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between him and the resplendence of day and night, through the blindness that attended his declining years. "Beautiful light! beautiful lamp of heaven! what marvel that the blinded and benighted heathen should ignorantly worship thee? What marvel, that a thousand altars, in a thousand ages, should have sent up their fumes of adoration unto thee, the mooned Ashtaroth-unto thee, the Ephesian Diana-unto thee, the nightly visitant of the young-eyed Endymion? What marvel, that to those who knew not, neither had they heard of the One, Uncreate, Invisible, Eternal, thou shouldst have seemed meet Deity to whom to bend the knee, thou first-born offspring of his first-created gift! thou blessed emanation from his own ethereal glory! What wonder, when I, his humble follower, his ardent though unworthy worshipper-when I, an honest though an erring Christian, do strive in vain to wean my heart from love of thee; indoctrinating my spirit, that I may kiss the rod, with which I am assured, too well, He soon will chasten me, in changing the fair light, that glorious essence in which my soul rejoiceth, for one black, everlasting, self-imparted midnight? Yet so it shall be. A few more revolutions of these puissant planets, a few more mutations of the sweet returning seasons, and to me there shall be no change again on earth for ever! no choice between the fairest and the foulest! no difference of night or day! no charm in the rich gorgeousness of flowery summer, above the sere and mournful autumn! no cheery aspect in the piled hearth of winter! no sweet communion with the human eye compassionate! no intercourse with the great intellects of old —dead, but surviving still in their sublime and solid pages!"

Upon first becoming visible in the course of a lunation, the moon is seen soon after sunset as a thin crescent in the west with its convex side towards the sun. Gradually the breadth of the crescent increases, the inner curve is changed into a straight line, and she exhibits a complete half circle in the heavens. Afterwards, the line becomes a curvature again, bulging out in a direction opposite to its former inclination, and the moon is said to be gibbous, that is, bunched or convex. The curve turned from the sun continues to strengthen, and the apparent breadth of the moon to increase, until she is a full or circular orb, when a repetition of the same phases in inverse order commences. At length she appears like a fine thread of light in the morning, a little west of the rising sun, and for a few days she is lost to view, being in conjunction with him. The lunar phases clearly prove that the material of the moon is in itself as dull and opaque as the rock we gaze upon in our own world, that she shines by virtue of the reflected light of the sun, a fact recognised in the earliest ages, and apparent from the different appearances presented by those parts of her surface which are turned to and from his beams. The earth appears in the diagram as

the central body, with the moon in eight different parts of her orbit, receiving the light of the sun. The outermost circle exhibits the appearances presented to a terrestrial spectator in each station of the lunar globe, a crescent, a semicircle, gib. bous, and full. It is evident, therefore, that the satellite is not self-luminous, otherwise she would always appear as a round full orb. After solar phenomena, the lunar phases are the most beautiful celestial objects; and but for their periodical return and frequent observation, they would excite enthusiastic admiration. If for long and indefinite intervals the earth was deserted by its attendant, the renewal of the crescent moon would meet with a marked and general welcome, like that which the inhabitants of polar regions give to the sun, when he appears above their horizon after a five months' absence from it.

The crescent moon presents a singular appearance in the sky. Under favourable circumstances, the whole lunar circlet may then be seen, the dark part appearing of somewhat smaller dimensions in proportion to the illuminated. The appearance is popularly described as that of the new moon with the old one in her arms. It arises from the light reflected from the earth to the lunar surface, hence called earthshine, and lumière cendrée by the French, or ashy light, on account of its inferiority in quantity and brightness, to that which is directly received from the sun. It only serves to render the unenlightened portion of the moon very faintly visible; and the dark part of her body appears disproportionate to the size of the crescent, owing to the optical illusion which the presence of a strong light creates, that of apparently augmenting the magnitude of objects. Two causes contribute to render the dark portion of the lunar disk invisible in other stages of her progress: the increase of her directly illuminated part diffusing a stronger light, which proportionably nullifies that which is reflected from the earth; and the actual diminution of the earthshine itself. When the moon is a crescent to us, the earth is about full to her, and, consequently, more light is then transmitted from the earth than in other circumstances, which has the effect of then bringing that portion of her disk, not exposed to the solar rays, into feeble visibility. The effect is not produced when the moon is half full, owing to the cause, for the reasons stated, being less influential.

