age far inferior to that which the manifestation of his attri butes demands.

God is known only by the manifestations which he makes of his character and perfections. The highest created intelligences can know nothing more of the Divinity than what is derived from the boundless universe he has presented to their view, the dispensations of his providence to certain orders of beings, and the special revelations he may occasionally vouchsafe, on certain emergencies, to particular worlds. Had man continued in primeval innocence, the contemplation of the vast creation around him, with all its diversified wonders and beneficent tendencies, would have led him to form correct views of the attributes of his Almighty Maker, and of the moral laws by which his conduct should be regulated; but it does not follow that, because the study of nature is now of itself an insufficient guide to the knowledge of the Creator and the enjoyment of eternal felicity, such studies are either to be thrown aside, or considered as of no importance in a religious point of view. To overlook the astonishing scene of the universe, or to view it with indifference, is virtually to "disregard the works of Jehovah, and to refuse to consider the operations of his hands." It is a violation of Christian duty, and implies a reflection on the character of the Deity for any one to imagine that he has nothing to do with God considered as manifes ed in the immensity of his works; for his word is pointed and explicit in directing the mind to such contemplations. "Hearken unto this; stand still, and consider the wonderful works of God." "Lift up thine eyes on high, and behold who hath created these orbs." "Remember that thou magnify his works which men behold." "Great and marvellous are thy works, Lord God Almighty! Thy saints shall speak of the glory of thy kingdom, and talk of thy power, to make known to the sons of men thy mighty operations and the glorious majesty of thy kingdom.”

3. The Christian revelation, throughout all its departments, is not only consistent with the views we have taken of the universe, but affords direct evidence of the magnificence of creation, and of the myriads of beings with which it is peopled. Of this position we have exhibited some proofs in the remarks and illustrations contained in Chapter XVII., which show, at the same time, the harmony which subsists between the discoveries of revelation and the discoveries which have been

made in the system of nature. There is no other system of religion or pretended revelation that was ever propagated in the world to which such a characteristic belongs. If we examine the Mohammedan Koran, the Shasters of Bramah, the system of Confucius, the mythology of the Greeks and Romans, and every other pagan code of religion, we shall find interspersed throughout the whole of them numerous sentiments, opinions, and pretended facts at utter variance with the true system of nature, and to what are known to be the established laws of the universe. This is strikingly exemplified in the extravagant stories and descriptions contained in the pretended revelations of Mohammed, and the absurd notions respecting the creation contained in the sacred books of the Hindoos, which assert that the universe consists of seven heavens and seven worlds, which are all at a future period to be absorbed into God, with many other absurdities. In opposition to all such foolish and absurd opinions, the inspired writings, when properly understood, and rationally interpreted according to the rules of just criticism, are uniformly found to be perfectly consistent with the discoveries of science, and the facts which are found to exist in the system of the universe; and this correspondence and harmony ought to be considered as a strong presumptive evidence that the revelations of Scripture and the scenes of the material universe proceed from the same All-wise and Omnipotent Author.

CHAPTER XX.

ON COMETS.

As this class of the celestial bodies forms a part of the solar system, it might have been more appropriate to have introduced the subject into our volume entitled "Celestial Scenery," which has for its principal object a description of the bodies connected with that system; but as that work swelled to a greater size than was at first foreseen, it was judged expedient to postpone the consideration of comets to the present volume. As our knowledge of these bodies, however, is very

limited, and no discoveries have yet been made which might lead us to form a decisive opinion of their nature and destination, I shall content myself with giving a brief detail of some of the leading facts which have been ascertained respecting them.

The word comet literally signifies a hairy star; because such bodies are generally accompanied with a nebulosity or train, which has the appearance of luminous hair. The luminous point near the centre of a comet, which is most brilliant, is called the nucleus. The haze or nebulosity which surrounds the nucleus is called the hair, and sometimes the envelope; and the nucleus and hair combined constitute what is usually termed the head of the comet. The luminous train, extending sometimes to a great distance from the head, is called the tail of the comet. These bodies have occasionally appeared in the heavens in all ages. The ancients were divided in their opinions respecting them; some considering them as wandering stars, others as meteors kindled in the atmosphere of the earth, subsisting for a time, and then dissipated; and others viewed them as prodigies indicating wars, famines, inundations, or pestilences. Aristotle, who believed that the heavens were incorruptible and unchangeable, maintained that comets were generated when they first made their appearance, and were destroyed when they ceased to be visible, and, consequently, that they could not be reckoned to belong to the heavenly bodies, but were only meteors or exhalations raised into the upper regions of the air, where they blazed for a while, and disappeared when the matter of which they were formed was consumed. And as the opinions of this ancient sage had a powerful influence on the philosophers and astronomers of later times, as his assertions were frequently regarded as little short of demonstrations, few persons had the boldness and independence of mind to call in question the positions he maintained on any subject discussed in his writings.

