XXXIX. Storms and rain obviously have some regular causes, but some that are accidental, or at all events not hitherto explained. For who can doubt that summer and winter and the yearly vicissitudes observed in the seasons are caused by the motion of the heavenly bodies? Therefore as the nature of the sun is understood to control the year's seasons, so each of the other stars also has a force of its own that creates effects corresponding to its particular nature. Some are productive of moisture dissolved into liquid, others of moisture hardened into frost or coagulated into snow or frozen into hail, others of a blast of air, others of warmth or heat, others of dew, others of cold. But it must not be thought that the stars are of the size that they appear to the sight, since the consideration of their immense altitude proves that none of them is smaller than the moon. Consequently each of them exercises its own nature in its own motion, a fact which the transits of Saturn in particular make clear by their storms of rain. Nor does this power belong to the moving stars only, but also to many of those that are fixed to the sky, whenever they are impelled forward by the approach of the planets or goaded on by the impact of their rays, as we observe occurring in the case of the Little Pigs, the Greek name for which is consequently the Hyades, a word denoting rain. Indeed some stars move of themselves and at fixed times - compare the rising of the Kids. But the rising of the constellation Arcturus is almost always accompanied by a hail-storm. 

XL. For who is not aware that the heat of the sun increases at the rising of the Lesser Dog-star, whose effects are felt on earth very widely? At its rise the seas are rough, wine in the cellars ripples in waves, pools of water are stirred. There is a wild animal in Egypt called the gazelle that according to the natives stands facing this dog-star at its rise, and gazing at it as if in worship, after first giving a sneeze. It is indeed beyond doubt that dogs throughout the whole of that period are specially liable to rabies.
 

XLI. Moreover also the parts of some constellations have an influence of their own - for instance at the autumnal equinox and at mid-winter, when we learn by the storms that the sun is completing its orbit; and not only by falls of rain and storms, but by many things that happen to our bodies and to the fields. Some men are paralysed by a star, others suffer periodic disturbances of the stomach or sinews or head or mind. The olive and white poplar and willow turn round their leaves at the solstice. Fleabane hung up in the house to dry flowers exactly on midwinter day, and inflated skins burst. This may surprise one who does not notice in daily experience that one plant, called heliotrope, always looks towards the sun as it passes and at every hour of the day turns with it, even when it is obscured by a cloud. Indeed persistent research has discovered that the influence of the moon causes the shells of oysters, cockles and all shell-fish to grow larger and again smaller in bulk, and moreover that the phases of the moon affect the tissues of the shrew mouse, and that the smallest animal, the ant, is sensitive to the influence of the planet and at the time of the new moon is always slack. This makes ignorance all the more disgraceful to man, especially as he admits that with some cattle diseases of the eyes increase and diminish with the moon. His excuse is the heaven's vastness, being divided at an enormous height into 72 signs, that is, shapes of things or of animals into which the learned have mapped out the sky. In them they have indeed noted 1600 stars as being specially remarkable for their influence or their appearance, for instance the seven which they have named the Pleiades in the tail of the Bull and the Little Pigs in his forehead, and Bootes, the star that follows the Seven Plough oxen.
 

XLII. I would not deny that rain and wind can arise from other causes than these; it is certain that the earth exhales a damp mist and at other times a smoky one due to vapour, and that clouds are formed out of moisture rising to a height or air condensed into moisture. Their density and bulk are conjectured with certain inference from the fact that they obscure the sun, which is otherwise visible even to those diving into water to whatever depth. 

