The length of the road, of which scattered fragments only remain, is
variously estimated, from fifteen hundred to two thousand miles; and
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.41 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 ! 42

Over some of the boldest streams it was necessary to construct
suspension bridges, as they are termed, made of the tough fibres of the
maguey, or of the osier of the country, which has an extraordinary degree
of tenacity and strength. These osiers were woven into cables of the
thickness of a man's body. The huge ropes, then stretched across the
water, were conducted through rings or holes cut in immense buttresses
of stone raised on the opposite banks of the river, and there secured to
heavy pieces of timber. Several of these enormous cables, bound
together, formed a bridge, which, covered with planks, well secured and
defended by a railing of the same osier materials on the sides, afforded a
safe passage for the traveller. The length of this aerial bridge, sometimes
exceeding two hundred feet, caused it, confined, as it was, only at the
extremities, to dip with an alarming inclination towards the centre, while
the motion given to it by the passenger occasioned an oscillation still
more frightful, as his eye wandered over the dark abyss of waters that
foamed and tumbled many a fathom beneath. Yet these light and fragile
fabrics were crossed without fear by the Peruvians, and are still retained
by the Spaniards over those streams which, from the depth or