One of the books I read on the summer cruise was, "1421, The Year
China Discovered America"

Makes a convincing case that about 70 years before Columbus and about
100 before Magellan an enormous Chinese fleet circumnavigated the
world. The Chinese introduced horses (before the Spanish reintroduced
them) and chickens to South America. They also colonized both the east
and west coasts of North America- there's a wrecked Chinese Junk in
the Sacaramento River that carbon dates to the early 1400's, and early
Spanish explorers of the California Coast recorded an encounter with
an "unusal Indian tribe that appears to speak Chinese".

Like the Europeans, the Chinese had no real talent for determining
longitude.
In fact, the Chinese determined latitude by observing a cluster of
stars surrounding the pole star.

The Chinese sailed to the Southern Hemisphere to locate stars that
would allow them to determine latitude in that hemisphere as well.
They were successful.

The map prepared by Turkish Admiral Piri Reis was copied from earlier
sources. Much of the material archived by Chinese scholars contains
drawings that match the outlines on Piri Reis pretty precisely. The
author of "1421.." contends that if allowance is made for the Chinese
inability to
determine precise longitude the southern hemisphere and Pacific Ocean
portions of Piri Reis are surprisingly accurate. The book speculates
that the Chinese map was captured by the Turks when they took a ship
commanded by an officer who had sailed with Columbus.

The second "compass rose" for the southern hemisphere on Piri Reis can
be coordinated with the star systems the Chinese used to navigate when
south of the equator.

Curious note: One of the major exports from America to China was
pottery.
Sounds silly with the Chinese reputation for porcelain and ceramics-
but apparently some of the advanced cultures in Central America had
devised a way to make much thinner pottery than the Chinese and it was
highly prized.

Of course there are two schools of thought on the author's theory.

Here's the author's web site: http://www.1421.tv/

There is also an "anti-1421" web site, of course: http://www.kenspy.com/Menzies/index.html