§2.8#18 ἀλλ᾿ ἐπειδὴ φανερὸν ὅτι ἀναγκαῖον καὶ ἀπὸ ὑγροῦ καὶ ἀπὸ ξηροῦ γίγνεσθαι ἀναθυμίασιν, ὥσπερ εἴπομεν ἐν τοῖς πρότερον, ἀνάγκη τούτων ὑπαρχόντων γίγνεσθαι τοὺς σεισμούς.
8 But since it is clear that it is necessary for exhalation to arise both from the wet and from the dry, as we said in our earlier discussions, it is necessary, when these conditions exist, that earthquakes should occur.
ὑπάρχει γὰρ ἡ γῆ καθ᾿ αὑτὴν μὲν ξηρά, διὰ δὲ τοὺς ὄμβρους ἔχουσα ἐν αὑτῇ νοτίδα πολλήν, ὥσθ᾿ ὑπό τε τοῦ ἡλίου καὶ τοῦ ἐν αὐτῇ πυρὸς θερμαινομένης πολὺ μὲν ἔξω πολὺ δ᾿ ἐντὸς γίγνεσθαι τὸ πνεῦμα· καὶ τοῦτο ὁτὲ μὲν συνεχὲς ἔξω ῥεῖ πᾶν, ὁτὲ δ᾿ εἴσω πᾶν, ἐνίοτε δὲ καὶ μερίζεται.
For the earth is in itself dry, but because of the rains it contains much moisture within itself, so that when it is warmed both by the sun and by the fire within itself, a great deal of wind is generated both outside and inside; and this wind sometimes flows entirely outside in a continuous stream, sometimes entirely inside, and sometimes it is divided.
εἰ δὴ τοῦτ᾿ ἀδύνατον ἄλλως ἔχειν, τὸ μετὰ τοῦτο σκεπτέον ἂν εἴη ποῖον κινητικώτατον εἴη τῶν σωμάτων· ἀνάγκη γὰρ τὸ ἐπὶ πλεῖστόν τε πεφυκὸς ἰέναι καὶ σφοδρότατον μάλιστα τοιοῦτον εἶναι.
If, then, this cannot be otherwise, we must next consider what kind of body is the most motive; for that which by nature is capable of going furthest and is most violent must necessarily be especially of this character.
σφοδρότατον μὲν οὖν ἐξ ἀνάγκης τὸ τάχιστα φερόμενον· πλήσσει γὰρ μάλιστα διὰ τὸ τάχος· ἐπὶ πλεῖστον δὲ πέφυκε διιέναι τὸ διὰ παντὸς ἰέναι μάλιστα δυνάμενον, τοιοῦτον δὲ τὸ λεπτότατον.
Now that which moves fastest is necessarily the most violent; for it strikes hardest because of its speed; and that which is best able to penetrate everywhere is by nature capable of going furthest, and such is the finest body.
ὥστ᾿ εἴπερ ἡ τοῦ πνεύματος τος φύσις τοιαύτη, μάλιστα τῶν σωμάτων τὸ πνεῦμα κινητικόν· καὶ γὰρ τὸ πῦρ ὅταν μετὰ πνεύματος ᾖ, γίγνεται φλὸξ καὶ φέρεται ταχέως.
Consequently, if the nature of wind is such, wind must be the most motive of bodies; for even fire, when it is accompanied by wind, becomes flame and moves rapidly.
οὐκ ἂν οὖν ὕδωρ οὐδὲ γῆ αἴτιον εἴη, ἀλλὰ πνεῦμα τῆς κινήσεως, ὅταν εἴσω τύχῃ ῥυὲν τὸ ἔξω ἀναθυμιώμενον.
Therefore, neither water nor earth would be the cause of the movement, but wind, when that which is evaporated outside happens to flow inwards.
διὸ γίγνονται νηνεμίας οἱ πλεῖστοι καὶ μέγιστοι τῶν σεισμῶν· συνεχὴς γὰρ οὖσα ἡ ἀναθυμίασις ἀκολουθεῖ ὡς ἐπὶ τὸ πολὺ τῇ ὁρμῇ τῆς ἀρχῆς, ὥστε ἢ ἔσω ἅμα ἢ ἔξω ὁρμᾷ πᾶσα.
Hence the majority of earthquakes and the greatest of them occur during calm weather; for the exhalation, being continuous, for the most part follows the impulse of its starting-point, so that it all rushes either inwards or outwards at once.
τὸ δ᾿ ἐνίους γίγνεσθαι καὶ πνεύματος ὄντος οὐδὲν ἄλογον· ὁρῶμεν γὰρ ἐνίοτε ἅμα πλείους πνέοντας ἀνέμους, ὧν ὅταν εἰς τὴν γῆν ὁρμήσῃ θάτερον, ἔσται πνεύματος ὄντος ὁ σεισμός.
