Signa autem horum et ad nostrum sensum saepe facta sunt. Iam enim terraemotus in quibusdam locis factus non prius desiit, antequam erumpens in eum qui super terram locum manifeste, ut ecnephias exivit qui movit ventus. Quale et circa Heracleam eam quae in Ponto factum fuit nuper, et prius circa Sacram insulam: haec autem est una Aeoli vocatarum insularum. In hac enim intumuit aliquid terrae, et ascendit velut collis moles cum sono; tandem autem rupta, exivit multus spiritus, et favillam et cinerem elevavit, et Liparaeorum civitatem non longe existentem omnem incineravit, et ad quasdam in Italia civitatum venit. Our theory has been verified by actual observation in many places. It has been known to happen that an earthquake did not cease until the wind that caused it burst through the earth into the air and appeared visibly like a hurricane. This happened lately near Heracleia in Pontus and some time past at the sacred island of Hiera, one of the group called the Aeolian islands, on which a portion of the earth swelled up and a lump like a mound rose with a noise: finally it burst, and a great wind came out of it and threw up live cinders and ashes which buried the neighboring town of Lipara and reached some of the towns in Italy. Et nunc ubi exsufflatio haec facta fuit, palam est: etenim facti ignis in terra hanc putandum esse causam, cum decisum accendatur, primo in parva disrupto aere. The spot where this eruption occurred is still to be seen. Indeed, this must be recognized as the cause of the fire that is generated in the earth: the air is first broken up in small particles and then the wind is beaten about and so catches fire. Argumentum autem est quod flant sub terra spiritus et quod fit circa has insulas: cum enim ventus debeat flare auster, praesignificat prius: sonant enim loca ex quibus fiunt exsufflationes, propterea quod mare propellatur iam de longe, ab hoc autem quod ex terra exsufflans repellatur iterum intus, qua quidem supergreditur mare hac. Facit autem sonum sine seismo, propter amplitudinem locorum (effunditur enim in immensum extra) et propter paucitatem repulsi aeris. A phenomenon in these islands affords further evidence of the fact that winds move below the surface of the earth. When a south wind is going to blow there is a premonitory indication: a sound is heard in the places from which the eruptions issue. This is because the sea is being pushed on from a distance and its advance thrusts back into the earth the wind that was issuing from it. The reason why there is a noise and no quake is that the underground spaces are so extensive in proportion to the quantity of the air that is being driven on that the wind slips away into the void beyond. Adhuc fieri solem caliginosum et obscuriorem sine nube, et ante matutinos terraemotus aliquando tranquillitatem et frigus forte, signum dictae causae est. Solem enim caliginosum et obscurum necessarium esse, incipiente spiritu progredi in terram, dissolvente aerem et disgregante, et ad auroram et matutinos tranquillitatemque et frigus: tranquillitatem quidem enim necessarium est ut in plurimum accidere, quemadmodum dictum est et prius, velut regressu intro facto spiritus, et magis ante maiores terraemotus: non discretum enim hoc quidem extra, hoc autem intus, sed totum simul latum necessarium valere magis. Frigus autem accidit propterea quod exhalatio intro vertitur, natura calida existens secundum se. Non videntur autem venti esse calidi quia movent aerem existentem plenum multo et frigido vapore, sicut spiritus per os exsufflatus: etenim hic quidem de prope est calidus, sicut et cum hiamus, sed propter paucitatem non similiter manifestum, de longe frigidus propter eandum causam ventis. Deficiente autem in terra tali virtute, conveniens propter humiditatem vaporosus defluxus facit frigus, in quibus accidit locis hanc fieri passionem. Again, a sign of our theory as to the cause of earthquakes is that the sun appears hazy and is darkened in the absence of clouds, and that there is sometimes calm and sharp cold before earthquakes at sunrise. For the sun is necessarily obscured and darkened when the evaporation which dissolves and rarefies the air begins to withdraw into the earth. The calm, too, and the cold towards sunrise and dawn follow from the theory. The calm we have already explained. There must as a rule be calm because the wind flows back into the earth: and it must be most marked before the more violent earthquakes, for when the wind is not part outside earth, part inside, but moves in a single body, its strength must be greater. But the cold comes because the evaporation which is naturally and essentially hot enters the earth. (Wind is not recognized to be hot, because it sets the air in motion, and that is full of a quantity of cold vapor. It is the same with the breath we blow from our mouth: close by it is hot, as it is when we open our mouth wide, but there is so little of it that it is not apparent in the same way, whereas at a distance it is cold for the same reason as wind.) Well, when this evaporation disappears into the earth the vaporous exhalation concentrates and causes cold in any place in which