In the ancient empires of Mexico and Peru, where there were no beasts fit for draught or for riding, magnificent roads were constructed for the treble purpose of facilitating the march of armies, accommodating the public traffic, and ministering to the convenience and luxury of the lordly rulers. In Peru two of these roads were from fifteen hundred to two thousand miles long, extending from Quito to Chili,--one by the borders of the ocean, and the other over the grand plateau by the mountains. Prescott says: "The road over the plateau was conducted over pathless sierras buried in snow; galleries were cut for leagues through the living rock; rivers were crossed by means of bridges that swung suspended in the air; precipices were scaled by stairways hewn out of the native bed; ravines of hideous depth were filled up with solid masonry; in short, all the difficulties that beset a wild and mountainous region, and which might appall the most courageous engineer of modern times, were encountered and successfully overcome. Stone pillars in the manner of European milestones were erected at stated intervals of somewhat more than a league all along the route. Its breadth scarcely exceeded twenty feet. It was built of heavy flags of freestone, and in some parts, at least, covered with a bituminous cement, which time has made harder than the stone itself. In some places where the ravines had been filled up with masonry, the mountain torrents, wearing on it for ages, have gradually eaten a way through the base, and left the superincumbent mass--such is the cohesion of the materials--still spanning the valley like an arch. "Another great road of the Incas lay through the level country between the Andes and the ocean. It was constructed in a different manner, as demanded by the nature of the ground, which was for the most part low, and much of it sandy. The causeway was raised on a high embankment of earth, and defended on either side by a parapet or wall of clay; and trees and odoriferous shrubs were planted along the margin, regaling the sense of the traveller with their perfume, and refreshing him by their shades, so grateful under the burning sky of the tropics.