On reaching the Danube from Thrace, he found the bridge of boats ready, and when the whole army had passed over, he ordered the Ionians to break it down, as well as to follow him in his land-march into Scythia;[498] the ships being left with nothing but the rowers and seamen essential to navigate them homeward. His order was on the point of being executed, when, fortunately for him, the Mitylenæan general Kôês ventured to call in question the prudence of it, having first asked whether it was the pleasure of the Persian king to listen to advice. He urged that the march on which they were proceeding might prove perilous, and retreat possibly unavoidable; because the Scythians, though certain to be defeated if brought to action, might perhaps not suffer themselves to be approached or even discovered. As a precaution against all contingencies, it was prudent to leave the bridge standing and watched by those who had constructed it. Far from being offended at the advice, Darius felt grateful for it, and desired that Kôês would ask him after his return for a suitable reward,—which we shall hereafter find granted. He then altered his resolution, took a cord, and tied sixty knots in it. “Take this cord (said he to the Ionians), untie one of the knots in it each day after my advance from the Danube into Scythia. Remain here and guard the bridge until you shall have untied all the knots; but if by that time I shall not have returned, then depart and sail home.”[499] After such orders he began his march into the interior. [498] Herodot. iv, 97. Δαρεῖος ἐκέλευσε τοὺς Ἴωνας τὴν σχεδίην λύσαντας ἕπεσθαι κατ᾽ ἤπειρον ἑωϋτῷ, καὶ τὸν ἐκ τῶν νέων στρατόν. [499] Herodot. iv, 98. ἢν δὲ ἐν τούτῳ τῷ χρόνῳ μὴ παρέω, ἀλλὰ διέλθωσι ὑμῖν αἱ ἡμέραι τῶν ἁμμάτων, ἀποπλέετε ἐς τὴν ὑμετέρην αὐτέων· μέχρι δὲ τούτου, ἐπεί τε οὕτω μετέδοξε, φυλάσσετε τὴν σχεδίην.