phantoms of this kind are white and resemble so many discs of the moon, for the reason that the sun’s light that they receive and reflect back is always oblique. If the cloud, on the contrary, is beneath the 3 sun and too near him, his rays dispel it: or again, if situated too far away, it does not reflect them nor produce any image. In ordinary experience in the same way mirrors withdrawn to a distance from us do not reproduce our features because our sight cannot carry back to us from them.
These suns, too--to employ the name given by the chroniclers,--are an indication of rain, especially if they have their position in a southern quarter, from which the most heavily-charged clouds chiefly come up. When such an image surrounds the sun on both sides, then, if we are to believe Aratus, a storm is brewing.
XIV It is now high time that I ran over the other varieties of celestial 1 fires, whose forms are diverse one from the other. Sometimes there is a shooting star, sometimes there are glowing lights, which are occasionally stationary, sticking to one spot, and at times able to rush through the air. Several species of these may be observed. There are, for example, _Bothynae_ (cave-like meteors) when within an outer circle there is a blazing gulf in the sky like a circular grotto excavated in it. Then there are _Pithitae_ (barrel-shaped meteors) when a vast circular mass of fire like a cask either rushes through the sky, or blazes away in one spot. There are _Chasmata_ (chasms), too, when 2 there is a subsidence of some portion of the heavens, which sends out hissing flame, as it were, from its hidden recesses. There are also a great number of colours in all these. Some are of brightest red, some of light insubstantial flame, some of white light, some glittering, some with a uniform glow of orange without sparks or rays. We see, therefore, The stars’ long tracks that gleam white behind.
These stars, for so they appear to be, dart forth and flit across 3 the sky, and by reason of their extraordinary rapidity seem to leave a long trail of fire. Our sight cannot follow their course, and wherever their career leads we imagine the heaven is all on fire.
Such is the swiftness of their flight that its separate portions are not distinguished and it can be grasped only as a whole. We are aware rather of the quarter in which the star appears than of its route. It, therefore, seems to mark its entire course with a line of continuous 4 fire, because the slowness of our vision fails to keep pace with the stages of its career and sees at the same moment the start and the finish; as happens in a flash of lightning, the fire seems a long train because the meteor traverses its path rapidly and the space through which it falls presents itself to our eyes as a whole. But, as a matter of fact, the fire does not extend itself all through the space crossed by the meteor. Nor have such long thin bodies strength enough for the 5 effort. How, then, it may be asked, do they issue forth? The answer is, the fire is kindled by the friction of the atmosphere and is urged headlong by the wind. Still, it does not always arise from wind or friction. Sometimes its origin is due to certain peculiar conditions in the atmosphere; for on high there are many elements, dry and hot and earthy, among which fire is generated. It then streams down in pursuit of fuel to sustain it, and therefore is hurried rapidly along.
The reason for the differences of colour it presents lies in the 6 nature of the material set on fire and in the degree of violence of the conflagration. A falling body of this kind betokens wind, which may be looked for in the quarter in which the meteor has burst out.
XV How, some one further inquires, are those bright gleams of light 1 which the Greeks call _Sela_ (luminosities) produced? In many ways, people say. They may arise from the violence of the winds, or from the fervent heat of the upper heavens. Fire is a very widely diffused element there, and sometimes catches the lower regions if they are combustible. The mere motion of the stars in their courses may kindle fire, and convey it to all that lies beneath them. Nay, is it not quite possible that the atmosphere should drive up even to the ether the germs of fire, from which may arise a glow or burning or darting resembling a star? Some of these gleams rush headlong like shooting 2 stars, some remain fixed in their place, emitting light sufficient to dispel darkness and reinstate daylight, until their fuel is used up, and they gradually grow dimmer, and by and by, just like a flame which is dying out, are by gradual subsidence reduced to nothingness. Some of these appear in the clouds, some above them: in such cases the thick 3 air nearer the earth feeds them for a long time, but eventually forces them right up to the stars. Certain of these last no considerable time: they straightway dart across the sky, or are extinguished just at their point of origin. These are called gleams because their appearance is fitful and short-lived, though their fall is not always unattended by injury: they have often caused as much damage as lightning. One has seen houses struck by them, what the Greeks call _astrapoplecta_[32] (= star-struck). Those that have a longer career and a stronger fire 4 which follows the motion of the heavens, or those that pursue an orbit of their own, are regarded by the Stoic philosophers as Comets: of which more anon. Different kinds of these are _pogoniae_ (bearded), _lampades_ (torches), and _cyparissiae_ (like cypress trees), and all the rest of them: they have a thin tail of fire. It is doubtful whether beams (_trabes_) and the rare barrel-meteors (_pithitae_) should be placed in this category or not. Such meteors require a great mass of 5 fire, since their immense orb sometimes surpasses in size that of the morning sun.
