Part 4

I am glad, said the Marchioness, you have given me this genealogy of the sciences; astronomy is the only one that will suit me: geometry, according to your account of it, requires a more selfish heart than mine; and I have not susceptibility enough to attempt poetry with success; I have, however, as much leisure as can be needful for the study of astronomy; it is another favourable circumstance that we are in the country, leading a pastoral life. Do not mistake madam, answered I, talking of planets and fixed stars is not all that constitutes a pastoral life. Was the conversation of the shepherds, in the golden age, confined to astronomy? Ah, said she, but it would be dangerous to conform one's mode of life to their's. No, that of the other shepherds you mention appears preferable to me; therefore let us converse, if you please, in the Chaldean style. After this disposition of the stars was remarked, what followed? The next thing, I replied, was to imagine the arrangement of the different parts of the universe; that is what the learned call making a system. But before I explain to you the first of these systems, give me leave to premise that we are all naturally disposed to the same sort of madness as a certain Athenian of whom you have heard, who had taken it in his head that every vessel which went into the port of Pyreum belonged to him. We chuse to believe that every thing in creation is destined to our service; and when we enquire of some philosophers the use of such a prodigious number of fixed stars, of which a smaller proportion would have been sufficient for all the offices they appear to perform; they coolly answer, they were made to gratify our sight. On this selfish principle it was for a long time supposed that the earth was motionless in the midst of the universe, whilst all the heavenly bodies were created for the sole purpose of journeying round, and distributing their light to her. Next to the earth they placed the moon, after the moon, Mercury, then Venus, the Sun, Mars, Jupiter, Saturn; beyond all these the firmament of fixed stars. It was imagined that the earth was stationed exactly in the middle of the circles described by these planets which extended in proportion to their distance from the earth, and that consequently the most remote planets required a longer time to perform their revolutions, which certainly is true. But, interrupted the Marchioness, I can't see why you should disapprove such an arrangement of the universe, it appears to me sufficiently commodious and intelligible, I really feel quite satisfied with it. I have taken pains, answered I, to represent this system in the most favourable point of view; if I were to explain it exactly as it was conceived by Ptolemy the author of it, and his disciples, you would be quite shocked. As the motions of the planets are irregular, being sometimes quicker, sometimes slower; going sometimes in one direction, sometimes in another; now nearer to the earth, then at a greater distance from it; the ancients figured to themselves an endless number of circles intersecting each other, by which they endeavoured to understand the great variety of movements. The confusion, however, caused by such an infinity of circles was so perplexing that, at the time no better system was known, one of the kings of Castile, a profound mathematician, was daring enough to say, that if the supreme Being had consulted him when he created the world, he would have given him some good advice. We are filled with horror at the impiety of this expression, but it serves to shew us how absurd must have been the hypothesis which could prompt it. The advice this man wished to have given, undoubtedly regarded the suppression of so many circles, which did but prevent the planetary motions from being understood. Probably he would likewise have expunged from the system two or three superfluous firmaments, supposed to be above the fixed stars. The philosophers, to explain some particular motion of the heavenly bodies, placed, beyond the heaven that bounds our view, a sky of crystal, which communicated this motion to the lower sky. Was a new movement discovered? they had nothing to do but to form a second crystal firmament. In short skies of crystal were made without any trouble. Why did they always chuse crystal? enquired the Marchioness; would nothing else have answered the purpose as well? No, answered I, it was necessary to have a substance, at once transparent and solid, for it was Aristotle's opinion that solidity was essential to the dignity of their nature, and as this was believed by a great man, nobody thought of doubting it. But since that time comets have been seen which, being higher than was formerly imagined, must have broken all the crystal of these skies, in passing through them, and by that mean, thrown the universe into confusion; it was therefore found necessary to change the matter of which these firmaments were composed, into a fluid, such as air.

