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very great force, and therefore cannot yield, like those of the comets, to a slight impulse. Hence we see the reason why the comets have tails, while none of the planetary bodies exhibit such a phenomenon. Whatever opinion may be entertained of this expla nation, it must, at least, be admitted, that if light is a material substance, the atmospherical particles of a comet may have their gravity diminished to such a degree, either by their distance from its centre, or by the rarity of the nucleus, as to yield to the impulse of the solar rays, and be forced behind the nucleus, in the same manner as smoke yields to the impulse of the gentlest breeze.

NOTE D.-Fixed Stars.

knowledge dissipated these gloomy apprehensions, | external strata are attracted towards them with a the absurdities of licentious speculation supplied their place, and all the ingenuity of conjecture was exhausted in assigning some rational office to these wandering planets. Even at the beginning of the 18th century, the friend and companion of Newton regarded them as the abode of the damned. Anxious to know more than what is revealed, the fancy of speculative theologians strove to discover the frightful regions in which vice was to suffer its merited punishment; and the interior caverns of the earth had, in general, been regarded as the awful prisonhouse in which the Almighty was to dispense the severities of justice. Mr. Whiston, however, outstripped all his predecessors in fertility of invention. He pretended not only to fix the residence of the damned, but also the nature of their punishment. Wheeled from the remotest limits of the system, "The first thing which strikes a scientific obthe chilling regions of darkness and cold, the comet server of the fixed stars, is their immeasurable diswafted them into the very vicinity of the sun; and tance. If the whole planetary system were lighted thus alternately hurried its wretched tenants to the up into a globe of fire, it would exceed, by many terrifying extremes of chilling cold and devouring millions of times, the magnitude of this world, and yet fire. By other astronomers, comets were destined only appear a small lucid point from the nearest of for more scientific purposes. They were supposed them. If a body were projected from the sun, with to convey back to the planets the electric fluid the velocity of a cannon-ball, it would take hundreds which is constantly dissipating, or to supply the sun of thousands of years before it described that mighty with the fuel which it perpetually consumes. They interval which separates the nearest of the fixed stars have been regarded also as the cause of the deluge; from our sun and from our system. If this earth, and we must confess, that if a natural cause is to be which moves at more than the inconceivable velocity sought for that great event, we can explain it only of a million and a half miles a-day, were to be hurby the shock of some celestial body. The transient ried from its orbit, and to take the same rapid flight effect of a comet passing near the earth, could scarce- over this immense tract, it would not have arrived ly amount to any great convulsion; but if the earth at the termination of its journey after taking all the were actually to receive a direct impulse from one time which has elapsed since the creation of the of these bodies, the consequences would be awful. world. These are great numbers, and great calcuA new direction would be given to its rotatory lations; and the mind feels its own impotency in motion, and the globe would revolve round a new attempting to grasp them. We can state them in axis. The seas, forsaking their ancient beds, would words. We can exhibit them in figures. We can be hurried by their centrifugal force, to the new demonstrate them by the powers of a most rigid and equatorial regions; islands and continents, the abodes infallible geometry. But, no human fancy can sumof men and animals, would be covered by the univer-mon up a lively or an adequate conception-can roam sal rush of the waters to the new equator, and every in its ideal flight over this immeasurable largeness— vestige of human industry and genius at once de- can take in this mighty space in all its grandeur, and stroyed. The chances against such an event, how-in all its immensity-can sweep the outer boundaries ever, are so very numerous, that there is no dread of such a creation or lift itself up to the majesty of of its occurrence. Various opinions have been enter- that great and invisible arm on which all is sustained by astronomers respecting the tails of comets. pended. They were supposed by Appian, Cardan, and Tycho Brahe, to be the light of the sun transmitted through the nucleus of the comet, which they believed to be transparent like a lens. Kepler thought, that the impulsion of the solar rays drove away the denser parts of the comet's atmosphere, and thus formed the tail. Descartes ascribes the tail to the refraction of light by the nucleus. Newton maintained, that it is a thin vapour raised by the heat of the sun from the comet. Euler asserts that the tail is occasioned by the impulsion of the solar rays driving off the atmosphere of the comet; and that the curvature observed in the tail is the joint effect of this impulsive force, and the gravitation of the atmospherical particles to the solid nucleus. Mairan imagines that comets' tails are portions of the sun's atmosphere. Dr. Hamilton of Dublin supposes them to be streams of electric matter; and Biot supposes with Newton, that the tails are vapours produced by the excessive heat of the sun; and also, that the comets are solid bodies before they reach their perihelion; but that they are afterwards either partly or totally converted into vapour by the intensity of the solar heat. Of all these theories, that of Euler seems to be most philosophical. Since the comets are composed chiefly of nebulous matter, and have very large atmospheres, the external atmospheric strata must be drawn towards the comet by very slight powers of attraction, and will therefore yield to the smallest impulse. From the great density of the planets, on the contrary, and the small size of their atmospheres, the

