Nihil autem prohibet et propter eam quae in circuitu lationem prohiberi nubes constare in superiori loco. Fluere enim necesse est omnem qui in circuitu aerem, quicumque non intra peripheriam capitur definitam, ut et terra sphaerica sit tota. Videtur enim et nunc ventorum generatio in stagnantibus terrae locis, et non excedere ventos altos montes. Fluit autem in circuitu, quia simul trahitur cum totius circulatione: ignis quidem enim cum eo quod sursum elemento, cum igne autem aer continuus est. Quare et propter motum prohibetur congregari in aquam. Sed semper quaecumque pars ipsius gravetur, extruso in superiorem locum calido, deorsum fertur, alia autem in parte simul fertur sursum exhalato igni: et sic continue hoc quidem perseverat aere plenum, hoc autem igne, et semper aliud et aliud fit unumquodque ipsorum. However, it may well be that the formation of clouds in that upper region is also prevented by the circular motion. For the air round the earth is necessarily all of it in motion, except that which is cut off inside the circumference which makes the earth a complete sphere. In the case of winds it is actually observable that they originate in marshy districts of the earth; and they do not seem to blow above the level of the highest mountains. It is the revolution of the heaven which carries the air with it and causes its circular motion, fire being continuous with the upper element and air with fire. Thus its motion is a second reason why that air is not condensed into water. But whenever a particle of air grows heavy, the warmth in it is squeezed out into the upper region and it sinks, and other particles in turn are carried up together with the fiery exhalation. Thus the one region is always full of air and the other of fire, and each of them is perpetually in a state of change. De eo quidem igitur quod est non fieri nubes neque in aquam congregationem, et quomodo oportet accipere de loco intermedio astrorum et terrae, et quo est corpore plenus, tanta dicta sunt. So much to explain why clouds are not formed and why the air is not condensed into water, and what account must be given of the space between the stars and the earth, and what is the body that fills it. De facta autem caliditate quam exhibet sol, magis quidem secundum seipsum et diligenter in his quae de sensu convenit dicere: calidum enim passio quaedam sensus est. Propter quam autem causam fit, non talibus existentibus illis secundum naturam, dicendum et nunc. As for the heat derived from the sun, the right place for a special and scientific account of it is in the treatise about sense, since heat is an affection of sense, but we may now explain how it can be produced by the heavenly bodies which are not themselves hot. Videmus itaque motum, quod potest disgregare aerem et ignire, ut et lata liquefacta videantur saepe. We see that motion is able to dissolve and inflame the air; indeed, moving bodies are often actually found to melt. Eius quidem igitur quod est fieri aestum et calorem, sufficiens est efficere et solis latio tantum: velocem enim oportet et non longe esse. Quae quidem igitur astrorum, velox quidem, longe autem; quae autem lunae, deorsum quidem, tarda autem; quae autem solis, ambo haec habet sufficienter. Now the sun's motion alone is sufficient to account for the origin of terrestrial warmth and heat. For a motion that is to have this effect must be rapid and near, and that of the stars is rapid but distant, while that of the moon is near but slow, whereas the sun's motion combines both conditions in a sufficient degree. Fieri autem magis simul cum sole ipso caliditatem, rationabile, sumentes simile ex his quae apud nos sunt: etenim hic violentia latis vicinus aer maxime fit calidus. Et hoc rationabiliter accidit: maxime enim motus solidi disgregat ipsum. Propter hanc igitur causam pertingit ad hunc locum caliditas. That most heat should be generated where the sun is present is easy to understand if we consider the analogy of terrestrial phenomena, for here, too, it is the air that is nearest to a thing in rapid motion which is heated most. This is just what we should expect, as it is the nearest air that is most dissolved by the motion of a solid body. This then is one reason why heat reaches our world. Et quia ambiens ignis per aereni spargitur motu frequenter, et fertur violentia deorsum. Another is that the fire surrounding the air is often scattered by the motion of the heavens and driven downwards in spite of itself. Signum autem sufficiens quod qui sursum locus non sit calidus neque ignitus, est discursus astrorum. Ibi quidem enim non fiunt, deorsum autem: quamvis quae magis moventur et citius, igniantur citius. Adhuc autem sol, qui maxime videtur esse calidus, videtur albus sed non igneus existens. Shooting-stars further suffix to prove that the celestial sphere is not hot or fiery: for they do not occur in that upper region but below: yet the more and the faster a thing moves, the more apt it is to take fire. Besides, the sun, which most of all the stars is considered to be hot, is really white and not fiery in color. 