Now we must admit that heat naturally proceeds outward to its own place and to its kindred element; and as there are two exits for the heat, the out through the body, and the other through the mouth and nostrils, when it moves towards the one, it drives round the air at the other, and that which is driven round falls into the fire and becomes warm, and that which goes forth is cooled. But when the heat changes its place, and the particles at the other exit grow warmer, the hotter air inclining in that direction and carried towards its native element, fire, pushes round the air at the other; and this being affected in the same way and communicating the same impulse, a circular motion swaying to and from is produced by the double process, which we call inspiration and expiration.

The phenomena of medical cupping-glasses and of the swallowing of drink and of the projection of bodies, whether discharged in the air or bowled along the ground, are to be investigated on a similar principle; and swift and slow sounds, which appear to be high and low, and are sometimes discordant on account of their inequality, and then again harmonical on account of the equality of the motion which they excite in us. For when the motions of the antecedent swifter sounds begin to pause and the two are equalised, the slower sounds overtake the swifter and then propel them. When they overtake them they do not intrude a new and discordant motion, but introduce the beginnings of a slower, which answers to the swifter as it dies away, thus producing a single mixed expression out of high and low, whence arises a pleasure which even the unwise feel, and which to the wise becomes a higher sort of delight, being an imitation of divine harmony in mortal motions. Moreover, as to the flowing of water, the fall of the thunderbolt, and the marvels that are observed about the attraction of amber and the Heraclean stones,-in none of these cases is there any attraction; but he who investigates rightly, will find that such wonderful phenomena are attributable to the combination of certain conditions-the non-existence of a vacuum, the fact that objects push one another round, and that they change places, passing severally into their proper positions as they are divided or combined.

τὸ θερμὸν δὴ κατὰ φύσιν εἰς τὴν αὑτοῦ χώραν ἔξω πρὸς τὸ συγγενὲς ὁμολογητέον ἰέναι· δυοῖν δὲ τοῖν διεξόδοιν οὔσαιν͵ τῆς μὲν κατὰ τὸ σῶμα ἔξω͵ τῆς δὲ αὖ κατὰ τὸ στόμα καὶ τὰς ῥῖνας͵ [79e] ὅταν μὲν ἐπὶ θάτερα ὁρμήσῃ͵ θάτερα περιωθεῖ͵ τὸ δὲ περιωσθὲν εἰς τὸ πῦρ ἐμπῖπτον θερμαίνεται͵ τὸ δ΄ ἐξιὸν ψύχεται. μεταβαλλούσης δὲ τῆς θερμότητος καὶ τῶν κατὰ τὴν ἑτέραν ἔξοδον θερμοτέρων γιγνομένων πάλιν ἐκείνῃ ῥέπον αὖ τὸ θερμότερον μᾶλλον͵ πρὸς τὴν αὑτοῦ φύσιν φερόμενον͵ περιωθεῖ τὸ κατὰ θάτερα· τὸ δὲ τὰ αὐτὰ πάσχον καὶ τὰ αὐτὰ ἀνταποδιδὸν ἀεί͵ κύκλον οὕτω σαλευόμενον ἔνθα καὶ ἔνθα ἀπειργασμένον ὑπ΄ ἀμφοτέρων τὴν ἀναπνοὴν καὶ ἐκπνοὴν γίγνεσθαι παρέχεται.

Καὶ δὴ καὶ τὰ τῶν περὶ τὰς ἰατρικὰς σικύας παθημάτων αἴτια [80a] καὶ τὰ τῆς καταπόσεως τά τε τῶν ῥιπτουμένων͵ ὅσα ἀφεθέντα μετέωρα καὶ ὅσα ἐπὶ γῆς φέρεται͵ ταύτῃ διωκτέον͵ καὶ ὅσοι φθόγγοι ταχεῖς τε καὶ βραδεῖς ὀξεῖς τε καὶ βαρεῖς φαίνονται͵ τοτὲ μὲν ἀνάρμοστοι φερόμενοι δι΄ ἀνομοιότητα τῆς ἐν ἡμῖν ὑπ΄ αὐτῶν κινήσεως͵ τοτὲ δὲ σύμφωνοι δι΄ ὁμοιότητα. τὰς γὰρ τῶν προτέρων καὶ θαττόνων οἱ βραδύτεροι κινήσεις ἀποπαυομένας ἤδη τε εἰς ὅμοιον ἐληλυθυίας͵ [80b] αἷς ὕστερον αὐτοὶ προσφερόμενοι κινοῦσιν ἐκείνας͵ καταλαμβάνουσιν͵ καταλαμβάνοντες δὲ οὐκ ἄλλην ἐπεμβάλλοντες ἀνετάραξαν κίνησιν͵ ἀλλ΄ ἀρχὴν βραδυτέρας φορᾶς κατὰ τὴν τῆς θάττονος͵ ἀποληγούσης δέ͵ ὁμοιότητα προσάψαντες͵ μίαν ἐξ ὀξείας καὶ βαρείας συνεκεράσαντο πάθην· ὅθεν ἡδονὴν μὲν τοῖς ἄφροσιν͵ εὐφροσύνην δὲ τοῖς ἔμφροσιν διὰ τὴν τῆς θείας ἁρμονίας μίμησιν ἐν θνηταῖς γενομένην φοραῖς παρέσχον. καὶ δὴ καὶ τὰ τῶν ὑδάτων πάντα ῥεύματα͵ [80c] ἔτι δὲ τὰ τῶν κεραυνῶν πτώματα καὶ τὰ θαυμαζόμενα ἠλέκτρων περὶ τῆς ἕλξεως καὶ τῶν Ἡρακλείων λίθων͵ πάντων τούτων ὁλκὴ μὲν οὐκ ἔστιν οὐδενί ποτε͵ τὸ δὲ κενὸν εἶναι μηδὲν περιωθεῖν τε αὑτὰ ταῦτα εἰς ἄλληλα͵ τότε διακρινόμενα καὶ συγκρινόμενα πρὸς τὴν αὑτῶν διαμειβόμενα ἕδραν ἕκαστα ἰέναι πάντα͵ τούτοις τοῖς παθήμασιν πρὸς ἄλληλα συμπλεχθεῖσιν τεθαυματουργημένα τῷ κατὰ τρόπον ζητοῦντι φανήσεται.