[32] The term might also mean _struck by lightning_. A commoner reading gives the meaning: which, when grazed by this means, the Greeks called plecta (= struck).
Among these should certainly be placed a phenomenon of which we often read in the chronicles--the heavens appeared to be on fire. The blaze of it is occasionally so high as to mount to the very stars; occasionally it is so low as to present the appearance of a distant fire. In the reign of Tiberius Caesar the fire brigade hurried off 6 to the relief of the colony at Ostia, supposing it to be in flames; during the greater part of the night there had been a dull glow in the sky, which appeared to proceed from a thick smoky fire. No one has any doubt that these burnings in the heavens contain flame as really as they display it: they have a certain substance in them. As to those formerly discussed, I mean rainbows and halos, it is a 7 question whether they deceive the sight and consist of an illusion; or really contain what appears in them. I and those who think with me cannot convince ourselves that the rainbow and halo have a basis of any definite material in them. For we judge that in a mirror there is nothing but a deception: the mirror only pretends to show a foreign body. What is revealed does not exist _in_ the mirror. Otherwise 8 it would not come out of it, nor would it be forthwith obscured by another image: nor would innumerable forms now fade from it, now be received by it. What follows, then? That these are mere phantoms and the insubstantial imitation of real bodies. Indeed, in certain instances, people have so arranged mirrors that the objects have been distorted and degraded in the reflection. For, as I have already said, there are some mirrors that twist the faces of those who look into them, some that enormously increase them until they exceed all size and proportions of these bodies of ours.
XVI At this point I wish to tell you a little story to show you how 1 unscrupulous lust is in seizing every instrument that will rouse passion: so resourceful is it in goading to madness its own morbid fury. There was one Hostius Quadra whose obscenity formed a model for everything that was lewd on the stage. He was rich and avaricious, a very slave to his millions. He was eventually murdered by his own slaves, but the late Emperor Augustus considered his murder undeserving of punishment, and as good as declared that he had been justly slain.
This man’s lust knew no distinction of sex. Among other things, he 2 had mirrors constructed of the kind just mentioned, that reflected images of abnormal size, causing, for example, a finger to exceed the size of an arm in length and thickness. He so arranged his mirrors that he could see all his accomplices’ movements, and could gloat over the imagined proportions of his own body. He raised a levy of scamps 3 like himself in all the public baths, where he chose men of the regulation height; this but whetted his appetite to have his scenes of riot reproduced in false unnatural proportions. Go to, you that say the mirror was invented for purposes of adornment! I could not soil my pen by recording the foul words and deeds of that monster: he deserved to be torn by his own jaws. To aggravate his guilt, mirrors faced him on every side that he might be a witness of his own infamy. Deeds of darkness, which lie heavy on the conscience, the 4 imputation of which ordinary men will indignantly spurn, weighed so lightly with him that he thrust them before his face, and into his very eyes. Crimes, in faith, usually dread the sight of themselves.
