affirms, that he has discovered mountains on the surface of this globe, one of which is 10, another 11, and a third 22 miles high. It appears also to be encompassed with an atmosphere, the densest part of which is about 16,000 feet high. About twice in the course of a century, this planet appears to pass, like a dark spot, across the sun's disk. This is termed the transit of Venus. The last transit happened June 3, 1769; the next will happen on December 8, 1874, which will be invisible in Europe. Another will hap pen on the 6th of December, 1882, which will be partly visible in Great Britain.

The Earth is the next planet in the system. It moves round the sun in 365 days, 5 hours, and 49 minutes, at the distance of 95 millions of miles, and round its axis in 23 hours, 56 minutes, 4 seconds. The former is called its annual, and the latter, its diurnal motion. That the earth is, in reality, a moving body, is a fact which can no longer be called in question; it is indeed susceptible of the clearest demonstration. But my limits will not permit to enter into a detail of the arguments by which it is suppprted. I have already adverted to one consideration, from which its diurnal rotation may be inferred. (See p. 23.) Either the earth moves round its axis every day, or the whole universe moves round it in the same time. To suppose the latter case to be the fact, would involve a reflection on the wisdom of its almighty Author, and would form the only exception that we know to that beautiful proportion, harmony, and simplicity, which appear in all the works of nature. Were it possible to construct a machine as large as the city of London, and to apply to it mechanical powers sufficient to make it revolve on an axis, so as to carry round a furnace for the purpose of roasting a joint of mutton, suspended in the centre of its motion-while we might admire the ingenuity and the energies displayed in its constructionall mankind would unite in condemning it as a display of consummate folly. But such an extravagant piece of machinery would not be half so

20 degrees, in 24 hours, 34 minutes, determined the time of its rotation to be 23 hours and 20 minutes.

On the other hand, Bianchini, from similar observa tions, concluded, that its diurnal period was 24 dan

and 8 hours. The difficulty of deciding between these two opinions, arises from the short time in which observations can be made on this planet, either before sun rise or after sun-set, which prevents us from tracing, with accuracy, the progressive motion of its spots for a sufficient length of time. And although an observer should mark the position of the spots, at the same hour, on two succeeding evenings, and find they had moved forward about 20 degrees in 24 hours, he would still be at a loss to determine, wither they had moved 20 degrees in all, since the prece ng observation, or had finished a revolution, and 20 de ees more.-In "Nicholson's Philosophical Journal, vol 36. I endeavoured to show how this point may be determined by observations on Venus in the day-time, by which, in certain cases, the progressive motion of her spots might be traced, without Interruption, for 12 hours or more, which would completely settle the period of rotation.

38

preposterous as to suppose, that the vast universe is daily revolving around our little globe, and that all the planetary motions have an immediate respect to it. And shall we dare to ascribe to him who is "the only wise God," contrivances which we would pronounce to be the perfection of folly in mankind? It is recorded of the astro nomer Alphonsus, king of Castile, who lived in the 13th century, that, after having studied the Ptolemaic system, which supposes the earth at rest in the centre of the universe, he uttered the following impious sentence: "If I had been of God's privy council, when he made the world, I would have advised him better." So that false conceptions of the system of nature, lead to erroneous notions of that adorable Being who is possessed of infinite perfection. We find that bodies much larger than the earth have a similar rotation. The planet Jupiter, a globe 295,000 miles in circumference, moves round his axis in less than ten hours; and all the other planetary bodies, on which spots have been discovered, are found to have a diurnal motion. Besides, it is found to be a universal law of nature that smaller globes revolve round larger; but there is no example in the universe, of a larger body revolving around a smaller. The moon revolves around the earth, but she is much smaller than the earth; the moons which move around Jupiter, Saturn, and Herschel, are all less than their primaries, and the planets which perform their revolutions around the sun are much less than that central luminary.

With regard to the annual revolution of the earth, if such a motion did exist, the planetary system would present a scene of inextricable confusion. The planets would sometimes move backwards, sometimes forwards, and at other times remain stationary; and would describe looped curves, so anomalous and confused, that no man in his senses could view the all-wise Creator as the author of so much confusion. But, by considering the earth as revolving in an orbit between Venus and Mars, (which all celestial observations completely demonstrate,) all the apparent irregularities of the planetary motions are completely solved and accounted for; and the solar system presents a scene of beauty, harmony and grandeur, combined with a simplicity of design which characterizes all the works of Omnipotence.

