"The siege operations were conducted vigorously both by land and water. Again before the eyes of the Spaniards stretched that fatal causeway--path of death amid the salt waters of Texcoco for so many of their brave comrades upon the _Noche Triste_ of their terrible flight from Tenochtitlan. And there loomed once more that dreaded _teocalli_, whence the war-drum's mournful notes were heard. Guarded now by the capable and persistent Guatemoc, the city refused an offer of treaty, and invited the destruction which was to fall upon it. From the _azoteas_, or roofs of their buildings and temples, the undaunted Mexicans beheld the white-winged brigantines, armed with those belching engines of thunder and death whose sting they well knew: and saw the ruthless hand of devastation laying waste their fair towns of the lake shore, and cutting off their means of life. "But the Spaniards had yet to learn to their cost the lengths of Aztec tenacity and ferocity. It will be recollected that the city was connected to the lake shores by means of four causeways, built above the surface of the water; engineering structures of stone and mortar and earth, which had from the first aroused the admiration of the Spaniards. These causeways, whilst they rendered the city almost impregnable from attack, were a source of weakness in the easy cutting-off of food supplies, which they afforded to the enemy. A simultaneous assault on all these approaches was organized by the Spaniards, under Sandoval, Alvarado and Cortes himself, respectively, whilst the brigantines, with their raking artillery, were to support the attack by water, aided by the canoes of the Tlascalan and Texcocan allies. A series of attacks was made by this method, and at last the various bodies of Spaniards advanced along the causeways and gained the city walls. But frightful disaster befel them. The comparative ease with which they entered the city aroused Cortes's suspicions; and at that moment, from the summit of the great _teocalli_, rang out a fearful note--the horn of Guatemoc, calling for vengeance and a concerted attack. The notes of the horn struck some ominous sense of chill in the Spaniards' breasts, and the soldier-penman, Bernal Diaz, who was fighting valiantly there, says that the noise echoed and re-echoed, and rang in his ears for days afterwards. The Spaniards, on this, as on other occasions, had foolishly neglected to secure the breaches in the causeways as they passed, or at least the rash Alvarado had not done so with his command, his earlier lesson unheeded; and when the Christians were hurled backwards--for their easy entrance into the great square of the city had been in the nature of a decoy--disaster befel them, which at one moment seemed as if it would be a repetition of that of the _Noche Triste_. 'The moment I reached that fearful bridge,' Cortes wrote in his dispatches, 'I saw the Spaniards returning in full flight.' Remaining to hold the breech if possible, and cover