XLIII. Consequently I would not go against the view that it is also possible for the fires of stars to fall from above into the clouds (as we often see happen in fine weather, and the impact of these fires unquestionably shakes the air since even weapons when flung make a hissing noise); and that when they reach the cloud, a hissing steam is produced, just as when red-hot iron is plunged into water, and a coil of smoke whirls up. And I agree that these produce storms, and if there is wind or steam struggling in the cloud, it gives out claps of thunder, if it bursts out on fire, flashes of lightning, if it forces its way on a longer track, heat-lightning. The latter cleaves the cloud, the flashes burst through it, and thunderclaps are the blows of the fires colliding, causing fiery cracks at once to flash out in the clouds. It is also possible for breath emerging from the earth, when pressed down by the counter-impact of the stars, to be checked by a cloud and so cause thunder, nature choking down the sound while the struggle goes on but the crash sounding when the breath bursts out, as when a skin is stretched by being blown into. It is also possible for this breath, whatever it is, to be set on fire by the friction during its headlong progress. It is also possible for it to be struck out by the impact of the clouds, as by that of two stones, with heat-lightning flashing out like sparks. But all these occurrences are accidental - they cause mere senseless and ineffectual thunder-claps, as their coming obeys no principle of nature - they merely cleave mountains and seas, and all their other blows are ineffectual; but the former are prophetical and sent from on high, they come by fixed causes and from their own stars. 

XLIV. Similarly I am not prepared to deny that it is possible for winds or rather gusts of air to be produced also by a dry and parched breath from the earth, and also possible when bodies of water breathe out a vapour that is neither condensed into mist or solidified into clouds; and also they may be caused by the driving force of the sun, because wind is understood to be nothing else than a wave of air; and in more ways as well. For we see winds arising both from rivers and bays and from the sea even when calm, and others, called altani, arising from the land; the latter when they come back again from the sea are called turning winds, but if they go on, offshore winds. 
The windings of mountains and their clustered peaks and ridges curved in an elbow or broken off into shoulders, and the hollow recesses of valleys, cleaving with their irregular contours the air that is consequently reflected from them (a phenomenon that in many place causes words spoken to be endlessly echoed) are productive of winds. So again are caverns, like the one with an enormous gaping mouth on the coast of Dalmatia, from which, if you throw some light object into it, even in calm weather a gust like a whirlwind bursts out; the name of the place is Senta. Also it is said that in the province of Cyrenaica there is a certain cliff, sacred to the South wind, which it is sacrilege for the hand of man to touch, the South wind immediately causing a sand-storm. Even manufactured vessels in many houses if shut up in the dark have peculiar exhalations. Thus there must be some cause for this. 

XLV. But there is a great difference between a gust of air and a wind. The latter, regular and blowing steadily, and felt not by some particular tract only but by whole countries, and not being breezes nor tempests but winds - even their name being a masculine word - whether they are caused by the continuous motion of the world and the impact of the stars travelling in the opposite direction or whether wind is the famous 'breath' that generates the universe by fluctuating to and fro as in a sort of womb, or air whipped by the irregular impact of the planets and the non-uniform emission of their rays, or whether they issue forth from these nearer stars which are their own or fall from those stars which are fixed in the heaven - it is manifest that the winds too obey a law of nature that is not unknown, even if not yet fully known. 
More than twenty Greek authors of the past have published observations about these subjects. This makes me all the more surprised that, although when the world was at variance, and split up into kingdoms, that is, sundered limb from limb, so many people devoted themselves to these abstruse researches, especially when wars surrounded them and hosts were untrustworthy, and also when rumours of pirates, the foes of all mankind, terrified intending travellers - so that now-a-days a person may learn some facts about his own region from the notebooks of people who have never been there more truly than from the knowledge of the natives - yet now in these glad times of peace under an emperor who so delights in productions of literature and science, no addition whatever is being made to knowledge by means of original research, and in fact even the discoveries of our predecessors are not being thoroughly studied. The rewards were not greater when the ample successes were spread out over many students, and in fact the majority of these made the discoveries in question with no other reward at all save the consciousness of benefiting posterity. Age has overtaken the characters of mankind, not their revenues, and now that every sea has been opened up and every coast offers a hospitable landing, an immense multitude goes on voyages - but their object is profit not knowledge; and in their blind engrossment with avarice they do not reflect that knowledge is a more reliable means even of making profit. Consequently in view of these thousands of persons who go on voyages I will give a more detailed account of the winds than is perhaps suited to the task I have set in hand. 