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"But what can those stars be which are seated so far beyond the limits of our planetary system! They must be masses of immense magnitude, or they could not be seen at the distance of place which they occupy. The light which they give must proceed from themselves; for the feeble reflection of light from some other quarter, would not carry through such mighty tracts to the eye of an observer. body may be visible in two ways. It may be visible from its own light, as the flame of a candle, or the brightness of a fire, or the brilliancy of yonder glorious sun, which lightens all below, and is the lamp of the world. Or it may be visible from the light which falls upon it, as the body which receives its light from a taper, or the whole assemblage of objects on the surface of the earth, which appear only when the light of day rests upon them or the moon, which, in that part of it that is towards the sun, gives out a silvery whiteness to the eye of the observer, while the other part forms a black and invisible space in the firmament or as the planets, which shine only because the sun shines upon them; and which, each of them, present the appearance of a dark spot on the side that is turned away from it. Now apply this question to the fixed stars. they luminous of themselves, or do they derive their light from the sun, like the bodies of our planetary system? Think of their immense distance, and the solution of this question becomes evident. The sun, like any other body, must dwindle into a less apparent magnitude as you retire from it. At the

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prodigious distance even of the very nearest of the fixed stars, it must have shrunk into a small indivisible point. In short, it must have become a star itself, and could shed no more light than a single individual of those glimmering myriads, the whole assemblage of which cannot dissipate, and can scarcely alleviate, the midnight darkness of our world. These stars are visible, not because the sun shines upon them, but because they shine of themselves, because they are so many luminous bodies scattered over the tracts of immensity; in a word, because they are so many suns, each throned in the centre of his own dominions, and pouring a flood of light over his own portion of these unlimitable regions.

butes-where He peoples immensity with his wonders; and travels in the greatness of His strength through the dominions of one vast and unlimited monarchy.

"The contemplation has no limits. If we ask the number of suns and of systems, the unassisted eye of man can take in a thousand, and the best telescope which the genius of man has constructed, can take in eighty millions. But why subject the dominions of the universe to the eye of man, or to the powers of his genius? Fancy may take its flight far beyond the ken of eye or of telescope. It may expatiate in the outer regions of all that is visible-and shall we have the boldness to say, that there is nothing there?-that the wonders of the Almighty are at an end, because we can no longer trace His footsteps?-that His omnipotence is exhausted because human art can no longer follow him?-that the creative energy of God has sunk into repose, because the imagination is enfeebled by the magnitude of its efforts, and can keep no longer on the wing through those mighty tracts, which shoot far beyond what eye hath seen, or the heart of man hath conceived. which sweep endlessly along, and merge into an awful and mysterious infinity."-Chalmers' Astrono mical Discourses.

CHAP. II.

OF ASTRONOMY AND GEOGRAPHY.