It was not before the time of the celebrated astronomer Tycho Brahe that the nature of comets began to be a little understood, and that they were considered as moving in the planetary regions. This astronomer observed with great diligence the famous comet which appeared in 1577; and, from many accurate observations during the time of its appearance, found that it had no sensible diurnal parallax, and therefore

was not only far above the limits of our atmosphere, but beyond the orbit of the moon itself. Its motions were likewise particularly observed by Hagecius, at Prague, in Bohemia, at the same time that they were observed by Tycho, at Uraniburg. These two places differ six degrees in latitude, and are nearly under the same meridian, and both measured the distance of the comet from the same star, which was in the same vertical circle with the comet; yet both observers found their distances the same, and, consequently, they both viewed the comet in the same point of the heavens, which could not have happened unless the comet had been in a higher region than the moon. After Tycho, Kepler had an opportunity of making observations on the comets which appeared in 1607 and 1618, and from all his observations he deduced this conclusion, "that comets move freely through the planetary orbs." From this period comets began to be more accurately observed, and to be considered as constituent parts of the solar system; and at length the illustrious Newton demonstrated that their motions are performed in long ellipses, having the sun in one of their foci.

Before proceeding to inquire into the nature and physical constitution of these bodies, I shall present the reader with

.

A brief sketch of the history of the most remarkable comets which have appeared in modern times.

One of the most remarkable comets which have appeared in modern times is that which made its appearance towards the close of the year 1680, and which was particularly observed by most of the astronomers of Europe. This comet, according to the accounts given by the astronomers of that period, appeared to descend from the distant regions of space with a prodigious velocity, almost perpendicular to the sun, and ascended again in the same manner from that luminary with a velocity retarded as it had before been accelerated. It was observed, particularly at Paris and Greenwich, by Cassini and Flamstead, by whom it was seen in the morning from the 4th to the 26th of November, 1680, in its descent towards the sun; and after it had passed its perihelion,* in the even

*The perihelion is that point in the orbit of any planet or comet which is nearest to the sun. It is also called the lower apsis. The aphelion is that point in the orbit which is farthest from the sun; called, also, the higher apsis.

ing, from the 12th of December to the 9th of March, 1681.The many exact observations made on this comet enabled Sir I. Newton to discover that so much of its orbit as could be traced by the motion of the comet, while it was visible, was, as to sense, a parabola, having the sun in its focus, and that it was one and the same comet that was seen all that time. This comet was remarkable for its very near approach to the sun. At its perihelion it was not above a sixth part of the sun's diameter from its surface; that is, about 146,000 miles from the surface of that luminary, and 584,000 from its centre. According to Sir Isaac Newton, the velocity of this comet when nearest the sun was 880,000 miles an hour. On taking its perihelion distance, as given by M. Pingré, Mr. Squire found, by two different calculations, that its velocity in its perihelion was no less than 1,240,000 miles an hour! This velocity was so great that, if continued, it would have carried it through 124 degrees in an hour; but its actual hourly motion during that interval, before and after it passed the perihelion, was 81 degrees, 47 minutes. At this period, the diameter of the sun, as seen from the comet, must have subtended an angle of more than a hundred degrees, which must nearly have filled its whole hemisphere.

From Dr. Halley's determination of its orbit, it appears that when in its aphelion, or greatest distance from the sun, it cannot be less than 13,000,000,000, or thirteen thousand millions of miles distant from that luminary; that is, seven times the distance of Uranus. According to the same astronomer, this comet, in passing through its southern node, came within the length of the sun's semidiameter of the orbit of the earth, that is, within 440,000 miles; and he remarks, "had the earth been then in that part of its orbit nearest that node of the comet, their mutual gravitation must have caused a change in the plane of the earth's orbit and in the length of our year; and if so large a body with so rapid a motion were to strike the earth, a thing by no means impossible, the shock might reduce this beautiful frame to its original chaos." Modern observations, however, render such deductions somewhat improbable. The period of this comet is supposed to be about 575 years. It is conjectured that it is the same comet which appeared in 1106, in the reign of Henry I., that was seen during the consulate of Lampadius and Orestes, about the year 531, and in the forty-fourth year before Christ, in which year