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of Mirk Monday. The darkness which attends full solar eclipses appears to vary, owing chiefly to a difference in the condition of the atmosphere, and the time of the day. Though strongly marked on all occasions, it is more peculiar than profound; and altogether confined to the brief period of totality. So long as the smallest portion of the lustrous

orb is visible, there is considerable light. Nature simply looks sobered and saddened till the moment of entire obscuration arrives. Then, besides the sensible diminution of light, a strange, spectre-like aspect is stamped upon the appearance of every object-sky, clouds, trees, buildings, mountains, streams, animals, and man-producing an effect which is unexpected, sublime, and even appalling. Equally startling and remarkable is the change upon the first re-appearance of the solar ray. It rushes out suddenly, and with brilliant effect from the limb of the overshadowed orb, and in an instant the day is restored to nature. An interesting anecdote appeared in the journal of the Lower Alps respecting the eclipse of July 8, 1842. "A poor child of the commune of Sièyes was watching her flock when it commenced. Entirely ignorant of the event which was approaching, she saw with anxiety the sun darken by degrees, for there was no cloud or vapour visible which might account for the phenomenon. When the light disappeared at once, she began to weep; and in the height of her terror, called out for help. Her tears were still flowing when the sun sent forth his first ray. Reassured by the aspect, the child crossed her hands, exclaiming, in the patois of the province, “O beou souleou!" "O beautiful sun!"

The eclipse just referred to excited extraordinary interest, as the lunar shadow travelled over a part of Europe studded with crowded cities, the north of Italy, and the southern provinces of France, Germany, and Russia. It was well observed at various stations by the leading astronomers of the age. M. Arago awaited its occurrence at Perpignan ; M. Valz at Marseilles; M. Petit at Montpelier; M. Carlini at Milan; MM. Santini and Conti at Padua; MM. Schumacher and Littrow at Vienna; MM. Otto Struve and Schidlowsky at Lipesk; while of our own countrymen, Mr Baily was posted at Pavia, and Mr Airy at the Superga near Turin. The sun was totally hidden 2 m. and 11 s. at Perpignan; and 3 m. 5 s. at Lipesk. The planet Mars, with Aldebaran, Capella, two stars of the constellation Gemini, and others, shone out. At Venice, the citizens remarked, with reference to a steamer on the Lagunes, that the column of smoke from the funnel ccased to be visible, while the sparks of fire which accompanied it were very distinct and striking. The obscurity had a wan and livid hue-a shade of grayish olive-which seemed to throw over nature an air of appalling sickliness, and imparted to the human countenance an aspect painful to contemplate. The heavens appeared of a grayish violet; horses and other animals employed in the fields halted at once, and obstinately refused to move; but, on the other hand, the fact was well ascertained, that horses in the diligences jogged on without seeming to be at all affected by the phenomenon. At Montpelier, the bats, thinking that night was come, left their retreats; an owl was seen to leave the church tower of St Peter, and fly over part of the town; the swallows disappeared; the fowls went to roost; a herd of cattle, feeding in a field, formed themselves into a circle, with their heads directed outwards, as if to resist an attack; and several plants, which usually shut up their leaves at night, were observed to close. A heavy dew fell at Perpignan, Turin, and Vienna, during the total obscuration; and the red stars Aldebaran and a Orionis appeared quite white. The fidelity with which this eclipse answered to previous calculations respecting the time of its occurrence, made a powerful impression upon the popular mind, with reference to the advanced state of science, and the regularity which marks the great clock-work of the universe. At Milan and Pavia the populace gave vent to their feelings in a general Huzzah! vivent les astronomes!

When totally obscured by the body of the moon, the place of the sun is made apparent by the brightness of that part of the heavens in which it is situated. This brightness appears

in the form of a corona, or luminous ring, encircling the moon and exhibiting a radiating

aspect. The most probable conclusion, founded upon its round shape, nebulous structure, and gradually diminishing density outwards, is, that the ring is due to the presence of an extensive atmosphere which encompasses the solar orb. Other striking features of total eclipses are ruddy spots, or protuberances, varying in colour from light pink to deep crimson, which appear upon the margin of the dark lunar disk. They have been compared by different observers to beautiful sheaves of flame, and to the snowy peaks of the Alps, rosecoloured by the morning or evening

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sun. These appearances are supposed to arise from clouds suspended in the atmosphere of the sun, which absorb nearly all the rays of the spectrum, except the red, as in the case of the terrestrial clouds when illuminated after sunset. It has been often remarked, that when the margin of the moon comes into contact with that of the sun, the appearance presented is that of a broken glimmer of light, which the late Mr Baily compared to a link of bright beads. The curious spectacle of "Baily's beads," as they are called, seems to be caused by the rough mountainous edges of the moon, which touch the margin of the sun, while transiently the sunlight gleams through the chinks or valleys between them.