XLVI. The ancients noticed four winds in all, corresponding to the four quarters of the world (this is the reason why even Homer mentions no more)- a dull-witted system, as it was soon afterwards considered; the following age added eight - this system on the other hand was too subtle and meticulous. Their successors adopted a compromise, adding to the short list four winds from the long one. There are consequently two winds in each of the four quarters of the heaven: Subsolanus blowing from the equinoctial sunrise (E). and Vulturnus from the winter sunrise (S.E.)- the former designated by the Greeks Apeliotes, the latter Eurus; Auster from the sun at midday (S.) and Africus from the winter sunset (S.W.)- named in Greek Notus and Libs; Favonius from the equinoctial sunset (W.), Corus from the sunset at the solstice (N.W.)- these the Greeks call Zephyr and Argestes; Septentrio from the North and Aquilo between him and sunrise at the solstice (N.E.) - called in Greek Aparctias and Boreas. The more numerous scheme had inserted four between these: Thrascias (N.N.W.) in the space between Septentrio (N.) and the sunset at the solstice (N.W.) and also Caecias (E.N.E.) in the space between Aquilo (N.E.) and the equinoctial sunrise (E.) on the side of the sunrise at the solstice, and Phoenix (S.S.E.) in the space between winter sunrise (S.E.) and midday (S.), and also between Libs (S.W.) and Notus (S.) the combination of the two, Libonotus (S.S.W.), midway between midday (S.) and winter sunset (S.W.). Nor is this the end, inasmuch as others have also added one named Meses between Boreas (N.E.) and Caecias (E.N.E.), and Euronotus between Eurus (S.E.) and Notus (S.). There are also certain winds peculiar to particular races, which do not go outside a special region, e.g. the Athenians have Sciron, slightly diverging from Argestes (N.W.), a name unknown to the rest of Greece - elsewhere the same breeze is called Olympias: customarily an these names are taken to denote Argestes. Some people call Caecias (E.N.E.) Hellespontias, and others have other variants for these names. Similarly in the province of Narbonne the most famous of the winds is Circius (W.N.W.), which is inferior to none other at all in force and which usually carries a vessel right across the Ligurian Sea to Ostia; the same wind is not only unknown in the remaining quarters of the sky, but it does not even touch Vienne, a city of the same province, a few miles before reaching which this mighty wind is checked by the obstacle of a moderate ridge of hills. Fabianus asserts that South winds also do not penetrate Egypt - which reveals the law of nature that even winds have their prescribed limits as well as seasons. 

XLVII. Accordingly the spring opens the seas to voyagers; at its beginning the West winds soften the wintry heaven, when the sun occupies the 25th degree of Aquarius; the date of this is Feb. 8. This also practically applies to all the winds whose positions I shall give afterwards, although every leap-year they come a day earlier, but they keep the regular rule in the period that follows. Certain persons give the name Chelidonias to the West wind on the 19th February, owing to the appearance of the swallow, but some call it Ornithias, from the arrival of the birds on the 71st day after the shortest day, when it blows for nine days. Opposite to the West wind is the wind that we have called Subsolanus (E.). The rise of the Pleiads in the same degrees of Taurus on May 10 brings summer; it is a period of South wind, Auster, the opposite of Septentrio. But in the hottest period of summer the Dog-star rises, when the sun is entering the first degree of Leo - this day is July 17. The Dog-star's rise is preceded for about eight days by North-east winds: these are called the Forerunners. But two days after his rising the North-east winds begin again, and continue blowing steadily for 30 days; these are called Etesian or Annual winds. They are believed to be softened by the sun's warmth being reinforced by the heat of the star; and they are the most regular of any of the winds. They are followed in turn by South winds, continuing to the rise of Arcturus, which occurs 40 days before the autumnal equinox. With the equinox begins the Northwest wind; this, the opposite of Volturnus, marks the beginning of autumn. About 44 days after the autumnal equinox the setting of the Pleiads marks the beginning of winter, which it is customary to date on November 11; this is the period of the winter Aquilo, which is very unlike the summer one mentioned above; it is opposite to the Southwest wind. But for six days before the shortest day and six days after it the sea calms down for the breeding of the halcyons from which these days derive their name. The rest of the time there is wintry weather. However, not even the fury of the storms closes the sea; pirates first compelled men by the threat of death to rush into death and venture on the winter seas, but now avarice exercises the same compulsion. 

