§2.1.29ὁ δὲ ταῦτα λαβὼν ἐξ ἑτοίμου καὶ δείξας, ὡς οἴεται, διότι ἡ Βαβυλὼν κατὰ Ἐρατοσθένη Θαψάκου ἀνατολικωτέρα ἐστὶ μικρῷ πλείοσιν ἢ χιλίοις σταδίοις, πάλιν ἄλλως πλάττει λῆμμα ἑαυτῷ πρὸς τὴν ἑξῆς ἀπόδειξιν καί φησιν, ἐὰν ἐννοηθῇ ἀπὸ Θαψάκου ἐπὶ μεσημβρίαν εὐθεῖα ἀγομένη καὶ ἀπὸ Βαβυλῶνος ἐπὶ ταύτην κάθετος, τρίγωνον ὀρθογώνιον ἔσεσθαι, συνεστηκὸς ἔκ τε τῆς ἀπὸ Θαψάκου ἐπὶ Βαβυλῶνα τεινούσης πλευρᾶς καὶ τῆς ἀπὸ Βαβυλῶνος καθέτου ἐπὶ τὴν διὰ Θαψάκου μεσημβρινὴν γραμμὴν ἠγμένης καὶ αὐτῆς τῆς διὰ Θαψάκου μεσημβρινῆς.
But he (Hipparchus), taking these things for granted and having shown, as he thinks, that according to Eratosthenes Babylon is further east than Thapsacus by a little more than one thousand stadia, again in another way devises a premise for himself for the subsequent proof, and says that if a straight line is conceived drawn from Thapsacus toward the south, and from Babylon a perpendicular to this, there will be a right-angled triangle, composed of the side extending from Thapsacus to Babylon, and the perpendicular drawn from Babylon to the meridian line through Thapsacus, and the meridian line through Thapsacus itself.
τούτου δὲ τοῦ τριγώνου τὴν μὲν ὑποτείνουσαν τῇ ὀρθῇ τὴν ἀπὸ Θαψάκου εἰς Βαβυλῶνα τίθησιν, ἥν φησι τετρακισχιλίων ὀκτακοσίων εἶναι, τὴν δʼ ἐκ Βαβυλῶνος εἰς τὴν διὰ Θαψάκου μεσημβρινὴν γραμμὴν κάθετον μικρῷ πλειόνων ἢ χιλίων, ὅσων ἦν ἡ ὑπεροχὴ τῆς ἐπὶ Θάψακον πρὸς τὴν μέχρι Βαβυλῶνος· ἐκ δὲ τούτων καὶ τὴν λοιπὴν τῶν περὶ τὴν ὀρθὴν συλλογίζεται πολλαπλάσιον οὖσαν τῆς λεχθείσης καθέτου· προστίθησι δὲ ταύτῃ τὴν ἀπὸ Θαψάκου πρὸς ἄρκτον ἐκβαλλομένην μέχρι τῶν Ἀρμενίων ὀρῶν, ἧς τὸ μὲν ἔφη μεμετρῆσθαι Ἐρατοσθένης καὶ εἶναι χιλίων ἑκατόν, τὸ δʼ ἀμέτρητον ἐᾷ.
And of this triangle, he assumes the side subtending the right angle to be the line from Thapsacus to Babylon, which he says is four thousand eight hundred, and the perpendicular from Babylon to the meridian line through Thapsacus to be a little more than one thousand, which was the amount of the excess of the line to Thapsacus over that to Babylon; and from these he calculates the remaining side about the right angle, which is many times the said perpendicular; and to this he adds the line produced from Thapsacus toward the north as far as the Armenian mountains, of which Eratosthenes said one part has been measured and is one thousand one hundred, but leaves the unmeasured part alone.
οὗτος δʼ ἐπὶ τοὐλάχιστον ὑποτίθεται χιλίων, ὥστε τὸ συνάμφω δισχιλίων καὶ ἑκατὸν γίγνεσθαι, ὃ προσθεὶς τῇ ἐπʼ εὐθείας πλευρᾷ τοῦ τριγώνου μέχρι τῆς καθέτου τῆς ἐκ Βαβυλῶνος πολλῶν χιλιάδων λογίζεται διάστημα τὸ ἀπὸ τῶν Ἀρμενίων ὀρῶν καὶ τοῦ διʼ Ἀθηνῶν παραλλήλου μέχρι τῆς ἐκ Βαβυλῶνος καθέτου, ἥτις ἐπὶ τοῦ διὰ Βαβυλῶνος παραλλήλου ἵδρυται.
But he (Hipparchus) assumes this at the minimum to be one thousand, so that the sum of both becomes two thousand one hundred, which, having added to the side of the triangle in a straight line as far as the perpendicular from Babylon, he calculates as a distance of many thousands of stadia from the Armenian mountains and the parallel through Athens as far as the perpendicular from Babylon, which is situated on the parallel through Babylon.
τὸ δέ γε ἀπὸ τοῦ διʼ Ἀθηνῶν παραλλήλου ἐπὶ τὸν διὰ Βαβυλῶνος δείκνυσιν οὐ μεῖζον ὂν σταδίων δισχιλίων τετρακοσίων, ὑποτεθέντος τοῦ μεσημβρινοῦ παντὸς τοσούτων σταδίων, ὅσων Ἐρατοσθένης φησίν.