A delicately luminous cone is sometimes seen accompanying the sun, extending from the horizon obliquely upwards in the direction of the zodiac, and, therefore, called the Zodiacal Light. It appears before sunrise and after sunset, but is never seen by us so well defined as in the equatorial regions, though it may frequently be discerned after the evening

Zodiacal Light.

twilight in March and April,
and before the morning twilight
in September and October.
The light resembles in appearance
the tail of a comet. The faintest
stars shine through it. Its colour
varies according to the state of
the atmosphere, but it is generally
of a pure rose tint. The bright-
ness also varies, and some years
it has never been seen at all.
Keppler appears to have been the
first who noticed this phenome-
non. Afterwards Cassini observed
it, and when Humboldt was tra-
velling in South America, he had
several distinct views of it at Ca-
raccas.
Its extent from the sun,
situated at its base to the vertex,

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varies from 45' to 50', and its breadth at the base from 20' to 30'. It has been conjectured that

it derives its form,-that of a long and narrow ellipsis, only the half of which we see, -from its rapid revolution with the sun on its axis; but the nature of the phenomenon itself is one of those points respecting which we are compelled to confess our ignorance.

The decline of the sun to the horizon is as imposing a spectacle as his advance to it, when the atmosphere favours the exhibition of the descent. The most gorgeous sunsets are those of the West Indies, during the rainy season. The sky is then sublimely mantled with gigantic masses of clouds, which are tinged with the glare of the descending luminary, and which seem to be impatiently waiting for his departure in order to discharge their pent-up wrath on the bosom of the night. In the South Atlantic the sunset has a milder and more sober aspect. In the Eastern tropics it has generally an overpowering fierceness, as though the last expression of the solar heat should be the greatest. But during the summer, in temperate latitudes, there is often a serenely beautiful horizon, a mellowness of light, together with a rich and varied colouring of the sky, which combine to render the European sunsets far more attractive than those which are intertropical. The milder radiance of the "great light" in parting from us presents a picture to the eye of the sentiment of the All-Merciful, "Again, a little while and ye shall see me.' And how open to observation are wise Contrivance and bountiful Design in the unvarying position of the sun in the centre of the system, and the axical rotation of his tributaries, which not only guarantee the regular return of their surfaces to his presence, but the undiminished power and splendour of his beams! If, instead of an instant creation, we suppose the masses of the sun and of the planets to have been gradually formed, under control of the law of attraction, the question still arises, how it came to pass, that the self-luminous matter was collected into one mass at the centre, and not gathered into many masses like the matter of the planets. So striking did this circumstance appear to Newton, that he remarked in his first letter to Bentley: "I do not think it explicable by mere natural causes, but am forced to ascribe it to the counsel and contrivance of a Voluntary Agent."

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To a superficial observer of the heavens at night when the moon is absent, only one class of objects will be apparent-the stars. But a little attentive observation will discover other bodies, which, besides taking part in the apparent revolution of the celestial concave, will be found to have independent movements. They seem stationary at intervals, then in motion from west to east, and going back again from east to west, their positions conThese stantly changing in regard to the earth, to each other, and to the host of stars. peculiarities were marked in very early times, and in allusion to them the Greeks applied to such bodies the term planet, which signifies to wander. Their course, capricious and uncertain to the ancient eye, is now discerned to be a direct and regular highway; and hence, if as yet they had received no general title, we should find one for them, expressing the prosecution of orderly rather than erratic travel. The planets are divided into primary and secondary. The former revolve round the common centre of gravity in the system; the latter officiate as satellites to the primaries in their great pilgrimage, and combine with it a revolution round them. The planets are also divided into inferior and superior, referring to their positions being within or without the path of the earth. The expressions are somewhat unfortunate, for the immediate idea conveyed by them refers to

magnitude rather than to situation, and in that sense is erroneous. Venus, an inferior planet, is far larger than Mars, one of the superior, and more resplendent than any of the rest. The words interior and exterior will exactly express what is intended, prevent confusion, and had better be adopted. The planets are denoted in astronomical writings by their respective symbols, as ğ Mercury, Venus, the Earth, & Mars, 4 Jupiter, h Saturn, Uranus, and Neptune.

