impetuosity of the current, would seem impracticable for the usual
modes of conveyance. The wider and more tranquil waters were crossed
on balsas--a kind of raft still much used by the natives--to which sails
were attached, furnishing the only instance of this higher kind of
navigation among the American Indians.43

The other 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 perfumes, and refreshing him by their
shades, so grateful under the burning sky of the tropics. In the strips of
sandy waste, which occasionally intervened, where the light and volatile
soil was incapable of sustaining a road, huge piles, many of them to be
seen at this day, were driven into the ground to indicate the route to the
traveller.44

All along these highways, caravansaries, or tambos, as they were called,
were erected, at the distance of ten or twelve miles from each other, for
the accommodation, more particularly, of the Inca and his suite, and
those who journeyed on the public business. There were few other
travellers in Peru. Some of these buildings were on an extensive scale,
consisting of a fortress, barracks, and other military works, surrounded
by a parapet of stone, and covering a large tract of ground. These were
evidently destined for the accommodation of the imperial armies, when
on their march across the country. The care of the great roads was
committed to the districts through which they passed, and a large number
of hands was constantly employed under the Incas to keep them in repair.