"At such an immense distance for observation, it is not to be supposed that we can collect many points of resemblance between the fixed stars and the solar star, which forms the centre of our planetary system. There is one point of resemblance, however, which has not escaped the penetration of our astronomers. We know that our sun turns round upon himself in a regular period of time. We also know that there are dark spots scattered over his surface, which, though invisible to the naked eye, are perfectly noticeable by our instruments. If these spots existed in greater quantity upon one side than upon another, it would have the general effect of making that side darker; and the revolution of the sun must, in such a case, give us a brighter and a fainter side, by regular alternations. Now, there are some of the fixed stars which present this appearance. They present us with periodical variations of light. From the splendour of a star of the first or second magnitude, they fade away into some of A SHORT SURVEY OF THE GLOBE, FROM THE LIGHT the inferior magnitudes; and one, by becoming invisible, might give reason to apprehend that we had lost him altogether; but we can still recognise him ALL the sciences are, in some measure, linked by the telescope, till at length he reappears in his own place, and, after a regular lapse of so many days with each other, and before the one is ended, and hours, recovers his original brightness. Now, the other begins. In a natural history, therethe fair inference from this is, that the fixed stars, fore, of the earth, we must begin with a short as they resemble our sun, in being so many luminous account of its situation and form, as given us by masses, of immense magnitude, they resemble him in this also, that each of them turns round upon his astronomers and geographers: it will be sufown axis; so that, if any of them should have an ficient, however, upon this occasion, just to hint inequality in the brightness of their sides, this revo-to the imagination, what they, by the most lution is rendered evident, by the regular variations in the degree of light which it undergoes. Shall we say, then, of these vast luminaries, that they were created in vain ? Were they called into existence for no other purpose than to throw a tide of useless splendour over the solitudes of immensity? Our sun is only one of these luminaries, and we know that he has worlds in his train. Why should we strip the rest of this princely attendance? Why may not each of them be the centre of his own system, and give light to his own worlds? It is true that we see them not; but could the eye of man take its flight into those distant regions, it would lose sight of our little world before it reached the outer limits of our system-the greater planets would disappear in their turn-before it had described a small portion of that abyss which separates us from the fixed stars, the sun would decline into a little spot, and all its splendid retinue of worlds be lost in the obscurity of distance-he would at last shrink into a small indivisible atom, and all that could be seen of this magnificent system, would be reduced to the glimmering of a little star. Why resist any longer the grand and interesting conclusion? Each of these stars may be the token of a system as vast and as splendid as the one which we inhabit. Worlds roll in these distant regions; and these worlds must be the mansions of life and of intelligence. In yon gilded canopy of heaven, we see the broad aspect of the universe, where each shining point presents us with a sun, and each sun with a system of worlds-where the Divinity reigns in all the grandeur of His attri

abstract reasonings, have forced upon the unhas been said before, one of those bodies which derstanding. The earth which we inhabit is, as circulate in our solar system; it is placed at a happy middle distance from the centre; and even seems, in this respect, privileged beyond all other planets that depend upon our great luminary for their support. Less distant from the sun than Saturn, Jupiter, and Mars, and yet less parched up than Venus and Mercury, that are situated too near the violence of its power, the earth seems in a peculiar manner to share the bounty of the Creator: it is not, therefore, without reason, that mankind consider themselves as the peculiar objects of his providence and regard.

Besides that motion which the earth has round the sun, the circuit of which is performed in a year, it has another upon its own axis, which it performs in twenty-four hours. Thus, like a chariot-wheel, it has a compound motion; for while it goes forward on its journey, it is at the same time turning upon itself. From the first of these two arises the grateful vicissitude of the seasons; from the second, that of day and night. It may be also readily conceived, that a boly

