Cortez speaks of the fine fields of corn on the east side of the lake. But they could not have been finer in his day than they are at present, though they furnished him with the supplies that supported his army. I reached the head of Tezcuco at noontide, where the heavy water of the salt lake was driving up toward the fresh water, as described by Cortez, but it was under the pressure of a strong north wind. THE AZTEC CAUSEWAYS. Now that I am on the new causeway, broad and spacious like all the others, it may be well to conclude the discussion of the physical condition of this valley by determining the size of the old Aztec causeways. An island embosomed in a marsh has always formed a favorite retreat for an Indian tribe, whether among the everglades of Florida, or the wild-rice swamps of north-western Canada. Such a retreat is still more desirable when, in addition to the security it affords from an enemy, it is likewise a resort for wild ducks, as was and is the case with the laguna of the Mexican valley. Hence, probably, the Aztecs selected this place as the site of their village; and to reach it, it was necessary to make one or more footpaths across the marsh. As the Aztecs had no beasts of burden, this must have been a task of no little magnitude. To have made it thirty feet wide would not only have been a work of immense difficulty, but would have destroyed the defensive character of their position. Still, we can, upon this occasion, afford to be a little liberal with the statements of Cortez, as we have had to cut his hundreds of thousands of warriors down to a few thousand of miserably-armed Indians, and reduce his magnificent cities to small Indian villages. In order to make the island of Mexico at all inhabitable, we have had to reduce his lakes from navigable basins of twelve feet or more in depth to mere evaporating ponds. His floating islands have been transformed into garden-beds built upon the mud; and his canals have sunk to mere ditches. Now I propose to be liberal to the old Conquistador in the matter of his famous causeways, and will therefore admit that they might have been twelve feet in width--as broad as the tow-path of the Erie Canal. CHAPTER XIX. The Street of Tacuba.--The Spaniards and the Indian Women.--The Retreat of Cortez.--The Aqueducts of Mexico.--The English and American Burying-grounds.--The Protestant President.--The rival Virgins.--An Image out of Favor.--The Aztecs and the Spaniards.