CHAPTER III. Moon:-Its Irregularities-Its Atmosphere-Its Quarters-The Tides-Attraction and Gravity. "O LORD our Lord, how excellent is thy Name in all the earth! for when I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained; what is man, that thou art mindful of him? and the son of man, that thou visitest him?" Such is the exclamation of David, the sweet Psalmist of Israel, when contemplating the vast subjects which have of late been occupying our minds; he also pondered over the works of creation, and celebrated its mighty wonders. The sun, and his genial influences, were the theme of his inspired melody; and he welcomes him as a "bridegroom coming out of his chamber, whose going forth is from the end of heaven, and his circuit unto the ends of it: and there is nothing hid from the heat thereof." This we have seen fulfilled in our previous chapter; it now remains for us to glance at the nature and character of the beauteous moon, whose pale, clear splendour enlivens the tedious hours of night, and supplies the absence of the more brilliant sun. 24 : IRREGULARITIES OF THE MOON. I would introduce her to your notice as a round opaque body, which borrows her light from that great luminary and, as you are well aware, is apparent to all the earth every twenty-four hours, completing her own revolution in rather less than twenty-eight days. I imagine you have often regarded this mighty visitant with curiosity and attention; you have seen the dark spots upon her surface, contrasted with the bright and luminous portions, and fancy has busily occupied herself in framing reasons for these appearances. To the astronomer we must look for a solution of the mystery; and he will tell us that the "irregularities we discern can be no other than mountains and valleys,”* because we see the shadows cast by the former in the exact proportion as to length which they ought to have been, when we take into the account the inclination of the sun's rays to that part of the moon's surface on which they stand." The highest of these mountains has been calculated to be about 1 English miles. It is very extraordinary how numerous they are, the surface being almost covered with them; while the dusky spots, which are generally termed seas, Sir John Herschel considers to be incompatible with the idea of deep waters, though he adds, "There are large regions totally level, and apparently of a watery nature.”‡ 66 In consequence of the moon revolving round her own axis in the same time as she is revolving round the earth, her face always remains the same; and as she derives her light from the sun, and reflects some of it upon the earth, so the earth performs the same office to her in return. "The moon has no clouds, nor any Herschel's Astronomy, p. 228. † Ibid. p. 228. other indications of an atmosphere; hence its climate must be very extraordinary; the alternation being that of unmitigated and burning sunshine, fiercer than an equatorial noon, continued for a whole fortnight; and the keenest severity of frost, far exceeding that of our polar winters, for an equal time."* If then she is inhabited, an inference which appears to be universally admitted, her occupants must be a very different order of beings to ourselves. Spirits or angels could alone suit such an "etherial medium." I am well aware that some young persons have much observation, and wish an explanation of the various phenomena they behold; while others, on the contrary, are perfectly heedless, and never care for the furtherance of their own improvement. To these, the above observations are of little value; while to the former class of my readers, every word is precious, and they will delight in accompanying me still further into the subject. To them a few words on the changes of the moon will prove deeply interesting, for its particular motion of turning round the earth from west to east will not have escaped their observation. After having placed herself between us and the sun, she retires from under that body, retreating daily towards the east. In fifteen days, she arrives at the most eastern part of the horizon just at the time the sun sets; this is called being in opposition. "In the evening she rises above our horizon, when the sun retires below it, and sets in the morning about the time the sun appears." At length she draws nearer to the sun; and in time can only be seen a little before he rises. The further she removes from it the more visible she Herschel's Astronomy, p. 230. becomes. At the end of seven days, when she has attained a quarter of her course round the earth, she discovers more and more of her illumined side, until the half is visible. The light part is then turned towards the sun, and the dark part casts no light on us; half of the moon is then illumined, and it is the half of that half which appears to us; and then it is said to be in the first quarter.* In seven days more, she is nearly opposite the sun, consequently her whole illumined disc is visible; then, as the sun sets in the west, she majestically rises in the east. The next day the light begins gradually to leave the western side, diminishing daily until it attains the form of a semicircle, and enters its last quarter. Oh how beautiful and complete are Jehovah's works! He has left us nothing to wish for or require; for, while we have seen the glorious sun performing his appointed course, and the shining stars proclaiming His mighty power, and affording us a magnificent idea of His sovereignty and care, we now behold the lovely moon shedding her pale light upon this favoured globe, her constant, faithful companion, and inseparable friend, perfectly supplying his absence; and, in fact, being indispensable in those inhospitable polar regions, where his light disappears for six long months together, and all nature appears to sleep. But the evident and remarkable connexion that subsists between the moon and the waters is well known, and worthy of our passing notice. Those of my young friends who have visited the coast, are accustomed to hear the word, Tide, frequently made use of, and, in all probability, without having the most * Sturm's Reflections, vol. ii. p. 185. remote idea of its meaning. They have seen in the distance many gallant ships at anchor, and wondered why their crews were satisfied to remain so far out at sea; but they were only waiting for the tide to bring them into port; while, on the other hand, numbers appeared to await the succeeding change that they may commence their destined voyage. This they must linger for, for were both wind and tide against them, they could not proceed; while, on the contrary, with only the latter in their favour, they oftentimes care little for the former. Strange as it may appear, it is nevertheless true, that the tides are influenced by the moon; for the time of high and low water comes to the parallel hour of the moon's age. The high tides are always about the new and full moon, and the low tides when she is in her different quarters. Thus the action of the moon upon the ocean produces these constant and beneficial changes. The height of the tides, on different days, also depends upon the age of the moon, "the principles of attraction and gravity being peculiarly applicable to the tides of the ocean."* Now, the moon, as I said before, "is the principal cause of this phenomenon; but the sun performs a secondary part in the production, which is proved by the circumstance, that the highest, or spring tides, take place when the sun, the moon, and the earth are all in a straight line; i. e., when the force of the attraction of the sun conspires with that of the moon; and that the lowest or neap tides take place when the lines drawn from the sun and moon to the earth are at right angles, i. e., when the force of the attraction of the sun acts in opposition to that of the moon."† * Saturday's Mag., 1833. + Brewster's Life of Newton. |