§4.1Διὰ τί οἱ μεσόνεοι μάλιστα τὴν ναῦν κινοῦσιν;
Why is it that those in the middle of the ship move the ship most?
Ἢ διότι ἡ κώπη μοχλός ἐστιν;
Or is it because the oar is a lever?
Ὑπομόχλιον μὲν γὰρ ὁ σκαλμὸς γίνεται (μένει γὰρ δἡ τοῦτο), τὸ δὲ βάρος ἡ θάλαττα, ἢν ἀπωθεῖ ἡ κώπη· ὁ δὲ κινῶν τὸν μοχλὸν ὁ ναύτης ἐστίν.
For the tholepin becomes the fulcrum (for indeed this remains stationary), and the weight is the sea, which the oar pushes away; and the one who moves the lever is the sailor.
§4.2Αεὶ δὲ πλέον βάρος κινεῖ, ὅσῳ ἄν πλέον ἀφεστήκῃ τοῦ ὑπομοχλίου ὁ κινῶν τὸ βάρος· μείζων γὰρ οὕτω γίνεται ἡ ἐκ τοῦ κέντρου, ὁ δὲ σκαλμὸς ὑπομόχλιον ὢν κέντρον ἐστίν.
And the one who moves the weight always moves more weight, by how much further he is distant from the fulcrum; for thus the radius from the center becomes greater, and the tholepin, being the fulcrum, is the center.
Ἐνμέση δὲ τῆ νηῒ πλεῖστον τῆς κώπης ἐντός ἐστιν· καὶ γὰρ ἡ ναῦς ταύτῃ εὐρυτάτη ἐστίν, ὥστε πλεῖον ἐπ’ἀμφότερα ἐνδέχεσθαι μέρος τῆς κώπης ἑκατέρου τοίχου ἐντὸς εἶναι τῆς νεώς.
And in the middle of the ship, the greatest part of the oar is inside; for the ship is widest at this part, so that it is possible on both sides for a larger part of the oar to be inside the ship from either wall.
§4.3Κινεῖται μὲν οὖν ἡ ναῦς διὰ τὸ ἀπερειδομένης τῆς κώπης εἰς τὴν θάλασσαν τὸ ἄκρον τῆς κώπης τὸ ἐντὸς προϊέναι εἰς τὸ πρόσθεν, τὴν δὲ ναῦν προσδεδεμένην τῷ σκαλμῷ συμπροϊέναι, ᾖ τὸ ἄκρον τῆς κώπης.
The ship moves, then, because, while the oar is pressed against the sea, the inner end of the oar goes forward, and the ship, being bound to the tholepin, goes forward with it, in the direction where the end of the oar goes.
§4.4Ἧι γὰρ πλείστην θάλασσαν διαιρεῖ ἡ κώπη, ταύτῃ ἀνάγκη μάλιστα προωθεῖσθαι· πλείστην δὲ διαιρεῖ ᾖ πλεῖστον μέρος ἀπὸ τοῦ σκαλμοῦ τῆς κώπης ἐστίν, Διὰ τοῦτο οἱ μεσόνεοι μάλιστα κινοῦσιν· μέγιστον γὰρ ἐν μέσῃ νηῒ τὸ ἀπὸ τοῦ σκαλμοῦ τῆς κώπης τὸ ἐντός ἐστιν.
For where the oar divides the most sea, there it must necessarily be propelled the most; and it divides the most where the part of the oar from the tholepin is greatest. For this reason, those in the middle of the ship move it most; for in the middle of the ship, the part of the oar from the tholepin which is inside is greatest.