It is now discovered with certainty, by the researches of later ages, that Venus and Mercury turn round the Sun, and not round the earth, on this subject the ancient system is absolutely exploded. I will now acquaint you with another which provides for every difficulty, one that does not require any amendments of the king of Castile, for its simplicity is so charming that one cannot refuse to believe it. Yours, interrupted the Marchioness, seems a sort of bargaining philosophy; whoever offers a system that is effected at the least expense, has the preference. 'Tis true, said I; we have no other chance of understanding the plan by which the operations of nature are carried on. Nature is a wonderful economist; if a work is to be effected, and two ways are practicable, we may be sure she will adopt that which costs her the least, however trifling the difference. This economy is notwithstanding in every respect consistent with the surprising magnificence which appears in all her productions. Magnificence is employed in the design, and frugality in the execution of it. Nothing should excite our admiration so much as a stupendous project effected by simple means: but we are apt to cherish ideas of a very different kind. We place the frugality in the designs of nature, and her grandeur in the execution. We imagine her forming a contracted plan, and executing it with ten times the labour that is requisite: what can be so ridiculous? I hope, she replied, that the system you are going to explain will strictly imitate nature; the simplicity you so admire will spare me a great deal of trouble in comprehending your instructions. Your hope will be realized, said I, we have now no useless incumbrances. At the appearance of a certain German named Copernicus, astronomy became simplified; he destroyed all the unnecessary circles, and crushed to pieces the crystalline firmaments. Animated with philosophic enthusiasm, he dislodged the earth from the central situation which had been assigned it, and in its room placed the sun, who was more worthy of such a mark of distinction. The planets were no longer supposed to perform their revolutions round the earth, and enclose it in the centre of their orbits. If they afford us light it is as it were by chance, and in consequence of passing us in their course. They all turn around the sun; the earth itself not excepted; and as a punishment for the indolent repose it had been thought to enjoy, Copernicus made it take an ample share of the general activity: in short of all these celestial attendants, appointed for the service of our little globe, the moon alone is left to move round it. Stop a moment, said the Marchioness, your imagination is so elevated with your subject, you have explained it in such pompous language, that I believe I have scarcely understood you. The sun, you say, is immoveable in the centre of the universe; which of the planets is next in succession? 'Tis Mercury, I replied. Mercury goes regularly round the Sun in nearly a circular orbit, of which that luminary is the central point. Next to Mercury is Venus, which turns in the same manner round the Sun. Afterwards comes the Earth, and being higher than Mercury and Venus, describes a larger circle round the Sun than either of those planets. Then follow Mars, Jupiter and Saturn, in the order I have named them; thus you see the circle of Saturn must be the most extensive of all; it likewise requires a longer time than the other planets to perform its revolution. But, exclaimed she, you have forgotten the moon. I shall recollect it presently, said I; the moon never abandons the earth, but is constantly going round it; but as the earth is continually moving onwards in a circle round the sun, the moon at once follows its motion, and revolves round it; this attendant planet, therefore only goes round the sun in consequence of invariably continuing near to the earth.

I understand you, said she, and I love the moon for remaining attached to us when we were forsaken by all the other planets. Confess that if your German could have alienated that too, he would have done it without regret; for one may see, in every part of his hypothesis, that he was but little inclined to favour the earth. He did well, I replied, to humble the vanity of men who chuse to claim the best situation in the universe; 'tis with pleasure I consider the world mixing in the crowd of planets. Pshaw! cried the Marchioness; do you think vanity can have any thing to do with a system of astronomy? Do you suppose I feel humbler for knowing that the earth goes round the sun? I assure you I esteem myself just as highly as I did before. Certainly, madam, I answered, men would be less concerned about the rank they held in the universe than that they enjoyed amongst their associates; neither would the disputes of two planets, for precedence, be so important in their judgement as those of two ambassadors. Nevertheless, the same disposition which induces a man of the world to aspire after the most honourable place in a room, will make a philosopher desirous of placing the globe on which he lives in the most distinguished situation in the universe. He likes to consider every thing made for his use; he encourages, without being aware of his vanity, so flattering an opinion, and his heart becomes deeply engaged about an affair of mere speculation. Upon my word, she exclaimed, you are calumniating human nature--how happened it that the opinions of Copernicus were received, since they are so very humiliating? Copernicus, answered I, was himself very doubtful of the reception they would meet with: it was a long while before he could resolve to publish his system; at last, however, he yielded to the entreaty of several distinguished characters; but what do you think was the consequence?--on the day they took him the first printed copy of his book, he died: so he made use of the shortest way to escape from all the contradictions he had been anticipating.

