310 



INUNDATIONS. 



Innndations. 



Increasing 

 liability. 



CHAP. xxrv. feet higher than the surface of Tezcuco ; while that ol 

 ~~ Chalco, at the southern extremity, is only 3-632 feet 

 more elevated than the great square of Mexico. 



In consequence of this peculiarity the city has for a 

 long series of ages beeij exposed to inundations. The 

 lake of Zumpango, swelled by an unusual rise of the 

 Rio de Guautitlan, flows over into that of San Christobal. 

 which again bursts tbe dike that separates it from 

 Tezcuco. The water of this last is consequently aug- 

 mented, and flows with impetuosity into the streets of 

 Mexico. Since the arrival of the Spaniards the town 

 has experienced five great floods, the latest of which 

 happened in 1G29. In more recent periods there have 

 been several alarming appearances, but the city was 

 preserved from any actual loss by the desague or canal, 

 which was formed for the purpose. 



The situation of the capital is more exposed to danger, 

 because the bed of the lake is progressively rising in 

 consequence of the mud carried into it, and the difference 

 between it and the level of the plain diminishing. Pre- 

 vious to the conquest, and for some time after, it was 

 defended by dikes ; but this method having been found 

 incff"ectual, the viceroy in 1607 employed Enrico Mar- 

 tinez, a native of Germany, to effect tlie evacuation of 

 the lakes. After making an exact survey of the valley 

 he presented two plans for canals, the one to empty 

 those of Tezcuco, Zumpango, and San Christobal, the 

 other to drain tliat of Zumpango alone. The latter 

 scheme was adopted, and, in consequence, the famous 

 subterraneous gallery of Nochistongo was commenced on 

 tlie 28th November 1607. Fifteen thousand Indians 

 were employed, and aftei eleven months of continued 

 labour the work was completed. Its length was more 

 than 21,6.54 feet, its breadth 11-482, and its height 13-78. 

 On the opposite side of the hill of Nochistongo is the 

 Rio de Tula, which runs into the Rio de Panuco, and 

 from the nortliern or further extremity of the gallery 

 an open trench, 28,215 feet long, was cut to carry the 

 water to the former river. Soon after tlic current began 



Plan for 

 averting 

 tlie danger. 