But he shows that the distance from the parallel through Athens to that through Babylon is not more than two thousand four hundred stadia, assuming the whole meridian to be of as many stadia as Eratosthenes says.
εἰ δὲ τοῦτο, οὐκ ἂν ἦν τὰ ὄρη τὰ Ἀρμένια καὶ τὰ τοῦ Ταύρου ἐπὶ τοῦ διʼ Ἀθηνῶν παραλλήλου, ὡς Ἐρατοσθένης, ἀλλὰ πολλαῖς χιλιάσι σταδίων ἀρκτικώτερα κατʼ αὐτὸν ἐκεῖνον.
And if this is so, the Armenian mountains and those of the Taurus would not be on the parallel through Athens, as Eratosthenes says, but many thousands of stadia further north according to that very man.
ἐνταῦθα δὴ πρὸς τῷ τοῖς ἀνεσκευασμένοις λήμμασι προσχρῆσθαι πρὸς τὴν τοῦ ὀρθογωνίου τριγώνου τάξιν καὶ τοῦτο λαμβάνει τὸ μὴ διδόμενον, τὸ τὴν ὑποτείνουσαν τῇ ὀρθῇ γωνίᾳ τὴν ἀπὸ Θαψάκου γραμμὴν εὐθεῖαν εἶναι μέχρι Βαβυλῶνος ἐν σταδίοις τετρακισχιλίοις ὀκτακοσίοις.
Here indeed, in addition to using the demolished premises for the arrangement of the right-angled triangle, he also assumes this which is not granted: that the line from Thapsacus, which subtends the right angle, is a straight line as far as Babylon in four thousand eight hundred stadia.
παρά τε γὰρ τὸν Εὐφράτην φησὶν εἶναι τὴν ὁδὸν ταύτην ὁ Ἐρατοσθένης, καὶ τὴν Μεσοποταμίαν σὺν τῇ Βαβυλωνίᾳ μεγάλῳ κύκλῳ περιέχεσθαι λέγων ὑπό τε τοῦ Εὐφράτου καὶ τοῦ Τίγριδος, τὸ πλέον δὲ τῆς περιοχῆς ὑπὸ τοῦ Εὐφράτου συμβαίνειν φησίν· ὥσθʼ ἡ ἀπὸ Θαψάκου εἰς Βαβυλῶνα εὐθεῖα οὔτʼ ἂν παρὰ τὸν Εὐφράτην εἴη οὔτʼ ἂν τοσούτων σταδίων οὐδʼ ἐγγύς.
For Eratosthenes says that this road is along the Euphrates, and in saying that Mesopotamia with Babylonia is encompassed in a great circuit by both the Euphrates and the Tigris, he says that the greater part of the circuit is made by the Euphrates; so that the straight line from Thapsacus to Babylon would neither be along the Euphrates nor of so many stadia, nor even close to it.
ἀνατέτραπται οὖν ὁ συλλογισμός·
Thus the calculation is overturned.
καὶ μὴν εἴρηταί γε, ὅτι οὐχ οἷόν τε δυεῖν δεδομένων γραμμῶν ἀπὸ τῶν Κασπίων πυλῶν κατάγεσθαι τὴν μὲν ἐπὶ Θάψακον τὴν δʼ ἐπὶ τὰ τῶν Ἀρμενίων ὄρη τὰ κατάλληλα τῇ Θαψάκῳ, ἀπέχοντα τῆς Θαψάκου τοὐλάχιστον κατʼ αὐτὸν τὸν Ἵππαρχον δισχιλίους καὶ ἑκατὸν σταδίους, ἀμφοτέρας παραλλήλους εἶναι καὶ ἀλλήλαις καὶ τῇ διὰ Βαβυλῶνος, ἣν νότιον πλευρὰν Ἐρατοσθένης ἐκάλεσεν.
And indeed, it has already been said that it is impossible, when two given lines are drawn from the Caspian Gates, the one to Thapsacus and the other to the Armenian mountains corresponding to Thapsacus (distant from Thapsacus at least two thousand one hundred stadia according to Hipparchus himself), for both to be parallel to each other and to the line through Babylon, which Eratosthenes called the southern side.
ἐκεῖνος μὲν οὖν οὐκ ἔχων καταμεμετρημένην εἰπεῖν τὴν παρὰ τὰ ὄρη ὁδόν, τὴν δʼ ἀπὸ Θαψάκου ἐπὶ Κασπίους πύλας, ταύτην εἶπε καὶ προσέθηκε τὸ ὡς τυπωδῶς εἰπεῖν· ἄλλως τε τῷ βουλομένῳ τὸ μῆκος εἰπεῖν τῆς μετὰ τὴν Ἀριανὴν μέχρι Εὐφράτου χώρας οὐ πολὺ διέφερε ταύτην ἢ ἐκείνην καταμετρεῖν.
He (Eratosthenes), therefore, because he was not able to speak of the road along the mountains as measured, spoke of this one from Thapsacus to the Caspian Gates, and added the expression "to speak roughly"; and besides, for one wishing to state the length of the country after Ariana as far as the Euphrates, it made no great difference to measure this one or that one.
ὁ δʼ ὡς παραλλήλους ὑπακούων λέγεσθαι τελέως ἂν δόξειε καταγινώσκειν παιδικὴν ἀμαθίαν τἀνθρώπου.
But he (Hipparchus), interpreting them as being said to be parallel, would seem to accuse the man of completely childish ignorance.