Listen to me, said the Marchioness: let us be just to every body: it certainly is difficult to imagine we turn round the sun, for we never change places; we rise in the morning where we went to rest at night----I see from your look that you are going to tell me, that as the earth moves altogether----. Assuredly, said I, it is the same thing as going to sleep in a boat which was sailing down a river; on waking, you would find yourself in the same boat, and in the same part of the boat. Yes, replied she, but here is a difference; when I awoke I should find an alteration in the shore, and that would prove that the boat had changed its place: it is not so with respect to the earth, I there find every thing as I left it. No, no, madam, you may observe an alteration in the shore, as you do in the boat: you will recollect that beyond all the planets are the fixed stars, these are what we must consider the objects on the shore. I am on the earth; the earth describes a large circle round the sun; when I look to the middle of this circle I find the sun, and were not its brightness so dazzling as to render the stars invisible, I should constantly see, by looking beyond the centre, some of the fixed stars opposite to the sun; by viewing them however at night, I can easily determine how they were situated in the day, which renders my observations equally accurate. If the earth remained in the same place I should always find the same fixed stars answering to the situation of the sun, but as the earth moves on in her orbit, I necessarily see other fixed stars at the point which I had before examined. Such is our shore, which is every day varying; and as the earth goes round the sun in a year, I observe the sun, during that space of time, successively answering to different fixed stars which compose a circle; this circle is called the Zodiac; shall I shew it you by tracing a figure on the earth? No, said she, I can dispense with that; it would give my park too learned an appearance. I think I have heard that a philosopher, shipwrecked on an island with which he was unacquainted, cried out to his companions on perceiving some lines and circles drawn on the sand; courage, my friends! the island is inhabited; here are the footsteps of men. You must consider that such footsteps ought not to be seen here.

It would certainly, I replied be more in character, to trace only the footsteps of lovers; that is to say, your name, engraved by your adorers on the bark of every tree. No more of adorers, cried she; let us talk of the sun. I understand perfectly why we imagined it performing the revolution which is merely effected by our own motion, but this circle requires a year; how, then, does the sun appear to go round us every day? You undoubtedly know, I replied, that if a ball were rolled along this walk it would have two sorts of motion; it would go towards the end of the walk, and at the same time turn several times on its own axis, so that the side of the ball which is at first uppermost will presently descend, and the other, of course, rise to the top. This is the case with the earth: whilst she is proceeding, through the year, in her orbit round the sun, she turns on her own axis every twenty-four hours: each part, therefore, of the earth loses, and recovers sight of the sun during that time. When in the morning we turn towards the sun, it seems to rise; and when, by continued rotation, we again are more distant from it, it appears to descend. That's curious enough, said she; the earth undertakes every thing, and the sun does nothing at all: and when the moon, the other planets, and the fixed stars appear to pass over us in four-and-twenty hours, it is merely imagination. Exactly so, I replied, and produced by the same cause. The planets perform their revolutions round the sun in unequal periods of time, in consequence of their different distances from it; and one which we see to day answer to a certain point in the zodiac, or circle of fixed stars, will to-morrow at the same hour answer to some other point: this is the effect both of the progress which the planet has made in its orbit and of that which we have made in ours. We move onward; the other planets do the same, but we do not continue all in a line: this occasions us to see them in such different situations, and renders their course apparently irregular. You now understand that such irregularity depends only on the different points from which we view them, and that, in reality all their movements are directed by the most exact order. It may be so, answered the Marchioness; but I should be glad if their order did not cost the earth so much: you seem to have very little consideration for it, and to require an astonishing agility in so large a body. But, said I, do you think it more reasonable for the sun, and all the other heavenly bodies, which are extremely large, to perform in four-and-twenty hours an immense journey round the earth? That the fixed stars, being in the largest circle, should travel, in the course of a day, more than twenty-seven thousand six hundred and sixty times two hundred millions of leagues? All this must be if the earth does not turn on her axis every twenty-four hours. Surely there is much more rationality in supposing our globe to turn, which would give to each part but a journey of nine thousand leagues. Consider what a trifle are nine thousand in comparison of the terrific number I have just mentioned.

