"Boats went there in the days of Columbus," Frank said. "A
companion of Columbus first discovered this great delta. The river
fertilizes two million square miles of territory, and is the
greatest water system in the world."

"Why," Harry observed, desiring to contribute something startling to
the discussion of the river, "the current is so strong that it
carries fresh water and sand five hundred miles out into the
Atlantic Ocean. It is just a fresh water river in a salt water sea
for five hundred miles!"

That night the boys kept the engines of the Black Bear going, one
remaining on watch all through the dark hours. They had plenty of
gasoline in the tank, and the tender, the Wolf, was carrying a load
of fuel which Jack declared would last them until the end of the
year!

It may be well to state here that the Black Bear, the Boy Scout
motorboat, was a specially constructed vessel, built by Harry's
father for river work. The materials were light yet strong, and the
boat could easily be taken apart and put together again when
occasion required. Between the cross-grained slices of tough wood
of which the craft was built were plates of steel, thus rendering
the boat virtually bullet proof.

The Black Bear was constructed so that it could be almost entirely
thrown open to the sunshine when so desired or closed tightly
against cold or rain. The roof could be rolled up in a bundle in
the middle like the curtain of a modern desk. The sides were