D

The paths of the planets are elliptical, as previously described; but the ellipses vary to some extent in their eccentricity, or as to the distance of the sun at s, from the centre of the oval, which here represents a planetary orbit. This distance in the case of Mercury is about seven millions of miles; in that of Venus it is less than half a million; in that of the Earth it is somewhat more than a million and a half; in that of Mars it is upwards of thirteen millions; while in that of Juno and Pallas it is sixty-four millions and a half. The orbits of the planets are more or less inclined to each other, instead of lying in the same plane. It may be desirable here to explain the meaning of this oft-recurring phrase. Referring to the earth, an imaginary smooth and thin surface, cutting through the centre of the sun, and reaching out to the fixed stars, is the plane in

which the earth moves in revolution round the sun. This is represented by the shaded part of the diagram. The stars to which it extends form the constellations of the zodiac, the circle A, B, C, D, being the ecliptic, which shows the sun's place in the heavens as seen from the earth, or the carth's as seen from the sun. The orbits of the other planets are in different degrees inclined to this plane, one half being below and the other half above it. If we suppose the shaded part of the diagram to be the surface of a basin of water, a ring held inclined so as to dip into it half way, will describe the relation between the plane of the earth's orbit and that of another planet. The mean velocity of the planets

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in their orbits exhibits great diversity, those which are nearer to the sun being far more rapid than those which are remote. Saturn prosecutes his circuit at the sober pace of little more than twenty thousand miles an hour, while Mercury rushes on at a rate which is more than five times that speed. The extraordinary swiftness of the interior planets is obviously necessary to counterbalance the powerful attraction of the solar mass, which acts with diminished force upon the bodies that are more distant from him.

MERCURY, the nearest planet to the sun, is the smallest primary in the system, with the exception of the asteroids. It is the fastest traveller also, having a velocity in space which is nearly twice the rate of the earth's orbital motion. It is the densest celestial body with which we are acquainted, supposed to be fourteen times that of water. A globe of lead therefore of the same volume, if weighed in the balances against its mass, would be found wanting. Yet notwithstanding this remarkable density, if loosened from the centrifugal force, it would require more than a fortnight for the planet to accomplish its dash headlong to the sun. The days and nights are about the same length as our own; but a whole cycle of seasons has been four times gone through, before the earth's

spring, summer, autumn, and winter have once revolved. Owing to comparatively near neighbourhood, the sun will occupy seven times more space in the Mercurian heavens than in ours, and afford a light and heat which would be intolerable to our organs without some modifying circumstances. We may, however, dismiss the idea of water always boiling at the surface, and an ever-burning heat seven times greater than the fiercest experienced at our equator, distinguishing its material. The sensible heat at the different planets may depend chiefly upon their substance being more or less adapted to combine with the solar influence; there is nothing improbable, therefore, in the supposition that the nearest may be as cool, and the remotest as warm, as the temperate zones of the earth. Besides, it is a proud presumption to imagine the organism of the terrestrials to be the standard and model of finite beings. We are bound to admit that the great Author of existence can as duly attemper to every dwelling-place the physical constitution of its inhabitants, as obtains with reference to our globe and its population.

Mercury is at the mean distance of thirty-seven millions of miles from the sun, and performs an orbital revolution in about 88 days, travelling at the rate of more than a hundred thousand miles an hour. This speed originated the name-that of the swiftwinged messenger of the gods. The planet. tates upon its axis in rather more than twenty-four hours, and has a diameter of 2950 miles. Its volume must therefore be increased upwards of twenty millions of times in order to equal the sun in magnitude; but the mass, if increased only two millions of times with matter of the same density, would be equal in weight. Mercury is an evening star when eastward of the sun, and a morning star when westward of him, but is quite invisible to the naked eye, owing to the vicinity of the solar splendour, except at or near the time of the greatest elongations. The telescope discovers phases like the moon, and atmospheric indications. Some have even professed to discern irregularities of outline, supposed to express superficial elevations; but of this we have no certainty. Not the least departure from the circular form in the shape of the planet was detected till the transit of November 1848, when micrometrical measurements, executed by the Rev. Mr Dawes, showed it to be slightly spheroidal.

Astronomers have been sorely plagued in their observation of Mercury-a giddy planet. -imperceptible generally, through a close attendance upon the sun-never at such a distance from him as to appear in a dark part of the heavens-and going at a rate through space, which is a perfect gallop when compared with the sober jog-trot of the earth. These circumstances, together with the smallness of the planet's mass, and a

a

peculiar quick scintillation, render it a very difficult object to examine. Copernicus is said. never to have seen Mercury through his whole life, and Delambre was only able to discern him twice with the naked eye. The description of one of the old writers. "squirting lacquey of the sun, who seldom shows his head in these parts, as if he were in debt"-however odd, is yet characteristic. The planet may be caught for a short time before sunrise in autumn, and after sunset in spring; and appears to shine with a brilliant white light, being alternately a crescent, a semicircle, and gibbous. When between us and the sun, and at the same time in the plane of the earth's orbit, Mercury transits the solar disk, and is seen as a small black speck

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