Even in those lost to shame, and exposed to every insult, the eye is still delicately susceptible. But that beast thought his unparalleled wickedness but a trifle; he summoned his eyes to witness it. Aye, not content with seeing his sin, he surrounded himself with mirrors to multiply and group his scenes of vice. Even when he could not see 5 directly, he employed the reflecting power of the mirrors to reveal scenes of revolting and abominable iniquity. The filthy blackguard left nothing that could be called a deed of _darkness_. He had no 6 dread of the daylight, but complacently applauded himself in all his bestial vice. Now, don’t you think he would have liked to have his portrait painted in that attitude? The ministers of public vice draw the veil of modesty over them in part: in fact, a house of ill-fame is in some degree shame-faced But that brute had made an exhibition of 7 his obscenity, and presented to his own sight what the darkest night is not deep enough to hide. I will be out and out bad, was the monster’s resolve; my eyes must share my lust, they must witness and superintend!
By my art I will defeat nature’s shyness: nobody must imagine that I 8 do not know what I am about! Nature is niggardly to man, she is more generous to the cattle. I will find means to thwart her, and to indulge my little weakness. My lust shall go one better than nature. I will construct a mirrored chamber that will reflect shapes of enormous size.
I only wish I could make the size real; but I must be content with 9 the belief of it. My vice must see more than it can compass, and must rest content with wonder at its own restraint.
Away with such a fellow! Perchance he met a speedy death even before he could gloat over the sight. He richly deserved to be offered up as a victim before his own mirror-idol.
XVII Go now and laugh at the philosophers for discussing the nature of 1 the mirror and inquiring why our face is reflected in it, and is turned toward us too. What did nature mean by giving us real bodies and then ordaining that phantoms of them also should be visible?
What was her purpose in providing material of the sort capable of receiving and returning images? Not, I trow, that we men might use a 2 looking-glass to pluck out the straggling hairs of our beard and polish up our face. Nature has never at any point merely provided resources for luxury. First of all, her motive was to show us the sun with his glare dulled, since our eyes are too weak to gaze at him direct, and without something to reflect him we should be wholly ignorant of his shape. No doubt one may study him as he rises and as he sets. But we 3 should know nothing of his true figure as he shines in fierce noonday brightness, without his softening ruddy glow, unless an image of him could be mirrored in some liquid where he shines less directly and is more easy to observe. In the second place, we should be unable to see or investigate the conjunction of two heavenly bodies, by which the daylight is wont to be interrupted, unless we could examine the reflections of sun and moon in basins on the ground with comparative freedom. In the third place, mirrors were discovered in order that 4 man might come to know himself.
Many benefits have ensued; first, the knowledge of self, after that, devices to secure specific results. The comely man was taught to shun conduct that would degrade him. The uncomely learned that bodily defects must be compensated by virtue of character. The young man was reminded by his vigour that youth was the time for learning and for performing daring deeds of chivalry. The grey-beard was warned to have respect for his hoary hair and turn his thoughts sometimes to death.
It was for this that even objects in nature have afforded us the 5 opportunity of seeing ourselves.[33] A clear fountain or a smooth stone gives each back his image. In the poet’s words: Lately I saw myself on the shore, When the sea stood calm without a breath of wind.
[33] The meaning may be, In addition, _i.e._ to artificial mirrors, objects in nature, etc.
