As the level of the surface of the land and the surface of the water at Mexicalzingo, at Mexico, and at the village Tezcuco, does not materially vary now from what it was in the time of Cortéz, if we can take for data the foundations of the church built by the Conquistadors at these several places, we shall have to look to another quarter for a supply of water for the city canals, which were sufficiently capacious for canoe navigation. This supply we readily obtain by allowing the waters of the canals Tacubaya and Chalco to pass through the streets of the city in ditches sufficiently large for canoes, instead of passing along the south and east fronts outside. By this hypothesis we obtain a current, a prerequisite to the very idea of a canal, particularly in the streets of a city.
The savans of Europe have shown their profound ignorance of the first principles of canal navigation in taking it for granted that the canals of Mexico were filled with stagnant water, that had "set back" from the stagnant pond of Tezcuco; and that the level of the pond must at all times have been so high as to fill the canals, thus keeping the city in constant danger from any sudden rise in the laguna. But, aside from the rules of canal construction, there is an important sanitary question involved. The present ditches in the middle of the streets, though they have a perceptible current, and a slight infusion of tequisquite, are an intolerable nuisance, and have a deleterious effect upon the public health. How much more so must they have been when, from the uncleanly habits of the Indians, they were the common receptacle of all kinds of filth, and were constantly stirred up to their very bottoms by the setting-poles of the navigators? The system of canalling is a system of slack-water navigation, but abhors stagnant water.
We come next to the question of the dimensions of these street canals. We know that they were intended only for the navigation of Indian canoes; that two of them, which intersected the causeway of the night retreat, Cortéz crossed with his army, all of them climbing down into the canal, wading across, and then climbing up on the other side while loaded with their armor, and fighting all the time against a superior force of the Aztecs; and that Alvarado actually leaped across one of the openings, shows conclusively that the canals could not have more than equaled in breadth the present canal of Chalco. On the hypothesis that Cortéz used scows that drew no more water than the scows that at present navigate the canals, his story becomes credible, so far, at least, as the possibility of making the circuit of the city in large boats in a season of rains.
TRUTH AGAINST FICTION.
It is an ungracious task to sift truth from fables. One man is displeased at seeing held up as a fiction a narrative which he has been accustomed to read with pleasure, and to take for truth, because it was elegantly written; and he requires an accumulation of proofs and arguments before he will abandon a belief which he has adopted without evidence. Another man, who deals only in matters of fact, is easily convinced, and is annoyed at an accumulation of proofs and arguments where one is sufficient. The superstitious man can not, of course, be convinced, for his belief does not rest upon evidence; and he is indignant that an attempt should be made to detract from the glory obtained by the Virgin Mary and the Church in this victory over the infidels. Had I attempted to prove that the feather which is now preserved with so much care in the Church of San Juan de Lateran at Rome did not fall from the wing of the angel Gabriel when he came to announce to Mary her conception, and that the whole history of that feather was a fable, notwithstanding it has received the attestations of so many of the Holy Fathers, I should be cursed for my impiety no more than I shall be for raising the question of the authenticity of the histories of the Conquest. With all these difficulties before me, I will venture to add one or two more reasons that have induced me to doubt the existence of those famous brigantines, which required a depth of twelve feet of water.
In support of the hypothesis that the street ditches, called canals, were independent of the Tezcuco for their supply, we have still the remains of an old Indian dike, which extended from near Iztapalapan, along the east part of the city, to Guadalupe or Tepeyaca, which must have been intended to shut off the Tezcuco when the water was high, and when it receded they probably opened a weir at the northern extremity, through which the waters of the city that had been discharged upon the flats of San Lazaro found an outlet.
The waters of the valley are now distributed in the best possible manner to favor evaporation; and yet so completely is this power taxed, that when, in 1629, a water-spout, bursting over the small river Guautitlan, had forced the waters of Zumpango over its barriers into the San Cristobal, and that again into the Tezcuco, the city was inundated to the depth of about three feet. Evaporation was unable to remove or materially lessen this new volume of water in a period of five years. This fully demonstrates that the average annual fall of water is equal to the full capacity of evaporation. The valley of Mexico is a very small one over which to dispose of the mass of water that the mountain-torrents in summer and the tropical rains pour into it, and with the small margin of six and a half feet for rising and falling, the city must have been in constant jeopardy. Still the floods have been much less frequent than would have been supposed, fully demonstrating the great uniformity in the fall of water in the Mexican season of rain. When a water-spout occurred in the Chalco in 1446, in the time of the Aztec kings, there was a flood, which probably ran off into the Tezcuco. Under the Spaniards the following floods are enumerated: the first in 1553; the second in 1580; the third in 1604; the fourth in 1607; the fifth in 1629.
After the flood of 1607, the tunnel of Huehuetoca was undertaken, and constructed in eleven months, for the purpose of letting out of the valley the waters of the River Guautitlan, so as to prevent it from falling into Tezcuco or flooding the city. For those times it was a great work, but we should say now that it was poorly engineered and badly managed, and not worthy the notice it has received in books on Mexico. Since that time, the great inundation of 1629 occurred while the mouth of the tunnel was closed. After that time, the Spaniards, instead of building inside of the tunnel an elliptical tube, actually, by a hundred years of misapplied labor, turned the tunnel into an open cut.
THE MAP OF CORTÉZ.
Cortéz furnished a map to illustrate his description. This map has the same defect as his narrative; that is, it was untrue at the time he made it. In order to bring Tezcuco about the city, he places the village of that 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.