of their details. I have seen nothing superior in this respect, or Detter adapted to the purpose of rational instruction, than Mr. Burrett's excellent work entitled "The Geography of the Heavens,' second edition, comprising 342 closely printed pages. It contains, in the first place, a full and interesting description of all the con stellations, and principal stars in the heavens, interspersed with a great variety of mythological, historical and philosophical informa tion, calculated to amuse and instruct the general reader, and to arrest the attention of the young. The descriptions of the bodies connected with the solar system, are both popular and scientific, containing a lucid exhibition of the facts which have been ascertained respecting them, and a rational explanation of the phenomena connected with their various aspects and motions. The Celestial Atlas which accompanies the work is varied, comprehensive, and judiciously constructed, and forms the most complete set of planispheres, for the purpose of teaching, which has hitherto been published. It consists of four maps about fourteen inches square, deineated on the same principles as geographical projections, exhiDiting the stars that pass near the meridian at a certain hour, along with the circumjacent constellations for every month, and for every day of the year. Besides these there are two circumpolar maps of the northern and southern hemispheres of the heavens, and a planisphere on the principle of Mercator's projection, which exhibits at one view the sphere of the heavens, and the relative positions of the different constellations and principal stars. With the assistance of these maps, which in a great measure supersede the use of a cclestial globe, an intelligent teacher may, at certain intervals in the course of a year, render his pupils familiar with most of the visible stars in the heavens; and they will make a deeper impres sion on their minds when taught in this way, than by the use of a globe. This work, on the whole, indicates great industry and research on the part of the author, and a familiar acquaintance with the various departments of the science of the heavens. He has derived his materials from the most valuable and modern works of science, and has introduced not a few illustrations and calculations of his own, which tend to enhance the general utility of the work. The moral and religious reflections which the objects of this science naturally suggest, have not been overlooked, and, I trust, will have a tendency to raise the minds of the young to hat Almighty Being whose power, wisdom, and superintending Ailence are so strizingly displayed throughout the regions of th 5 wam 'ut.

PRELIMINARY CHAPTER.

In entering upon this study, the phenomena of the heavens, as they appear in a clear evening, are the first objects that demand our attention. Our first step is to learn the names and positions of the heavenly bodies, so that we can identify, and distinguish them from each other.

In this manner, they were observed and studied ages before books were written, and it was only after many, careful and repeated observations, that systems and theories of Astronomy were formed. To the visible heavens, then, the attention of the pupil should be first directed, for it is only when he shall have become in some measure, familiar with them, that he will be able to locate his Astronomical knowledge, or fully comprehend the terms of the science.

For the sake of convenient reference, the heavens were early divided into constellations, and particular names assigned to the constellations and to the stars which they contain. A constellation may be defined to be a cluster or group of stars embraced in the outline of some figure. These figures are in many cases, creations of the imagination, but in others, the stars are in reality so arranged as to form figures which have some resemblance to the objects whose names have been as signed to them.

These divisions of the celestial sphere, bear a striking analogy to the civil divisions of the globe. The constellations answer to states and kingdoms, the most brilliant clusters to towns and cities, and the number of stars in each, tc their respective population. The pupil can trace the boundaries of any constel lation, and name all its stars, one by one, as readily as he can trace the bounda ries of a state, or name the towns and cities from a map of New England. In this sense, there may be truly said to be a Geography of the Heavens.

The stars are considered as forming, with reference to their magnitudes, six classes; the brightest being called stars of the first magnitude, the next brightest, stars of the second magnitude, and so on to the sixth class, which consists of the smallest stars visible to the naked eye. In order to be able

Why, in entering upon the study of Astronomy, should the attention of the pupil ba Arst directed to thể vísible heavens? Why were the heavens early divided into con stellations, and names assigned to the constellations and the stars? What is a con stellation? Do these figures really exist in the skies? In what sense may there truly be said to be a Geography of the Heavens? How many classes are the stars considered as forming with reference to their magnitude.

to designate, with precision their situations, imaginary circles have been considered as drawn in the heavens, most of which correspond to and are in the same plane with similar circles, supposed, for similar purposes, to be drawn on the surface of the Earth.

In order to facilitate the study of it, artificial representations of the heavens, similar to those of the surface of the Earth, have been made. Thus, a Celestial Atlas, composed of several maps, accompanies this work. Before, however, proceeding to explain its use, it is necessary to make the pupil acquainted with the imaginary circles alluded to above.

CIRCLES OF THE SPHERE.-The Axis of the Earth is an imaginary line, passing through its centre, north and south, about which its diurnal revolution is performed.

The Poles of the Earth are the extremities of its axis. The Axis of the Heavens is the axis of the Earth produced both ways to the concave surface of the heavens.

The Poles of the Heavens are the extremities of their axis. The Equator of the Earth is an imaginary great circle passing round the Earth, east and west, everywhere equally distant from the poles, and dividing it into northern and southern hemispheres.

The Equator of the Heavens, or Equinoctial, is the great circle formed on the concave surface of the heavens, by producing the plane of the Earth's equator.

A plane is that which has surface but not thickness. The plane of a circle is that imaginary superficies which is bounded by the circle.

The Rational Horizon is an imaginary great circle, whose plane, passing through the centre of the Earth, divides the heavens into two hemispheres, of which the upper one is called the visible hemisphere, and the lower one, the invisible hemisphere. It is the plane of this circle which determines the rising and setting of the heavenly bodies.

The Sensible or Apparent Horizon, is the circle which terminates our view, where the Earth and sky appear to meet.