XLVIII. The actually coldest winds are those that we have stated to blow from the North, and their neighbour Corus (N.W.); these check the other winds and also drive away the clouds. The Southwest and especially the South are for Italy the damp winds; it is said that on the Black Sea the Eastnorth-east also attracts clouds. The North-west and South-east are dry, except when they are falling. The North-east and North are snow winds; the North brings hailstorms, and so does the North-west. The South wind is hot, the South-east and West warm; the latter are also drier than the East wind, and in general all the northerly and westerly winds are drier than the southerly and easterly. The healthiest of all is the North wind; the South is harmful, and more so when dry, perhaps because when damp it is colder; living creatures are believed to be less hungry when it is blowing. Etesian winds usually cease at night and rise at eight o'clock in the morning; in Spain and Asia they are East winds, on the Black Sea North, and in other regions South. But they also begin to blow at midwinter (when they are called the Birdwinds), but more gently and only for a few days. Two winds also change their nature with their geographical position: the South wind in Africa is fine and the North-east cloudy. All the winds blow in their own turns, usually the one opposite to the one that ceases beginning. When those next to the ones falling rise, they go round from left to right like the sun. The fourth moon usually decides about the course of the winds for the month. Vessels by means of slacking sheets can sail in contrary directions with the same winds, so that collisions occur, usually at night, between ships on opposite tacks. The South wind causes larger waves than the Northeast because the former being below blows from the bottom of the sea but the latter from the top; consequently earthquakes following South winds are specially destructive. The South wind is more violent at night and the North-east wind in the daytime; and easterly winds continue longer than westerly. North winds usually stop after blowing an odd number of days, an observation that holds good in many other departments of nature also: this is why the odd numbers are thought to be masculine. The sun both increases and reduces the force of the wind - the former when rising and setting, the latter at midday in summer seasons; consequently the winds are usually lulled at midday or midnight, because either excessive cold or excessive heat makes them slack. Also winds are lulled by rain; but they are most to be expected from quarters where the clouds have broken, revealing a clear sky. 
Eudoxus however thinks that (if we choose to study the minimal circuits) there is a regular recurrence of all phenomena - not only of winds but largely of other sorts of bad weather as well - in four-yearly periods, and that the period always begins in a leap-year at the rising of Sirius. 
These are our observations with regard to the winds that are regular. 

XLIX. Now as to sudden blasts which arise as has been said from exhalations of the earth, and fall back again to the earth drawing over it an envelope of cloud; these occur in a variety of forms. The fact is that their onrush is quite irregular, like that of mountain torrents (as we have pointed out is the view of certain persons), and they give forth thunder and lightning. If travelling with a heavier momentum they burst a great gap in a dry cloud, they produce a storm called by the Greeks a cloudburst; but if they break out from a downward curve of cloud with a more limited rotation, they cause a whirl unaccompanied by fire - I mean by lightning - that is called a typhoon, which denotes a whirling cloudburst. This brings down with it a portion of heat torn from a cloud, which it turns and whirls round, increasing its own downward velocity by its weight, and shifting from place to place with a rapid whirl; it is specially disastrous to navigators, as it twists round and shatters not only the yards, but the vessels themselves, leaving only the slender remedy of pouring out vinegar in advance of its approach, vinegar being a very cold substance. The same whirlwind when beaten back by its very impact snatches things up and carries them back with it to the sky, sucking them high aloft. 

