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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 Senora 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 Motezuma.
The extraordinary rise of the river Guautitlaa 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 7f 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 fart, in 1.580, at the epoch of the great inundation, two intelligent men, the licenciado Obregon, 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 Mexican 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 marie 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, Aloriso 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 desague 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 conducted the water from the lake to the gallery was filled up by depositions of mud, and the
* 104,987 feet. Trans.
desague was only useful then for the Rio de Guautitlan, which was turned from its course; so that when M. Mier recently undertook the' direct evacuation of the lakes of San Christobal and Zumpango, it was hardly remembered at Mexico that 188 years before the same work had already been carried into execution with respect to the former* of these great basins.
The famous subterraneous gallery of Noehistongo was commenced on the 28th November, 1607. The viceroy, in presence of the audiencia, applied the first pick-axe. Fifteen thousand Indians were employed at this work, which was terminated with extraordinary celerity, because the work was carried on in a number of pits at the same time. The unfortunate Indians were treated with the greatest severity. The use of the pick-axe and shovel was sufficient to pierce such loose and crumbling earth. After eleven months of continued labour, the gallery (el socabon) was completed. Its length was more than 6600 metresf (or 1.48 common leagues^), its breadth S". 6||, and its height 4m. 2§. In the month of December, 1608, the viceroy and archbishop of
• The author evidently means Zumpango, which, as the sentence is constructed, is not the former, but the latter* Trans.
f 21,653 feet. Trans.
X Of 25 to the sexagesimal degree, 4443 metres each.
[[ 11,482 feet. Trans. § 13779 feet. Trans.