What, think you, was the style of life of the people who dressed at a mirror of this kind? The age was unsophisticated, satisfied with what supplies chance presented. It did not as yet degrade a boon into a vice, or turn nature’s invention to purposes of lust and luxury. At first, chance revealed to each his form. In due time the inherent 6 self-love of mankind endeared the sight of their own figure, and they came to look more frequently into the mirror held up by nature in which they had first beheld their image. Later on, when a worse race of men ransacked the very bowels of the earth for treasure better hid more deeply, iron first came into use; its production might have caused no damage had the world produced only that one metal. But then in good 7 earnest were brought to light the other precious banes of earth. Their smooth surface presented the image of their possessors, who had in view some quite different purpose. One saw his reflection in a cup, another in a brass vessel procured for some ordinary use. Presently a round mirror was constructed specially to render this service: it was not as yet of polished silver, but of a common brittle ware. [33] The men of ancient days lived a homely life; they thought themselves smart enough if they washed off in the stream of the river the dirt contracted in their work. But even then they bestowed pains on dressing their hair and combing out their flowing beards. In this part of the toilet each attended to himself and at the same time helped his neighbour. The 8 thick streaming hair of the men, which it was of old the fashion to wear, was, of course, combed out by the wives. But sometimes they thought themselves handsome enough without any such artistic hand, and they just shook it out for themselves as spirited animals do their mane. Afterwards, when luxury had now gained sway, embossed mirrors of gold and silver of full-length size were made, and at last they were actually adorned with precious stones. One of these has ere now cost a woman more than the amount of a dowry given in the old days at the public expense to the penniless daughters of famous generals.
Do you suppose Scipio’s daughters bought mirrors chased with gold 9 from the iron money that their dowry was paid in? Happy the poverty that gave occasion to earn such a title to glory! The Senate would not have dowered them if they had been able to afford mirrors. Whoever the man was to whom the Senate acted the part of father-in-law, he knew that he had got a wife that was above suspicion. Nowadays the whole of the dowry that the Roman people gave Scipio would not be enough to buy a single looking-glass for some of the loose, silly daughters of our freedmen! Luxury has been gradually developed merely by the 10 possession of wealth, and has now gone to oppressive lengths; therewith vices have received an immense accession of strength. In short, everything has got so mixed up through our perverted refinements that all that used to be regarded as the decoration of women has become part and parcel of the outfit of man; I am understating, it is now an essential portion of a soldier’s kit. The mirror was introduced for the sake of the toilet; nowadays there is no vice to which it is not an indispensable adjunct.
BOOK II [THE NATURE OF AIR. THUNDER AND LIGHTNING] I Every inquiry into the nature and constitution of the universe falls 1 into three divisions--astronomy, meteorology, and geography. The first investigates the nature of the heavenly bodies, the size and shape of the fires that ring-in the world. It inquires whether the heavens are solid, composed of strong rigid material, or woven of a fine thin stuff; whether they receive or impart motion; whether the heavenly bodies are beneath them or fixed in their texture; in what manner the sun maintains the succession of the seasons; whether he returns upon his track or not, and all the other questions of a similar character.
The second division deals with what lies between heaven and earth, to 2 wit, clouds, rain, snow, and Thunder that frights the heart of man: in short, all that the atmosphere does or suffers. This subject is called meteorology (_sublimia_ = raised on high), because it deals with phenomena exalted above the low earth. The third part inquires about waters, lands, trees, crops, or to use a legal phrase, everything that is contained in the soil.
How comes it, you ask me, that you have put the question of 3 earthquakes in the division under which you are going to treat of thunder and lightning? For that is my plan. Well, the earthquake is due to air, and air is the atmosphere in violent motion. Now, though the air may enter the earth in order to produce earthquakes, the treatment of earthquakes does not fall under geography, but more properly belongs to meteorology, which deals with the sphere to which nature has assigned the atmosphere. I can tell you something that will sound stranger still: I must speak of the earth when dealing with the heavenly bodies. Why? you ask. For this reason: we discuss in 4 their own proper place, as part of geography, the properties of the earth, for example, whether it is broad, projecting unequally in a huge bulge to one side, or whether it all assumes the shape of a ball, gathering up its parts into a globe; whether it binds its waters or is itself bound by them; whether it is an animal or a lifeless mass without feeling, full of air no doubt, but not its own breath. These, and all other questions of the kind, as often as they crop up, will 5 be relegated to geography, and be placed in the lowest category. But when the question comes to be the situation of the earth, the part of the universe in which it has settled, its position with respect to the heavens and heavenly bodies, then the inquiry will take its place in the higher category,[34] and obtain higher rank so to speak.