But that some earthquakes should occur even when there is wind is not at all unreasonable; for we sometimes see several winds blowing at the same time, and when one of these rushes into the earth, the earthquake will occur while there is wind.
ἐλάττους δ᾿ οὗτοι τὸ μέγεθος γίἐπεὶ γνονται διὰ τὸ διηρῆσθαι τὴν ἀρχὴν καὶ τὴν αἰτίαν αὐτῶν.
These, however, are smaller in magnitude because their starting-point and their cause have been divided.
νυκτὸς δ᾿ οἱ πλείους καὶ μείζους γίγνονται τῶν σεισμῶν, οἱ δὲ τῆς ἡμέρας περὶ μεσημβρίαν· νηνεμώτατον γάρ ἐστιν ὡς ἐπὶ τὸ πολὺ τῆς ἡμέρας ἡ μεσημβρία (ὁ γὰρ ἥλιος ὅταν μάλιστα κρατῇ, κατακλείει τὴν ἀναθυμίασιν εἰς τὴν γῆν· κρατεῖ δὲ μάλιστα περὶ τὴν μεσημβρίαν), καὶ αἱ νύκτες δὲ τῶν ἡμερῶν νηνεμώτεραι διὰ τὴν ἀπουσίαν τὴν τοῦ ἡλίου· ὥστ᾿ ἔσω γίγνεται πάλιν ἡ ῥύσις, ὥσπερ ἄμπωτις, εἰς τοὐναντίον τῆς ἔξω πλημμυρίδος, καὶ πρὸς ὄρθρον μάλιστα· τηνικαῦτα γὰρ καὶ τὰ πνεύματα πέφυκεν ἄρχεσθαι πνεῖν.
Moreover, the majority of earthquakes and the larger ones occur at night, and those of the day occur around noon; for noon is for the most part the calmest time of the day (since the sun, when its power is greatest, shuts the exhalation up in the earth, and its power is greatest around noon), and the nights are also calmer than the days because of the absence of the sun; so that the flow takes place inwards again, like an ebb tide, in the opposite direction to the outward flow, and especially towards dawn; for at that time the winds also are by nature accustomed to begin to blow.
ἐὰν οὖν εἴσω τύχῃ μεταβάλλουσα ἡ ἀρχὴ αὐτῶν ὥσπερ Εὔριπος, διὰ τὸ πλῆθος ἰσχυρότερον ποιεῖ τὸν σεισμόν.
If, then, their starting-point happens to change inwards like the Euripus, it makes the earthquake stronger because of the quantity.
ἔτι δὲ περὶ τόπους τοιούτους οἱ ἰσχυρότατοι γίγνονται τῶν σεισμῶν, ὅπου θάλαττα ῥοώδης ἢ ἡ χώρα σομφὴ καὶ ὕπαντρος· διὸ καὶ περὶ Ἑλλήσποντον καὶ περὶ Ἀχαΐαν καὶ Σικελίαν, καὶ τῆς Εὐβοίας περὶ τούτους τοὺς τόπους· δοκεῖ γὰρ διαυλωνίζειν ὑπὸ τὴν γῆν ἡ θάλαττα· διὸ καὶ τὰ θερμὰ τὰ περὶ Αἰδηψὸν ἀπὸ τοιαύτης αἰτίας γέγονε.
Moreover, the strongest earthquakes occur in such places where the sea is full of currents or the land is porous and full of caves; which is why they occur about the Hellespont, and Achaea, and Sicily, and about those parts of Euboea; for the sea seems to flow through channels under the earth; indeed, the warm springs near Aedepsus have arisen from a cause of this kind.
περὶ δὲ τοὺς εἰρημένους τόπους οἱ σεισμοὶ γίγνονται μάλιστα διὰ τὴν στενότητα· τὸ γὰρ πνεῦμα γιγνόμενον σφοδρὸν καὶ διὰ τὸ πλῆθος τῆς θαλάττης πολλῆς προσφερομένης ἀπωθεῖται πάλιν εἰς τὴν γῆν, τὸ πεφυκὸς ἀποπνεῖν ἐκ τῆς γῆς.
In the places mentioned, earthquakes occur especially because of the narrowness; for the wind, becoming violent and being driven back into the earth by the mass of the sea which flows in abundantly, is pushed back, though it has a natural tendency to blow out from the earth.
αἵ τε χῶραι ὅσαι σομφοὺς ἔχουσι τοὺς κάτω τόπους, πολὺ δεχόμεναι πνεῦμα σείονται μᾶλλον.
And those countries which have porous places below, receiving much wind, are shaken more.