One of the most remarkable structures connected with it, was the Aqueduct bridge across the valley of Maintenon. This was designed to be entirely of masonry, having three ranges of arches, one above another. The length of this Aqueduct bridge would have been three and a quarter miles, and the height from the lowest part of the valley would have been 234 feet. The whole number of arches designed for this bridge was 685. Some of the piers and arches of the lower tier were constructed, but have since been suffered to crumble and fall. Many deep valleys were filled with embankments, and the canal was completed for a portion of the distance, but the course of the work is now but faintly marked by the remains of these structures. _Aqueduct of Lisbon._ The site of Lisbon, as well as the ground in its vicinity, consists chiefly of limestone and basalt, which render it necessary to obtain good water, at about three leagues distance, for the beverage, and other uses of the inhabitants. The source consists of several springs that are near to the village of Bellas, and their produce is conveyed to Lisbon by an Aqueduct, constructed of a kind of white marble, and finished in 1738. In some parts its course has been excavated through hills; but near to Lisbon it is carried over a deep valley, for a length of 2400 feet, by means of several bold arches, of which the largest has a height of about 250 feet, by a breadth of 115. The arches being pointed have an interesting aspect, particularly when viewed from below, the interior of the spacious vaults being not only majestic in appearance, but reverberating every sound. The water flows through a stone tunnel, or covered arch-way, about 8 feet wide, formed in the middle of the structure; and on each side there is a foot-path, with a parapet wall, having a sufficient width for two persons to walk. The Aqueduct enters the town on its northern side, at a place called da Amoreira, where it branches into several others, in order to supply the different fountains, from which the inhabitants are supplied. Persons, denominated _gallegos_, obtain a subsistence by selling the water, which they procure at the fountains in small barrels, and afterwards cry it through the streets. _Aqueducts of Mexico and the adjacent States._ The people who, in remote times, inhabited the region of Mexico, were advanced in civilization and in the arts; they had regularly organized states and established forms of government, and their immense cities, their roads, Aqueducts and other public works, give evidence of the advanced state of the arts among them and their knowledge of the sciences.