Oh! replied the Marchioness; the sun and stars are made of fire, a swift motion is nothing to them, but the earth does not seem formed for motion. And should you think, I answered, if experience had not proved the fact, that a large ship, carrying a hundred and fifty pieces of cannon, three thousand men, and a heavy freight of merchandize, could be formed for motion?--Yet a gentle breeze is sufficient to move it forwards, because the water, being liquid, and easily divided, makes a very slight resistance to the progress of the ship, or if it be in the middle of a river, it follows without difficulty the current of the water, since there is then no impediment. In like manner the earth, notwithstanding its weight, is with facility carried through the sky which is infinitely more fluid than water, and which fills the immense space occupied by all the planets. To what could the earth be fastened so strongly as to resist the current of this celestial fluid and remain motionless? We might as well imagine a little wooden ball could resist the tide of a river.

But, said she, how can a body so ponderous as the earth be suspended in your celestial fluid, which from its great fluidity must be extremely light? It does not follow, I replied, that a substance must be extremely light because it is fluid. What do you think of the great ship we have been talking of, which, with all its lading, is lighter than the water that supports it? I won't have any more to say to you, answered she, half angrily, if you mention your ship again. But tell me, is it not dangerous to inhabit such a whirli-gig as you represent the earth? If you are afraid, said I, let us have the world supported by four elephants, as the Indians do. Well! cried she, here is a new system. I like those people for providing such good foundations for the earth to rest on, whilst we Copernicans are imprudent enough to swim at random in this celestial fluid. I dare say if the Indians knew there was the least danger of the earth's being moved, they would double the number of elephants.

It would be worth while, I replied, laughing at the thought, we must not be sparing of elephants if they can enable us to sleep in peace; if you would find them serviceable to-night we'll put as many as you please, and then remove them one or two at a time as you find your courage return. No, said she, I don't think there is any need for them, and to speak seriously, I feel courageous enough to let the world turn round. And I can venture to predict, answered I, that in a little while its turning will give you pleasure; will even inspire the most delightful ideas, I sometimes imagine myself raised above the surface of the earth, and remaining motionless whilst its daily rotation continues. All the different inhabitants pass in review; some fair, some copper-coloured, some black. Now I see heads covered with hats; then with turbans; some shaven, others with flowing hair. As the towns pass before me, I observe some have steeples, some long spires with crosses on them, others are ornamented with towers of porcelaine. Then I behold large countries with no other buildings than little huts: afterwards, immense seas; then frightful deserts; and in short, all the boundless variety which is to be found on the face of the earth.

Really, she replied, it would be worth while to devote four-and-twenty hours to such a sight. If I understand you, when we move, other countries with their inhabitants pass into the situation we are leaving, and so on, till in four-and-twenty hours we again arrive at the same place.

Copernicus himself, said I, could not have comprehended it more clearly. The first that would succeed us would be the English: we should probably find them arguing on some political topic with less gaiety than we are discussing our philosophy. When we had dismissed them we should discover a vast sea, on which perhaps would be some vessel, less at her ease than we. Then come the Iroquois, eating one of their prisoners of war, who does not even utter a groan though still alive when they begin to devour him. After them the women of Jesso, who employ all their time in preparing victuals for their husbands, and painting their lips and eye-brows blue to appear handsome in the eyes of the most disgusting men in the world. Then the Tartars, very devoutly going on a pilgrimage to their high priest, who dwells in an obscure recess, enlightened only by lamps, the rays of which direct these votaries to the object of their adoration. Afterwards the beautiful Circassians who make no ceremony of granting all their favours to the first that solicits them, except what they believe the essential prerogative of their husbands. Then the inhabitants of Little Tartary, who go to steal women for the Turks and Persians. Last of all our countrymen, whom we should find entertaining each other with the vagaries of their imagination.

It is amusing enough, said the Marchioness, to fancy oneself in a situation to see all these things: but if I were taking the view I should wish for the power of hastening or retarding the earth's motion, according to the feelings with which each object inspired me: I assure you I should soon push on those that argued on politics, and the others that devoured their enemies; but there are some of the people you have been speaking of that would excite my curiosity; the handsome Circassians, for instance, whose customs are so peculiar. But a serious difficulty occurs to me respecting your system. If the earth turns, we every moment change our atmosphere, and respire that of a new climate. By no means, madam, I replied; the air which surrounds the earth rises only to a certain height, twenty leagues perhaps at farthest; this atmosphere always turns with us. You have doubtless observed the sort of shell in which a silk-worm imprisons itself, and which it forms with such astonishing art. It is composed of silk closely woven, but covered with a light down. Thus it is with regard to the earth, it is a solid body covered with an atmosphere extending to a certain height, which adheres to, and moves with it, as the down does with the firmer substance beneath it. Above our atmosphere is the celestial matter, incomparably more pure, subtile and active than air.