29. Soluta quaestione de ordinatione elementorum, solvit quaestionem de inspissatione nubium. Et ponit duas solutiones. 29. Having solved the question about the order of the elements, he now solves the one about the thickenings which produce clouds. And he gives two solutions. Quarum primam concludit ex praedictis, dicens quod hanc existimandum est esse causam quare in superiori parte aeris non congregantur nubes, quia pars eius superior, quae communiter vocatur aer, non solum est aer, sed magis est quasi ignis, ut dictum est. Sed quia etiam multo inferius infra illam partem adhuc non generantur nubes, necesse fuit ut poneret aliam solutionem. He derives the first solution from the foregoing, saying that the cause why clouds are not formed together in the upper region of the air must be considered to be the fact that this upper region, which is commonly called "air," is not only air but is something more akin to fire, as has been said. But because clouds are not formed even much below this region, it was necessary to present another solution. 30. Unde secundam solutionem ponit ibi: nihil autem prohibet et cetera. Et dicit quod nihil prohibet etiam propter motum aeris in circuitu, prohiberi quod nubes non congregentur in superiori loco: quia necessarium est quod totus aer qui est in circuitu terrae, fluat circulariter motus. 30. Hence he presents a second solution at however, it may well be (340b32), and says that nothing prevents the air's motion in its circuit from inhibiting the gathering of clouds in the upper region; for it is necessary that all the air on the circumference of the earth flow with a circular motion. Sed ab isto fluxu excipit illum aerem qui capitur inter peripheriam, idest circumferentiam, definitam, idest quae continetur infra partes terrae, ut sic tota terra inveniatur esse sphaerica cum aere incluso inter partes terrae. Et sic ille aer qui excedit omnem altitudinem montium, in circuitu fluit: aer autem qui continetur infra montium altitudinem, impeditur ab hoc fluxu ex partibus terrae immobilibus. Et propter hoc generatio ventorum videtur esse nunc in locis terrae stagnantibus, idest in aere qui continetur infra partes terrae, ac si essent stagna aeris quiescentis. Si enim aer in quo generantur venti, moveretur circulariter, oporteret quod omnes venti cum eo circulariter circumferrentur: nunc autem videmus ex diversis partibus ventos flare. But he does not include in that flow the air trapped inside the defined periphery, i.e., the circumference, namely, air enclosed within the parts of the earth, thus making a perfect sphere by virtue of the air enclosed between the parts. Therefore that air exceeding the height of all mountains flows in an orbit, while the air contained below the heights of the mountains is prevented from this flowing, blocked by the immovable parts of the earth. This is the reason why winds seem now to be generated in stagnant areas of the earth, i.e., in air which is trapped between the parts of the earth, as though constituting pools of still air. For if the air where winds are born were moved circularly, it would be necessary that all winds accompany it along its circular orbit; but now we observe that winds blow out of diverse regions. Et quia in aere fluenti non generantur venti, sed in quiescenti, propter hoc venti non excedunt montes altos: dicitur enim ab antiquis quod, sacrificiis factis in altissimis montibus, post annum inveniebatur cinis adhuc salvus, in eodem loco manens. Et hoc quod venti non generantur ibi, est signum quod etiam nubes ibi non condensantur in pluvias. Quare autem aer qui excedit montes fluat, ostendit, subdens quod ideo fluit in circuitu, quia simul trahitur cum circulatione caeli: ignis enim est continuus, idest contiguus, cum corpore caelesti, aer autem cum igne. And because winds are born not in the flowing air, but in the still air, they never exceed the high mountains; for it is said by the ancients that, when sacrifices were made on the loftiest mountains, the ashes, a year later would be found still in the same place intact. The fact that winds are not generated there is a sign, too, that clouds are not condensed into rain there. But why the air above the mountains flows he explains by saying that the reason it flows along in its course is that it is drawn along by the circling of the heaven; for fire is continuous, i.e., contiguous, with the heavenly body, and air with fire. Quia ergo superior aer fluit, per eius motum prohibetur congregari in aquam: quia motus rarefacit et congregationem impedit. Sed si qua pars illius aeris aliquo modo condensetur, aut aliquod spissum aliquo modo feratur per aliquam violentiam, feretur deorsum, idest in locum aeris propinqui terrae: et si quid calidum erat in ea, feretur sursum. Et alia pars illius aeris, quae non gravatur, feretur sursum simul cum igne exhalato. Therefore, because the upper air flows along, its motion prevents its being gathered into water, for movement rarefies things and prevents coalescence. But whenever a portion of that air condenses in some way, something denser