name due east of Mexico, although he well knew that it was nearly north, as the two towns are distinctly in sight, although at a distance of about six leagues. Now, if we carry the village of Tezcuco and the shore of the lake with it to its correct position, we shall have the Laguna of Tezcuco in about its present form and size. The apology for his defeat at Iztapalapan, by the breaking open of the dike and letting in the salt water, is, of course, inadequate, as the dike could not have supported a head of water sufficient to drown his men, nor could so great a head of salt water be obtained at that point.
In this survey of the ponds of Mexico, I have drawn upon the experience which has been acquired in the process of evaporation at the extensive salt manufactories of Syracuse and the surrounding villages in Western New York, and also the experience of our engineers Upon the Erie Canal, and the engineers upon the dikes or levees at Sacramento, where the nature of the soil resembles that of Mexico. And I may now conclude this long survey of the canals and lagunas of Mexico, by saying that it is a wise provision of Providence that all bodies of water that have no outlet are found to contain a considerable infusion of salt, otherwise their accumulations of decaying matter would be such that mankind could not live in their vicinity. This valley is an illustration of that truth. Tezcuco, surrounded by barrenness, is not deleterious to life, while the fresh-water lagunas, though continually changing their volume, render Mexico unhealthy in summer by the gases which they exhale from decaying vegetation.
ANCIENT POPULATION OF THE VALLEY.
I have pretty thoroughly described this small valley, and have also stated how large a portion of it is flooded with surface-water, and how large a portion of this water is infused with salt. In the vicinity of Tacubaya the land is remarkably fertile, and there is good tillable land as the mountains are approached, especially about