this disappearance occurs. Idem autem causa et signi consueti aliquando fieri ante terraemotum: aut enim per diem, aut parum post occasum, serenitate existente, nubecula subtilis apparet porrecta et longa, velut lineae longitudo quam plurimum recta, spiritu deficiente propter translationem. Simile autem accidit et in mari circa litora; quando quidem enim fluctuans inciderit, vehementer grossae et distortae fiunt rhegmines; quando autem placatio fuerit, propterea quod parva sit segregatio, subtiles sunt et rectae. Quod quidem igitur mare facit circa terram, hoc spiritus circa eam, quae in aere, caliginem, ut quando fuerit facta tranquillitas, omnis recta et subtilis derelinquatur, tanquam nubecula sit rhegmis aeris. A sign which sometimes precedes earthquakes can be explained by the same cause. Either by day or a little after sunset, in fine weather, a little, light, stretched-out and long cloud is seen, like a long very straight line. This is because the wind is leaving the air and dying down. Something analogous to this happens on the sea-shore. When the sea breaks in great waves the surf leaves marks on the shore that are very thick and crooked, but when the sea is calm they are slight and straight (because the secretion is small). As the sea is to the shore so the wind is to the cloudy air; so, when there is calm, this very straight and thin cloud is left, a sort of wave-mark in the air. Propter eandem causam autem et circa eclipses aliquando lunae accidit fieri terraemotum: quando enim iam prope fuerit interpositio, et nondum quidem omnino sit deficiens lumen et quod a sole calidum ex aere, iam autem marcefactum, tranquilitas fit, contratranslato spiritu in terram, qui facit terraemotum ante eclipses: fiunt enim et venti ante eclipses saepe, in principio quidem noctis ante eclipses mediae noctis, in media autem nocte ante diluculares. Accidit autem hoc propter marcescere calidum quod a luna, cum prope fuerit latio, in qua facta erit eclipsis. Remisso igitur quo detinebatur aer et quiescebat, iterum movetur, et fit spiritus tardioris eclipsis tardior. An earthquake sometimes coincides with an eclipse of the moon for the same reason. For when it is near the point of interposition, but the light and heat of the sun has not quite vanished from the air but is dying away, the wind, which causes the earthquake before the eclipse, turns off into the earth and calm ensues. For there also often are winds before eclipses: at nightfall if the eclipse is at midnight, and at midnight if the eclipse is at dawn. They are caused by the lessening of the warmth from the moon when its sphere approaches the point at which the eclipse is going to take place. So the influence which restrained and quieted the air weakens and the air moves again and a wind rises, and does so later, the later the eclipse. 226. Sed quoniam manifestum et cetera. Postquam Philosophus reprobavit opiniones aliorum de terraemotu, hic determinat de eo secundum suam opinionem. 226. We have already shown, etc. (365b21). After the Philosopher has rejected the opinions of others about earthquakes, he here determines them according to his own opinion. Et primo assignat causam terraemotus; And first, he assigns the cause of earthquakes. secundo causam quorundam accidentium circa ipsum, ibi: cum autem fortis factus fuerit et cetera. Second, he gives the cause of certain accidents surround them, at a severe earthquake (367b32; [238]). Circa primum duo facit: Concerning the first, he does two things. primo assignat causam terraemotus; First, he assigns the cause of eartquakes. secundo ostendit causam esse bene assignatam, ibi: existit enim terra. Second, at the earth is essentially dry (365b24), he shows that the cause is well assigned. Dicit ergo primo quod dictum est in praecedentibus duplicem esse exhalationem: unam vaporosam quae resolvitur ab humido, alteram fumosam quae resolvitur a sicco, et ex hac causatur terraemotus. He says, therefore, that it was said in what has come before that there is a twofold evaporation: a steamy evaporation that is released from wet, and a smoky evaporation that is released from dry, and it is from this evaporation that an earthquake is caused. Secundo ibi: existit enim terra etc., probat causam bene esse assignatam. Second, at the earth is essentially dry (365b24), he proves that the cause is well assigned. Et primo per rationem; And first, he proves this by argument. secundo per signa, ibi: propter quod fiunt et cetera. Second, he proves it through signs, at hence, since the evaporation (366a5; [229]). Utitur autem tali ratione: exhalatio sicca ventum causat, unde cum infra terram retinetur causat ventum infra terram; ventus autem maxime est motivus corporum; a vento igitur rationabile est fieri terraemotum. Circa hanc rationem tria facit. But he makes use of this sort of argument: dry evaporation causes wind; hence, when it is held beneath the ground it causes wind under the ground; but wind is what has the greatest force for moving bodies; therefore, it is reasonable for an earthquake to be caused by wind. Concerning this argument, he does three things. Primo manifestat quod exhalatio sicca