off the Cordilleras, many hundred leagues away, after having swept
across the huge plain of the Sacramento. Had the raft been provided
with masts and sails she would have felt the effects of the breeze,
and her speed would have been greater; but owing to the sinuosities
of the river and its abrupt changes, which they were bound to follow,
they had had to renounce such assistance.

In a flat district like that through which the Amazon flows, which is
almost a boundless plain, the gradient of the river bed is scarcely
perceptible. It has been calculated that between Tabatinga on the
Brazilian frontier, and the source of this huge body of water, the
difference of level does not exceed a decimeter in each league. There
is no other river in the world whose inclination is so slight.

It follows from this that the average speed of the current cannot be
estimated at more than two leagues in twenty-four hours, and
sometimes, while the droughts are on, it is even less. However,
during the period of the floods it has been known to increase to
between thirty and forty kilometers.

Happily, it was under these latter conditions that the jangada was to
proceed; but, cumbrous in its movements, it could not keep up to the
speed of the current which ran past it. There are also to be taken
into account the stoppages occasioned by the bends in the river, the
numerous islands which had to be rounded, the shoals which had to be
avoided, and the hours of halting, which were necessarily lost when
the night was too dark to advance securely, so that we cannot allow
more than twenty-five kilometers for each twenty-four hours.

In addition, the surface of the water is far from being completely