You represent the earth in a very contemptible light, said the Marchioness. Nevertheless on this silk-worm's shell we find stupendous works, furious wars, and universal agitation. Yes, answered I, and while all this is going on, nature, who does not concern herself about such frivolous things, carries us all along, with an uninterrupted motion, and amuses herself with the little ball.

It appears very ridiculous, replied she, to give way to so much anxiety, whilst one is living on a thing that is perpetually turning; but unfortunately we are not assured that it does turn, for, to tell you the truth, all the precautions you take to convince me that we should not feel its motion are unsatisfactory. How could it avoid giving some indication by which we should be sensible of it? The most common and natural motions, said I, are the least felt: this observation is true even in a moral sense: the motions of self-love are so frequent in our minds, that for the most part we are not sensible of them, but believe ourselves actuated by other principles. Ah! you are beginning to moralize, said she; moralizing and explaining natural philosophy are a little different; I fancy you grow tired of your subject: let us return home, we have had enough for the first lecture. To-morrow we will come here again--you with your systems, and I with my ignorance.

In our way to the house, to give her a complete history of systems, I told her that a third had been invented by Ticho Brahe, who, from a determination to keep the earth in a state of rest, placed her in the centre of the universe, making the sun revolve round her, and the planets round the sun; for in consequence of some discoveries which had been lately made, he found it impossible to make the planets go round the earth. The Marchioness, with her usual discernment, concluded that it was mere whim to exempt the earth from moving round the sun, when so many other larger bodies were allowed to perform the revolution; that the sun was rendered more unfit for turning round the earth when incumbered with the other planets, and in short that this system was only calculated to support a prejudice in favour of the earth's immobility, without offering any thing to convince the judgment; we therefore resolved to retain that of Copernicus, which is more uniform and pleasing, and at the same time unmixed with prejudice. In fact its simplicity convinces, whilst its boldness excites admiration.

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SECOND EVENING.

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THE MOON IS A HABITABLE GLOBE.

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The next morning as soon as the Marchioness was awake, I sent to enquire how she did, and whether she had been able to sleep whilst the globe was turning? I received for answer, that she already felt quite accustomed to the motion; and had slept as undisturbedly as Copernicus himself. Soon afterwards, some company came to spend the whole day with her; a tiresome custom which is always observed in the country; yet long as the visit was, we considered it a great kindness in the guests, not to prolong it to the next day; which I find is a common practice in this part of the world: however, as they had the civility to leave us, the Marchioness and I had the evening to ourselves. We immediately went to the park and resumed our astronomical conversation. She understood so perfectly all I had said on the former evening, that she disdained to hear any repetition of the subject, and desired me to enter on a new one.--Well then, said I, since the sun, which we concluded is immovable, can no longer be considered a planet; and the earth is proved to be one, and to move round the sun; you will be the less surprised to hear, that the moon is a world like ours; and to all appearance, inhabited.--I never heard speak of peopling the moon; she replied, but as a ridiculous, visionary hypothesis.--It may be so, answered I; I only adopt the interest of any party, in these cases, as people do in civil wars; in which the uncertainty of the event, induces them to hold a correspondence with opposite sides, and even, when possible, with their enemies. For my part, though I believe the moon is inhabited, I can be very civil to any one that disbelieves it; and I always retain the power of going over to their side without disgracing myself, if I found they had the advantage: but in the present state of the question I have the following reasons for thinking the moon is inhabited.

Let us suppose that no communication had ever been carried on between Paris and St. Dennis; and that a Parisian who had never gone out of his own city should stand on one of the towers of Notre-Dame, and at that distance view St. Dennis: were he asked if he believed that St. Dennis was inhabited like Paris, he would without hesitation answer, No; I see inhabitants in Paris, but I can discover none at St. Dennis, nor did I ever hear of any being there. Somebody standing by, might answer, that we certainly cannot see them from the towers of Notre-Dame, but that is, because we are at too great a distance; that from all we can discern of St. Dennis it is very much like Paris; that it has steeples, houses, walls; and therefore is very probably inhabited. All this makes no impression on our citizen; he insists upon it that St. Dennis is uninhabited because he does not see any body in it. The moon is our St. Dennis, and each of us is this Parisian who has never left the city in which he resides.

