§3.4#14 ἡ δʼ ἶρις ὅτι μέν ἐστιν ἀνάκλασις, εἴρηται πρότερον· ποία δέ τις ἀνάκλασις, καὶ πῶς καὶ διὰ τίνʼ αἰτίαν ἕκαστα γίγνεται τῶν συμβαινόντων περὶ ταύτην, λέγωμεν νῦν.
4 That the rainbow is a reflection has been stated before; but what kind of reflection it is, and how and for what cause each of the phenomena connected with it occurs, let us now state.
ἀνακλωμένη μὲν οὖν ἡ ὄψις ἀπὸ πάντων φαίνεται τῶν λείων, τούτων δʼ ἐστὶν καὶ ἀὴρ καὶ ὕδωρ.
Now, vision is seen to be reflected from all smooth surfaces, and among these are both air and water.
γίγνεται δὲ ἀπὸ μὲν ἀέρος, ὅταν τύχη συνιστάμενος.
And reflection occurs from air when it happens to be condensing.
διὰ δὲ τὴν τῆς ὄψεως ἀσθένειαν πολλάκις καὶ ἄνεω συστάσεως ποιεῖ ἀνάκλασιν, οἷόν ποτε συνέβαινέ τινι πάθος ἡρέμα καὶ οὐκ ὁξὺ βλέποντι· ἀεὶ γὰρ εἴδωλον ἐδόκει προηγεῖσθαι βαδίζοντι αὐτῷ, ἐξ ἐναντίας βλέπον πρὸς αὐτόν.
But because of the weakness of vision, it often produces reflection even without condensation, as once occurred as a affection to a certain man who saw weakly and not sharply; for an image always seemed to go before him as he walked, looking at him from the opposite direction.
τοῦτο δʼ ἔπασχε διὰ τὸ τὴν ὄψιν ἀνακλᾶσθαι πρὸς αὐτόν· οὕτω γὰρ ἀσθενὴς ἦν καὶ λεπτὴ πάμπαν ὑπὸ τῆς ἀρρωστίας, ὥστʼ ἔνοπτρον ἐγίγνετο καὶ ὁ πλησίον ἀήρ, καὶ οὐκ ἐδύνατο ἀπωθεῖν—ὡς ὁ πόρρω καὶ πυκνός· διόπερ αἵ τʼ ἄκραι ἀνεσπασμέναι φαίνονται ἐν τῇ θαλάττῃ, καὶ μείζω τὰ μεγέθη πάντων, ὅταν εὖροι πνέωσι, καὶ τὰ ἐν ταῖς ἀχλύσιν, οἷον καὶ ἥλιος καὶ ἄστρα ἀνίσχοντα καὶ δύνοντα μᾶλλον ἢ μεσουρανοῦντα.
And he suffered this because his vision was reflected back to himself; for it was so weak and entirely thin owing to illness that even the neighboring air became a mirror, and it was not able to push it away—just as the distant and dense air does; wherefore also the promontories appear elevated in the sea, and the sizes of all things appear larger when east winds blow, and also things in mists, as indeed the sun and stars when rising and setting appear larger than when they are at mid-heaven.
ἀπὸ δὲ ὕδατος μάλιστα ἀνακλᾶται, καὶ ἀπὸ ἀρχομένου γίγνεσθαι μᾶλλον ἔτι ἢ ἀπʼ ἀέρος· ἕκαστον γὰρ τῶν μορίων ἐξ ὧν γίγνεται συνισταμένων ἡ ψακὰς ἔνοπτρον ἀναγκαῖον εἶναι μᾶλλον τῆς ἀχλύος.
But it is reflected especially from water, and from that which is beginning to be formed even more so than from air; for each of the particles from which the raindrop is formed by condensation must necessarily be more of a mirror than mist.
ἐπεὶ δὲ καὶ δῆλον καὶ εἴρηται πρότερον ὅτι ἐν τοῖς τοιούτοις ἐνόπτροις τὸ χρῶμα μόνον ἐμφαίνεται, τὸ δὲ σχῆμα ἄδηλον, ἀναγκαῖον, ὅταν ἄρχηται ὕειν καὶ ἤδη μὲν συνιστῆται εἰς ψακάδας ὁ ἐν τοῖς νέφεσιν ἀήρ, μήπω δὲ ὕῃ, ἐὰν ἐξ ἐναντίας ᾖ ὁ ἥλιος ἢ ἄλλο τι οὕτω λαμπρὸν ὥστε γίγνεσθαι ἔνοπτρον τὸ νέφος, καὶ τὴν ἀνάκλασιν γίγνεσθαι πρὸς τὸ λαμπρὸν ἐξ ἐναντίας, γίγνεσθαι ἔμφασιν χρώματος, οὐ σχήματος.
And since it is both clear and has been stated before that in such mirrors only the color is reflected, while the shape is invisible, it is necessary, when it begins to rain and the air in the clouds is already condensing into raindrops but it is not yet raining, if the sun or some other thing so bright as to make the cloud a mirror is opposite, and the reflection occurs to the bright object from the opposite side, that there should be an appearance of color, not of shape.
