flowed into Tezcuco, conveying with them the infinitesimal infusion of tequisquite that had instilled itself into the Chalco. Had the volume of Chalco and Xochimulco been increased several feet, then the slight Indian barriers and the long grass would no longer have been able to retard the progress of the water till evaporation had diminished its quantity, but, precipitating itself in a mass into the Tezcuco, it would have overwhelmed the town of Tezcuco and all other villages upon the shores, and established an equilibrium of surface in the two ponds.
All the lagunas, canals, and ditches that have been described are navigated by small scows that draw but a few inches of water, which are the medium of an extensive internal commerce. Through the lagunas and canal of Chalco come from Cuatla all the supplies of the products of the hot country for the city and surrounding region. This commerce exceeds the whole foreign trade of the republic. This kind of boat was probably introduced by Cortéz, and in this convenient form his thirteen brigantines were probably made; for, had his brigantines been of a larger draught of water, they could not have navigated canals intended only for Indian canoes. One of these vessels, when supplied with a sail, a cannon, and a movable keel or side-board, would be a formidable auxiliary in an assault upon the city at the present day. And if one such scow was placed in the ditch on each side of the southern causeway, as Cortéz alleges, it would enable an assailing enemy to present just so much more front as the additional width of two boats would give him.
THE CAUSEWAYS AND CANALS.
Writers have expressed their surprise at the existence of two navigable canals to each causeway, one on either side, as an immense expenditure of unnecessary labor. The explanation of this is found in the fact that in the construction of a pathway (for Cortéz says that it was only 30 feet in width) through wet and marshy ground, a broad ditch is ordinarily made on either side to obtain earth for the embankment, and to keep the