way from ten to twelve feet wide, raised slightly
in the centre, paved with stones, and the edges defined by larger stones
sunk firmly in the ground. Where this road descends from the elevated
_puna_--a sheer descent of almost four thousand feet into the valley of
Yucay--it zigzags on a narrow shelf cut in the face of the declivity,
and supported here and there, where foothold could not otherwise be
obtained, by high retaining-walls of cut stone, looking as perfect and
firm as when first built centuries ago.

High mountain-ranges and broad and frigid deserts, swept by fierce,
cold winds, are not the sole obstacles to intercommunication in the
Altos of Peru, and among those snow-crowned monarchs of the Andes and
Cordilleras. There are deep valleys, gorges, and ravines among the
mountains, or cut deep in the plains that alternate with them, in which
flow swelling rivers or rapid torrents, fed by the melting snows in the
dry season, and swollen by the rains in the wet season. They are often
unfordable, but still they must somehow be passed by the traveller. A
few bridges of stone were constructed by the Spaniards, some after the
Conquest, and a few others have been erected by their descendants; but,
as a rule, the rivers and mountain-torrents are passed to-day by the
aid of devices the same as were resorted to by the Incas, and at points
which they selected.

Had the principle of the arch been well understood by the ancient
inhabitants, who have left some of the finest stone-cutting and masonry
to be found in the world, there is no doubt the interior of Peru would
have abounded in bridges rivalling those of Rome in extent and beauty.
As it was, occupying a country destitute of timber, they resorted to
suspension-bridges, no doubt precisely like those now constructed by
their descendants and successors,--bridges formed of cables of braided
withes, stretched from bank to bank, and called _puentes de mimbres_
(bridges of withes). Where the banks are high, or where the streams are
compressed between steep or precipitous rocks, these cables are anchored
to piers of stone. In other places they are approached by inclined
causeways, raised to give them the necessary elevation above the water.
Three or four cables form the floor and the principal support of the
bridge, over which small sticks, sometimes only sections of cane or
bamboo, are laid transversely, and fastened to the cables by vines,
cords, or thongs of raw hide. Two sm