L. But if it bursts out of a larger cavern of downward pressing cloud but not so wide a one as in the case of a storm, and is accompanied by a crashing noise, this is what they call a whirlwind, which overthrows everything in its neighbourhood. When the same rages hotter and with a fiery flow, it is called a prester, as while sweeping away the things it comes in contact with it also scorches them up. But a typhoon does not occur with a northerly wind, nor a cloudburst with snow or when snow is lying. If it flared up as soon as it burst the cloud, and had fire in it, did not catch fire afterwards, it is a thunderbolt. It differs from a fiery pillar in the way in which a flame differs from a fire: a fiery pillar spreads out its blast widely, whereas a thunderbolt masses together its onrush. On the other hand a tornado differs from a whirlwind by returning, and as a whizz differs from a crash; a storm is different from either in its extent - it is caused by the scattering rather than the bursting of a cloud. There also occurs a darkness caused by a cloud shaped like a wild monster - this is direful to sailors. There is also what is called a column, when densified and stiffened moisture raises itself aloft; in the same class also is a waterspout, when a cloud draws up water like a pipe. 

LI. Thunderbolts are rare in winter and in summer, from opposite causes. In winter, owing to the thicker envelope of cloud, the air is rendered extremely dense, and all the earth's exhalation being stiff and cold extinguishes whatever fiery vapour it receives. This reason renders Scythia and the frozen regions round it immune from the fall of thunderbolts, while conversely the excessive heat does the same for Egypt, inasmuch as the hot and dry exhalations from the earth condense very rarely, and only form thin and feeble clouds. But in spring and autumn thunderbolts are more frequent, their summer and winter causes being combined in each of those seasons; this explains why they are frequent in Italy, where the milder winter and stormy summer make the air more mobile, and it is always somewhat vernal or autumnal. Also in the parts of Italy that slope down from the north towards the warmth, such as the district of Rome and the Campagna, lightning occurs in winter just as in summer, which does not happen in any other locality. 

LII. Of thunderbolts themselves several varieties are reported. Those that come with a dry flash do not cause a fire but an explosion. The smoky ones do not burn but blacken. There is a third sort, called 'bright thunderbolts,' of an extremely remarkable nature; this kind drains casks dry without damaging their lids and without leaving any other trace, and melts gold and copper and silver in their bags without singeing the bags themselves at all, and even without melting the wax seal. Marcia, a lady of high station at Rome, was struck by lightning when enceinte, and though the child was killed, she herself survived without being otherwise injured. Among the portents in connexion with Catiline, a town-councillor of Pompei named Marcus Herennius was struck by lightning on a fine day. 

LIII. The Tuscan writers hold the view that there are nine gods who send thunderbolts, and that these are of eleven kinds, because Jupiter hurls three varieties. Only two of these deities have been retained by the Romans, who attribute thunderbolts in the daytime to Jupiter and those in the night to Summanus, the latter being naturally rare because the sky at night is colder. Tuscany believes that some also burst out of the ground, which it calls 'low bolts,' and that these are rendered exceptionally direful and accursed by the season of winter, though all the bolts that they believe of earthly origin are not the ordinary ones and do not come from the stars but from the nearer and more disordered element: a clear proof of this being that all those coming from the upper heaven deliver slanting blows, whereas these which they call earthly strike straight. And those that fall from the nearer elements are supposed to come out of the earth because they leave no traces as a result of their rebound, although that is the principle not of a downward blow but of a slanting one. Those who pursue these enquiries with more subtlety think that these bolts come from the planet Saturn, just as the inflammatory ones come from Mars, as, for instance, when Bolsena, the richest town in Tuscany, was entirely burnt up by a thunderbolt. Also the first ones that occur after a man sets up house for himself are called 'family meteors,' as foretelling his fortune for the whole of his life. However, people think that private meteors, except those that occur either at a man's first marriage or on his birthday, do not prophecy beyond ten years, nor public ones beyond the 30th year, except those occurring at the colonization of a town. 