ἑκάστου δʼ ὄντος τῶν ἐνόπτρων μικροῦ καὶ ἀοράτου, τῆς δʼ ἐξ ἁπάντων αὐτῶν συνεχείας τοῦ μεγέθους ὁρωμένης, ἀνάγκη συνεχὲς μέγεθος τοῦ αὐτοῦ φαίνεσθαι χρώματος· ἕκαστον γὰρ τῶν ἐνόπτρων τὸ αὐτὸ ἀποδίδωσι χρῶμα τῷ συνεχεῖ.
And since each of the mirrors is small and invisible, while the continuous size of all of them is seen, it is necessary that a continuous size of the same color should appear; for each of the mirrors yields the same color to the continuous whole.
ὥστ᾿ ἐπεὶ ταῦτ᾿ δέχεται συμβαίνειν, ὅταν τοῦτον ἔχῃ τὸν τρόπον ὅ τε ἥλιος καὶ τὸ νέφος καὶ ἡμεῖς ὦμεν μεταξὺ αὐτῶν, ἔσται διὰ τὴν ἀνάκλασιν ἔμφασίς τις.
Therefore, since these things are capable of happening when the sun and the cloud are in this relation and we are between them, there will be some appearance because of the reflection.
ἀλλὰ μὴν καὶ φαίνεται τότε καὶ οὐκ ἄλλως ἐχόντων γιγνομένη ἡ ἶρις.
And indeed, the rainbow is seen to occur then, and when things are not otherwise.
ὅτι μὲν οὖν ἀνάκλασις ἡ ἶρις τῆς ὄψεως πρὸς τὸν ἥλιόν ἐστι, φανερόν· διὸ καὶ ἐξ ἐναντίας ἀεὶ γίγνεται, ἡ δ᾿ ἅλως περὶ αὐτὸν· καίτοι ἄμφω ἀνάκλασις· ἀλλ᾿ ἥ γε τῶν χρωμάτων ποικιλία διαφέρει· ἡ μὲν γὰρ ἀφ᾿ ὕδατος καὶ μέλανος γίγνεται ἀνάκλασις καὶ πόρρωθεν, ἡ δ᾿ ἐγγύθεν καὶ ἀπὸ ἀέρος λευκοτέρου τὴν φύσιν.
That the rainbow, therefore, is a reflection of vision to the sun is clear; wherefore it also always occurs opposite, while the halo is around the sun itself; yet both are reflections; but the variety of colors differs; for the one is a reflection from water and a dark object, and from a distance, while the other is from near at hand and from air that is by nature whiter.
φαίνεται δὲ τὸ λαμπρὸν διὰ τοῦ μέλανος ἢ ἐν τῷ μέλανι (διαφέρει γὰρ οὐδέν) φοινικοῦν (ὁρᾶν δ᾿ ἔξεστι τό γε τῶν χλωρῶν ξύλων πῦρ, ὡς ἐρυθρὰν ἔχει τὴν φλόγα διὰ τὸ τῷ καπνῷ πολλῷ μεμεῖχθαι τὸ πῦρ λαμπρὸν ὂν καὶ λευκόν)· καὶ δι᾿ ἀχλύος καὶ καπνοῦ ὁ ἥλιος φαίνεται φοινικοῦς.
And a bright object seen through a dark one or in a dark one (for it makes no difference) appears crimson (as indeed one can see the fire of green wood, how it has a red flame because the fire, being bright and white, is mixed with much smoke); and through mist and smoke the sun appears crimson.
διὸ ἡ μὲν τῆς ἴριδος ἀνάκλασις ἡ μὲν πρώτη τοιαύτην ἔχειν φαίνεται τὴν χρόαν (ἀπὸ ῥανίδων γὰρ μικρῶν γίγνεται ἡ ἀνάκλασις), ἡ δὲ τῆς ἅλω οὔ.
Wherefore the reflection of the rainbow indeed has its first part of such a color (for the reflection occurs from small drops), but that of the halo does not.
περὶ δὲ τῶν ἄλλων χρωμάτων ὕστερον ἐροῦμεν.
But concerning the other colors we shall speak later.
ἔτι δὲ περὶ αὐτὸν μὲν τὸν ἥλιον οὐ γίγνεται διατριβὴ τοιαύτης συστάσεως, ἀλλ᾿ ἢ ὕει ἢ διαλύεται.
Furthermore, around the sun itself there is no long duration of such a condensation, but it either rains or dissolves.
ἐκ δὲ τῶν ἐναντίων ἐν τῷ μεταξὺ τῆς τοῦ ὕδατος γενέσεως γίγνεταί τις χρόνος· τούτου γὰρ μὴ συμβαίνοντος ἦσαν ἂν κεχρωματισμέναι αἱ ἅλως ὥσπερ ἡ ἶρις.
But in the opposite direction, in the interval of the generation of water, some time occurs; for if this did not happen, halos would be colored just like the rainbow.