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 CORTEZ.

Cortez 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