Jeff wrote:

This is total nonsense. The compass was in common usage for 200 years
before Columbus. In the first millennium, only one round trip from
Italy to the Middle East was possible each year. The Winter storms and
fog necessitated hauling ships for the Winter.

That, plus the poor standard of construction & maintenance
(partly due to the poor tools & materials) meant that the
vessels had to be rebuilt for every voyage.


.... By the late 13th
century, compasses (and charts annotated with compass courses) were so
common that trade flourished all year long.

http://en.wikipedia.org/wiki/Portolan_chart

http://mundi.net/locus/locus_003/

http://www.princeton.edu/~his291/Portolan.html

One feature of the portolan chart not discussed so much is
that it was individualized... this was before printing, so
each chart was hand drawn... the time of a skilled
cartographer, with all the references needed, was very
valuable. One reason why mariners developed the habit of
sailing in fleets is that often only one captain would have
a chart.

Another factor is that each chart would have small coded
notes written on it by the navigator, referring to a
seperate book with entries on depth, current, weather,
landmarks on shore, bearings, etc etc. In other words, most
of the info we find on a modern chart was not on a portolan
chart, it was in the pilot's book.


Use of the compass spread to Spain and Portugal, and to Northern Europe
within a hundred years. In Portugal, Henry the Navigator sponsored
extensive exploration and colonization, as far out as the Azores, 900
miles off shore. They also developed early celestial navigation,
primarily to map the coast of Africa to document its colonization. (The
"famous" school at Sagres appears to be a myth.)

As it turned out, Columbus was quite adept in using the compass, and
startlingly accurate in his dead reckoning (when you considered his
private logs) but he never mastered the more modern techniques. For
instance, he was unable to reliably determine the latitude of his early
discoveries.


Nobody was able to reliably determine longitude with any
available technology in 1492. One thing Colombus did have,
which relatively few navigators of his era knew about, was a
table of compass deviation. It was thought by many (and
Columbus may have believed this too) that the magnetic
deviation from true north varied directly with longitude.
This actually is true for large section of earth & sea but
you have to know where the deviation begins to swing back again!

There are some accounts which credit Columus with having a
chart or map or pilot book from China, this would explain
why he kept thinking he knew where he was in the Caribbean
and also how he got financing from the monarchy of Spain.
Ferdinand and Isabella were more interested in uniting Spain
& driving out the Moors than in exploration. They had
already turned down other similar explorers and in fact
turned Columbus down, but then reconsidered. It's likely
that when they turned him down, he revealed just enough of
his secret book or chart to convince them to change their minds.


Personally, I lean towards the theory that there were numerous European
voyages to America long before Columbus.

Very possible. There are extant records of Basque whaling
voyages which made temporary bases at land that sounds a lot
like Cape Cod & Nantucket. And of course there were some
records of the Viking voyages, long disbelieved.

For some reason, everybody wants to think that previous
generations had no clue.

Fresh Breezes- Doug King