The moon is situated in external space at a mean distance of 237 thousand miles from the earth. Great as this interval is when compared with terrestrial extent, it is only about th part the earth's distance from the sun, and little more than one fourth the diameter of the solar body. It is owing to this proximity to us, that she occupies so large a space in the heavens, for the lunar diameter is only 2160 miles. Our own globe is equal in magnitude to forty-nine such bodies, and the sun to near seventy millions. If loosened from the action of other forces, the earth and the moon would fall together by the power of mutual attraction; but the earth being not only the larger body but the most dense, and its attraction being far the most powerful, the moon would descend to it, passing the intervening space in less than five days, our own planet courteously advancing about the distance of its semidiameter to meet the satellite. To the lovers of singular coincidences, the following may be acceptable, respecting the three bodies with which we are principally concerned.

Diameter of the Moon,

Miles.

2160 x 110= 237,600, average mean distance from the earth. 870,320 × 110 = 95,735,200, average mean distance from the earth. 7912 × 110 = 870,320, estimated diameter of the sun.

Diameter of the Sun Diameter of the Earth, There are two proper motions belonging to the moon, besides the annual pilgrimage around the great central orb accomplished in company with the earth. If her place with reference to a neighbouring star on any clear night be ascertained, the next night she will be found to have moved about 13° further eastward, and each night the distance will have widened, until from an opposite quarter of the heavens she will appear advancing towards the same proximity to the star. This proves her motion in an orbit round the earth; but great irregularities belong to it, which accurately to estimate is one of the most difficult problems and highest achievements of astronomy. The lunar tour through the heavens is accomplished in 27d 7h 43m 11, after which time, she returns to nearly the same position in relation to the stars. But the interval between one conjunction with the sun and another, or her synodical period, the lunar month, is 29d 12h 44m 2′, because of her partnership in the orbital motion of the earth. To compare and reconcile the motions of the sun and moon with each other, bringing a certain number of months and years to coincide, was an object to which the ancients applied themselves with great care

and industry. To Meton, the Athenian, the invention is ascribed, of the celebrated lunisolar period of 6940 days, supposed to be equal to 19 years, or 235 lunations. This period, called the Metonic cycle, was adopted in the year 432 B. C. It was published amid the applause of the Greeks at the Olympic games, who decreed a statue to the inventor, and declared him victor of the first class. The coincidence, however, is not exact, for 6940 days exceed 19 tropical years by about 9 hours, and exceed 235 lunations by 74 hours, an error which the Calippic period was designed to rectify, by the leap of a day in four Metonic cycles, or in an interval of seventy-six years. This brought 940 lunations into correspondence with 27,759 days, within 5h 54m, an inaccuracy which became important by accumulation in the civil usage of the period, and eventually entailed the necessity of the Gregorian reform of the calendar.

While, in the course of her monthly circuit, the moon passes between the sun and the earth, and deflects a shadow upon the latter, the compliment is returned in another part of her orbit, by the earth's shadow being cast upon the face of the satellite. A lunar eclipse, as well as a solar one, would occur every month if the moon revolved in the same plane with the earth, but she escapes the terrestrial shadow owing to the inclination of her orbit 5° to the ecliptic, carrying her above or below it, and only suffers an eclipse, when, besides being in opposition to the sun, she is in or near the plane of the earth's path. The shadow of our globe is computed to extend 800,000 miles into space. It is long enough, therefore, to reach a body three times the distance of the moon. The diagram represents the immersion of the satellite in it. The lunar globe, however, when