The Moon.-Next to the sun, the moon is to us the most interesting of all the celestial orbs. She is the constant attendant of the earth, and revolves around it in 27 days, 8 hours; but the period from one new or full moon to another is about 29 days, 12 hours. She is the nearest of all the heavenly bodies; being only about two hundred and forty thousand miles distant from the earth. She is much smaller than the carth; being only 2,180 miles in diameter. Her surface, when viewed with a telescope, presents an inte

resting and a variegated aspect; being diversified with mountains, valleys, rocks, and plains, in every variety of form and position. Some of these mountains form long and elevated ridges, resembling the chains of the Alps and the Andes; while others, of a conical form, rise to a great height, from the middle of level plains, somewhat resembling the Peak of Teneriffe. But the most singular feature of the moon, is, those circular ridges and cavities which diversify every portion of her surface. A range of mountains of a circular form, rising three or four miles above the level of the adjacent districts, surrounds, like a mighty rampart, an extensive plain; and, in the middle of this plain or cavity, an insulated Iconical hill rises to a considerable elevation. Several hundreds of these circular plains, most of which are considerably below the level of the surrounding country, may be perceived, with a good telescope, on every region of the lunar surface. They are of all dimensions, from two or three miles to forty miles in diameter; and, if they be adorned with verdure, they must present to the view of a spectator, placed among them, a more variegated, romantic, and sublime scenery than is to be found on the surface of our globe. An idea of some of these scenes may be acquired by conceiving a plain of about a hundred miles in circumference, encircled with a range of mountains, of various forms, three miles in perpendicular height, and having a mountain near the centre, whose top reaches a mile and a half above the level of the plain. From the top of this central mountain, the whole plain, with all its variety of objects, would be distinctly visible; and the view would appear to be bounded on all sides by a lofty amphitheatre of mountains, in every diversity of shape, rearing their summits to the sky. From the summit of the circular ridge, the conical hill in the centre, the opposite circular range, the plain below, and some of the adjacent plains, which encompass the exterior ridge of the mountains, would form another variety of view; and a third variety would be obtained from the various aspects of the central mountain, and the surrounding scenery, as viewed from the plains below.

The lunar mountains are of all sizes, from a furlong to five miles in perpendicular elevation. Certain luminous spots, which have been occasionally seen on the dark side of the moon, seem to demonstrate that fire exists in this planet. Dr. Herschel and several other astronomers suppose, that they are volcanoes in a state of eruption. It would be a more pleasing idea, and perhaps as nearly corresponding to fact, to suppose, that these phenomena are owing to some occasional splendid illuminations, produced by the lunar inhabitants, during their long nights. Such a scene as the burning of Moscow, the conflagration of an extensive forest, or the splendid illumination of a large city with gas-lights, might present simi

lar appearances to a spectator in the moon. The bright spots of the moon are the mountainous regions; the dark spots are the plains, or more level parts of her surface. There may probably be rivers or small lakes on this planet; but there are no seas or large collection of water. It appears highly probable, from the observations of Schroeter, that the moon is encompassed with an atmosphere; but no clouds, rain, nor snow seem to exist in it. The illuminating power o the light derived from the moon, according to the experiments made by Professor Leslie, is about the one hundred and fifty thousandth part of the illuminating power of the sun. According to the experiments of M. Boguer, it is only as 1 to S00,000.

The Moon always presents the same face to us; which proves, that she revolves round her axis in the same time that she revolves round the earth. As this orb derives its light from the sun, and reflects a portion of it upon the earth, so the earth performs the same office to the moon. A spectator on the lunar surface would behold the earth, like a luminous orb, suspended in the vault of heaven, presenting a surface about 13 times larger than the moon does to us, and appearing sometimes gibbous, sometimes horned, and at other times with a round full face. The light which the earth reflects upon the dark side of the moon may be distinctly perceived by a common telescope, from three to six or eight days after the change. The lunar surface contains about 15 millions of square miles, and is, therefore, capable of containing a population equal to that of our globe, allowing only about 53 inhabitants to every square mile. That this planet is inhabited by sensitive and intelligent beings, there is every reason to conclude, from a consideration of the sublime scenery with which its surface is adorned, and of the general beneficence of the Creator, who appears to have left no large portion of his material creation without animated existences; and it is highly probable, that direct proofs of the moon's being inhabited may hereafter be obtained, when all the varieties on her surface shall have been more minutely explored.*

The planet Mars.-Next to the earth and moon, the planet Mars performs his revolution round the sun, in one year and ten months, to the distance of 145 millions of miles. His diameter is about 4,200 miles, and he is distinguished from all the other planets, by his ruddy appearance, which is owing to a dense atmos phere with which he is environed. With a good telescope, his surface appears diversified by a variety of spots; by the motion of which it is found, that he turns round his axis in 24 hours and 40 minutes. The inclination of his axis to the plane of his orbit being about 28° 42′, the

•See Appendix, No. III.

days and nights, and the different seasons in this planet, will bear a considerable resemblance to those we experience in our terrestrial sphere.* At his nearest approach to the earth, his distance from us is about 50 millions of miles; and, at his greatest distance, he is about 240 millions of miles; so that in the former case he appears nearly 25 times larger than in the latter. To a spectator in this planet, our earth will appear, alternately, as a morning and evening star, and will exhibit all the phases of the moon, just as Venus does to us, but with a less degree of apparent magnitude and splendour. A luminous zone has been observed about the poles of Mars, which is subject to successive changes. Dr. Herschel supposes that it is produced by the reflection of the sun's light from his frozen regions, and that the melting of these masses of polar ice is the cause of the variation in its magnitude and appearance. This planet moves, in its orbit, at the rate of fifty-five thousand miles an hour.

