boy throw a ball out of his hand, besides going forwards, it turns round on its axis; and this is the precise motion of the earth and planets. The moon always keeps the same side towards the earth, so that she turns once on her axis as she moves round the earth, and her day and night are consequently as long as her period from new moon to full moon. But the earth acts also as a moon to her, being at the same time far more luminous; when it is new moon to the earth it is a full earth to the moon, and the contrary. As the moon shines with no light besides that which she reflects from the sun, it is evident that her shape must depend on her position in regard to the sun. When the earth is exactly in the middle, the whole illumined side of the moon will be towards the earth, and it will be a full moon. When the moon is in the middle, her dark side will be presented to the earth, and it will be new moon. As she proceeds from new to full, more and more of her light side will appear, or it will increase, and on going from full to new it will of course decrease. Besides affording us light, the moon attracts the waters, and raises high tides, which obey her influence as the seas pass beneath her. But as she moves forward in her orbit 12 or 13 degrees every day, and consequently passes over every sea 50 minutes later one day than the day before, so the time of high water is always 50 minutes later each following day. There are two tides in every twenty-four hours, and one is evidently but a returning vibration, stroke, or effect of the preceding tide. If the moon were to be destroyed, and not to reproduce the effect on the following day, the vibration of the waters would probably continue for many days till it gradually ceased, like the motion of a pendulum. Many mathematicians have puzzled themselves in calculating the relative forces acting on the near surface, centre, and remote surface of the earth, but to little purpose, as the effect is so much better accounted for by the vibratory property of fluid bodies. The sun and moon concur in raising the tides; and hence we have high or spring tides, when their actions concur at the new and full moon; and low or neap tides, when the attraction is in opposite directions, as at the quarters, or when the moon is half way between the conjunction and opposition. On small seas not readily communicating with others, and on which the moon acts generally at the time of its passages, there are no tides. All the terrestrial phenomena, and all the problems on the globes, may be reduced to one general principle-that the sun always illumines one half the earth, and that the other half is in darkness; and that, from every part of the earth, we always see one half of the heavens, and that the other half is invisible. It must also be remembered, that the circumference of the earth, the heavens, and of all circles, great or small, is supposed to be 360 parts or degrees; consequently, half a circle, or half the heavens, is 180 degrees, and a fourth 90 degrees. On the surface of the earth each degree is 694 miles, but the size of a degree as carried out to the heavens is indefinite. Hence, if the sun illumines half the earth, he illumines 180 degrees of the earth, or 90 degrees every way from the place over which he is vertical. Hence also it is 180 degrees from the north to the south pole, and 90 degrees from each is the middle of the earth, called the Equator. Hence, as half the heavens are always visible, 180 degrees are visible, and from the point over head it will be 90 degrees to that line, while the earth and the heavens appear to the eye to meet, called the Horizon. Hence also, an inhabitant of the equator can see the stars as far as each pole, i. e. he can see 90 degrees each way. EVENING. WELCOME to me is yon majestic moon, My thoughts to nature's purest laws. 'Tis solemn sweet, and all around Calls forth the soul. To the Almighty Father, God Supreme.-D. W. THE SUN A BODY OF ICE.-Many opinions have been formed concerning the sun, which philosophers have sometimes ridiculed, and sometimes seriously refuted. But of all the paradoxical assertions respecting that luminary, none equals Mr. Palmer's, for that gentleman positively asserts it to be a body of ice! The following is the title of Mr. Palmer's book: "A Treatise on the sublime science of Heliography, satisfactorily demonstrating (!) our great orb of light, the sun, to be absolutely no other than a body of ice. By Charles Palmer, Gent." 8vo. 1799. SINGULAR NOTIONS RESPECTING COMETS.-John Bodin, a French lawyer, published his opinion of comets, in a work entitled Universæ Naturæ Theatrum, 1575, which assigns to upon them a new character. "I have reflected," says he, the opinion of Democritus, and with him am induced to think that comets are spirits, which, having lived on the earth innumerable ages, and having at last completed their term of existence, celebrate their last triumphs, or are recalled to heaven, in the form of shining stars!" A more extraordinary fancy was entertained by Kepler, who, though in some measure the father of modern astronomy, yet had very incorrect notions respecting the system of nature in general. The planets he imagined to be animals swimming round the sun by means of fins acting upon the ethereal fluid; and, agreeably to this strange belief, he held comets to be also huge uncommon creatures, generated in the celestial spaces, and that they "were made to the end that the ethereal fluid might not be more void of monsters than the ocean is of whales, and other great thieving fishes; and that a gross fatness being thus gathered together, as excrements into an apostume, the ethereal medium might thereby be purged, lest the sun should be obscured, as he was for a year together when Julius Cæsar was slain; when, being weakened by a bloody colour, he cast a dim and disdainful light!" He even supposes that the faculty of the earth, which he fancied to be animated like all the other planets, is so terrified at the approach of a comet, that it-" sweats out a great quantity of vapour through terror, and that hence arise great rains and floods."