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thus wheeling in circles will most probably be | brown colour, and quite naked. Upon a nearer itself a sphere. The earth, beyond all possibility approach, however, they are found replete with of doubt, is found to be so. Whenever its shadow many different veins of coloured stone, here and happens to fall upon the moon, in an eclipse, it there spread over with a little earth, and a appears to be always circular, in whatever posi- scanty portion of grass and heath. The internal tion it is projected; and it is easy to prove, that parts of the country are still more desolate and a body which in every position makes a circular deterring. In wandering through these solitudes, shadow, must itself be round. The rotundity of some plains appear covered with ice, that, at the earth may be also proved from the meeting first glance, seem to promise the traveller an of two ships at sea: the topmasts of each are the easy journey. But these are even more formifirst parts that are discovered by both, the under dable and more unpassable than the mountains parts being hidden by the convexity of the globe themselves, being cleft with dreadful chasms, which rises between them. The ships, in this in- and everywhere abounding with pits that threatstance, may be resembled to two men who ap- en certain destruction. The seas that surround proach each other on the opposite sides of a hill; these inhospitable coasts are still more astonishtheir heads will first be seen, and gradually as they | ing, being covered with flakes of floating ice, come nearer they will come entirely into view. that spread like extensive fields, or that rise out However, though the earth's figure is said to of the water like enormous mountains. These, be spherical, we ought only to conceive it as which are composed of materials as clear and being nearly so. It has been found in the last transparent as glass, assume many strange and age to be rather flatted at both poles, so that its fantastic appearances. Some of them look like form is commonly resembled to that of a turnip. churches or castles, with pointed turrets; some The cause of this swelling of the equator is like ships in full sail; and people have often ascribed to the greater rapidity of the motion given themselves the fruitless toil to attempt with which the parts of the earth are there car- piloting the imaginary vessels into harbour. ried round; and which, consequently, endeavour- There are still others that appear like large ing to fly off, act in opposition to central attrac-islands, with plains, valleys, and hills, which tion. The twirling of a mop may serve as a homely illustration; which, as every one has seen, spreads and grows broader in the middle as it continues to be turned round.

As the earth receives light and motion from the sun, so it derives much of its warmth and power of vegetation from the same beneficent source. However, the different parts of the globe participate of these advantages in very different proportions, and accordingly put on very different appearances; a polar prospect, and a landscape at the equator, are as opposite in their appearances as in their situation.

The polar regions, that receive the solar beams in a very oblique direction, and continue for onehalf of the year in night, receive but few of the genial comforts which other parts of the world enjoy. Nothing can be more mournful or hideous than the picture which travellers present of those wretched regions. The ground," which is rocky and barren, rears itself in every place in lofty mountains and inaccessible cliffs, and meets the mariner's eye at forty leagues from shore. These precipices, frightful in themselves, receive an additional horror from being constantly covered with ice and snow, which daily seem to accumulate, and to fill all the valleys with increasing desolation. The few rocks and cliffs that are bare of snow, look at a distance of a dark

1 Other proofs of the earth's rotundity might be adduced, the most practical of which is that derived from the many voyages performed around it-navigators pursuing a due course east or west having returned to the same place whence they set out, which could not have happened were the earth a plane.ED.

2 Crantz's History of Greenland, p. 3.

often rear their heads two hundred yards above the level of the sea; and although the height of these be amazing, yet their depth beneath is still more so; some of them being found to sink three hundred fathom under water.

The earth presents a very different appearance at the equator, where the sunbeams, darting directly downwards, burn up the lighter soils into extensive sandy deserts, or quicken all the moister tracts with incredible vegetation. In these regions, almost all the same inconveniencies are felt from the proximity of the sun, that in the former were endured from its absence. deserts are entirely barren, except where they are found to produce serpents, and in such quantities, that some extensive plains seem almost entirely covered with them.5

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It not unfrequently happens also, that this dry soil, which is so parched and comminuted by the force of the sun, rises with the smallest breeze of wind; and the sands, being composed of parts almost as small as those of water, they assume a similar appearance, rolling onward in waves like those of a troubled sea, and overwhelming all they meet with inevitable destruction. On the other hand, those tracts which are fertile, teem with vegetation even to a noxious degree. The grass rises to such a height as often to require burning; the forests are impassable from underwoods, and so matted above, that even the sun, fierce as it is, can seldom penetrate. These are so thick as scarcely to be extirpated; for the

3 Crantz's History of Greenland, p. 22.
4 Ibid. p. 27.

5 Adanson's Description of Senegal.
Linnai Amænit. vol. vi. p. 67

But to increase the beauties of the face of nature, the landscape is enlivened by springs and lakes, and intersected by rivulets. These lend a brightness to the prospect; give motion and coolness to the air; and, what is much more im

tops being so bound together by the climbing | plants that grow round them, though a hundred should be cut at the bottom, yet not one would fall, as they mutually support each other. In these dark and tangled forests, beasts of various kinds, insects in astonishing abundance, and ser-portant, furnish health and subsistence to anipents of surprising magnitude, find a quiet re- mated nature. treat from man, and are seldom disturbed except by each other.

