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that point furtheft from the moon, and where, if we could fee through the fuppofed globe of water, we fhould view her beneath our feet; I say, as we advance to this point, we find high water again, and another heap of waters affembled, forming another hill.

. If the attractive power of the moon were always the fame, at all distances, this fecond high tide could never happen; but fince this power decreases as we increase our distance from the body of the moon, we fee that its effects ought to be much diminished, as we are now further from her by the whole diameter of the globe; thefe waters being therefore lefs attracted than any other part of this fuppofed covering of water, they are by fo much lighter, and less attached to the globe; they will therefore, in a sense, recede from it, fo far as they can; and all round about them will proportionably partake of the fame inclination, and endeavour to affemble in one body; not only as being less attracted than any which have contributed to form the first high tide, but as following the natural course of fluids, and endeavouring to maintain an equilibrium.

As the moon proceeds round the earth in her monthly course, the naturally changes the fituation of this afflux of waters; and as by the diurnal motion of the earth fhe feems daily to go round it, the depth of tide we have mentioned, regularly accompanies her; and would always actually appear fo to do, were it not checked by the following caufes (1.) though the waters feel her influence immediately, yet they must have fome time to affemble in, and thofe from


any confiderable diftance, have fundry impediments to overcome, fuch as the refiftance of the water before them-the difficulty of rifing to a level-and their inclination to preserve the equality of the water behind them. The time of highwater, therefore, in the most open places, follows the time of the moon's coming to the meridian about two hours. (2) In countries where the coafts are irregular, that irregularity has its influence; and in rivers, or arms of the sea, which run far in-land, the time of high-water varies with circumstances, If the moon took no longer than the fun to go round the earth daily, the tides would happen every twelve hours; but as a lunar day is longer than a folar day, the interval between the tides is prolonged alfo. A lunar day is about twelve hours fifty minutes.

The reafon of deeper tides happening in fome parts of the month than in others, is because the attractive influence of the fun is at thofe times to be added to that of the moon; the reafon of fhallower tides at fome times than at others, is because the influence of the fun is to be fubtracted from that of the moon. Thus, fuppofe the moon alone might raife. the waters ten feet, and the fun two feet; when thefe bodies are in conjunction, and their forces confequently united, they may, together, raife the waters twelve feet; on the contrary, suppose these bodies to be at right angles with each other, it will follow that what one would raife, the other will deprefs, and eight feet will be the height of the tide.

As the moon is not always equidiftant from the earth (her courfe not being a circle, but fomewhat oval), fhe has fomeXI. 3 B


times more influence than at others; on the fame principle, the earth not being always equidiftant from the fun, that luminary has sometimes more power than at others: and the perihelion of our planet being in winter, we may in winter expect the greatest force from his attraction.-The greatest tides happen about February (before the equinox), and about November (after the equinox), but always dependent on the nearest distance of the moon.

The greatest tide we know, is that at the mouth of the river Indus; where the water rifes thirty feet. What an object for Alexander, who had never before feen fuch a phenomenon! but whofe knowledge was limited to the gentle, and almoft motionlefs, waters of the Mediterranean! no wonder he thought the fea deities were by fome means offended; and endeavoured, by offerings and facrifices, to avert impending fury. Sufpenfe, and awe, and curiofity, must have agitated the breast of this intrepid warrior, who, had he endeavoured to affign a caufe for this event, had little needed to have fighed for other worlds to conquer,—fince even his preceptor Ariftotle, was vexed to find it among things beyond his knowledge.--The most remarkable tides are at Tonquin; for here is but one ebb and one flow in twenty-four hours; and twice in each month is no tide, the water being ftagnant. These appearances were folved by Sir Ifaac Newton, with great fagacity, and by him attributed to two tides entering from different quarters; of each of these tides two come fucceffively every day, two at one time greater; two at another time less; the two greater compofe high tide; the


two smaller are the ebb; and the balancing of these tides accounts for the apparent interval.

Though the tides are the greateft inftance of the mutability of water, yet others are fufpected by curious obfervers; and could we contrive inftruments fufficiently accurate, we fhould probably discover the fame caufes operating in a wonderful variety of effects. 1 fhall juft hint, it has been fufpected, that, the kind of madness which arifes from an accumulation of water in the brain, follows pretty closely the phafes of the moon; and as the fubjects of it are usually worse at new, and full moon (the times of high tides), fome have hinted that a kind of tide takes place in the feat of the diforder.

We have another phenomenon in extenfive oceans, which does not appear in fmaller bodies of water: I mean, the SURGES, which, in enormous waves, almoft overwhelm the fhores. These are most frequent about the equator, and feem to be occafioned by the diurnal motion of the earth, which being moft fenfible in thofe parts, has the greatest effect on the restlefs deep. The motion of the globe is fteady with regard to the terra firma, but the buoyant waves being thrown forward by this motion, are impelled beyond their natural velocity, and in confequence they exert a force upon the land, which contributes, in fucceffion of ages, to undermine or overwhelm it. Being thrown forward in one part, they are of course taken from fome other; but this being contrary to their established law of equality, as a fluid, they are perpetually endeavouring to restore the loft equilibrium, and



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their waves roll backward, with little lefs rapidity than for ward; and by rolling upon each other, in the course of fo many leagues of water, by the time they reach the shore, they become of great height; and upon these shores there is no landing by boats, and little fafety for veffels.

There are many points of allufion which moralists have fuggefted, in comparing the ocean to the human mind: now calm and flattering, now tempeftuous and stormy; fuch is the man governed by his paffions !-Or, would they depict a mifer grafping after further additions to his useless stores, they tell us, "all the rivers run into the fea, but the fea is not full."-The banks of a refervoir, or wear of water, are eafily broken, but who fhall close them? "The commencement of ftrife is like letting out of water."-Streams, and brooks, and rivers, enlarge in extent and importance as they proceed; they gladden the thirsty foil, they refresh the drooping plantation, they furnish beauty to every vegetable; where they flow life is vigorous, and pleasure abundant; they seem indeed to deftroy, but they really contribute to increase; and though a few acres might be recovered were a river annihilated, who would accept the exchange?

Such are the gifts of Providence; partial ills, perhaps, but general benefits: it strikes us evidently in the river, and would do in the ocean, but that the ocean is beyond our calculation. Why ftorms and tempefts? that like rivers they may do much good at little expence. Such is the appointment of him who fpeaks the wild waves into peace, and controuls the ocean; hitherto halt thou go, but no further."


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