[34] Viz. that of the heavenly bodies which constitute the subject matter of astronomy.
II Having described the three divisions into which all the material of 1 nature falls, I must add a few general remarks on the subject. And this must be premised, that the atmosphere belongs to the class of bodies that possess unity. What exactly this means, and why it must be laid down as an axiom, will appear if I go back a little, and entering more fully into the subject, tell you that certain bodies are continuous, and certain formed, by a union of different elements.[35] Continuity may be defined as unbroken union of parts one with another. Unity 2 is continuity without a break; it is the contact of two bodies joined to one another. There can be no shadow of doubt that of the bodies around us which we see and handle, and which are either perceived or perceive, certain are composite. They are so either through nexus or 3 through mere accumulation; take as illustrations a rope, corn, a ship.
Again, there are bodies that are not composite, as a tree, a stone.
You must, therefore, grant that likewise among the objects that elude sense, and are grasped only by thought, some are possessed of unity[36] [while some arise from junction of parts]. See how careful I am of your susceptibilities. If I had chosen to employ the jargon of philosophy, 4 I might have got out of the difficulty by merely saying “united bodies.” You must, in turn, be duly grateful for this concession to your weakness! What am I driving at? This: if at any time I speak of “unity” in this connection, bear in mind that it is not used of number, but has reference to the composition of a body that coheres through no external aid, but by its own unity. To this category the atmosphere belongs.
[35] This difficult passage, according to Gercke’s text, runs: You will understand the meaning of this, and the necessity for my axiomatic position if I take up the argument a little farther back, and say that there is one kind of body possessing unity, another that is continuous, and another that is formed by junction. For junction is the contact of two bodies joined one to another, continuity is the uninterrupted joining of parts one to another, unity is continuity without junction (_i.e._ without a break).
[36] That is, are not composite.
III The universe embraces all the objects that fall, or that can fall, 1 under our cognisance. Of these some are its parts, the remaining ones must form its material. Nature, just like every manual art everywhere, requires material. Let me make this a little plainer. In ourselves 2 the parts are hand, bones, sinews, eyes; the material is the sap of the digested food, which will be distributed for the nourishment of the parts. Again, blood is in a certain sense a part of us, but still it is material as well. For it goes to form other parts, and, none the less, it is among the parts that go to make up the whole body.
IV So the atmosphere is a part, a most necessary one, of the world. 1 This it is that joins heaven and earth, separating highest and lowest in such a way as yet to unite them. It separates by coming in between, it unites by rendering possible communication between the two. It transmits to the higher regions what it receives from the earth; and again, it transfuses terrestrial objects with the influences of the heavenly bodies. I call it a part of the world in the same sense as animals and trees are parts. The whole class of animals and trees forms 2 part of the universe, since it has to be taken in to make up the whole, and without it the universe is not complete. A single animal or tree is a quasi-part: though it is lost, that from which it is lost is still entire. Now the atmosphere, as I have been saying, adheres both to sky and earth. In both it is inborn. Whatever is an inborn part of anything else possesses unity, for without unity nothing can be born.
V The earth is at once part and material of the world. You are not, I 1 think, more likely to ask why it is a part than why the sky is a part.
The one is just as essential as the other to the existence of the whole, which they go to make up, and from which [from the one no less than from the other][37] sustenance is provided for all animals and crops and stars. From the earth all the strength of every man, all 2 the energy of the world with its ceaseless demands, are supplied. Hence proceeds the force that, by day and by night, sustains in their labours so many stars, so active and so eager, and that provides their food.
The universal nature derives from this source what suffices for its nourishment. The world has appropriated all that it requires throughout eternity. To adopt a tiny illustration of a great subject: eggs enclose within them as much moisture as they require for the completion of the creature that is to be hatched.
[37] The words in brackets are in all probability spurious, the addition of some commentator. The whole passage is very uncertain.