Such are the most obvious and tranquil objects that everywhere offer: but there are objects of a more awful and magnificent kind; the moun

In this manner the extremes of our globe seem equally unfitted for the comforts and convenien-tain rising above the clouds, and topped with cies of life; and although the imagination may find an awful pleasure in contemplating the frightful precipices of Greenland, or the luxurious verdure of Africa, yet true happiness can only be found in the more moderate climates, where the gifts of nature may be enjoyed, without incurring danger in obtaining them.

snow; the river pouring down its sides, increasing as it runs, and losing itself, at last, in the ocean; the ocean spreading its immense sheet of waters over one-half of the globe, swelling and subsiding at well-known intervals, and forming a communication between the most distant parts of the earth.

If we leave those objects that seem to be natural to our earth, and keep the same constant tenor, we are presented with the great irregularities of nature: the burning mountain; the abrupt precipice; the unfathomable cavern; the headlong cataract; and the rapid whirlpool.

It is in the temperate zone, therefore, that all the arts of improving nature, and refining upon happiness, have been invented and this part of the earth is, more properly speaking, the theatre of natural history. Although there be millions of animals and vegetables in the unexplored for- | ests under the line, yet most of these may for ever continue unknown, as curiosity is there repressed by surrounding danger. But it is other wise in these delightful regions which we inhabit, and where this art has had its beginning. Among us there is scarce a shrub, a flower, or an insect, without its particular history; scarce a plant that could be useful, which has not been propa-heavy. We shall find, almost wherever we make gated; nor a weed that could be noxious, which has not been pointed out.

CHAP. III.

A VIEW OF THE SURFACE OF THE EARTH.

If we carry our curiosity a little further, and descend to the objects immediately below the surface of the globe, we shall there find wonders still as amazing. We first perceive the earth, for the most part, lying in regular beds or layers, || every bed growing thicker in proportion as it lies deeper, and its contents more compact and

our subterranean inquiry, an amazing number of shells that once belonged to aquatic animals. Here and there, at a distance from the sea, beds of oyster-shells, several yards thick, and many miles over; sometimes testaceous substances of various kinds on the tops of mountains, and often in the heart of the hardest marble. These, which are dug up by the peasants in every country, are regarded with little curiosity; for being so very common, they are considered as substances entirely terrene. But it is otherwise with the inquirer after nature, who finds them, not only in

those that are found in the sea; and he, therefore, is at a loss to account for their removal.

WHEN we take a slight survey of the surface of our globe, a thousand objects offer themselves, which, though long known, yet still demand our curiosity. The most obvious beauty that every-shape, but in substance, every way resembling where strikes the eye is the verdant covering of the earth, which is formed by a happy mixture of herbs and trees of various magnitudes and uses. It has been often remarked, that no colour refreshes the sight so much as green and it may be added, as a further proof of the assertion, that the inhabitants of those places where the fields are continually white with snow, generally become blind long before the usual course of na-he inquires how and why the surface of the earth ture.

This advantage, which arises from the verdure of the fields, is not a little improved by their agreeable inequalities. There are scarcely two natural landscapes that offer prospects entirely resembling each other; their risings and depressions, their hills and valleys, are never entirely the same, but always offer something new to entertain and refresh the imagination.

Yet not one part of nature alone, but all her productions and varieties, become the object of the speculative man's inquiry; he takes different views of nature from the inattentive spectator; and scarcely an appearance, how common soever, but affords matter for his contemplation;

has those risings and depressions which most men call natural; he demands in what manner the mountains were formed, and in what consists their uses; he asks from whence springs arise, and how rivers flow round the convexity of the globe; he enters into an examination of the ebbings and flowings, and the other wonders of the deep; he acquaints himself with the irregularities of nature, and endeavours to investi.

gate their causes; by which, at least, he will become better versed in their history. The internal structure of the globe becomes an object of his curiosity; and although his inquiries can fathom but a very little way, yet, if possessed with a spirit of theory, his imagination will supply the rest. He will endeavour to account for the situation of the marine fossils that are found in the earth, and for the appearance of the different beds of which it is composed. These have been the inquiries that have splendidly employed many of the philosophers of the last and present age, and, to a certain degree, they must be serviceable. But the worst of it is, that, as speculations amuse the writer more than facts, they may be often carried to an extravagant length; and that time may be spent in reasoning upon nature, which might be more usefully employed in writing her history.