is carried along in some way by some constrained motion, it will be carried downward, i.e., to the place of the air close to the earth; and if anything warm was in it, it would be carried upward. And the other part of that air, which did not become heavy, would be carried upward along with the exhaled fire. Et sic, dum eorum quae resolvuntur a terris et aquis aliquid manet in loco aeris, aliquid autem fertur ad locum ignis, continue unus locus manet plenus aere, et alius plenus igne: non tamen ita quod semper maneat idem aer et ignis numero incorruptus; sed semper, corrupta una parte aeris vel ignis, vel per violentiam ad terram expulsa, generatur alia, quae sursum a terra et aqua elevatur. And so, while, of those things which are resolved out of earth and water, something remains in the region of air, and something is carried upward where fire is, one place continues to be filled with air and another filled with fire; but not in such a way that the same air and fire always remain incorrupt in number. What happens is, rather, that, as one portion of air or fire corrupts or is violently expelled toward the earth, another portion is always generated and rises upward from the earth and from the water. Et ita, licet semper maneat in loco aeris aer, et in loco ignis ignis, tamen semper unumquodque ipsorum fit aliud et aliud per continuam generationem et corruptionem; sicut in fluvio decurrenti patet, in quo semper manet aqua, non tamen eadem numero, sed una defluente et alia succedente. In this way, although there is always air in the region of air, and fire in the region of fire, yet there is always a continual turnover as a result of continuous generation and corruption. An analogy of this is seen in a flowing stream, in which there is always water, yet not the same numerical water, but as some flows on, other flows into its place. 31. Deinde recolligit ea quae dicta sunt, ibi: de eo quidem igitur etc., et dicit: tanta sunt dicta a nobis de eo quod non fiunt nubes, neque inspissatio vaporum in aquam, in superiori parte aeris; et etiam de hoc, quomodo oporteat accipere de loco qui est inter suprema astra et terram, quo scilicet corpore plenus est. 31. Then he summarizes and says, so much to explain (341a9), and he says, so much for what we have to say about the fact that in the upper region of air clouds do not form and no thickening of vapors into water takes place; and also about how we must think of the region between the highest star and the earth, i.e., as to what sort of body it is filled with. 32. Deinde cum dicit: de facta autem caliditate etc., solvit tertiam quaestionem. Et circa hoc duo facit. 32. Then when he says, as for the heat (341a12), he solves the third question. About this he does two things: Primo dicit de quo est intentio: dicens quod de caliditate quam sol facit in istis inferioribus, magis conveniret dicere secundum se et diligenter, idest perfecte, in his quae dicenda sunt in libris de sensu: quia calidum est quaedam sensuum passio, est enim obiectum sensus tactus; sensus autem et sensibile habent eandem scientiam, cum adinvicem dicantur quodammodo. Sed quia materia praesens hoc requirit, dicendum est nunc propter quam causam, cum corpora caelestia non sint calida in sui natura, fit ab eis caliditas in istis inferioribus. First, he states his intention and says that, as to the heat produced in these lower bodies by the sun, it would be more suitable to discuss this formally and diligently, i.e., perfectly, among the matters to be discussed in the books dealing with sense; for "hot is a certain passion of the senses, being the object of the sense of touch. But the sense and the sensible object are treated in the same science, for they are in a certain way referred to each other. However, since the matter at hand demands it, we must now discuss why it is that, though heavenly bodies are not hot as to their nature, yet heat is produced by them in these lower bodies. 33. Secundo ibi: videmus itaque etc., solvit quaestionem. Et dividitur in duas partes: 33. second at we see that (341a17), he solves the question. And it is divided into two parts: primo ponit quaestionis solutionem; first, he presents the solution to the question; secundo probat verum esse quod in quaestione supponebatur, ibi: signum autem sufficiens et cetera. second, he proves what he had presupposed in the question, at shooting-stars further suffix to prove (341a31). Prima dividitur in duas, secundum duas causas quas assignat: The first is divided into two parts, according to the two causes assigned; secunda incipit ibi: et quia ambiens et cetera. the second begins at another is that the fire surrounding (341a28). Circa primum tria facit. With respect to the first he does three things. Primo assignat causam propter quam a corporibus caelestibus non calidis existentibus, calor in istis inferioribus generatur. Et dicit quod sensibiliter videmus quod motus, quia potest disgregare aerem et rarefacere, potest etiam eum ignire: nam raritas et igneitas se consequuntur, sicut frigiditas et spissitudo; et propter hoc ea quae feruntur, sicut sagittae, si habeant plumbum et ceram, saepe videntur liquefieri, quasi motu ea calefaciente. Unde nihil inconveniens est, si caelum suo motu calefacit ista inferiora. First he assigns the cause on account of which heat is generated in these lower bodies by heavenly bodies not themselves hot. And he says that by sense observation we see that movement, since it can separate and rarefy air, can also inflame it: for rarity and combustion go hand in hand, just as do cooling and thickening; and on this account, things borne along, such as arrows, if they include lead and wax, are often seen to melt, as though motion were making them hot. Hence it is not inconceivable that the heaven, by its motion, should heat these lower bodies. 