Oh! you wrong us, interrupted the Marchioness; we are not so stupid as your citizen; when he sees that St. Dennis is constructed exactly on the same plan as Paris, he must be out of his senses not to believe it inhabited: but the moon is very different from the earth. Be cautious, madam, said I; if the moon's resemblance to the earth prove it habitable, I shall force you to believe that it is inhabited. I confess, answered she, that if you can shew me the similarity, I cannot pretend to deny its being inhabited, and I see so much confidence in your looks that I am afraid you will be triumphant. The two different motions of the earth, which I never before knew any thing about, make me fearful of hastily rejecting any other opinion; but still, can it be possible that the earth is luminous like the moon?--that you know is essential to their similarity. Indeed, madam, I replied, the luminous quality of planets depends on less than you imagine. The sun alone is, in his nature, luminous; but the planets only reflect the light they receive from him. He enlightens the moon; the moon reflects his rays on the earth, and the earth is undoubtedly in the same manner a source of light to the moon; it is not farther from us to the moon, than from the moon to us.

But, enquired the Marchioness, is the earth equally capable of reflecting the sun's light? I see, answered I, you have an invincible partiality for the moon. Light is composed of globules which rebound from a solid substance, but pass through any thing in which they find interstices, such as air or glass: the moon, therefore, gives us light in consequence of being a hard, solid body, which sends back these globules. I suppose you will not dispute the hardness and solidity of the earth. See then the effect of an advantageous situation--because the moon is at a distance we only view her as a luminous body instead of a large mass of matter similar to the earth. Our globe, on the contrary, from having the ill luck to be more closely inspected, appears only a mass of dark soil, fit for nothing but to produce food for animals; we do not perceive the splendour of her light, because we cannot remove to a distance from her. So it is, answered the Marchioness, with the different ranks of society: we are dazzled with the grandeur of situations superior to our own, without considering how much every condition of human life resembles all the rest.

'Tis precisely the same thing, I replied; we take upon us to decide on every thing, but we are never in a proper place for making our observations. We would form an opinion of ourselves, and we are too near; we would judge of others; they are too distant from our view. We should be placed between the earth and the moon to form a just comparison; a spectator, not an inhabitant of the world. I shall be inconsolable for the injustice we do our world, said she, and the partial regard we have for the moon, unless you can assure me that the inhabitants of that planet are as ignorant of their advantages, and consider our globe a luminous body, without knowing that from their own we derive so much light. I can make you easy on that head, answered I; we are certainly a luminary to them: they do not, it is true, see us describe a circle round them, but that does not signify. The reason of our appearing to remain in the same place is this;--the side of the moon which was turned towards us at the creation, has always continued so; we always observe the same eyes, mouth, and other features of the face which, by the help of imagination, we have contrived out of the spots on her surface. If the other half were presented to us, we should see spots arranged in a different form: this does not arise from the moon's not turning on her axis; she turns in the same time that is employed in going round the earth, that is, a month; but whilst she is performing part of her revolution on her axis, she at the same time performs an equal part of her circle round the earth, and thus, by putting herself in a new situation, continues to shew the same side: therefore although with regard to the sun and the rest of the heavenly bodies the moon evidently turns on her axis, yet when viewed from the earth she does not appear to do so. All the other luminaries seem to the moon to rise and set in the space of a fortnight, but she constantly sees our globe in the same part of the heavens. This apparent immobility, were it invariable, would be thought inconsistent with the nature of a planet; but the moon has a sort of vibratory motion which sometimes conceals a small part of the face, and exhibits a part of the other side. Now, I can venture to say that the inhabitants attribute this motion to us, and imagine that we vibrate in the heavens, like a pendulum.

