"It is not our intention to follow the progress of the canal of Huehuetoca through all the various changes which occurred in the plans pursued with respect to it from 1637, when the direction of the work was again taken from Martinez and confided to the Franciscan monks, until 1767, when, under the viceroyalty of the Marques de Croix, the Consulado or corporate body of Mexican merchants, engaged to complete this great national undertaking. The necessity of converting the tunnel of Martinez into an open cut, had long been acknowledged, it having been found impossible to prevent the tunnel from being continually choked up by the sand and rubbish deposited by the water on its passage; but as the work was only prosecuted with vigor when the danger of an inundation became imminent, and was almost suspended in the dry years, two thousand three hundred and ten varas of the northern gallery remained untouched, after the expiration of one hundred and thirty years when the Consulado was intrusted with the completion of the arduous task. As the old line of the gallery was to be preserved, it became necessary to give the cut which was to be sunk, perpendicularly upon it, an enormous width at the top, in order to prevent the sides from falling in; and in the more elevated parts, between the mountains of Sincoque and the hill of Nochistongo, for the space of two thousand six hundred and twenty-four feet, the width, across, varies from two hundred and seventy-eight to six hundred and thirty feet, while the perpendicular depth is from one hundred and forty-seven to one hundred and ninety-six feet. The whole length of the cut from the sluice called the _vertideros_ to the _salto_ or fall of the river Tula, is sixty-seven thousand five hundred and thirty-seven feet or twenty-four thousand five hundred and thirty Mexican varas. The highest point of the hill of Nochistongo is that called Boveda Real, and it would be difficult when looking down from it, upon the stream below, and, following with the eye the vast opening through which it seeks an issue, to conceive that the whole is, indeed, the work of man, did not the mounds on either side, as yet but imperfectly covered with vegetation, and the regular outline of the terraces, denote both the recentness of its completion, and the impossibility of attributing it to any natural convulsion.