34. Secundo ibi: eius quidem igitur etc., assignat causam quare calor in istis inferioribus causatur magis ex motu solis, quam ex motu alicuius alterius corporis superioris. Et dicit quod sol solus sufficiens est facere aestuantem calorem in istis inferioribus: nam calor qui fit ex aliis corporibus caelestibus, est quasi insensibilis respectu caloris qui fit a sole. Huius autem ratio est, quia motus qui causat vehementem calorem, oportet quod sit velox, et quod propinquus nobis. Motus autem astrorum tam fixorum quam quinque errantium quae sunt supra solem, secundum opinionem Aristotelis, scilicet Saturni, Iovis, Martis, Veneris et Mercurii, est quidem velox, remotus tamen a nobis longe; motus autem lunae, licet sit propinquus, est tamen tardus; motus autem solis habet utrumque sufficienter ad causandum calorem in istis inferioribus, scilicet et velocitatem et propinquitatem. Quod autem hic dicitur de velocitate motus solis, referendum est ad motum quo movetur secundum motum diurnum, non ad proprios motus stellarum. Manifestum est enim quod motum diurnum omnia astra eodem temporis spatio peragunt: quanto autem aliquod caelestium corporum est propinquius centro, tanto minorem circumferentiam circuit, unde tardius movetur. Secundum autem proprios motus, luna velocissime movetur. 34. second at now the sun's motion alone (341a19), he assigns the cause why heat is caused in these lower bodies more by the motion of the sun than by the motion of some other superior body. And he says that the sun by itself suffices to produce a burning heat in these lower bodies: for the heat produced from other heavenly bodies is almost imperceptible when compared to the heat caused by the sun. The reason for this is that if a motion is to cause vehement heat it must be rapid and close to us. Now the motions, both of the fixed stars, and of the five wandering stars [planets], which are, according to Aristotle, above the sun, namely, Saturn, Jupiter, Mars, Venus and Mercury, are indeed rapid, but they are far from us; on the other hand, the motion of the moon, although it is near, is, however, slow. But the motion of the sun has both, i.e., speed and nearness, in a manner sufficient to cause heat in these lower bodies. What is said here about the velocity of the sun's motion is to be referred to its diurnal motion and not to the proper motions of the stars. For it is plain that all the stars complete their diurnal motion during the same period of time: but the closer a heavenly body is to the center, the smaller is the circumference of its orbit and the slower is it moved. But with respect to proper motions, the moon is moved most rapidly. 35. Tertio ibi: fieri autem magis etc., assignat causam quare magis generatur calor ex motu ipsius solaris corporis, quam ex motu sphaerae eius. Et dicit quod rationabile est quod caliditas fiat magis cum ipso solari corpore. Et huius simile possumus sumere ex his quae sunt apud nos: quia etiam hic, aer vicinus rebus spissis quae feruntur per violentiam, maxime fit calidus. Et hoc accidit etiam rationabiliter: quia maxime motus corporis solidi disgregat aerem; unde cum ipsum corpus solare sit magis solidum quam ceterae partes sphaerae ipsius, cum non sit diaphanum, magis ex motu eius generatur calor, quam ex motu sphaerae eius. Sic igitur propter causam istam caliditas a sole pertingit ad locum istum, quamvis sol non sit calidus. 35. third at that most heat (341a23), he assigns the cause why heat is generated more by the motion of the body of the sun than by the motion of its sphere. And he says that it is reasonable for heat to be produced more by the solar body itself. Something akin to this can be discerned from what happens where we are [on earth]: for here also the air close to thick objects being moved along through violence becomes very hot. And it is reasonable that this should happen: because it is especially the motion of a solid body that dissolves air; hence, since the solar body is more solid than the other parts of its sphere, since it is not diaphanous, heat is generated more from its motion than from the motion of its sphere. This, therefore, explains why heat from the sun reaches this place, even though the sun itself is not hot. Nec huic causae impedimentum praestat quod luna est inter solem et nos, quae calefieri non potest: quia licet non