To a person standing on a plain, this circle is but a few miles in diameter. I the eye be elevated five feet, the radius of the sensible horizon will be less than two miles and three quarters; if the eye be elevated six feet, it will be just three miles. The observer being always in the centre of the sensible horizon, it will move as he moves, and enlarge or contract, as his station is elevated or depressed.

What expedient has been devised for designating, with precision, the situations of the heavenly bodies? What is the axis of the Earth? What are the poles of the Earth? What is the axis of the heavens? What are the poles of the heavens? What is the equator of the Earth? What is the equator of the heavens or the equinoctial? What is #plane? What is the plane of a circle? What is the rational horizon? What is the sensible or apparent horizon? What is the diameter of this circle to a person standing on a plain? What will its radius be if the eye be elevated five feet? If it be e vated six feet? On what does the place of its centre and its circumference dependi

The Poles of the Horizon are two points, of which the one is directly over head, and is called the Zenith; the other is directly under foot, and is called the Nadir.

Vertical Circles are circles drawn through the Zenith and Nadir of any place, cutting the horizon at right angles.

The Prime Vertical is that which passes through the east and west points of the horizon.

The Ecliptic is the great circle which the Sun appears to describe annually among the stars. It crosses the Equinoctial, a little obliquely, in two opposite points which are called the Equinoxes. The Sun rises in one of these points on the 21st of March; this point is called the Vernal Equinox. It sets in the opposite point on the 23d of September; this point is called the Autumnal Equinox. One half of the ecliptic lies an the north side of the Equinoctial, the other half on the south side, making an angle with it of 234°. This angle is called the obliquity of the Ecliptic. The axis of the Ecliptic makes the same angle with the axis of the heavens; so that the poles of each are 2310 apart.

This angle is perpetually decreasing. At the commencement of the Christian era, it was about 236 45'. At the beginning of 1836, it was only 23° 27′ 38 ", showing an annual diminution of about half a second, or 45′′.70 in a hundred years. A time will arrive, however, when this angle, having reached its minimum, will again increase in the same ratio that it had before diminished, and thus it will continue to oscillate at long periods, between certain limits, which are said to be comprised within the space of 20° 42′′′.

The ecliptic, like every other circle, contains 360°, and it is divided into 12 equal arcs of 30° each, called signs, which the ancients distinguished by particular names. This division commences at the vernal equinox, and is continued eastwardly round to the same point again, in the following order: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpro, Sagittarius, Capricornus, Aquarius, Pisces. The Sun, commencing at the first degree of Aries, about the 21st of March, passes, at a mean rate, through one sign every month.

The Zodiac is a zone or girdle, about 16 degrees in breadth, extending quite round the heavens, and including all the heavenly bodies within 8° on each side of the ecliptic. It includes, also, the orbits of all the planets, except some of the asteroids, since they are never seen beyond 8° either north or south of the ecliptic.

Parallels of Latitude are small circles imagined to be

What are the poles of the horizon? What are vertical circles? What is the prime vertical? What is the ecliptic? What are the equinoxes? The vernal equinox? The autumnal equinox? How is the ecliptic situated with respect to the equinoctial? What is the obliquity of the ecliptic? Describe the manner in which this angle varies. De scribe the division of the ecliptic into signs. How much, at a mean rate, does the Sun advance in the ecliptic every month? What is the zodiac? What are parallels of Latitude?

drawn on the Earth's surface, north and south of the equator, and parallel to it.

Parallels of Declination are small circles, imagined to be drawn on the concave surface of the heavens, north and south of the equinoctial, and parallel to it; or they may be consid ered as circles formed by producing the parallels of latitude to the heavens.

The Tropic of Cancer is a small circle, which lies 2310 north of the equinoctial, and parallel to it. The Tropic of Capricorn is a small circle, which lies 2310 south of the equinoctial, and parallel to it. On the celestial sphere, these two circles mark the limits of the Sun's farthest declination north and south. On the terrestial sphere, they divide the torrid, from the two temperate zones. That point in the ecliptic which touches the tropic of Cancer, is called the Summer Solstice; and that point in the ecliptic which touches the tropic of Capricorn, is called the Winter Solstice.

The distance of these two points from the equinoctial, is always equal to the obliquity of the ecliptic, which, in round numbers, is 23c°; but as we have seen the obliquity of the ecliptic is continually changing; therefore the position of the tropics inust make a correspondent change.

The Colures are two great circles which pass through the poles of the heavens, dividing the ecliptic into four equal parts, and mark the seasons of the year. One of them passes through the equinoxes at Aries and Libra, and is thence called the Equinoctial Colure; the other passes through the solstitial points or the points of the Sun's greatest declination north and south, and is thence called the Solstitial Colurê.

The Sun is in the equinoctial points the 21st of March and the 23d of Septem ber. He is in the solstitial points the 22d of June and the 22d of December.

The Polar Circles are two small circles, each about 6610 from the equator, being always at the same distance from the poles that the tropics are from the equator. The northern is called the Arctic circle, and the southern the Antarctic circle.

Meridians are imaginary great circles drawn through the poles of the world, cutting the equator and the equinoctial at right angles.

Every place on the Earth, and every corresponding point in the heavens, is onsidered as having a meridian passing through it; although astronomers apply

What are parallels of declination? What is the tropic of cancer? What is the tropic of capricorn? What is the summer solstice? What is the winter solstice? What ts their distance from the equator, compared with the obliquity of the ecliptic? Is this distance always the same? What are the colures? What is the equinoctial colure? What is the solstitial colure? On what days of the year is the sun in the equinoctial points? On what days, is he in the solstitial points? What are the polar circles? By what names, are they distinguished? What are meridians? How many meridians are there? How many, do astronomers apply to the heavens?