COMETS.--These objects of extraordinary interest form a part in the economy of the solar system. Since the time when the presence of a comet was considered by nations to be the sure precursor of war, famine, and pestilence, up to the present period, these visitors have created much speculation and excitement; and, no longer ago than the fall of 1853, it was predicted by an eminent "professor" that one of these waifs in the heavens would come in collision with the earth, and destroy a portion of China. This, however, like many other pieces of mischief which had been predicted it would accomplish, failed, and the professor has retired from observation covered with the laurels won by his research. A comet, so brilliant that it could be seen at noonday, made its appearance seventy-three years before the birth of our Saviour. This date was just after the death of Julius Cæsar, and by the Romans the comet was believed to be his metamorphosed soul, armed with fire and vengeance. This comet appeared again in 1106, and then resembled the sun in brightness, being of great size, and having an immense trail. In 1456, a large comet made its appearance. The terror it created extended through all classes, and the belief was universal that the day of judgment was at hand. At this time, the Turks, with their victorious armies, seemed destined to overrun all Europe. This added to the gloom and terror. The people became regardless of the present, and anxious only for the future. To prepare the world for its expected doom, Pope Callixtus III. ordered the Ave Maria to be repeated three times instead of twice a day, and to it was added, "Lord, save us from the Devil, the Turk, and the Comet!" and thrice each day these obnoxious personages suffered excommunication. At length, the comet began to retire from eyes in which it found no favor, and the Turks retired to their own dominions. The comet of 1680 was of the largest size, having a trail ninety-six millions of miles in length. Dawning science, however, robbed it of its terrors, assisted by the signal failure of its illustrious predecessor. Such are many of the fantasies which these peculiar visitors have called up. The beautiful comet of 1811, the most splendid of modern times, was considered, even by many intelligent persons, as the harbinger of the war which was declared the spring following; and the remembrance will be fresh in the minds of many of an indefinite apprehension of some dreadful catastrophe, which pervaded both continents, in anticipation of Bela's comet in 1832. Comets, unlike the planets, observe no one direction in their orbits, but approach to and recede from their great centre of attraction in every possible direction. Some seem to come up from immeasurable depths below the ecliptic, and, having doubled the heaven's mighty cape, again plunged downward with their fiery trains, "On the long travel of a thousand years."