phenomena to those in our immediate neighbourhood. The agitations of the atmosphere, its masses of clouds, and its refractive and reflective properties— the rise and subsidence of the great waters—the alternations of light and darkness—and a diversity of seasons, are universal over the globe. Columbus opened a new world to the knowledge of the old, but in the new as in the old the general laws of nature were the same-the tides flowing and ebbing along the coasts, electricity operating in the atmosphere, the magnetic needle pointing to the pole, day and night, summer and winter interchanging. The general structure and physical properties of its human inhabitants, its plants and animals, are accordant, and their subordinate diversities may in most cases be traced to the action of laws which universally produce the same effects where the circumstances are the same. But leaving the ball upon which we live, and viewing the kindred orbs associated with it in the solar universe, the intimations of uniform plan are equally strong. Let us dwell upon some of the unities of the system. Omitting for obvious reasons the telescopic planets, though in many respects they harmonize with the rest, the following phenomena are prominent:-1. All the planets have a projectile motion in space in the same direction from west to east. 2. They move in nearly the same plane. Taking the plane of the earth's orbit as a horizontal base, the planes of the other orbits exhibit only a slight divergence from it. 3. All the satellites move in the same direction as their primaries, and nearly in the same plane, with the exception of the moons of Uranus. 4. The orbits of the planets and satellites exhibit only slight variations in their amount of eccentricity. 5. These different bodies have a motion of rotation in the same direction with the sun, and their own motions of projection. 6. The planets exhibit traces of atmospheres more or less decided. These are confessedly striking phenomena. They clearly exclude the operation of chance-medley from the system. They are unities which speak intelligibly of One causing and governing Mind, and significantly proclaim the simultaneous origin of the solar universe under the control of common laws. When we consider that the bodies which compose it maintain their present stations, motions, and distances, by their mutual action on each other— that neither could be where it is, nor as it is, unless they were all co-existent the inference is strong, and seems philosophically certain, that they obtained contemporaneously, or nearly so, that arrangement, and those positions in which we now behold them, under the action of the same physical cause. The force of the solar attraction to Mercury is in some degree counteracted by that of Venus and the Earth, and the orbital motions of the former are the result of the nice adjustment of these complicated forces. This fact, true of all the planets, is a strong indication that their formation was simultaneous, and remarkably supports the nebular hypothesis. But if, in relation to the terrestrial world, uniformity characterises the general plan, the detail displays an endless diversity. Its great divisions of land and water, its mountains, plains, and valleys, have each distinguishing peculiarities. Plants of the same genus have no perfect similarity, nor have their stems, flowers, and leaves. The grains of sand and the blades of grass differ. The same fact is true of the human race, and of animals of the same species; and hereby property can be claimed in the latter, friendship recognise its objects of affection, and justice its criminals, in the former. In like manner, all the knowledge we have of the creation exterior to our globe assures us of the stamp of variety being impressed upon it. Thus the planets, alike in dependence upon a cen tral orb, in rotation and orbital motion, differ in their distances, magnitudes, densities, velocities, and construction. Some are more gorgeously fitted up than their companion globes. The day of Mercury nestling near the sun, and that of Uranus so distant from him the moonless night of Mars, and that of Saturn with his rings and satellites - must be widely discordant, while each planet experiences a real day and night. The arrangements of the system do not more strongly declare the one-ness of its authorship, than the boundless resources of that author. The relative distances of the planets from the central source of light and heat exhibit great discrepancies. Taking that of the earth as 1, the proportionate distance of Mercury is, Venuso, Mars 11, Ceres 24, Jupiter 51, Saturn 91, Uranus 19. This diversity of position must produce diverse physical effects; but even to the farthest planet the Sun is still a SUN, and will afford an illumination several hundred times surpassing our largest supply of lunar light. The apparent diameter of the sun, as seen from the earth, is 32'. As seen from the other planets, it will be, The comparative size of the solar orb from these several stations may be thus pictorially expressed : Mercury. Venus. Earth. Mars. Ceres. Jupiter. Saturn. Uranus. While a motion of translation in an orbit and one of axical rotation belong to all the planets, as far as observation has gone, constituting to each respectively its year, and its day and night, the length of these periods widely