The Mexicans gazed with astonishment on this warlike machinery, and, as the rolling fortresses advanced, belching forth fire and smoke from their entrails, the enemy, incapable of making an impression on those within, fell back in dismay. By bringing the _mantas_ under the walls of the houses, the Spaniards were enabled to fire with effect on the mischievous tenants of the _azoteas_, and, when this did not silence them, by letting a ladder, or light draw-bridge, fall on the roof from the top of the _manta_, they opened a passage to the terrace, and closed with the combatants hand to hand. They could not, however, thus approach the higher buildings, from which the Indian warriors threw down such heavy masses of stone and timber as dislodged the planks that covered the machines, or, thundering against their sides, shook the frail edifices to their foundations, threatening all within with indiscriminate ruin. Indeed, the success of the experiment was doubtful, when the intervention of a canal put a stop to their further progress. The Spaniards now found the assertion of their enemies too well confirmed. The bridge which traversed the opening had been demolished; and, although the canals which intersected the city were, in general, of no great width or depth, the removal of the bridges not only impeded the movements of the general’s clumsy machines, but effectually disconcerted those of his cavalry. Resolving to abandon the _mantas_, he gave orders to fill up the chasm with stone, timber, and other rubbish drawn from the ruined buildings, and to make a new passageway for the army. While this labor was going on, the Aztec slingers and archers on the other side of the opening kept up a galling discharge on the Christians, the more defenceless from the nature of their occupation. When the work was completed, and a safe passage secured, the Spanish cavaliers rode briskly against the enemy, who, unable to resist the shock of the steel-clad column, fell back with precipitation to where another canal afforded a similar strong position for defence.[140]