of her orbit (which is represented by the circle,) is between the base and the apex of the shadow, the Moon is necessarily immersed in the shadow, and we thus have the phenomenon known as an eclipse of the Moon. If the Moon happen to be at one of her nodes at the time of full Moon, then we have a central and total eclipse; but if she be at any part of her orbit not exceeding 11° 21' from the node, the eclipse will be partial. In the latter case, the three bodies cannot be in a perfectly straight line; so that the Moon dips more or less of its body into the shadow of the Earth, but not the whole of its body.

Some time before the commencement of an eclipse of the Moon, she is seen to be partially obscured, as if a mist covered the illuminated surface: this arises from the circumstance that she has to go through the Earth's penumbra, or partial shadow, before her immersion in the umbra, or real shadow. In our figure, rays of light from the two extreme edges of the Sun a a', pass by the edges of the Earth bb', (having previously crossed at c,) and go on in the direction b d and b'e: but still the upper part of the penumbra dbf, receives light from the upper part of the Sun, although the Earth prevents it from receiving light from the lower part; and, again, the lower part gb'e of the penumbra receives light from the lower part of the Sun, although the upper rays are also excluded by the Earth. From this circumstance, therefore, the real shadow is surrounded by a partial shadow, which imparts to the Moon the dusky appearance just mentioned, which duskiness becomes more decided as the Moon approaches the real shadow, and receives still fewer rays from the If there be inhabitants in the Moon, they, of

course, see a solar eclipse; and, while they are in the Earth's penumbra, the Sun appears to them partially eclipsed, which solar eclipse increases until the Moon enters into the Earth's umbra; when the Sun appears to the Moon, and the Moon appears to the Earth, totally eclipsed.

By comparing the foregoing circumstances, we find that a solar eclipse can be visible to only a portion of the enlightened hemisphere of the Earth: while a lunar eclipse may be seen by half the globe of the Earth. Moreover a lunar eclipse always begins on the eastern edge of the Moon, because her motion is from west to east; so that her eastern edge first enters into the shadow of the Earth: but, in the case of a solar eclipse, the dark body, of the Moon appears first on the western limb of the Sun, on account of the motion of the Moon from west to east, as mentioned in the former case.

During a total, or large partial eclipse of the Sun, the dark side of the Moon is not wholly invisible. We can, therefore, descry its general outline, owing to the Sun's light being reflected strongly from the surface of the Earth to the Moon; and this reflected light is again reflected from the Moon, and constitutes the faint light on her surface seen during a solar eclipse, and also in a very interesting manner, when the Moon is only two or three days old. The disk of the Earth appearing to the Moon nearly thirteen times as large as the Moon appears to us, the light which the Earth gives the Moon must be very great. Now, when the Moon is two or three days old, the Earth appears as a large gibbous figure of light to the Moon; and so we see not only the sun-lit part of the Moon, but also the rest of its disk, seeming of a dirty white plaister colour. As

the light of the Sun increases upon the disk of the Moon, the Earth's light to the Moon wanes, and we no longer notice this appearance.

In a total eclipse of the Moon this body is still seen, even when enveloped in the shadow of the Earth, by reason that the rays of light from the Sun are bent round the margin of the Earth by the refracting power of its atmosphere, and are thus carried on through space till they arrive at the Moon; from the surface of which they are again reflected. It is further evident that an eclipse of the Sun cannot be identical as to time and appearance, to any two spectators situated at different points on the Earth's surface; because the Sun loses no light, but is only hidden, as it were, by a screen, scarcely, or just big enough to hide it: but an eclipse of the Moon is identical as to time and appearance, because it loses its light, and that too, at a certain precise point of time :—that is to say, we may see the Sun at the time of a solar eclipse, and be ignorant that he is eclipsed; bnt a lunar eclipse is seen by all who see the Moon.

Hence, though the solar eclipses are more numerous than the lunar, the latter are more likely to be observed, being visible to a whole hemisphere. The usual number of eclipses is about four, two of the Sun and two of the Moon; but there cannot be more than seven, nor fewer than two: when there are only two, they will be of the Sun, as is the case this year.

A lunar eclipse cannot last longer than 5 hours, from first entering into the Earth's penumbra to quitting it she cannot be eclipsed partially and totally more than 3 hours and she cannot be totally eclipsed more than 12 hours.

CHAPTER VII.

THE SEASONS. THE CIRCLES OF THE GLOBE. PARALLELISM OF THE EARTH'S AXIS.

SUN IN SUMMER AND WINTER.

ALTITUDES OF THE CONSTELLATIONS. THE

ZODIAC. EQUINOXES, PRECESSION OF. MOTION OF

THE SUN IN THE SIGNS OF THE

ZODIAC. DAY AND

REFRACTION.

NIGHT. SOLSTICES. THE HORIZON.

THE SEASONS.

Wished Spring returns; and from the hazy south,
While dim Aurora slowly moves before,

The welcome Sun, just verging up at first,

By small degrees extends the swelling curve !
Till seen at last for gay rejoicing months,
Still round and round, his spiral course he winds,
And as he nearly dips his flaming orb,

Wheels up again, and re-ascends the sky.

THERE are but few phenomena presented to the notice of man more beautiful, and, at the same time, more instructive to him, than the regular succession of seasons, and the varied benefits which they confer. The cold and bleak temperature of our winter is rendered less rigorous by the artificial processes by which we obtain warmth within our dwellings; but still the genial and refreshing air of spring is looked forward to by all as a delightful change from the dreariness of winter. The pleasing associations connected with spring, when both animal and vegetable life seem to acquire new vigour, and a new lease, as it were, of existence, would not alone suffice for the wants, either natural or artificial, of man. The summer's Sun is required to ripen and bring to perfection