166 MEXICO. 



water to the height of three feet, and remained submerged 

 till 1634. 



Many projects were set afloat in the interval, and even 

 the propriety of abandoning the present site, and rebuild- 

 ing the metropolis on the rising ground beyond Tacuba 

 agitated ; but at length it was determined to convert the 

 tunnel through the hill of Nochistongo into an open cut. 

 This was effected, after years of labour, and infinite delay, 

 expense, and loss of Indian life ; and the completion of the 

 work dates from the year 1789- The cost of this pro- 

 digious canal, and of the various dikes raised in further- 

 ance of the same design, among which that of San Cris- 

 tobal is to be included, amounted to far above the sum 

 of six millions of dollars. 



The morning after our arrival, a visit to the Desague 

 Real was our only business, and we accordingly rode 

 along its whole line, to the summit of the hill through 

 whose bowels it has been carried. 



At the summit it presents an enormous excavation, cut 

 to the depth of one hundred and ninety-six feet perpen- 

 dicular, through alternate beds of clay, and loose gravel 

 and sand, with a breadth of upward of three hundred 

 feet at the top. Northward the eye loses it in the dis- 

 tance, as it runs towards the fall of the Tula : and south- 

 ward, it appears like a deep groove, stretching straight 

 across the plain, towards the northeastern angle of Lake 

 Zumpango ; beyond which you descry the Cerro de Cris- 

 tobal ; and, far in the distance, the snowy summits of 

 Iztaccihuatl and Popocatepetl. From one extremity to 

 the other the length of the desague exceeds 67,000 feet, 

 or upward of twelve miles. 



At the time we visited it, a most insignificant stream 

 was passing to the northward ; and it appeared to us 

 probable that the quantity of rubbish brought down into 

 the cavity by the crumbling beds of gravel above, and 

 the washing of the clayey strata, might become a serious 

 impediment in course of time, if not attended to. There 

 is no doubt that this costly enterprise has so far answered 

 the purpose for which it was undertaken ; yet should an 

 extraordinary but yet possibly chain of circumstances 