All the planets, said the Marchioness, are like us human beings, who always attribute to others what belongs to ourselves. The earth says; it is not I who turn, it is the sun. The moon says; it is not I who vibrate, but the earth: there is error throughout. I would not advise you to attempt making any reform, answered I; you had better consider the remaining proofs of the resemblance which the earth and moon bear to each other. Figure to yourself those two globes suspended in the heavens. You know the sun always enlightens one half of a circular body, whilst the other half remains in the shade. There is then one half of both the earth and the moon, which is enlightened by the sun, or in other words, in which it is day, and the other half in which it is night. Observe likewise that as a ball moves with less force and celerity after it has struck against a wall from which it flies off to an opposite place, so the light is weaker when reflected to us from a body that only receives it. The pale light of the moon is in reality the brilliancy of the sun, but as we receive it merely by reflection, in coming to us, it is deprived of its strength. Of course, it shines with much greater splendour on the moon, and for the same reason the dazzling light received by our globe, from the sun, must appear faint, when reflected back to the moon. That part of the moon which to us appears luminous during the night, is the side which has day-light; and the part of the earth which is illuminated by the day, when turned toward the dark side of the moon, affords equal light to her. All this depends on the mutual position of the earth and moon. During the first days of the month, when the moon is not discernible, she is placed between the sun and us, and proceeding in the day time with the sun: the luminous side is therefore necessarily turned to the sun, whilst the dark part is towards the earth. We are unable to see the unenlightened side of the moon, but this dark half viewing the part of our globe in which it is day, is assisted by our light, and though invisible to us, has the advantage of seeing the earth as a full moon: it is then to the lunar inhabitants full-earth, if I may so express myself. After this, the moon advancing in her monthly round, and no longer between the sun and earth, turns towards us a small part of her enlightened half, and that we call the crescent. At the same time that part of the moon which is involved in the obscurity of night, ceases so see all the luminous side of the earth, and finds it continue to decrease.

Enough--said the Marchioness, in her lively manner; I shall easily learn the rest when I like: let me stop a moment, and trace the moon through her monthly circle. I see that in general that planet and the earth have very different degrees of light, and I imagine that when we have the full-moon all the luminous side of the moon is turned toward all the part of our globe which is obscure; and that, at that time, the inhabitants cannot discern us at all, but say they have new-earth. I should not chuse to be obnoxious to reproach for obliging you to enter into a long explanation of any thing so easily understood, but the eclipses--how are they effected? You could guess it without difficulty, I replied. When we have a new moon, and she, being between us and the sun, presents her dark side to our luminous half, the shadow of this obscure part falls on the earth; so that wherever the moon is in a direct line under the sun, she hides that luminary from our sight, and darkens a part of the enlightened side of our globe; this, then, forms an eclipse of the sun to us during the day-time, and an eclipse of the earth to the moon during her night. When the moon is at the full, the earth is between her and the sun, the shaded side of the earth towards the light side of the moon. If the earth's shadow fall directly on the moon, it darkens the luminous half that we see; 'tis then we have an eclipse of the moon in our night, and the moon, an eclipse of the sun in her day. What prevents an eclipse every time the moon is between the sun and us, or the earth between the sun and moon, is this; it often happens that these three bodies are not placed exactly in a line, in which case the one that would occasion the eclipse throws its shadow on one side of the other and consequently does not obstruct its light.

I am very much astonished, said the Marchioness, that there is so little mystery in eclipses, and that being produced by such simple means, every body does not discover the cause of them. In truth, answered I, there are many people, who from the emotions they feel at one of these phenomena, appear to have little chance of finding out the occasion of them at present. Throughout the East-Indies, when the sun and moon are eclipsed, the inhabitants believe that a great dragon with his black claws is going to seize these luminaries; and all the time the eclipse lasts, you may see whole rivers covered with the heads of these Indians, who have put themselves up to the throat in water, because, according to their notions, this is a very religious act, and will induce the sun or moon to defend itself bravely against the dragon. In America, it was thought that the sun and moon were angry when they were eclipsed, and every kind of absurdity was practised to regain their favour. The Grecians too, who had arrived at such a height of refinement--did they not, for a long time, believe that the moon was eclipsed by the power of sorcery, and that the magicians caused her to descend from the skies and cast a baneful influence on the herbs? And were not we likewise in great alarm, but two-and-thirty years ago, at a total eclipse of the sun? Did not an immense number of people shut themselves up in caves and cellars; and were they easily persuaded to leave them by the philosophers who wrote so much to re-assure them?

Really, replied she, all that is too ridiculous. There ought to be a decree passed to prevent any body from ever talking of eclipses, lest the memory of these follies should be perpetuated. The decree, said I, should extend so far as to obliterate the memory of every subject, for I can think of nothing in the world which is not the monument of some human folly.