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Too much speculation in natural history is certainly wrong; but there is a defect of an opposite nature that does much more prejudice; namely, that of silencing all inquiry, by alleging the benefits we receive from a thing, instead of investigating the cause of its production. If I inquire how a mountain came to be formed; such a reasoner, enumerating its benefits, answers, because God knew it would be useful. If I demand the cause of an earthquake, he finds some good produced by it, and alleges that as the cause of its explosion. Thus such an inquirer has constantly some ready reason for every appearance in nature, which serves to swell his periods, and give splendour to his declamation; every thing about him is, on some account or other, declared to be good; and he thinks it presumption to scrutinize its defects, or to endeavour to imagine how it might be better. Such writers, and there are many such, add very little to the advancement of knowledge. It is finely remarked by Bacon, that the investigation of final causes is a barren study; and like a virgin dedicated to the Deity, brings forth nothing. In fact, those men who want to compel every appearance and every irregularity in nature into our service, and expatiate on their benefits, combat that very morality which they would seem to promote. God has permitted thousands of natural evils to exist in the world, because it is by their intervention that man is capable of moral evil; and he has permitted that we should be subject to moral evil, that we might do something to deserve eternal happiness, by showing that we had rectitude to avoid it.

1 Buffon, Woodward, Burnet, Whiston, Kircher, Bourquat, Leibnitz, Steno, Ray, &c. 2 Investigatio causarum finalium sterilis est, et vel

uti virgo Deo dedicata nil parit.

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CHAP. IV.

A REVIEW OF THE DIFFERENT THEORIES OF THE EARTH.

HUMAN invention has been exercised for several ages to account for the various irregularities of the earth. While those philosophers, mentioned in the last chapter, see nothing but beauty, symmetry, and order; there are others, who look upon the gloomy side of nature, enlarge on its defects, and seem to consider the earth, on which they tread, as one scene of extensive desolation.1 Beneath its surface they observe minerals and waters confusedly jumbled together; its different beds of earth irregularly lying upon each other; mountains rising from places that once were level;2 and hills sinking into valleys; whole regions swallowed by the sea, and others again rising out of its bosom. All these they suppose to be but a few of the changes that have been wrought in our globe; and they send out the imagination to describe its primeval state of beauty.

Of those who have written theories describing the manner of the original formation of the earth, or accounting for its present appearances, the most celebrated are Burnet, Whiston, Woodward, and Buffon. As speculation is endless, so it is not to be wondered that all these differ from each other, and give opposite accounts of the several changes, which they suppose our earth to have undergone. As the systems of each have had their admirers, it is, in some measure, incumbent upon the natural historian to be acquainted, at least, with their outlines; and, indeed, to know what others have even dreamed in matters of science is very useful, as it may often prevent us from indulging similar delusions ourselves, which we should never have adopted, but because we take them to be wholly our own. However, as entering into a detail of these theories is rather furnishing a history of opinions than things, I will endeavour to be as concise as I can.

The first who formed this amusement of earthmaking into system, was the celebrated Thomas Burnet, a man of polite learning and rapid imagination. His Sacred Theory, as he calls it, describing the changes which the earth has undergone, or shall hereafter undergo, is well known for the warmth with which it is imagined, and the weakness with which it is reasoned; for the elegance of its style, and the meanness of its philosophy. "The earth," says he, "before the deluge, was very differently formed from what it is at present: it was at first a fluid mass; a chaos composed of various substances, differing both in density and figure: those which are most heavy, sunk to the centre, and formed in

1 Buffon's second discourse.
2 Senec. Quæst. lib. vi. cap. 21.

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