XIV. Cæsar was still at Amiens, ignorant of the events which had just taken place. Cicero immediately wrote to him, and promised great recompenses to those who should succeed in delivering his letters to him; but all the roads were watched, and nobody could reach him. During the night twenty towers were raised, with an incredible celerity, by means of the wood which had been already brought for fortifying the camp,[431] and the works were completed. Next day, the enemies, whose forces had increased, returned to the attack and began to fill the fosse. The resistance was as energetic as the day before, and continued during the following days; among these heroic soldiers constancy and energy seemed to increase with the peril. Each night they prepare everything necessary for the defence on the morrow. They make a great number of stakes hardened by fire, and _pila_ employed in sieges; they establish with planks the floors of the towers, and by means of hurdles make parapets and battlements. They work without intermission: neither wounded nor sick take repose. Cicero himself, though a man of feeble health, is day and night at work, in spite of the entreaties of his soldiers, who implore him to spare himself. Meanwhile, the chiefs and _principes_ of the Nervii proposed an interview to Cicero. They repeated to him what Ambiorix had said to Sabinus: “All Gaul is in arms; the Germans have passed the Rhine; the quarters of Cæsar and his lieutenants are attacked.” They added: “Sabinus and his cohorts have perished; the presence of Ambiorix is a proof of their veracity; Cicero would deceive himself if he reckoned on the succour of the other legions. As to them, they have no hostile intention, provided the Romans will discontinue occupying their country. The legion has full liberty to retire without fear whither it likes.” Cicero replied “that it was not the custom of the Roman people to accept conditions from an enemy in arms; but that, if they consented to lay them down, he would serve them as a mediator with Cæsar, who would decide.” Deceived in their expectation of intimidating Cicero, the Nervii surrounded the camp with a rampart nine feet high, and a fosse fifteen wide. They had observed the Roman works in the preceding campaigns, and learnt from some prisoners to imitate them. But, as they did not possess the necessary instruments of iron, they were obliged to cut the turf with their swords, to take the earth with their hands, and to carry it in their cloaks. We may judge of their great number by the fact that in less than three hours they completed a retrenchment of 15,000 feet in circuit.[432] On the following days, they raised towers to the height of the _vallum_, prepared hooks (_falces_), and covered galleries (_testudines_), which they had similarly been taught by the prisoners.[433]