"The plan of Martinez appears to have embraced two distinct objects, the first of which extended to the lakes of Tezcoco and San Cristoval, while the second was confined to the lake of Zumpango whose superfluous waters were to be carried into the valley of Tula by a subterraneous canal into which the river Guautitlan was likewise compelled to flow. The second of these projects only was approved by the government; and the line of the canal having been traced by Martinez between the Cerro or hill of Sincoque and the hill of Nochistongo to the north-west of Huehuetoca, where the mountains that surrounded the valley are less elevated than in any other spot,--the great subterraneous gallery of Nochistongo was commenced on the 28th of November, 1607. Fifteen thousand Indians were employed in this work, and as a number of air shafts were sunk, in order to enable them to work upon the different points at once, in eleven months a tunnel of six thousand six hundred metres[38] in length, three metres five in breadth and four metres two in height, was concluded. "From the northern extremity of this tunnel called la boca de San Gregorio, an open cut of eight thousand six hundred metres conducted the waters to the _salto_ or fall of the river Tula, where, quitting the valley of Mexico, they precipitate themselves into that of Tula, from a natural terrace of twenty Mexican varas in height, and take their course towards the bar of Tampico where they enter the gulf of Mexico. An enterprise of such magnitude could hardly be free from defects, and Martinez soon discovered that the unbaked bricks, of which the interior of the tunnel was composed, were unable to resist the action of water, which, being confined within narrow limits, was at times impelled through the tunnel with irresistible violence. A facing of wood proved equally ineffectual, and masonry was at last resorted to; but even this, though successful for a time, did not answer permanently, because the engineer, instead of an elliptical arch, constructed nothing but a sort of vault, the sides of which rested upon a foundation of no solidity. The consequence was that the walls were gradually undermined by the water, and that the vault itself in many parts fell in. "This accident rendered the government indifferent to the fate of the gallery which was neglected, and finally abandoned in the year 1623, when a Dutch engineer, named Adrian Boot, induced the viceroy to resume the old system of dyke and embankments, and to give orders for closing the tunnel of Nochistongo. A sudden rise in the lake of Tezcoco caused these orders to be revoked, and Martinez was again allowed to proceed with his works which he continued until the 20th of June, 1629, when an event took place, the real causes of which have never been ascertained."