the Horizon

What is the Horizon 7

It is the circle which separates the visible part of the Heavens from the invisible.

How many horizons are there ?

Two ; Sensible and Rational.

What is the Sensible Horizon ?

The sensible or apparent Horizon is that circle vhich bounds our prospect where the earth and sky appear to meet.

What is the Rational Horizon ?

It is a great circle whose plane is parallel to the plane of the visible horizon, and divides the earth into upper and lower hemispheres.

What is the Wooden Horizon 7

It is that circular plane circumscribing the artificial globe, which represents the rational horizon.

What are the cardinal points of the horizon ?

They are east, west, north, and south.

What are the cardinal points in the heavens ?

The Zenith and Nadir.

What are the Poles of the horizon ?

The Zenith and Nadir.

What is the Zenith I

It is the point in the heavens exactly over our heads.

What is the Nadir 7

It is the point in the heavens opposite to the zenith, or directly under our feet.

What is the Mariner's Compass 7

It is a representation of the horizon, and is divided into 32 equal parts.

What is the variation of the compass 7

It is the deviation of the north and south points of the magnetic needle, from the north and south points of the horizon, either east or west.

What is an Azimuth or Vertical Circle 7

It is a circle passing through the zenith and nadir, cutting the horizon at right angles.

What is the Azimuth of an object in the heavens ?

It is that part of the horizon contained between a vertical circle passing through the body, and the north or south points of the horizon.

What is a Prime Vertical 7

It is that azimuth circle which passes through the east and west points of the horizon.

What is the Altitude of a heavenly object?

It is the distance from the object to the horizon, reckoned on a vertical circle.

What is the Zenith Distance of a heavenly body % 2*

L8

It is tae distance from the body to the 'zenith, reckoned on a vertical circle.

What is the Polar Distance of an object ?

It is its distance from the pole, reckoned on a meridian.

What is the Amplitude of a heavenly body 7

It is the distance which it rises from the east, or sets from the west point of the horizon.

What is Twilight 7

It is that faint light, which appears before the sun rises and after it sets.

What is the Diurnal Arch 7

It is the course described by any body from its rising to its setting.

What is the Nocturnal Arch 7

It is the course described by any body from its setting till it rises again above the horizon.

SECTION VI. Of the Tropics

What are the Tropics 7

They are two small circles parallel to the equator, at about twenty-three degrees and a half from it.

Through what points do they pass ?

Through the solstitial points.

What are they called ?

The northern is called the Tropic of Cancer.

The southern, the Tropic of Capricorn.

What do they limit?

They limit the sun's declination, because when it arrives at one of them it turns towards the other.

When does a place have a vertical sun ?

When the sun is directly over that place.

What places have a vertical sun ?

Those only which are within the tropics ; and thoso have a vertical sun twice every year.

SECTION VII. Of the Polar Circles

What are the Polar Circles 7

They are two small circles described round the poles at the distance of about twenty-three degrees and a half from the poles, and parallel to the equator.

What is their diameter ?

What are they called ?

The one described round the north pole is called the northern or arctic circle ; the other the southern or antarctic circle.

How far are they distant from each other, from the equator, and from the tropics ?

1. From each other 133 degrees*

2. From the equator 66^ degrees.

3. From the tropics 43 degrees.

SECTION VIII. Of the Zones

What is a Zone 7

It is a portion of the surface of the earth contained within the polar circles, or between two small circles parallel to the equator.

How many zones are there ?

There are jive, one Torrid, two Temperate, and two Frigid Zones.

What is the Torrid Zone 7

It is the space included between the two tropics, and the equator passes through the middle ol it.

How wide is it ?

About 47 degrees, or 23i degrees each side of the equator.

What are the principal countries in the torrid zone ?

The southern part of North America, the northern half of South America, the West India Islands, the East India Islands, a great part of Africa, the southern parts of Arabia, Hindostan, and China, and the northern part of New Holland.

How many Temperate Zones are there ?

Two ; Northern and Southern.

Describe the north temperate zone ?

It is that space included between the northern tropic and north polar circle.

What are the principal countries in it ?

The United States, East and West Florida, New Mexico, most of the British possessions in North America, the north part of Africa, nearly all of Europe, Persia, and a great part of China, and Russia in Asia.

Describe the southern temperate zone.

It is that space included between the southern tropic and south polar circle.

What are the principal countries in it ?

New-Zealand, the southern part of South America, the Cape of Good Hope, and southern part of New Holland.

Describe the North Frigid Zone.

It is that space included within the north polar circle, having the north pole for its centre.

How wide is it ?

What countries are in it 7

Spitzbergen, and the northern extremities of North America, Europe, and Asia.

What is said of its day and night ?

The places directly under the poles have continnal day for six months, while the sun is north of the equator, and continual night for the six months it is south of the equator. And all the places in this zone have their day longer or shorter according as they are near to, or distant from the pole.

What is the South Frigid Zone ?

It is that space included in the south polar circle.

How wide is it ?

What is said of its day and night ?

They are the same as in the north frigid zone, only it is night when the sun is north of the equator, and day when it is south of the equator.

What are the Atwphiscii ?

They are the inhabitants of the torrid zone, so called because they cast their shadows both north and south at different times of the year.

What are the Heteroscii ?

It is a name given to the inhabitants of the temperate zones, because at noon they cast their shadows only one way during the year.

What are the Periscii ?

It is a name given to the inhabitants of the frigid zones, because during one revolution of the earth on its axis, their shadows are directed to every point of the compass.

What are the Antceci ?

They are those who live under the same meridian, and have equal degrees of latitude ; but one has north latitude, and the other south latitude ; but when it is winter with one, it is summer with the other.

What are the Periceci 7

They are those who live in the same latitude, but in opposite longitudes ; when it is noon with one, it is midnight with the other.

What are the Antipodes 7

They are those inhabitants of the earth who live diametrically opposite to each other, so that the feet of one point towards the feet of the other. — Their latitudes, longitudes, seasons of the year, days and nights, are all contrary to each other.

What is a Climate 7

It is a part of the surface of the earth contained between two parallels of latitude ; it diminishes in breadth towards the polar circles.

Why have places in the same climate different temperatures 1

These differences are produced by the influence of woods, lakes, mountains, sandy deserts, &e. upon the atmosphere.

SECTION I. What is a System ?

It is a supposed arrangement of the heavenly bodies.