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166 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 rebuilding 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 prodigious canal, and of the various dikes raised in furtherance of the same design, among which that of San Cristobal 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 perpendicular, 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 distance, as it runs towards the fall of the Tula: and southward, 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 Cristobal; 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 possible chain of circumstances