calefiat a sole, aliquo tamen modo immutatur ab eo, videmus enim quod illuminatur ab eo; non semper autem eadem specie immutationis immutatur medium et extremum, sicut radius solis non inflammat vas vitreum plenum aqua, sed stupam oppositam. Apparet etiam ratio quare, ubi est umbra, non est tantus calor quantus est in loco ubi radii solares proiiciuntur: quia scilicet umbra causatur ex aliquo corpore opposito soli, quod interrumpit continuationem transmutationis quae est a sole; sed actio solis pertingit ad locum umbrae per quandam reflexionem. Nec tamen putandum est quod motus solis, inquantum est motus tantum, causet calorem: sed inquantum est motus talis corporis, in sua natura habentis virtutem calefaciendi. Omnes enim formae corporum inferiorum reducuntur in corpora caelestia sicut in quaedam principia: et inde est quod diversa corpora caelestia diversos effectus in rebus corporalibus habent, non solum secundum calidum, sed etiam secundum alias passiones et formas. Nor is any obstacle to this cause offered by the presence between us and the sun of the moon which cannot become hot; for although it is not heated by the sun, it is nevertheless influenced in a certain manner by the sun, for we observe that it is illuminated by the sun. Yet a medium and an extreme are not always changed with the same species of change: thus a ray of the sun does not ignite a [magnifying] glass filled with water, but the piece of flax placed beyond. Also the reason is apparent why, where a shadow is, there is not as much heat as in a place where the sun's rays strike: it is because a shadow is caused by a body blocking the sun and interrupting the continuing transmutation deriving from the sun; however, the action of the sun does reach the place where a shadow is by a sort of reflexion. Nor should it be supposed that the sun's motion, as motion only, causes heat; rather, it is in so far as it is the motion of such a body, i.e., of a body having in its nature the power to cause heat. For all the forms of the lower bodies are reduced back to the heavenly bodies as to certain principles: that is why diverse heavenly bodies produce diverse effects in bodily things, not only so far as heat is considered, but as far as other passions and forms are concerned. 36. Deinde cum dicit: et quia ambiens etc., ponit propriam causam caliditatis generatae ex motu solis: quae tamen non est universalis, sed particularis. Unde dicit quod frequenter ignis qui ambit inferiores partes mundi, ex motu corporis caelestis, fertur quadam violentiam deorsum, et spargitur per aerem: quia, sicut supra dictum est, superior pars aeris et ignis quendam fluxum habet ex motu caeli. 36. Then when he says, another is that the fire surrounding (341a28), he presents a proper cause of heat generated from the motion of the sun: yet not the universal cause but a particular cause. Hence he says that the fire which surrounds the lower parts of the world as a result of a heavenly body's motion is often violently thrust downwards and scattered through the air: because, as was said above, the upper part of the air and fire have a flow on account of the motion of the heaven. 37. Deinde cum dicit: signum autem sufficiens etc., manifestat quod quaestio supponebat, scilicet quod corpora caelestia non sunt calida aut ignita: et hoc per duo signa. 37. Then when he says, shooting-stars further suffix to prove (341a31), he shows something which the question supposed, namely, that heavenly-bodies are not hot or fiery; this he does by two signs. Primum est quia ibi non apparent discursus astrorum quae videntur cadentia, quae ex ignitione generantur in inferiori loco: quod non esset si corpora caelestia essent calida aut ignita; quia ubi est motus maior et velocior, ibi citius aliquid ignitur. The first is that in that region we do not see the paths of those stars which seem to be falling [i.e., shooting stars], which are generated by combustion in the lower regions. This would not be the case if heavenly bodies were hot and fiery, because, wherever there is a greater and speedier motion, there something is ignited more readily. Secundum signum est quod sol, qui maxime videtur esse calidus ex effectu, videtur coloris albi et non ignei. The second sign is that the sun, which especially seems to be hot, considering its effects, is seen to be of a white, and not a fiery, color. Lectio 6 Lecture 6 De causis et generatione discurrentium siderum et similium meteororum—differentia inter ea Shooting stars and meteors—their cause and difference His autem determinatis, dicamus propter quam causam flammae accensae apparent circa caelum, et discurrentia sidera, et vocati a quibusdam dali et aeges: haec enim omnia sunt idem, et propter eandem causam, differunt autem per magis et minus. Having determined these principles let us explain the cause of the appearance in the sky of burning flames and of shooting stars, and of 'torches', and 'goats', as some people call them. All these phenomena are one and the same thing, and are due to the same cause, the difference between them being one of degree.