CHAPTER XIV

any injury to the city by a too rapid flow to the northward. Xochimulco is the pond, or open space in the marsh, that extends from the Chalco to near Mexicalzingo. Tezcuco is the lowest water in the valley, being 6½ feet below the Grand Plaza of the city. It receives the surplus of the waters that have not already been evaporated in the other ponds. At this great elevation, 7500 feet, evaporation does its work rapidly all over the valley, but it is in Tezcuco that the residuum of the waters is deposited.