differs, as the annexed table shows: The planets are spheroids more or less oblate, but their magnitudes vary prodigiously. Taking the earth as 1, the comparative volume of Mercury will be, Venus, Mars, Ceres, Jupiter 1,300, Saturn 900, Uranus 80. Their apparent diameters, as seen from the sun, will be, Their relative bulk may be brought before the eye as they are represented on the next page. To express the proportionate volume of the sun, a circle with nearly a diameter of one foot would be required. The following illustration of the relations of the sun and his attendants is taken from Sir John Herschel and Dr. Nichols. If we conceive the sun to be a globe two feet in diameter, then a grain of mustard seed, at eighty-two feet distance, will represent the size and place of Mercury. A pea, at the distance of one hundred and forty-two feet, will be the similitude of Venus; and another, slightly larger, at two hundred • Mercury. Venus. Earth. Mars. • Ceres. and fifteen feet, will be the appropriate representative of the earth. A good pin's head, removed three hundred and twenty-seven feet from the central globe, will stand for Mars; and a few of the smallest grains of sand, placed at the distance of five hundred feet, will denote the Asteroids. An orange of moderate size, distant a quarter of a mile, will indicate Jupiter. Saturn may be shown by a lesser one, at two-fifths of a mile; and Uranus by a cherry, at three quarters of a mile. There are remarkable differences as to the material of the solar and planetary orbs. Their weight, compared with that of the earth taken as 1, is, Jupiter. Saturn. Uranus. What striking diversities! While our planet, weighed in the balance against an equal volume of water, is four times heavier, the matter of Mercury is four times heavier still, while that of Saturn has only half the density of the fluid. If cast therefore upon an ocean capacious enough to receive them, Mercury would sink with as great a momentum as a globe of lead, while Saturn would be buoyant as a vessel of cork upon the deep. Upon the magnitude and density of the planetary spheroids, the force of gravity or the weight of bodies at their surface depends. Hence, though the solar substance is so much less dense than that of the earth, yet, owing to its vast bulk, a man weighing 140 pounds at the terrestrial equator would weigh more than 3500 at the surface of the sun. Jupiter is still less dense, but on account of his superior magnitude the force of gravity at his surface is eight times as great as at the earth's, so that a terrestrial inhabitant transported thither would be burdened with eight times his present weight, would move with eight times the difficulty, and would fall with eight times the force. But upon the diminutive telescopic planets, owing to their feeble gravity, a race of terrestrials might play such high fantastic tricks as would realise the dreams of fairy legends, bounding across a chasm of no trifling span, with the same muscular effort as here will only enable us to compass a step, and alighting with no greater shock than is felt in one of the paltry leaps of childhood. We may however infer a nice adjustment between the planetary worlds and their respective occupants, from the beautiful adaptation, which meets us here, of the constitution of man, animals, and plants, to the circumstances of their dwelling-place. Supposing that constitution to remain the same, and the earth's volume to be increased to the size of Jupiter; the intensity of the force of gravity would suspend the functions of animal and vegetable existence. The tiger would cease to spring upon his prey from the sheer impossibility of doing it; the swift gazelle would become a laggard upon the plain; the soaring flight of the eagle would terminate; the sap would fall in the trees to rise no more; plants and flowers would be unable to circulate their juices; and man himself would sink down to the level of a slow-moving quadruped like the sloth. There is thus with us an express adaptation of the varieties of living existence to the magnitude and circumstances of our globe; and it is philosophical to accept this fact as a guarantee that a similar adjustment obtains throughout the system with which we are connected. And whence this adjustment? Whence this marvellous proportioning of the power of the humble crocus peeping above the snow, and the magnificent rein-deer bounding across it, to the earth's volume and mass, so that the force of gravity is not too strong in the one case for the development of the flower, nor muscular energy too great in the other for the purposes of the animal? Epicurus, upon reading the well-known lines of Hesiod in his youth "Eldest of beings, Chaos first arose, Thence Earth wide-stretch'd, the steadfast seat of all is said to have proposed the natural question to his preceptor, "And Chaos whence ?" The philosopher originated a theory in his riper years which assigned the creation to a fortuitous concourse of atoms; but how natural the inquiry, overlooked by the theory, "And atoms whence?" A sober understanding will not stop short of recognising a presiding Providence in adapting the economy of terrestrial life to terrestrial conditions; and even so are we warranted, from the evidence of what is near, to look upon the remote, as the scene of similar adaptations, the operation