Having thus, by the occupation of Tacuba, commenced the investment of the great and populous city of Mexico, we soon found the enemy around us in great numbers; and as the first operation, it was determined on the following day, that our divisions should march to Chapoltepec to destroy the aqueduct at that place, by which the city of Mexico was supplied with fresh water. We set out accordingly with our allies, and although the enemy attacked us on our march, we repelled them and succeeded in our object of cutting off the pipes, so that from that time the city of Mexico was deprived of fresh water. It was now determined to endeavour to penetrate to the city of Mexico by the causeway of Tacuba, or at least to attempt getting possession of the first bridge on that causeway; but on our arrival there, the prodigious number of boats which covered the water on both sides, and the multitude of Mexican troops which thronged the causeway to oppose us, was perfectly astonishing. By the first flight of arrows which they discharged against us, three of our men were slain and thirty wounded; yet we advanced to the bridge, the enemy retiring before us, as if by a concerted stratagem, so that we were exposed on both flanks, on a narrow road only twenty feet wide, as a butt for the innumerable arrows of the Mexicans in the canoes, and neither our musquetry nor crossbows were of any avail against the people in the canoes, as they were effectually protected by high wooden screens. The horses of our cavalry were all wounded, and when at any time they made a charge upon the enemy, they were almost immediately stopt by barriers and parapets which the enemy had drawn across the causeway for the purpose, and from whence they defended themselves with long lances. Likewise, when the infantry advanced along the causeway, instead of abiding our attack, the enemy threw themselves into the water and escaped by swimming or into their canoes, returning incessantly to the attack. We were thus engaged for more than an hour to no useful purpose, the enemy continually increasing in number, by reinforcements from every part of the lake; and our allies, instead of being serviceable, only encumbered the causeway and hindered our movements. Finding that we were unable any longer to resist the multitude of enemies who assailed us perpetually from the water, and almost with entire impunity, we determined to retreat to our quarters in Tacuba, having eight of our men slain and above fifty wounded, and were closely followed up and much harassed by the enemy during our retreat. De Oli laid the blame of the disaster of this day on the rashness of Alvarado.

Next day53, though we were all extremely solicitous for the two captains to remain together, De Oli proceeded with his division to take possession of Cojohuacan, according to the orders he had received from Cortes; but this separation was assuredly extremely ill judged; as, if the enemy had known the smallness of our numbers at the two stations, they might have fallen upon and destroyed us separately, during the four or five days that we remained divided before the arrival of Cortes with the brigantines. In all that time we never ventured to make any more attempts against the Mexican causeways, but the enemy frequently sent bodies of their troops to the main land to make attacks on our quarters, on which occasions we always drove them away.

Sandoval with his division did not leave Tezcuco until the fourth day after the feast of Corpus Christi54, when he marched through a friendly country by the south side of the lake, and arrived without interruption in front of Iztapalapa. Immediately on his arrival, he commenced an attack on the enemy, and burnt many of the houses in that part of the town which stood on the firm land; but fresh bodies of Mexican warriors came over in canoes and by the causeway of Iztapalapa to relieve their friends in the town, and made a determined resistance against Sandoval. While the engagement was going on, a smoke was observed to arise from a hill above the town, which was answered by similar signals at many other points around the lake, which were afterwards found to have been made to apprize the enemy of the appearance of our flotilla on the lake. On this, the efforts of the enemy against Sandoval were much relaxed, as their canoes and warriors were recalled to oppose our naval force; and Sandoval was thus enabled to take up his quarters in a part of the town of Iztapalapa; between which and Cojohuacan the only means of communication was by a causeway or mound dividing the lake of Chalco from that of Mexico or Tezcuco, which passage was at that time impracticable in the face of the enemy.

"Before proceeding to the narrative of the siege of Mexico, it may be proper to give some account of the situation of the city of Mexico, and the mounds or causeways by which it communicated with the land at the several posts which were occupied by Cortes for its investment55. The city of Mexico was built partly on an island and partly in the water, at the west side of a considerable salt lake, named sometimes the lake of Tezcuco, and sometimes the lake of Mexico, and appears to have been about a mile from the firm land. It communicated with the land by three mounds or causeways; that of Tepejacac on the north, about three miles long, measuring from the great temple in centre of Mexico; that usually called of Iztapalapa on the south, nearly five miles in length; and that of Tacuba or Tlacopan on the west, about two miles long, likewise measuring from the temple; but at least a mile may be abstracted from each of these measurements, on account of the extent of the city from the great temple to the commencement of the causeways. About the middle of the southern causeway called that of Iztapalapa, another causeway branched off obliquely to the south-east, to the town of Cojohuacan; and at the place where these two causeways united stood the town of Xoloc, partly on the sides of the causeways, but chiefly in the water intersected by canals and ditches. Besides these three grand causeways for communicating with the land, there was a smaller mound about two miles south from the causeway of Tacuba, from a town named Chapoltepec, along which the aqueduct, or pipes, for supplying Mexico with fresh water was carried; but this appears to have been too narrow for allowing any passage, at least the Spaniards do not seem to have availed themselves of it, in their long and arduous endeavours to force their way into Mexico. Near the south-west angle of the salt lake of Mexico, it communicated by a narrow neck or strait with the fresh water lake of Chalco; and at their junction a mound or causeway had been constructed across, to prevent the admixture of the salt and fresh lakes, having a town called Mexicaltzinco at the eastern extremity of this mound. Iztapalapa stood in the western end of the peninsula, between the lakes of Mexico and Chalco, but on the borders and in the waters of the former. The whole fertile vale of Mexico or Anahuac, around these two lakes, and some others to the north of the great lake, was thickly planted with cities, towns, and villages, and highly cultivated, containing and giving subsistence to a prodigious population. The extent of this extraordinary valley, elevated nearly 8000 feet above the level of the sea, is about 50 miles from north to south, and forty miles from east to west; being surrounded on every side by ridges of lofty mountains, some of them perpetually covered with snow, and rising to about 10,000 feet in perpendicular elevation above the ocean."