The execution of this plan was begun. The city ends of the causeways were captured and held; street after street was demolished, and canal after canal filled up amid scenes of incessant fighting and slaughter. Day after day the Spaniards returned to their work; day after day with admirable tenacity the inhabitants of Tenochtitlan disputed the ground inch by inch, watered with the blood of themselves, their women and their children. Their supplies cut off, famine and pestilence wrought more terrible havoc among them--crowded as they gradually became into one quarter of the city--than the arms of the Spaniards and the Tlascalans. At the termination of each day's work the Spanish prepared an ambuscade for the enemy, drawing them on by seeming to retire, and massacring them with the artillery and gun-fire and lances, to say nothing of the weapons of their savage allies. On one of these occasions "the enemy rushed out yelling as if they had gained the greatest victory in the world," Cortes wrote in his despatches, and "more than five hundred, all of the bravest and principal men, were killed in this ambush." He added, and it was a common occurrence, "our allies"--the Indians--"supped well that night, cutting up and eating their captives!" During the days of this terrible siege the famous catapult was made, an extraordinary engine to discharge great stones upon the enemy. This was to enable the Spaniards to husband their powder, which was getting low, and the Aztecs watched the construction of this machine with certain fear. It was completed and set to work, but the builder, a Spanish soldier of inventive faculty, nearly played the part of the engineer hoist with his own petard, for the great stone fired rose, it is true, but went straight up and descended again upon the machine, which was ever afterwards the laughing-stock of the army. Further severe losses were now inflicted upon the beleaguered inhabitants, as more ammunition had been obtained. Peace had again been offered by the Spaniards, and again refused by the Aztecs. An Aztec chief of high rank had been captured, and then returned to Guatemoc as a peace envoy. The Mexicans' reply was to execute and sacrifice the unfortunate emissary, and then collecting their forces they poured out upon the causeways like a furious tide, which seemed as if it would sweep all before it. But the Spaniards were prepared. The narrow causeways were commanded by the artillery, which poured such a deadly hail upon the enemy's numbers that they returned fleeing to the city.