That satrap, however, after twenty days, at last came back, with his army prepared to return to Ionia,—with the king’s daughter whom he had just received in marriage,—and with another grandee named Orontas. Tissaphernes took the conduct of the march, providing supplies for the Greek troops to purchase; while Ariæus and his division now separated themselves altogether from the Greeks, and became intermingled with the other Persians. Klearchus and the Greeks followed them, at the distance of about three miles in the rear, with a separate guide for themselves; not without jealousy and mistrust, sometimes shown in individual conflicts, while collecting wood or forage, between them and the Persians of Ariæus. After three days’ march (that is, apparently, three days, calculated from the moment when they began their retreat with Ariæus) they came to the Wall of Media, and passed through it,[120] prosecuting their march onward through the country on its other or interior side. It was of bricks cemented with bitumen, one hundred feet high, and twenty feet broad; it was said to extend a length of twenty parasangs (or about seventy miles, if we reckon the parasang at thirty stadia), and to be not far distant from Babylon. Two days of farther march, computed as eight parasangs, brought them to the Tigris. During these two days they crossed two great ship canals, one of them over a permanent bridge, the other over a temporary bridge laid on seven boats. Canals of such magnitude must probably have been two among the four stated by Xenophon to be drawn from the river Tigris, each of them a parasang distant from the other. They were one hundred feet broad, and deep enough even for heavy vessels; they were distributed by means of numerous smaller channels and ditches for the irrigation of the soil; and they were said to fall into the Euphrates; or rather, perhaps, they terminated in one main larger canal cut directly from the Euphrates to the Tigris, each of them joining this larger canal at a different point of its course. Within less than two miles of the Tigris was a large and populous city named Sittakê, near which the Greeks pitched their camp, on the verge of a beautiful park or thick grove full of all kinds of trees; while the Persians all crossed the Tigris, at the neighboring bridge.