The new planets.-Between the orbits of Mars and Jupiter, four planetary bodies have been lately discovered, accompanied with circumstances somewhat different from those of the other bodies which compose our system. They are named Ceres, Pallas, Juno, and Vesta. The planet Ceres was discovered at Palermo, in Sicily, by M. Piazzi, on the first day of the present century. It is of a ruddy colour, and appears abour the size of a star of the 8th magnitude, and is consequently invisible to the naked eye. It performs its revolution in 4 years and 7 months, at the distance of 260 millions of miles from the sun, and is reckoned, by some astronomers, to be about 1624 miles in diameter, or about half the diameter of Mercury. It appears to be surrounded with a large dense atmosphere. -Pallas was discovered the following year, namely, on the 28th of March, 1802, by Dr. Olbers of Bremen. It is supposed to be about 2000 miles in diameter, or nearly the size of the moon. It revolves about the sun in 4 years and 7 months, or nearly in the same time as Ceres, at the distance of 266 millions of miles; and is surrounded with a nebulosity or atmosphere, above 400 miles in height, similar to that of Ceres.-The planet Juno was discovered on the 1st September, 1804, by Mr. Harding of Bremen. Its mean distance from the sun is about 253 millions of miles; its revolution is completed in 4 years and 130 days, and its diameter is computed to be about 1425 miles. It is free from the nebulosity which surrounds Pallas, and is distinguished from all the other planets by the

The inclination of the earth's axis to the ecliptic, or, in other words, to the plane of its annual orbit, is 23 degrees and 25 minutes, which is the cause of the diversity of seasons, and of the different length of days and nights. Were the axis of the earth per pendicular to its orbit, as is the case with the pla he Jupiter, there would be no diversity of seasons,

great eccentricity of its orbit; being, at its east distance from the sun, only 189 millions of miles. and at its greatest distance 316 millions.-Vesta was discovered by Dr. Olbers on the 29th March, 1807. It appears like a star of the 5th or 6th magnitude, and may sometimes be distinguished by the naked eye. Its light is more intense and white than any of the other three, and it is not surrounded with any nebulosity. It is distant from the sun about 225 millions of miles, and completes its revolution in 3 years and 240 days. Its diameter has not yet been accurately ascertained; but from the intensity of its light, and other circumstances, it is concluded, that it exceeds in magnitude both Pallas and Juno.

These planetary globes present to our view a variety of anomalies and singularities, which appear incompatible with the regularity, proportion, and harmony which were formerly supposed to characterize the arrangements of the solar system. They are bodies much smaller in size than the other planets-they revolve nearly at the same distances from the sun, and perform their revolutions in nearly the same periodstheir orbits are much more eccentric, and have a much greater degree of inclination to the ecliptic, than those of the old planets-and, what is altogether singular, (except in case of comets,) their orbits cross each other; so that there is a possibility that two of these bodies might happen to interfere, and to strike each other, in the course of their revolutions. The orbit of Ceres crosses the orbit of Pallas. Vesta may sometimes be at a greater distance from the sun than either Ceres, Pallas or Juno, although its mean distance is less than that of either of them, by several millions of miles; so that the orbit of Vesta crosses the orbits of all the other three. From these and other circumstances, it has, with a high degree of probability, been concluded-that these four planets are the fragments of a large celestial body which once revolved between Mars and Jupiter, and which had been burst asunder by some immense irruptive force. This idea seems to have occurred to Dr. Olbers after he had discovered the planet Pallas, and he imagined that other fragments might possibly exist. He concluded, that, if they all diverged from the same point, "they ought to have two common points of reunion, or two nodes in opposite regions of the heavens, through which all the planetary frag ments must sooner or later pass." One of these nodes he found to be in the constellation Virgo, and the other in the Whale; and it is a remarkable coincidence, that it was in the latter of these regions that the planet Juno was discovered by Mr. Harding. In order to detect the remaining fragments (if any existed) Dr. Olbers examined, three times every year, all the small stars in Virgo and the Whale; and it was actually in the consellation Virgo, that he dis covered the planet Vesta. It is not unlikely

that other fragments of a similar description may be discovered. Dr. Brewster attributes the fall of meteoric stones* to the smaller fragments of these bodies happening to come within the sphere of the earth's attraction. His ingenious reaBonings on this subject, and in support of Dr. Olbers' hypothesis above stated, may be seen in Edin. Ency. vol. ii. p. 641, and in his "Supplementary chapters to Ferguson's Astronomy."

