When the indigenous race in former times had to pass any river on their route, their engineers supplied, as best they could, the wants of science by that natural sagacity which belongs to their living posterity. When their particular course allowed, they placed their simple bridge near the origin of the stream, or outlet of the lake whence it happened to flow; as we see at the lakes of Lauricocha and Pomacocha. As the waters of the lake can never rise many feet above the usual level, the purpose of a more scientific bridge is served by the Indian method of laying down large stones at short intervals from bank to bank; and, as these stones rise high above the surface of the water, they serve as pillars or supporters, over which are laid transversely large flags, that form an even and safe path for the passage of men and cattle. At the places mentioned, the single stones, too wide apart for stepping-stones, are still to be seen firm in their places; though the transverse flags, probably removed by human hands, are no longer found; at least, at Pomacocha not a vestige of them remains. A more ingenious bridge of ancient invention, and still used in Peru, is the swing or soga bridge. It is made by ropes twined from the pliable bejuco, twigs of willow, or any other flexible and vegetable filaments; and these are well secured at the ends on the opposite banks of the water: on these, bundles of maguey leaves, broom, or other long-branched and yielding shrubs, are laid crosswise, and bound very closely and firmly by tough ligaments or slips of the maguey leaf (“cabuia”), which answer as well as the best cordage. In this way the bridge is made of sufficient breadth for foot-passengers; and a hand-rope runs along each side of it, by which the traveller can steady himself while walking across. A specimen of this sort is the soga bridge of modern Huanuco. At Oroya also, over the river Jauja, is a very strong one of this kind for cargo-mules to cross upon. The ropes, or rather _cables_, extending from bank to bank, are made of bullock’s hide; and the cross-bars, bound down with thongs, are of squared pieces of wood, and broad enough to allow the animals to pass with confidence. As this bridge is kept up at unusual expense, and situated on the post-road to the interior, we paid toll at it for passing our saddle-beasts. The rope or swing-bridge is very convenient where the river is too broad to be spanned by any trees to be found in the neighbourhood; but where the stream is not much too wide to be crossed by long trees and beams, of which the temperate altitudes afford appropriate materials in the wood known by the name of perijil or roble, the natives manage to form a strong and pretty durable bridge, by constructing a large and massy stone breast-work on each side the water. In these bulwarks they fix strong timbers, which are made to project over the stream as far as may be required, while the larger portion of the