places; which places, (except a deviation that will be noticed in treating on the precession of the Equinoxes) are the first of the Ram, and the first of the opposite sign the Balance.

The Sun, as seen from the Earth, is on the 20th of March (the Vernal equinox) in the first part of the constellation called the Ram. On the 21st of June, we see the Sun in the first of the Crab; on the 23d September (when the Autumnal equinox takes place) we see the Sun in the first of the Balance; and on the 21st of December, in the first of the Goat. It is the motion of the Earth which causes us to suppose that the Sun travels through the ecliptic; in thus describing its motion we yield to appearances. But if instead of being go verned by what is apparent, we were only to describe the real, we should, instead of saying that the Sun as seen from the Earth on the 20th of March is in the first of the Ram, say that the Earth as seen from the Sun is in the first of the Balance; that on the 21st June the Earth is in the first of the Goat; on the 23d September, in the first of the Ram; and on the 21st December, in the first of the Crab. But as it is more common in astronomical demonstration, as well as more con

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venient, to teach by what is apparent than by what is real, the Sun's apparent path is described instead of the Earth's real path. Hence the Sun is said to proceed in the order of the signs; appearing on the 20th of March in the first of the Ram, on the 21st of June in the beginning of the Crab, on the 23d of September in the first of the Balance, and on the 21st of December in the first of the Goat. Being on the 20th of March (at the vernal equinox) in the beginning of the Ram, the Sun by the 21st of June seems to have advanced to the beginning of the Crab, being that part of the ecliptic which is the Sun's utmost apparent height above the equator, viz. 23 degrees; and as we live in northern regions, and the Sun is then opposite to certain parts of the Earth which are north of the equator, we have our longest day.* Descending through the Crab, Lion and Virgin southwards, the Sun appears to depart from his elevation, our days shorten, the Sun's warmth decreases; and on his appearing to enter the first of the Balance on the 23d September, day and night are again equal — the Sun is in the equinoctial. Still descending towards the south through the Balance, Scorpion, and the Archer, he appears to enter the Goat on the 21st of December; when, being at his greatest distance, 234 degrees, below the equator, and at his least distance from us, our days are shortest: appearing to rise northward from that time, the Sun traverses the signs the Goat, Water-bearer, and the Fishes; and on the 20th of March again seems to us

* The north pole of the Earth constantly inclines toward the beginning of the Crab, while that of Venus is constantly turned the other way; namely, to the beginning of the Water-bearer; so that it is nearly midwinter in the northern parts of Venus, at our Midsummer, and vice versa.

in the first of the Ram: he is then in the equinoctial, and we have equal day and night again.

Let us repeat that all these appearances are owing, not to the motion of the Sun, but to the Earth's moving constantly round it, having its pole or axis declining from the perpendicular about 23 degrees. Let us carry a little globe round a candle and convince ourselves of the fact; and we shall then also see that owing to this declination of the Earth's axis, the north pole is illuminated by the Sun's rays for six months together, and the south pole for the other six months.

As the Sun appears to us to pass through the signs the Ram, the Bull, the Twins, the Crab, the Lion, and the Virgin, between the 20th March and 23d September, these are termed the Summer signs; and as he also appears to pass through the Balance, the Scorpion, the Archer, the Goat, the Water-bearer, and the Fishes, between the 23d of September and the 20th of March, these are termed Winter signs; and being at his utmost northern elevation above the equator on the 21st of June, and then appearing in the first of Crab, and being at his greatest distance south of the equator on the 21st of December, when he is in the first of the Goat; the Crab, Lion, Virgin, Balance, Scorpion and Archer, are called Descending signs; and the Goat, Water-bearer, Fishes, Ram, Bull and Twins, are called Ascending signs.

But we must not forget duly to consider some important consequences of the Earth's daily revolution on its axis. Many of them are connected with the subjects that have already been considered. It is owing to this, that the sphere of the Fixed stars, as well as the Sun, seems to revolve around us once every twenty-four hours. But there is one point that has not been sufficiently adverted

to. We say that in every year the Sun is vertical to every place under the ecliptic; but, more correctly speaking, he is twice in the year vertical to every place within about 23 degrees north and south of the equator.

a A

In this figure, the Earth is shewn in the position in which it is at Midsummer (see the preceding diagram). The line E C therefore is the ecliptic. The portion of the Earth at C is then opposite to the Sun; but as the Earth turns on its axis every twenty-four hours, that part of the Earth at a (which is at the same distance on one side of the north pole that C is on the other), will, in twelve hours, have turned round towards the Sun; and in the succeeding twelve hours, C will be opposite to the Sun again. Therefore on the 21st of June the Sun is vertical once in the twenty-four hours to all places beneath a circle (which is the tropic of Cancer, or of the Crab)* of which a C is one half. The same reasoning applies to the Earth at mid-winter; for, as will be ob vious on consulting the preceding diagram, E is then opposite to the Sun. He is therefore vertical on the 22d of December to all the places under the circle E b, which is the tropic of Capricorn. By the same rule, the Sun is vertical to all places under the equator, at the equinox, when the Earth is in the Ram, in passing from the Goat to the Crab. But in six months afterwards, the equinox occurs again, when the Earth in passing

* So called because the Sun then appears in the Crab. The Sun then appears in the Goat.

from the Crab to the Goat, is in the Balance ;-the Sun is then again vertical to all places under the equator. And as the Sun is twice in the year vertical to all places under the equator, he must also be vertical twice in the year to all places between the tropics.

Having ascertained the important point that the orbit of the earth and the ecliptic are on the same plane; that the equator on the Earth, and the equinoctial in the heavens are corresponding circles; having made ourselves acquainted with the progress of the Earth round the ecliptic, and shewn the intimate connection of the Earth's motions with the Zodiac, whose signs also be long to the ecliptic; we may proceed to the illustration of a point relative to the orbits of the other planets, and regarding their inclination to that of the Earth. As a greater or less inclination exists in the orbit of every planet, no two of them being on the same plane; so the orbit of the Earth, for reasons already given, is considered by astronomers as being in a horizontal position, and the orbit of every other planet is in part above, in part below the orbit of the Earth; the places at which each rises above and descends below it, are termed the nodes of the planet, from the Latin nodus, a knot or tie. The orbit of every planet crosses the plane of the Earth's orbit at a different place; and the places at which each crosses when the planet is ascending from south to north, is termed the ascending node; and on the contrary, when going from north to south, it is called the descending node, and the true places of these nodes have been thus determined.

We have said that the Zodiac is divided into twelve constellations, consisting each of a vast number of par