-We need not, then, be surprised to find the descriptions given by the historians and professed astronomers so deeply tinged with the superstition by which the age was characterized, and often so highly coloured or caricatured, as to render it even difficult to recognize the thing described to be a comet. When, for instance, we read of comets which resembled flaming swords and glittering spears, or one which, as Lubienitz relates, came out from an opening in the heavens, like a dragon with blue feet, and a head covered with snakes, we only pity the degradation of the human mind which either could invent or tolerate such monstrous absurdities. The following remarkable description is taken from the " Exempla Cometarum" of Kossenburgh :- :-" In the year 1527, about four in the morning, not only in the Palatine of the Rhine, but nearly all over Europe, appeared for an hour and a quarter a most horrible comet in this sort. In its length it was of a bloody colour, inclining to saffron. From the top of its train appeared a bended arm, in the hand whereof was a huge sword in the instant posture of striking. At the point of the sword was a star. From the star proceeded dusky rays, like a hairy tail; on the side G of them, other rays, like javelins or lesser swords, as if imblued in blood, between which appeared human faces of the colour of blackish clouds, with rough hair and beards." VELOCITY OF LIGHT.-The extraordinary precision with which the astronomical skill of modern times enables men to foretell the times of remarkable appearances or changes among the heavenly bodies, has served for the detection of the fact that light is not an instantaneous communication between distant objects and the eye, as was formerly believed, but a messenger which requires time to travel; and the rate of travelling has been ascertained in the same way. The eclipses of the satellites or moons of the planet Jupiter had been carefully observed for some time, and a rule was ob tained which foretold the instants in all future time when the satellites were to glide into the shadow of the planet, and disappear, or again to emerge into view. Now it was found that these appearances took place sixteen minutes and a half sooner when Jupiter was near the earth, or on the same side of the sun with the earth, than when it was on the other side; that is to say, more distant from the earth by one diameter of the earth's orbit, and at all intermediate stations the difference diminished from the sixteen minutes and a half, in exact proportion to the less distance from the earth. This proves, then, that light takes sixteen minutes and a half to travel across the earth's orbit, and eight minutes and a quarter for half that distance, or to come down to us from the The velocity of light, ascertained in this way, is such, that in one second of time-namely, during a single vibration of a common clock pendulum-it would go from London to Edinburgh and back, 200 times, and the distance between these is 400 miles. This velocity is so surprising, that the philosophic Dr. Hooke, when it was first asserted that light was thus progressive, said he could more easily believe the passage to be absolutely instantaneous, even for any distance, than that there should be a progressive movement so inconceivably swift. The truth, however, is now put quite beyond a doubt by many collateral facts bearing upon it. As regards all phenomena upon earth, they may be regarded as happening at the very instant when the eye perceives them, the difference of time being too small to be appreciated; for, if our sight could reach from London to Edinburgh, we should perceive a phenomenon there in the four-hundredth part of a second after its occurrence. It is hence usual, and not sensibly incorrect, when we are measuring the velocity of sound, as when a cannon is fired, by observing the time between the flash and the report, to suppose that the event sun. takes place at the very moment when it is perceived by the eye. In using a telegraph, no sensible time is lost on account of light requiring time to travel. A message can be sent from London to Portsmouth in a minute and a half; and, at the same rate, a communication might pass to Rome in about half an hour, to Constantinople in forty minutes, to Calcutta in a few hours, and so on. IMPORTANCE OF HEAT.- In the winter of climates, where the temperature is for a time below the freezing-point of water, the earth, with its waters, is bound up in snow and ice; the trees and shrubs are leafless, appearing every where like withered skeletons; countless multitudes of living creatures, owing either to the bitter cold or the deficiency of food, are perishing in the snows-nature seems dying or dead. But what a change when spring returns; that is, when heat returns! The earth is again uncovered and soft, and rivers flow; the lakes are again liquid mirrors; the warm showers come to foster vegetation, which soon covers the ground with beauty and plenty. Man, lately inactive, is recalled to many duties; his water-wheels are every where at work, his boats are again on the canals and streams, his busy fleets of industry are along the shores-winged life in new multitudes fills the sky; finny life similarly fills the waters, and every spot of earth teems with vitality and joy. Many persons regard these changes of season as if they came like the successive positions of a turning wheel, of which one necessarily brings the next; not adverting to the fact that it is the single circumstance of change of temperature which does all. But if the colds of winter arrive too early, they unfailingly produce the wintry scene: and if warmth come before its time in spring, it expands the bud and the blossom, which a return of frost will surely destroy. A seed sown in an icehouse never awakens to life. Again, as regards climates, the earthy matters forming the exterior of our globe, and therefore entering into the composition of soils, are not different for different latitudes,-at the equator for instance, and near the poles. That the aspect of nature, then, in the two situations exhibits a contrast more striking still than between summer and winter, is owing merely to an inequality of temperature, which is permanent. Were it not for this, in both situations the same vegetables might grow, and the same animals might find their befitting support. But now, in the one, namely, where heat abounds, we see the magnificent scene of tropical fertility: the earth covered with luxuriant vegetation in endless lovely variety, and even the hard rocks festooned with green, perhaps with the vine, rich in its |