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lake, consisted of a wall of stones and clay, supported on each side by a range of pallisadoes, of which considerable remains are yet to be seen in the plains of San Lazaro. This dike of Motezuma I. was enlarged and repaired after the great inundation in 1498, occasioned by the imprudence of king Ahuitzotl. This prince, as we have already observed, ordered the abundant sources of Huitzilopochco to be conducted into the lake of Tezcuco. He forgot that the lake of Tezcuco, however destitute of water in time of drought, becomes so much the more dangerous in the rainy season, as the number of its supplies is increased. Ahuitzotl ordered Tzotzomat. zin, citizen of Coyohuacan, to be put to death, because he had courage enough to predict the danger to which the new aqueduct of Huitzilopochco would expose the capital. Shortly afterwards the young Mexican king very narrowly escaped drowning in his palace. The water increased with such rapidity, that the prince was grievously wounded in the head, while saving himself, by a door which led from the lower apartments to the street.
The Aztecs had thus constructed the dikes (calzadas) of Tlahua and Mexicaltzingo, and l'Albaradon, which extends from Iztapalapan to Tepeyacac (Guadalupe), and of which the ruins at present are still very useful to the city of Mexico. This system of dikes, which the Spa.
niards continued to follow till the commencement of the 17th century, afforded means of defence, which, if not quite secure, were at least nearly adequate, at a period when the inhabitants of Tenochtitlan sailing in canoes were more indifferent to the effects of the more trifling inundations. The abundance of forests and plantations afforded them great facilities for constructions on piles. The produce of the floating gardens (chinampas) was adequate to the wants of a frugal nation. A very small portion of ground fit for cultivation was all that the people required. The overflow of the lake of Tezcuco was less alarming to men who lived in houses, many of which could be traversed by canoes.
When the new city, rebuilt by Hernan Cortez, experienced the first inundation in 1553, the viceroy, Velasco I. caused the Albaradon de San Lazaro to be constructed. This work, executed after the model of the Indian dikes, suffered a great deal from the second inundation of 1580. In the third of 1604 it had to be wholly rebuilt. The viceroy Montesclaros then added, for the safety of the capital, the Presa d'Oculma, and the three calzadas of Nuestra Señora de Guadalupe, San Christobal, and San Antonio Abad.
These great constructions were scarcely finished, when, from a concurrence of extraordinary circumstances, the capital was again inundated in 1607. Two inundations had never before followed so closely upon one another; and the fatal cycle of these calamities has never since been shorter than sixteen or seventeen years. Tired of constructing dikes (albaradones) which the water periodically destroyed, they discovered at last that it was time to abandon the old hydraulical system of the Indians, and to adopt that of canals of evacuation. This change appeared so much the more necessary, as the city inhabited by the Spaniards had no resemblance in the least to the capital of the Aztec empire. The lower part of the houses was now inhabited ; few streets could be passed through in boats; and the inconveniences and real losses occasioned by the inundations were consequently much greater than what they had been in the time of Mote. zuma.
The extraordinary rise of the river Guautitlan and its tributary streams being looked upon as the principal cause of the inundations, the idea naturally occurred of preventing this river from discharging itself into the lake of Zumpango, the mean level of the surface of which is 77 metres * higher than the Plaza Mayor of Mexico. In a valley circularly surrounded by high mountains, it was only possible to find a vent for the Rio de Guautitlan through a subterraneous gallery, or an open canal through these very mountains.
In fact, in 1580, at the epoch of the great inundation, two intelligent men, the licenciado Obre. gon, and the maestro Arciniega, proposed to government to have a gallery pierced between the Cerro de Sincoque, and the Loma of Nochistongo. This was the point which more than any other was likely to fix the attention of those who had studied the configuration of the Mex. ican ground. It was nearest to the Rio de Guautitlan, justly considered the most dangerous enemy of the capital. Nowhere the mountains surrounding the valley are less elevated, and present a smaller mass than to the N.N.W. of Huehuetoca, near the hills of Nochistongo. One would say on examining attentively the marle soil of which the horizontal strata fill a porphyretical defile, that the valley of Tenochtitlan formerly communicated at that place with the valley of Tula.
In 1607, the Marquis de Salinas, viceroy, employed Enrico Martinez to carry through the artificial evacuation of the Mexican lakes. It is generally believed in New Spain that this celebrated engineer, the author of the Desague de Huehuetoca, was a Dutchman or a German. His name undoubtedly denotes that he was of foreign descent; but he appears, however, to have received his education in Spain. The king conferred on him the title of cosmographer; and there is a treatise of his on trigonometry, printed
at Mexico, which is now become very scarce. Enrico Martinez, Alonso Martinez, Damian Davila, and Juan de Ysla, made an exact survey of the valley, of which the accuracy was ascertained by the operations of the learned geometrician Don Joaquim Velasquez in 1774. The royal cosmographer, Enrico Martinez, presented two plans of canals, the one to evacuate the three lakes of Tezcuco, Zumpango, and San Christobal, and the other the lake of Zumpango alone ; and, agreeably to both projects, the evacuation of the water was to take place through the subterraneous gallery of Nochistongo, proposed in 1580 by Obregon and Arciniega. But the distance of the lakes of Tezcuco from the mouth of the Rio de Guautitlan being nearly 32,000 metres*, the government confined themselves to the canal of Zumpango. This canal was so constructed as to receive at the same time the waters of the lake, and those of the river of Guautitlan; and it is consequently not true that the desugue projected by Martinez was negative in its principle, that is to say, that it merely prevented the Rio de Guautitlan from discharging itself into the lake of Zumpango. The branch of the canal which con. ducted the water from the lake to the gallery , was filled up by depositions of mud, and the
* 104,987 feet.