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wholly immersed, is rather obscured than hid from view, owing to the inflexion of the rays of light to her orb from the terrestrial atmosphere. She appears frequently of a dark copper colour, because the red rays, which have the greatest momentum, are those which principally reach her. During the eclipse of September 2d, 1830, the moon exhibited a deep blood-red hue, as seen from the metropolis. Upon comparing the ancient observations of eclipses recorded by Ptolemy, with those of Albutegnius in the ninth century, and of modern astronomers, Halley discovered the acceleration of the mean lunar motion, a phenomenon which Laplace referred to its true cause, that of a diminution of the eccentricity of the earth's orbit, owing to the disturbing forces of the planets. The terrestrial orbit is gradually changing from an ellipse into a circle, its eccentricity decreasing at the rate of about forty-one miles annually, thereby accelerating the mean motion of the moon; and should the decrease proceed equably, the earth's path will be reduced to a circle in 37,527 years. But, like all the other phenomena depending on gravitation, there is redress laid up in store for this perturbation, through the disturbing forces of the planets beginning to act in a contrary direction, which will produce a change towards eccentricity in the earth's orbit, and proportionably retard the mean motion of the moon. It may require thousands of ages for one part of this cycle of change to transpire; but the fact itself is not without interest to us, as one of the most sublime and beautiful results which the mind has mastered, and an illustration of the permanence of the system under all its disturbances. While lunar eclipses have thus been watched by the eye of science, and knowledge enlarged by their means respecting the condition of the system, they have created no small alarm among barbarian races. The Landers give an interesting account of an eclipse of the moon, Sept. 2. 1830, during their stay at Boossa in Central Africa: "The earlier part of the evening had been mild, serene, and remarkably pleasant. The moon had arisen with uncommon lustre,

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and being at the full, her appearance was extremely delightful. It was the conclusion of the holidays, and many of the people were enjoying the delicious coolness of a serene night, and resting from the laborious exertions of the day; but when the moon became gradually obscured, fear overcame every one. As the eclipse increased, they became more terrified. All ran in great distress to inform their sovereign of the circumstance, for there was not a single cloud to cause so deep a shadow, and they could not comprehend the nature or meaning of an eclipse. Groups of men were blowing on trumpets, which produced a harsh and discordant sound; some were employed in beating old drums; others again were blowing on bullocks' horns. The diminished light, when the eclipse was complete, was just sufficient to enable us to distinguish the various groups of people, and contributed in no small degree to render the scene still more imposing. If an European, a stranger to Africa, had been placed on a sudden in the midst of the terror-struck people, he would have imagined himself among a legion of demons, holding a revel over a fallen spirit."

Besides the orbital motion, there is another lunar movement, not so obvious, but plainly demonstrable. It is a well known fact, that the same portion of the moon's surface, or nearly so, is always turned towards the earth. It necessarily follows, that during each revolution she must rotate upon herself, and accomplish one rotation in the time of one revolution. If we suppose an individual to walk round a tree, and to keep his face turned towards it, he will see completely round the horizon during his circuit, and will of course turn round upon himself. The alterations are slight as to the face which the moon presents to us in all her revolutions. On the eastern and western sides, and also on the northern and southern edges, small portions of disk alternately appear and disappear, as though the lunar globe oscillated and swung to and fro in space; and hence these appearances are termed librations, from libra, a balance, the former being in latitude, and the latter in longitude. There is, however, no real oscillation, but the orbital motion being irregular, while that on the axis is uniform, the effect is, alternately to extend and diminish the sides of the exhibited surface, as though an actual vibration of the whole body took place. These variations do not affect the correctness of the general statement, that the moon always shows the same face to us; and this is the consequence of the coincidence between the time in which she moves round the earth and rotates upon her axis. Here we have a law to which none of the primary bodies in the system are subject, though it is probable that all the secondary bodies are. There is the same correspondence between the period occupied by the satellites of Jupiter in revolving round that planet and rotating upon their axes. The reasons of the law are at present inscrutable. It is one of those mechanical arrangements, the design of which we have yet to apprehend.

It will be seen from the preceding statements, that though the moon is our near neighbour, and has been for ages a faithful companion orb, the acquaintance is very partial and reserved. Almost one half of the satellite is perpetually turned from the earth, and to those regions that are thus concealed from us the earth is never visible. The lunarians, if such there are, inhabiting the districts beyond and opposite to the exhibited side of the moon, never catch a glimpse of the earth, unless they travel into the hemisphere presented. A parallel case on our globe would be, for the moon never to appear in the nocturnal sky of Europe and Africa, and for an Englishman to know nothing of the luminary, unless he should travel towards the heart of Asia, or land upon the shores of America. To an inhabitant of the moon on the border of her visible disk, the earth will appear in the horizon. One about the centre of the visible disk will have the earth near his zenith, but through the wide extent beyond the border, embracing nearly half the lunar surface, the earth is never seen. The hemispheres of the moon

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