The southern causeway to Iztapalapan was two leagues in length, and provided with seven drawbridges, besides a strong fortress, which rendered it impassable to an enemy. The northern, leading to Tepeyacac, was one league long, while the shortest, conducting westward to Tlacopan, half a league distant, was broken by only three bridges.10 Cortés resolved to undertake the passage by this last named causeway. During the night had been completed three mantas, of light framework and planks, each to hold twenty musketeers and archers, with which it was hoped to check the assailants on the roofs. These mantas were built with two chambers, provided with loop-holes; the upper ranged on a level with the house-tops of ordinary one-story buildings of the city, and had doors, so as to allow of sallies upon the roofs.11
The following morning, June 28th, Cortés placed himself at the head of five hundred Spaniards and over three thousand allies, and took the direction of the Tlacopan causeway.12 By a sudden charge the cavalry drove back the Indians and allowed the free passage of the mantas, which were drawn and pushed by Tlascaltecs, and protected by bodies of infantry. A corps of pioneers accompanied them with pickaxes, mattocks, crow-bars, and ladders, to destroy barricades and walls, and to scale buildings. Four cannon were also brought. The rear was protected by a portion of the cavalry. The Aztecs were at first amazed at the curious moving turrets, and feared that they might contain more terrible destroyers even than the grape-charged guns; but finding them less dangerous, they continued their efforts, and fast and thick poured the stones and arrows on the line of advance, particularly on the engines, which were severely damaged. The march proceeded, however, with more or less interruption till a raised bridge was reached on the main road, where the Indians had gathered in vast numbers, with an evident determination to check the