causet ventum infra terram. Et dicit quod licet terra per se sit sicca, tamen propter imbres quos recipit multam humiditatem habet, ut sic tum ex calore solis, tum ex calore incluso in terra qui est a sole et stellis, causatur multa fumositas exhalata ex terra ex qua multum de vento causatur. Et aliquando tota materia venti a terra elevatur et causatur ventus in aere; aliquando autem tota materia retinetur intus infra terram et causat infra terram ventum; aliquando autem partim retinetur infra terram et partim elevatur supra, et sic utrobique ventus causatur. First, he shows that the dry evaporation would cause wind underground. And he says that although the earth is essentially dry, nevertheless, because it receives rain, it has much moisture. While thus, first from the heat of the sun, then from the heat enclosed inside the ground, which is from the sun and stars, much smokiness is evaporated from the ground from which much of the wind is caused. And sometimes all the matter is held inside, beneath the earth and causes wind there; but sometimes it is partly kept beneath the earth partly lifted above it, and thus wind is caused in both places. 227. Secundo ibi: si itaque hoc etc., ostendit quod ventus maxime habet virtutem ad movendum corpora. Et dicit quod cum praedictae impossibile sit aliter se habere, oportet considerare quid sit maxime motivum corporum. Ad quod duo requiruntur, quorum unum est quod possit ad multam distantiam moveri: cum enim corporalia moventia non moveant nisi moveantur, oportet quod maxime motivum est ad multum moveri; secundo oportet quod sit vehemens et violentum ad hoc quod fortiter impellat. Sed quod aliquid sit vehementissimum ad violenter impellendum convenit ex velocitate motus, quia quod velociter fertur fortiter percutit; sed quod aliquid ad magnam distantiam possit transire covenit ex subtilitate ratione cuius potest per omnia penetrare. Haec autem duo conveniunt vento, scilicet velocitas motus et subtilitas, unde sequitur quod ventus maxime possit movere corpora. Et hoc non solum per rationem, sed etiam ad sensum apparet, quia quando igni adhibetur ventus, fit inflammatio et velociter fertur. 227. Second, at if, therefore, it is impossible (365b28), he shows that wind has the greatest power for moving bodies. And he says that since it is impossible for what was said before to be otherwise, one should consider what is the greatest motive force. Two things are required for this. One of which is that it can move to a great distance: for since bodily movers do not move unless they are moved, it must be that what is moved the most is able to move much. Second, it must be that it is vigorous and violent in order to impel strongly. But that something be the most violent, in order to impel violently, is fitting with that which is so from the speed of its motion, because what is borne swiftly also impacts strongly. And that something be what can go to a great distance is fitting with that which is so from its rarity, by reason of which it can penetrate through everything. But these two requirements fit with the wind, namely, the speed of its motion and its rarity; hence, it follows that wind is able to move bodies in the highest degree. And this is apparent not only through argument, but also through the senses, since when wind is added to fire, it becomes a conflagration and moves quickly. 228. Tertio ibi: non igitur aqua, inducit conclusionem principaliter intentam, scilicet quod causa terraemotus non est neque aqua, ut dixit Democritus, neque terra, ut dixit Anaximenes, sed ventus, quando scilicet fluxus exhalationis infra terram retinetur. 228. Third, at so not water (366a3), he bring in the conclusion he principally intended, namely, that the cause of an earthquake is neither water, as Democritus said, nor earth, as Anaximenes said, but wind, when, that is, the stream of evaporation is kept beneath the earth. 229. Deinde cum dicit: propter quod fiunt etc., manifestat causam assignatam per signa. 229. Then, when he says, hence, since the evaporation (366a5), he shows the cause he has given through signs. Et primo per signa accepta ab ipsis ventis; And first, he shows the cause through signs taken from the winds themselves. secundo per signa accepta ab inferioribus rebus, ibi: adhuc autem circa loca; Second, he shows the cause through signs taken from lower things, at the severest earthquakes (366a23; [230]) tertio <per signa accepta> a rebus in alto existentibus, ibi: adhuc solem fieri caliginosum. Third, he shows the cause through signs taken from things existing on high, at again, a sign of our theory (367a20; [235]) Circa primum tria facit. Concering the first, he does three things. Primo ponit signum a ventis sumptum generaliter. Et dicit quod quia terraemotus fit a vento infra terram retento, plurimi et maximi terraemotuum fiunt quando aer est tranquillus a ventis, quia cum tota exhalatio quae resolvitur a terra et est materia venti sit quasi aliquid unum continuum, ut in pluribus sequitur impetum principii; unde si id quod primo exhalat feratur infra terram, tota exhalatio infra terram continebitur, et sic omnes venti erunt infra terram causantes