of the same First Cause. In regarding the planetary worlds as the abodes of sentient life and of forms of existence kindred to those which occupy the earth, we are in advance of what is written, or what observation detects, but not beyond what the sobrieties of reason will justify. It may be hard to imagine how life can be sustained under the apparent heat of Mercury, or amid the seeming cold, the tremendous storms, and rapid atmospheric changes of Jupiter. But, ignorant of facts, a parallel difficulty would be a stumbling-block to us, in relation to our own planet, when we consider the high temperature of its equatorial regions and the intense cold of its polar circles. Yet we have great families of men and animals in each extreme. We meet with human life upon the sultry plains of Delhi, and on the ice-bound shores of Greenland; and where the citron, the myrtle, and the palm will not flourish, the pines, the mosses, and the lichens grow. It is impossible to naturalise the elk in England, owing to its warmth; and turn the giraffe adrift, and how long would it survive the chill of the climate? Yet each animal, in circumstances to which it is adapted, is stately and vigor ous. All the planets are plainly of one family as to their physical character, their general configuration, their motions of revolution and rotation, and the alternation of day and night; and these are resemblances which may reasonably lead us to suspect other analogies. The fact is also clear, of Mercury, Venus, Mars, Jupiter, and Saturn being surrounded with atmospheres ;-a constitution which strongly indicates their occupancy with some varieties of organised being. We know, in the case of our own globe, the important uses of its atmosphere in maintaining animal life, transmitting sound and light, and in advancing the arts which tend to civilise society. Without such a gaseous envelope, bound inseparably around the earth, its partner in all its motions,-yet no emanation from it, but a separate element, - the ear would have no office to perform, the tongue would be speechless, and the service of the eye be greatly abridged. The song of birds, the hymns of religion, the eloquence of senates, and the utterance of relative kindness would perish. The fiercest waves would dash in sullen silence upon the strand; and mankind would have no medium of inter-communication beyond that of sign and gesture. We may well believe, therefore, that our world has been furnished with this elastic and essential apparatus, in order to adapt it for the reception of animal existence and intelligent inhabitants; and the inference is just, that a similar arrangement distinguishing other planets, points to the same destination. It is a possible conception, - but we should smile at the credulity of the man who believed it real,- that a fleet of ships navigating the ocean, with sails unfurled and pennons flying, did so without a cargo in the hold, a crew on board, or an object in view. CHAPTER V. COMETS. F all the celestial objects which have arrested the attention of mankind, none have excited such general and lively apprehension as those upon the consideration of which we now enter. Undoubtedly their sudden appearance, rapid movements, and occasionally extraordinary aspect, were calculated to awaken terror in ages of ignorance and superstition, and to originate the wild conjectures that are on record respecting their character and office. The Romans regarded a comet which was seen in the year 44 before our era as a celestial chariot conveying the soul of Cæsar, who had been assassinated a short time before its advent, to the skies. Cometary bodies have been deemed the vehicles in which departed spirits are shipped by their guardian angels for the realms of Paradise; and on the other hand, they have been viewed as the active agents of natural and moral evil upon the surface of the earth, and been formally consigned to ecclesiastics for excommunication and cursing. A volume of no inconsiderable dimensions might be compiled, and not without interest, from the accounts of old chronicles respecting their appearances, registering the quaintly expressed opinions of the chroniclers concerning them, the terrestrial events they have tacked to them as effects to a cause, and the deportment to which men have been moved by the apparition of "the blazing star Threat'ning the world with famine, plague, and war: To princes, death; to kingdoms, many crosses; To all estates, inevitable losses; To herdsmen, rot; to ploughmen, hapless seasons; We have the word comet from the Greek xóun, or hair, a title which had its origin in the hairy appearance often exhibited, a nebulosity, haze, or kind of luminous vapour, being one of the characteristics of these bodies. Their general features are a definite point or nucleus-a nebulous light surrounding the nucleus, the hair, called by the French chevelure-and a luminous train preceding or following the nucleus. Milton refers to one of these attributes in a passage which countenances the popular superstition: Anciently, when the train "Satan stood Unterrified, and like a comet burned, That fires the length of Ophiucus huge, In th' arctic sky, and from its horrid hair, preceded the nucleus, as is the case when a comet has passed its perihelion, and recedes from the sun, it was called the beard, being only termed the tail |