These messengers were instructed to urge upon the people that, unless Cæsar and his army were at once expelled from Alexandria, there was imminent danger that the national independence of Egypt would be forever destroyed. The Romans, they were to say, had extended their conquests over almost all the rest of the world. They had sent one army into Egypt before, under the command of Mark Antony, under the pretense of restoring Ptolemy Auletes to the throne. Now another commander, with another force, had come, offering some other pretexts for interfering in their affairs. These Roman encroachments, the messengers were to say, would end in the complete subjugation of Egypt to a foreign power, unless the people of the country aroused themselves to meet the danger manfully, and to expel the intruders. As Cæsar had possession of the island of Pharos and of the harbor, Ganymede could not cut him off from receiving such re-enforcements of men and arms as he might make arrangements for obtaining beyond the sea; nor could he curtail his supply of food, as the granaries and magazines within Cæsar's quarter of the city contained almost inexhaustible stores of corn. There was one remaining point essential to the subsistence of an army besieged, and that was an abundant supply of water. The palaces and citadels which Cæsar occupied were supplied with water by means of numerous subterranean aqueducts, which conveyed the water from the Nile to vast cisterns built under ground, whence it was raised by buckets and hydraulic engines for use. In reflecting upon this circumstance, Ganymede conceived the design of secretly digging a canal, so as to turn the waters of the sea by means of it into these aqueducts. This plan he carried into effect. The consequence was, that the water in the cisterns was gradually changed. It became first brackish, then more and more salt and bitter, until, at length, it was wholly impossible to use it. For some time the army within could not understand these changes; and when, at length, they discovered the cause, the soldiers were panic-stricken at the thought that they were now apparently wholly at the mercy of their enemies, since, without supplies of water, they must all immediately perish. They considered it hopeless to attempt any longer to hold out, and urged Cæsar to evacuate the city, embark on board his galleys, and proceed to sea. Instead of doing this, however, Cæsar, ordering all other operations to be suspended, employed the whole laboring force of his command, under the direction of the captains of the several companies, in digging wells in every part of his quarter of the city. Fresh water, he said, was almost invariably found, at a moderate depth, upon sea-coasts, even upon ground lying in very close proximity with the sea. The diggings were successful. Fresh water, in great abundance, was found. Thus this danger was passed, and the men's fears effectually relieved.