The Prefect had undertaken the defence of all the gates on the right bank of the Tiber; the new Porta Aurelia on the Ælisian Bridge near the Mausoleum, the Porta Septimiana, the old Aurelian Gate, which was now named the Pancratian; and on the left bank, that of St. Paul. The next gate to the east, the Ardeatinian, was again under the protection of a Byzantine garrison, commanded by Chilbudius. The besiegers and the besieged proved themselves equally indefatigable and equally inventive in plans of attack and defence. For a long time the only thing the Goths could attempt was to harass the Romans before storming the walls. On their side, the Romans prepared to defend them when attacked. The Goths--lords and masters in the Campagna--sought to distress the besieged by cutting off all the fourteen splendid aqueducts which supplied the city with water. As soon as Belisarius learned this fact, he hastened to block the mouths of the aqueducts within the city. "For," Procopius had said to him, "since you, O great hero, Belisarius, have crept into Neapolis through such a water-runnel, the same idea might occur to the barbarians, and they would scarcely think it a shame to crawl into Rome by a similar hero-path." The besieged were now obliged to deny themselves the luxury of their baths; the wells in the quarters of the city at a distance from the river scarcely sufficed for drinking water. But by cutting off the supply of water, the barbarians had also deprived the Romans of bread. At least it seemed so, for all the water-mills of Rome were stopped. The garnered grain bought in Sicily by Cethegus, and that which Belisarius had, by force, caused to be brought into Rome from all the neighbouring country, in spite of the outcry of farmers and husbandmen, could no longer be ground. "Let the mills be turned by asses and oxen!" cried Belisarius. "Most of the asses and oxen were too wise to allow themselves to be shut up with us here, O Belisarius," said Procopius; "we have only as many as we shall want for the shambles, and it is impossible that they should first drive the mills and then be still fat enough to afford meat to eat with the bread thus gained." "Then call Martinus. Yesterday, as I stood by the Tiber counting the Gothic tents, I had an idea----" "Which Martinus must translate from the Belisarian into the possible! Poor man! But I will go and fetch him." But when, on the evening of the same day, Belisarius and Martinus caused the first boat-mills that the world had ever known to be erected in the Tiber, by means of boats ranged one near the other, Procopius said admiringly: "The bread of these boat-mills will rejoice men longer than your greatest deeds. Flour, ground in this wise, savours of immortality." And indeed these boat-mills, imagined by Belisarius and practically carried out by Martinus, fully compensated to the besieged, during the whole siege, for the loss of the powerless water-mills.