terraemotum et extra erit tranquillitas; e converso autem erit si principium exhalationis feratur extra. First, he provides a sign taken from the winds in general. And he says that because an earthquake happens because of wind kept beneath the earth, most earthquakes and the greatest happen when the air is calm from winds, because since the whole evaporation, which is released from the earth and is the matter of the wind, is as something one and continuous, it generally follows in the direction in which it first started; hence, if that which first evaporates is carried beneath the earth, the whole evaportation will be contained there, and thus all the winds will be below the earth causing an earthquake, and outside, there will be calm. But the converse will be the case if the source of the evaporation is carried outwards. Secundo ibi: quosdam autem fieri, excludit quandam obiectionem quae posset fieri ex hoc quod aliquando terraemotus accidunt etiam ventis in aere existentibus. Et dicit quod hoc non est irrationabile: videmus enim quod etiam in aere quandoque flant plures venti simul, sicut ex superioribus patet, unde cum causentur duo venti quorum unus feratur infra terram faciens terraemotum et alius sit in aere, sequetur quod terraemotus sit simul cum vento in aere. Sed tamen necesse est quod huiusmodi terraemotus sint minores, quia exhalatio quae est causa et principium est divisa, partim fluens extra et partim retenta intus. Second, at, it is true that some take place (366a8) he excludes a certain objection that can be brought up from the fact that sometimes earthquakes happen even when there winds do exist in the air. And he says that this presents no difficulty. For we sometimes find that even in the air ther are many winds blowing simultaneously, as is clear from above; hence, if two winds are caused, and one of these is borne beneath the earth, making an earthquake, and the other is in the air, it would follow that earthquake would occur simulataneously with the wind in the air. But, nevertheless, it would be necessary that an earthquake of this sort would be less severe because the evaporation that their source and cause would be divided, part of it flowing outside and part of it kept inside. Tertio ibi: nocte autem, prosequitur istud signum quod a ventis assumpsit in quibusdam specialibus. Et dicit quod in nocte fiunt plures et maiores terraemotus quam in die, sed illi qui fiunt de die sunt maiores qui sunt circa meridiem. Et assignat causam quare diurnorum terraemotuum sunt maximi qui sunt circa meridiem, quia scilicet haec hora diei ut in pluribus est maxime tranquilla a ventis, quia quando sol maxime habet victoriam super terram, facit exhalationem causantem ventos declinare infra terram: illud enim quod tunc elevatur in altum propter victoriam solis rarefactum consumitur et dispergitur; sed quia non habet tantam victoriam infra terram, resolvit quidem exhalationem, sed non consumit eam; et inde est quod quando maxime sol obtinet super terram, maxime exhalatio includitur infra terram. Unde cum maxime habeat victoriam in hora meridiei, tunc maxime exhalatio declinat infra terram tranquillitate in aere existente, et ideo diurnorum terraemotuum maximi fiunt in meridie. Sed in nocte fiunt adhuc magis, quia in nocte fit tranquillitas in aere, quia exhalationes causantes ventos non ita elevantur propter absentiam solis sicut in die, etsi aliquando contingant in nocte venti propter exhalationes prius elevatas; et ideo facta resolutione exhalationum in die apud praesentiam solis, quia cessat causa elevans in nocte, recurrunt exhalationes in contrarium, scilicet infra terram, et ideo terraemotus causantur in noctibus; et maxime circa diluculum, quia de nocte exhalationes infra terram retente quasi congelantur, sed circa diluculum propter appropinquationem solis resolvuntur exhalationes et excitantur venti; unde si principium ventorum inveniatur sub terra, faciet fortiorem terraemotum propter multitudinem materiae recurrentis infra terram, sicut accidit de motu Eurippi, qui propter recursum aquae fortiter movetur. Third, at, again, most earthquakes (366a13), he describes that sign taken from winds in certain special cases. And he says that most earthquakes and the severest occur at night rather than in the day, but that if they occur during the day, they are more severe about noon. And he gives the reason why, of earthquakes that occur during the day, the most severe are those that happen about noon, namely, that these hours are generally the part of the day where there there is the greatest calm from the winds, because when the sun fully triumphs over the earth, it makes the evaporation that causes the winds to recede beneath the earth. For the rarefied evaporation which is then raised on high because of the triumph of the sun is consumed and dispersed. But because the sun does not have such a triumph beneath the earth, it indeed melts the evaporation but does not consume it; and hence it is that when the sun fully prevails over the earth, the evaporation is fully enclosed beneath it. Hence, when the sun fully triumphs at noon, then the evaporation fully recedes below the