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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 danger. ous 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 porphy. retical 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 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

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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 Nochistongo 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 metrest (or 1.48 common leagues!), its breadth 3". 5||, and its height 4". 29. 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. + 21,653 feet. Trans.

Of 25 to the sexagesimal degree, 4443 metres each.
11.482 feet. Trans. § 13.779 feet. Trans.

Mexico were invited by Martinez to repair to Huehuetoca, to see the water flow* from the lake of Zumpango and the Rio de Guautitlan through the gallery. The Marquis de Salinas, the viceroy, according to Zepeda's account, entered more than 2000 metrest on horseback into this subterraneous passage. On the opposite side of the hill of Nochistongo is the Rio de Moctesuma (or Tula), which runs into the Rio de Panuco. From the northern extremity of the socabon, called the Boca de San Gregorio, Martinez carried on an open trench for a direct distance of 8600 metres I which conducted the water from the gallery to the small cascade (salto) of the Rio de Tula. From this cascade the water has yet to descend according to my measurement, before it reaches the gulph of Mexico, near the bar of Tampico, nearly 2153 metresll, which gives for a length of 323,000 metres a mean fall of 63 metres in the 1000.

A subterraneous passage serving for a canal of evacuation, of 6600 metres in length, and an aperture of 104 square metres in section , finish

* The water flowed for the first time on the 17th Septenber, 1608.

+ 6561 feet. Trans. 28,214 feet. Trans.
Il 7056 feet. Trans. $ 1,059,714 feet. Trans.

The aperture was said a little before to be 3m, 5 in breadth, and 4m, 2 in height. The square of this is not 105 but 14.7 metres, which correspond to 158 square feet. Trans.

ed in less than a year, is a hydraulical operation which in our times, even in Europe, would draw the attention of engineers. It is only, in fact, since the end of the 17th century, from the example set by the illustrious Francis Andreossy in the canal of Languedoc, that these subterraneous apertures have become common. The canal which joins the Thaines with the Severn passes, near Sapperton, for a length of more than 4,000 metres*, through a chain of very elevated mountains. The great subterraneous canal of Bridgewater, which, near Worsley, in the neighbourhood of Manchester, serves for the carriage of coals, has an extent, including its different ramifications, of 19,200 metrest (or 41common leagues). The canal of Picardy, which is at present going on, ought, according to the first plan, to have a subterraneous navigable passage of 13,700 metres in length, 7 metres in breadth, and 8 metres] in heights.

* 13,123 feet. Trans. + 62,991 feet. Trans.

# 45.300 feet in height, 26.965 in breadth, and 26.246 in height. Trans.

Miblar and Vazic on canals, 1807. The Georg-Stolten in the Harz, a gallery begun in 1777, and finished in 1800, contains 10,438 metres in length (34,244 feet), and cost 1,600,000 francs (71,1722.). Near Forth coal mines are worked for more than 3000 metres (9842 feet) under the sea without being exposed to filtrations. The subterraneous canal of Bridgewater is in length equal to two thirds of the breadth of the Straits of Dover.

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