mouth of the tunnel, without communicating to any one his intention to do so. The effect was instantaneous; and, in one night, the whole town of Mexico was laid under water, with the exception of the great square, and one of the suburbs. In all the other streets the water rose upwards of three feet, and during five years, from 1629 to 1634, canoes formed the only medium of communication between them. The foundations of many of the principal houses were destroyed; trade was paralyzed; the lower classes reduced to the lowest state of misery; and orders were actually given by the court of Madrid to abandon the town and build a new capital in the elevated plains between Tacuba and Tacubaya, to which the waters of the lakes, even before the conquest, had never been known to extend.
"The necessity of this measure was obviated by a succession of earthquakes in the dry year of 1634, when the valley was cracked and rent in various directions, and the waters gradually disappeared; a miracle for which due credit should be given to the Virgin of Guadalupe, by whose powerful intercession it is said to have been effected.
"Martinez, who had been thrown into confinement in 1629, was released upon the termination of the evils which his imprudence was said to have occasioned; and was again placed by a new viceroy,—the Marques de Cerralvo,—at the head of the works by which similar visitations were to be averted in future. Under his superintendence the great dyke, or Calzada of San Cristoval was put in order,5 by which the lake of that name is divided from that of Tezcoco. This gigantic work which consists of two distinct masses, the first, one league, and the second, one thousand five hundred varas in length, is ten varas in width or thickness throughout, and from three and a half to four varas in height. It is composed entirely of stone, with buttresses of solid masonry on both sides, and three sluices, by which, in any emergency, a communication between the lakes can be effected and regulated at the same time. The