VI The atmosphere is in unbroken contact with the earth, in such close 1 juxtaposition that it must always occupy the space that she has just quitted. It is a part, as I have said, of the universe. At the same time it receives all that the earth sends forth for the nourishment of the heavenly bodies; so that, of course, it should be understood in this connection as material rather than part. It is these earthy elements that cause its fickleness and constant turmoil. Some authorities believe the atmosphere to be composed of separate bodies as dust is, but they are sadly in error. For there can never be internal effort in a body held together in any other way than by unity,[38] 2 since the elements must be in agreement in order to contribute their united strength toward the tension. Now, the atmosphere, if assumed to be cut up into atoms, must be dispersed. Scattered elements cannot hold together as one body. But, as a matter of fact, the tension of the atmosphere is proved by inflated objects that will not yield to a blow. It is proved, too, by weights carried up to a great height merely by the support of the wind. It is proved by the sound of voices sinking or swelling, according to the stirring (= vibration) of the air. For what is voice save tension of the air moulded by a 3 stroke of the tongue so as to become audible? What is all running and motion? Are they not the effects of tense air? This it is that imparts strength to the sinews, and endows the runner with his speed. When, being violently stirred, it has twisted itself into an eddy, it uproots trees and woods, carries aloft and shatters whole buildings. When the sea lies all peaceful, the air raises it in waves. Or, to descend to 4 less violent manifestations, what song can be sung without tension of breath? Or, take horns and trumpets, or those organs that by means of hydraulic pressure can produce a greater volume of sound than the mouth is capable of doing: is it not through atmospheric tension that they display their functions? Or, let us note what an enormous force is 5 exerted in secret by quite tiny seeds, whose smallness has allowed them to find a lodgment in the clefts of stones. Their slender diminutive roots gather strength enough to dislodge huge boulders, split statues, and cleave crags and rocks. And to what is this due but air tension, 6 without which there is no strength, over which no strength can prevail?
The unity of the atmosphere may, in fact, be inferred from the mere coherence of our bodies. What else is it that holds them together save air? What else is it by which the soul is stirred (literally, moved)?[39] What constitutes that motion if it be not tension? What 7 tension can there be except from unity? What unity could there be unless it were in the air? What else, too, brings forth from the earth its fruits and slender grain, and sets erect the verdant trees, and stretches out their branches, or sets them on high, but the tension and unity of air?
[38] Or, except in a body of uniform texture.
[39] Nisard translates, What imparts movement, in man, to the vital principle?
VII Some writers believe that the air is rent and separated into small 1 parts with void spaces, as they suppose, between. They consider the easy flight of birds through it a proof that it has not a compact body, but has large empty spaces: fowls, great and small, pass through it without difficulty. But this is a mistake. For water also affords the same easy motion, and there is no doubt of its unity. When it 2 receives bodies, it always retreats in the direction opposite to them.
This the Stoics call displacement, in Greek it is peristasis,[40] which takes place in air just as it does in water. For it literally stands round every body by which it is pressed. There is no need to assume an admixture of vacuum with the element. But more of this another time.
[40] περίστασις = a standing around. The Latin equivalent in the text is _circumstantia_, rendered “displacement.”
VIII From what has been said it must be inferred that in nature there 1 exists a principle of activity of enormous force. For there is nothing that does not become more active through tension; and it is no less true, nothing will be found capable of tension from another body unless it have in itself capacity of tension.[41] In the same way we say that nothing could be moved by another body without possessing the quality of mobility in itself. But what element can be conceived more likely to possess tension in itself than air? Will any one deny that it can be subject to that force after seeing how it tosses about the earth 2 with its mountains, houses, and walls and towers, and great cities with their inhabitants, seas, and whole coast-lines? The tension of air is proved, too, by its velocity and expansion. Illustrations of these properties are common: in an instant the eye extends its sight over many miles; a single voice resounds at the same moment through whole cities; light does not creep forth little by little, but is shed simultaneously over the whole world.