LIV. Historical record also exists of thunderbolts being either caused by or vouchsafed in answer to certain rites and prayers. There is an old story of the latter in Tuscany, when the portent which they called Olta came to the city of Bolsena, when its territory had been devastated; it was sent in answer to the prayer of its king Porsina. Also before his time, as is recorded on the reliable authority of Lucius Piso in his Annals I, this was frequently practised by Numa, though when Tullus Hostilius copied him with incorrect ritual he was struck by lightning. We also have groves and altars and rites, and among the other Jupiters, the Stayers and Thunderers and Receivers of Offerings, tradition gives us Jupiter the Invoked. On this matter the opinion of mankind varies, in correspondence with our individual dispositions. It takes a bold man to believe that Nature obeys the behests of ritual, and equally it takes a dull man to deny that ritual has beneficent powers, when knowledge has made such progress even in the interpretation of thunderbolts that it can prophecy that others will come on a fixed day, and whether they will destroy a previous one or other previous ones that are concealed: this progress has been made by public and private experiments in both fields. In consequence although such indications are certain in some cases but doubtful in others, and approved to some persons but in the view of others to be condemned, in accordance with Nature's will and pleasure, we for our part are not going to leave out the rest of the things worth recording in this department. 

LV. It is certain that when thunder and lightning occur simultaneously, the flash is seen before the thunderclap is heard (this not being surprising, as light travels more swiftly than sound); but that Nature so regulates the stroke of a thunderbolt and the sound of the thunder that they occur together, although the sound is caused by the bolt starting, not striking; moreover that the current of air travels faster than the bolt, and that consequently the object always is shaken and feels the blast before it is struck; and that nobody hit has ever seen the lightning or heard the thunder in advance. Flashes on the left are considered lucky, because the sun rises on the left-hand side of the firmament; and their approach is not so visible as their return, whether after the blow a fire springs from it or the breath returns when its work is done or its fire used up. 
In making these observations the Tuscans divided the heaven into sixteen parts: the first quarter is from the North to the equinoctial sunrise (East), the second to the South, the third to the equinoctial sunset (West), and the fourth occupies the remaining space extending from West to North; these quarters they subdivided into four parts each, of which they called the eight starting from the East the left-hand regions and the eight opposite ones the right-hand. Of these the most formidable are those lying between West and North. Hence the line of approach and the line of retirement of thunderbolts is of very great importance. It is best for them to return to parts in the region of sunrise. Accordingly it will be a portent of supreme happiness when they come from the first part of the sky and retire to the same part - a sign that history records to have been vouchsafed to the dictator Sulla; but all the others are less fortunate or actually direful, in accordance with the division of the actual firmament where they occur. Some people think it wrong to give or to listen to reports of thunderbolts, except if they are told to a guest or a parent. The great folly of paying attention to these occurrences was discovered when the Temple of Juno at Rome was struck by lightning in the consulship  of Scaurus, who was afterwards head of the state. 
Lightning unaccompanied by thunder occurs more often by night than in the daytime. Man is the one creature that is not always killed when struck - all others are killed on the spot; nature doubtless bestows this honour on man because so many animals surpass him in strength. All things (when struck) fall in the opposite direction to the flash. A man does not die unless the force of the blow turns him right round. Men struck from above collapse. A man struck while awake is found with his eyes shut; while asleep, with them open. It is not lawful to cremate a man who loses his life in this manner, religious tradition prescribes burial. No living creature can be burnt by lightning without being killed. The temperature of the wound of those struck is lower than that of the rest of the body. 

LVI. Among things that grow in the ground, it does not strike a laurel bush. It never penetrates more than five feet into the earth; consequently when in fear of lightning men think caves of greater depth are the safest, or else a tent made of the skin of the creatures called sea-calves, because that alone among marine animals lightning does not strike, just as it does not strike the eagle among birds; this is why the eagle is represented as armed with a thunderbolt as a weapon. In Italy in the time of the Caesarian war people ceased to build towers between Terracina and the Temple of Feronia, as every tower there was destroyed by lightning.