The facts to which I have now adverted seem to unfold a new scene in the history of the dispensations of the Almighty, and to warrant the conclusion, that the earth is not the only globe in the universe which is subject to physical changes and moral revolutions.

The Planet Jupiter.-This planet is 490 millions of miles distant from the sun, and performs its annual revolution in nearly twelve of our years, moving at the rate of twenty-nine thousand miles an hour. It is the largest planet in the solar system; being 89,000 miles in diameter, or about fourteen hundred times larger than the earth. Its motion round its axis is performed in nine hours and fifty-six minutes; and, therefore, the portions of its surface about the equator move at the rate of 28,000 miles an hour, which is nearly twenty-seven times swifter than the earth's diurnal rotation. The figure of Jupiter is that of an oblate spheroid, the axis, or diameter passing through the poles, being about 6000 miles shorter than that passing through the equator. The Earth, Saturn, and Mars are also spheroids; and it is highly probable that Mercury, Venus, and Herschel are of a similar figure, though the fact has not yet been ascertained by actual observation. When viewed with a telescope, several spots have been occasionally discovered on the surface of this planet, by the motion of which, its rotation was determined.

But what chiefly distinguishes the surface of Jupiter is several streaky appearances, or dusky strips, which extend across his disk, in lines parallel to his equator. These are generally

• Meteoric stones, or, what are generally termed aerolites, are stones which sometimes fall from the upper regions of the atmosphere, upon the earth.The substance of which they are composed is, for the most part, metallic; but the ore of which they consist is not to be found in the same constituent proportions in any terrestrial substances. Their fall is generally preceded by a luminous appearance, a hissing noise, and a loud explosion; and, when found immediately after their descent, are always hot.Their size differs, from small fragments, of inconsi derable weight, to the most ponderous masses. Some of the largest portions of these stones have been found to weigh from 300 lbs. to several tons; and

they have often descended to the earth with a force

sufficient to bury them many feet under the soil.Some have supposed that these bodies are projected from volcanoes in the moon; others, that they proceed from volcanoes on the earth; while others imagine that they are generated in the regions of the atmosphere; but the true cause is, probably, not yet ascertained. In some instances, these stones have penetrated through the roofs of houses, and proved destructive to the inhabitants.

termed his belts. Three of these belts, or zones nearly equi-distant from each other, are most frequently observed; but they are not regular or constant in their appearance. Sometimes (aly one is to be seen, sometimes five, and sometimes seven or eight have been distinctly visible; and. in the latter case, two of them have been known to disappear during the time of observation. On the 28th May, 1780, Dr. Herschel perceived "the whole surface of Jupiter covered with small curved belts, or rather lines, that were not con❤ tinuous across his disk." Though these belts are generally parallel to each other, yet they are not always so. Their breadth is likewise variable; one belt having been observed to grow narrow, while another in its neighbourhood has increased in breadth, as if the one had flowed into the other. The time of their continuance is also uncertain; sometimes they remain unchanged for several months, at other times, new belts have been formed in an hour or two. What these belts or variable appearances are it is difficult to determine. Some have regarded them as strata of clouds floating in the atmosphere of Jupiter; while others imagine, that they are the marks of great physical revolutions which are perpetually changing the surface of that planet. The former opinion appears the most probable. But, whatever be the nature of these belts, the sudden changes to which they are occasionally subject, seem to indicate the rapid operation of some powerful physical agency; for some of them are more than five thousand miles in breadth; and since they have been known to disappear in the space of an hour or two, and even during the time of a casual observation-agents more powerful than any with which we are acquainted must have produced so extensive an effect.

Jupiter is attended by four satellites or moons, which present a very beautiful appearance when viewed through a telescope. The first moon, or that nearest the planet, is 230,000 miles distant from its centre, and goes round it in 42 hours; and will appear from its surface four times larger than our moon does to us. The second moon, being farther distant, will appear about the size of ours; the third, somewhat less; and the fourth, which is a million of miles distant from Jupiter, and takes sixteen days to go round him, will appear only about one-third the diame ter of our moon. These moons suffer frequent eclipses from passing through Jupiter's shadow, in the same way as our moon is eclipsed by passing through the shadow of the earth. By

↑ A representation of these belts, in the positions in which they most frequently appear, is exhibit ed in the engraving, Fig. 2. Fig. 1. represents the double ring of Saturn, as it appears when viewed through a powerful telescope-Figures 1, 2, 3, 4, and 5, represent Saturn, Jupiter, Herschel, the Earth and Moon, in their relative sizes and pro portions.