[41] The reading at several points is so uncertain that one cannot be at all sure of the meaning. Probably the whole passage is very corrupt. So far as the main theme is concerned, the argument seems to be, As mobility is a presupposition of motion, so tensibility is a necessary condition of actual tension produced in a body by another body. One is tempted to employ “elasticity,” but the term contains implications with which the author was apparently unfamiliar.
IX Again, how could water be subject to tension without the aid of 1 air? You entertain no doubt, I suppose, that the jet of water in the amphitheatre, which is thrown from the centre of the arena to the highest pinnacle, is accompanied by tension of the water? And yet neither hand[42] nor any other engine can send or force water more effectively than air. It lends itself readily to the influence of the 2 air, by the compelling force of which within the pipe it is raised. Its nature is to flow down, but under pressure it mounts and accomplishes great results contrary to its nature. Yes, and do not heavily laden vessels also prove that it is the resistance of air, not of water, that prevents their sinking? The water of itself would give way, and would be unable to bear up the burthens, were it not itself upborne. So, too, a quoit thrown from a height into a pond does not fall straight 3 in, but recoils, and that merely because the air bears it back. In what way, again, could the sound of a voice be transmitted through the thick barrier of a wall unless the solid masonry contained some air to receive and transmit the sound from without? The tension of the air, of course, affects not only what is exposed, but what is concealed and enclosed as well. This is easy for it to do, since it is never 4 divided, but maintains an unbroken continuity even through the centre of objects by which it appears to be parted. The interposition of walls and high mountains renders it impassable by us, but is no obstacle to itself. The air is there all the same,[43] but a portion is enclosed and we cannot follow it through; that’s all.
[42] A conjecture widely adopted gives “crane.”
[43] The general sense is clear, but the particular text is uncertain.
X Thus the air passes through the middle of an obstacle by which it is 1 apparently divided. It not merely surrounds and encircles all objects, but permeates them likewise. It is shed abroad from the bright ether on high down to the very earth. It is nimbler and rarer and more exalted than the earth, and no less so than the waters of earth; but, on the contrary, it is thicker and heavier than the ether, and is naturally cold and dark, its light and heat coming from without. It is not of the same specific quality in every region, but borrows its qualities from its surroundings. The highest part of it is extremely dry and 2 hot, and so, very rare also, from the proximity of the eternal fires, the endless motions of the stars, and the constant revolution of the heavens. But the lowest portion next the earth is dense and dark, because it forms a receptacle for the exhalations of the earth. The intermediate portion, in dryness and rarity, runs to neither extreme as compared with the highest and lowest strata, but is colder than either.
The reason is this: The higher parts are affected by the heat of the 3 heavenly bodies that are close by; and again the lower parts are warmed in the first place by the earth’s breath which is charged with heat, while in addition the sun’s rays are reflected from the ground, and as far as the reflection extends it renders the atmosphere kindlier and more genial. Besides, the temperature of the lower air is raised by the warm breath of all animals, trees, and crops, whose life is dependent on heat. Add to this also fires on the earth, not merely the 4 artificial ones about which we know, but also those concealed beneath it, some of which have ere this broken out, and myriads of which are blazing away in the hidden depths incessantly. Add, too, that all the fertile parts of the earth have some degree of heat which is exhaled into the air: heat is a condition of generation, the frigid is sterile.
So, then, the middle portion of the atmosphere being remote from all these influences abides in its native cold: for air is by nature chilly.
XI Such being the divisions of the atmosphere, I may observe that in 1 its lowest layer it is most variable, unstable, and changeful. It is near the earth that the air is, so to speak, most enterprising and most long-suffering, as it tosses or is tossed. But withal, it is not all affected in the same way, but at different times at different points its different parts are in unrest and turmoil. The reasons of the changefulness and inconstancy are in part derived from the earth: her position turning hither and thither is a potent factor in determining the quality of the atmosphere. Other reasons are due to the heavenly bodies, chiefly the sun, whose course directs the year,