The army of Darius reached the banks of the Danube at last, and they found that the fleet of the Ionians had attained the point agreed upon before them, and were awaiting their arrival. The vessels were soon arranged in the form of a bridge across the stream, and as there was no enemy at hand to embarrass them, the army soon accomplished the passage. They were now fairly in the Scythian country, and immediately began their preparations to advance and meet the foe. Darius gave orders to have the bridge broken up, and the galleys abandoned and destroyed, as he chose rather to take with him the whole of his force, than to leave a guard behind sufficient to protect this shipping. These orders were about to be executed, when a Grecian general, who was attached to one of the bodies of troops which were furnished from the provinces of Asia Minor, asked leave to speak to the king. The king granted him an audience, when he expressed his opinion as follows: "It seems to me to be more prudent, sire, to leave the bridge as it is, under the care of those who have constructed it, as it may be that we shall have occasion to use it on our return. I do not recommend the preservation of it as a means of securing a retreat, for, in case we meet the Scythians at all, I am confident of victory; but our enemy consists of wandering hordes who have no fixed habitation, and their country is entirely without cities or posts of any kind which they will feel any strong interest in defending, and thus it is possible that we may not be able to find any enemy to combat. Besides, if we succeed in our enterprise as completely as we can desire, it will be important, on many accounts, to preserve an open and free communication with the countries behind us." The king approved of this counsel, and countermanded his orders for the destruction of the bridge. He directed that the Ionian forces that had accompanied the fleet should remain at the river to guard the bridge. They were to remain thus on guard for two months, and then, if Darius did not return, and if they heard no tidings of him, they were at liberty to leave their post, and to go back, with their galleys, to their own land again. Two months would seem to be a very short time to await the return of an army going on such an expedition into boundless and trackless wilds. There can, however, scarcely be any accidental error in the statement of the time, as the mode which Darius adopted to enable the guard thus left at the bridge to keep their reckoning was a very singular one, and it is very particularly described. He took a cord, it is said, and tied sixty knots in it. This cord he delivered to the Ionian chiefs who were to be left in charge of the bridge, directing them to untie one of the knots every day. When the cord should become, by this process, wholly free, the detachment were also at liberty. They might thereafter, at any time, abandon the post intrusted to them, and return to their homes.