earth while there is calm in the air, and therefore the severest earthquakes that happen during the day happen at noon. But, in the night, they are still greater because in the night there is calm in the air (for the evaporations that cause winds are not so raised as in the day, because the absence of the sun, even if sometimes it happens that there are winds in the night because of evaporations raised before. And therefore, after the release of the evaporations caused in the day in the presence of the sun, because the cause that raises them ceases to be at night, the evaporations hasten back, corresponding to the outward flow, namely, they return beneath the earth, and therefore, the earthquakes are caused at night. And this happens especially towards dawn, because at night the evaporations are held beneath the earth as if frozen, but towards the dawn, because of the approach of the sun, the evaporations are melted and winds are raised up. Hence, if the source of the winds is found underground, it will make a more violent earthquake because the quantity of matter returning beneath the earth happens like the motion of the Euripus, which is forcefully moved because because of the water's return. 230. Deinde cum dicit: adhuc autem circa loca, manifestat praedictam causam terraemotus per signa a rebus inferioribus accepta. 230. Then, when he says, the severest earthquakes (366a23), he shows the aforementioned cause of an earthquake through signs taken from lower things. Et primo ponit signa generalia; And first, he lays down general signs. secundo quaedam signa specialia, ibi: signa autem horum. Second, at our theory has been verified (366b30; [233]), he lays down specific signs. Circa primum tria facit: Concering the first, he does three things. primo ponit signa accepta a locis; First, he gives signs taken from places. secundo signa accepta a temporibus, ibi: et vere autem et autumno; Second, at for the same reason (366b2; [231]), he gives signs taken from the seasons. tertio signa accepta a nostris corporibus, ibi: oportet enim intelligere. Third, at we must suppose (366b14; [232]), he gives signs taken from our bodies. Dicit ergo primo quod quia terraemotus causantur ex vento infra terram retento, inde est quod circa illa loca fiunt maximi terraemotus in quibus vel mare habet magnum fluxum vel terra est spongiosa et cavernosa. Et ponit exemplum de quibusdam locis, sicut est in Ellesponto et in Achaia et in Sicilia, et circa quaedam alia loca in quibus videtur mare penetrare sub terra propter cavernositatem terrae. Et ex ista causa, quia scilicet terra est subantrosa et mare fortiter impellit, dicit esse factas in quodam loco thermas, id est emanationes aquarum calidarum: nam propter impulsionem quae fit ex motu maris infra terram, excitatur calor et ignitio interius, et maxime si sint loca cavernosa in quibus aer contineatur, et per huiusmodi adustionem redditur terra sulfurea. Dicit autem quod circa loca praedicta quae sunt vicina mari fluxili maximi fiunt terraemotus propter angustationem interioris venti ab impulsu maris ipsum exhalare non permittentis, quia ventus vehemens qui natus erat exire a terra repellitur iterum in terram propter multitudinem maris quae impellitur a vento exteriori versus terram. Assignat etiam causam quare in locis cavernosis fiunt terraemotus. Et dicit quod quaecumque regiones habent sub terra loca cavernosa quae dicuntur inania, quia non sunt plena corpore solido, magis concutiuntur per terraemotus, quia in huiusmodi cavernis recipiunt multum de vento. First, therefore, he says that because earthquakes are caused from wind held beneath the ground, it follows that the most severe earthquakes happen around those places in which either the sea has a great flow or the earth is spongy and full of caverns. And he provides an example from certain places, as is seen in the Hellespont and in Achaea and in Sicily and those certain parts in which the sea flows in channels below the earth because of the earth being full of caverns. And from that cause, because, namely, the earth is cavernous and the sea pushes strongly, he says it makes hot springs, that is, emanations of hot water, in a certain place. For because of the pushing that is caused from the motion of the sea beneath the earth, heat and internal fire is stirred up, and especially if there are cavernous places in which air is contained; and through burning of this sort, the earth is made sulfurous. But he says that in the aforementioned places that are near greatly flowing seas, earthquakes are caused by the narrow confining of the interior wind from the impulse of the sea not allowing it to breathe out, for the violent wind that would naturally leave away from the earth is thrust back into the earth by the onrush of the sea in a great mass which itself is driven against the earth by the external wind. He also gives the reason why earthquakes happen in cavernous places. And he says that whichever countries have cavernous places beneath the earth, which are hollow because not full with solid bodies, are exposed to the shaking of earthquakes, because they receive so much wind into caverns of this sort.