§9.19.1καὶ μὴν Νικίας ὁ τῶν Ἀθηναίων στρατηγός, δυνάμενος σῴζειν τὸ περὶ τὰς Συρακούσας στράτευμα, καὶ λαβὼν τῆς νυκτὸς τὸν ἁρμόζοντα καιρὸν εἰς τὸ λαθεῖν τοὺς πολεμίους, ἀποχωρήσας εἰς ἀσφαλές, κἄπειτα τῆς σελήνης ἐκλειπούσης δεισιδαιμονήσας, ὥς τι δεινὸν προσημαινούσης, ἐπέσχε τὴν ἀναζυγήν.
And indeed, Nicias the general of the Athenians, though he was able to save the army around Syracuse, and had found the fitting time of night to escape the notice of the enemy by retreating to safety, yet when the moon was eclipsed, became superstitious, as if it portended something terrible, and delayed the departure.
§9.19.2καὶ παρὰ τοῦτο συνέβη κατὰ τὴν ἐπιοῦσαν αὐτοῦ νύκτα ποιησαμένου τὴν ἀναζυγήν, προαισθομένων τῶν πολεμίων, καὶ τὸ στρατόπεδον καὶ τοὺς ἡγεμόνας ὑποχειρίους γενέσθαι τοῖς Συρακοσίοις.
And owing to this, when he made the departure on the following night, the enemy having got wind of it beforehand, it happened that both the army and the leaders fell into the hands of the Syracusans.
§9.19.3καίτοι γε παρὰ τῶν ἐμπείρων ἱστορήσας μόνον περὶ τούτων δυνατὸς ἦν οὐχ οἷον παραλιπεῖν διὰ τὰ τοιαῦτα τοὺς ἰδίους καιρούς, ἀλλὰ καὶ συνεργοῖς χρήσασθαι διὰ τὴν τῶν ὑπεναντίων ἄγνοιαν· §9.19.4ἡ γὰρ τῶν πέλας ἀπειρία μέγιστον ἐφόδιον γίνεται τοῖς ἐμπείροις πρὸς κατόρθωσιν.
And yet, by merely inquiring about these matters from those with experience, he would have been able not only not to lose his own opportunities on account of such occurrences, but even to turn them to his own advantage owing to the ignorance of his opponents; for the ignorance of one's neighbors becomes the greatest resource to the experienced for achieving success.
§9.19.5ἐκ μὲν οὖν ἀστρολογίας μέχρι τῶν προειρημένων πολυπραγμονητέον.
So far, then, as concerns astronomy, one must study it up to the limit mentioned.
περὶ δὲ τῆς τῶν κλιμάκων συμμετρίας τοιοῦτός τίς ἐστιν ὁ τρόπος τῆς θεωρίας.
But as for the proportion of ladders, the method of calculation is somewhat as follows.
§9.19.6ἐὰν μὲν γὰρ διά τινος τῶν συμπραττόντων δοθῇ τὸ τοῦ τείχους ὕψος, πρόδηλος ἡ τῶν κλιμάκων γίνεται συμμετρία· οἵων γὰρ ἂν δέκα τινῶν εἶναι συμβαίνῃ τὸ τοῦ τείχους ὕψος, τοιούτων δώδεκα δεήσει τὰς κλίμακας δαψιλῶν ὑπάρχειν.
For if the height of the wall is given by one of the accomplices, the proper proportion of the ladders becomes obvious; for of whatever ten units the height of the wall happens to be, of twelve such units must the ladders be in generous measure.
§9.19.7τὴν δʼ ἀπόβασιν τῆς κλίμακος πρὸς τὴν τῶν ἀναβαινόντων συμμετρίαν ἡμίσειαν εἶναι δεήσει τῆς κλίμακος, ἵνα μήτε πλεῖον ἀφιστάμεναι διὰ τὸ πλῆθος τῶν ἐπιβαινόντων εὐσύντριπτοι γίνωνται μήτε πάλιν ὀρθότεραι προσερειδόμεναι λίαν ἀκροσφαλεῖς ὦσι τοῖς προσβαίνουσιν.
And the distance of the foot of the ladder from the wall, for the balance of those ascending, must be half the length of the ladder, so that they may neither, by being placed too far away, be easily broken on account of the weight of the crowd stepping on them, nor again, being placed too upright, be extremely precarious for those climbing.
§9.19.8ἐὰν δὲ μὴ δυνατὸν ᾖ μετρῆσαι μηδʼ ἐγγίσαι τῷ τείχει, ληπτέον ἐξ ἀποστάσεως παντὸς ὕψους τὸ μέγεθος τῶν πρὸς ὀρθὰς ἐφεστώτων τοῖς ὑποκειμένοις ἐπιπέδοις.
But if it is not possible to measure it or to approach the wall, one must take from a distance the size of any height of those things which stand at right angles to the underlying levels.
§9.19.9ὅ τε τρόπος τῆς λήψεως καὶ δυνατὸς καὶ ῥᾴδιος τοῖς βουλομένοις πολυπραγμονεῖν τὰ παρὰ τῶν μαθηματικῶν.
And the method of taking this measurement is both possible and easy for those who wish to study the principles of mathematicians.