> Why did Bishop Landa alter Colon's log books? To hide the
> actual longitude of the New World locations, as a major Treaty
> between Spain and Portugal established in 1498. Had the proper
> longitudes been given, as clearly the 4th trip would have been
> established by a trained navigator, the majority of Spain's
> New World lands would have belonged to Portugal.
My main source is Samuel Eliot Morison _The European Discovery of
America: The Southern Voyages 1492-1616_ New York: Oxford
University Press, 1974. All page references to Morison are to
this volume.
"A total eclipse of the moon took place on 14 September [1494]
while the fleet lay [at Saona Island, off Hispaniola] and
Columbus, who had an almanac which gave the time of the eclipse
at Nuremberg, tried by timing it at Saona to calculate the
longitude. It was a simple enough calculation---15 degrees to an
hour's time---but something went wrong and the Admiral worked out
a longitude too far west by 23 degrees. Building on that gross
error, it was easy for Columbus to persuade himself that he had
been well on his way around the world when he turned back from
Cuba." (pages 133-4)
"At Mexico City in 1541 a mighty effort was made by the
intelligentsia to determine the longitude of that place by timing
two eclipses of the moon. The imposing result was 8h 2m 32s (120
degrees 38 minutes) west of Toledo; but the correct difference of
longitude between the two places is 95 degrees 12 minutes. Thus
the Mexican savants made an error of some 25 1/2 degrees, putting
their city into the Pacific! Even in the late seventeenth century
Pe\re Labat, the earliest writer (to my knowledge) to give the
position of Hispaniola correctly, adds this caveat: "I only
report the longitude to warn the reader that nothing is more
uncertain, and that no method used up to the present to find
longitude has produced anything fixed and certain." (page 175).
By Eighteenth Century standards, not to mention those of the
Twentieth, Columbus's observational technique was primitive. His
observation of the moon was by naked eye. His "clock" was a
half-hour sand-glass which periodically (one hopes that day) was
calibrated with the sun at noon. (Morison page 163 says that such
a noon sight "could not be counted on to give true noon nearer
than 15 or 20 minutes").
It is interesting to note that the Saona and Mexico City
observations had almost the same error (23 degrees versus
25 1/2). Coincidence?
I can identify four sources of error in Columbus's 1494 attempt.
1). timing of the eclipse
2). error in the almanac
3). psychological error, either conscious or unconscious
4). deliberate alteration of the report
For 1) I simply cannot come up with an error budget that would
reach an hour and a half. The error in calibrating to solar noon
is on the order of 20 minutes. A sand glass is less than
accurate by even Seventeenth Century standards, but running more
than a few minutes fast in one day is unlikely (and by now
Columbus would have a good handle on how inaccurate his sand
glass was.) The only gross error to be expected is if the ship's
boy who was supposed to turn the glass when it emptied was
inattentive or asleep (this happened to Columbus at least once;
see Morison page 163), but presumably such an error would be
spotted either by someone watching the position of the stars
around Polaris, or by someone complaining that local noon was
occurring well into the afternoon watch.
For 2) we need to know just how accurate the almanac was.
Computing the date of an eclipse is relatively easy (apparently
the builders of Stonehenge could do it), but getting the exact
time is more difficult, particularly as before Kepler nobody knew
about elliptical orbits and their resulting time variations.
Does anyone on this list have information on almanacs ca. 1500?
3) is the simplest explanation. Columbus wanted to prove he was
near Asia and either fudged his figures or let his desire lead
his calculations astray. He had argued that Japan was 68 degrees
west of the Canary Islands (Morison page 30), and so he wished to
believe that he was already about that far west of the Canaries.
In fact, he was much closer to 50 degrees west of the Canaries.
4) is a more complicated theory than it seems at first glance.
Diego de Landa (no relation to this writer) joined the
Franciscans in 1541 and came to the New World some time later,
that is, AFTER the longitude observations at Mexico City. Of
course if he altered Columbus's record of a half-century earlier
he might have been thorough enough to alter that of the Mexico
City observations.
In the 1540's, after half a century of Spanish settlements
in the Caribbean, would a legal argument based on the Treaty of
Tordesillas (7 June 1494, not 1498, see Morison page 217) have
been taken seriously? Perhaps some of the Ibero-American members
of our list can answer that question.
Morison (page 477) gives the Demarcation Line from the Treaty of
Tordesillas as longitude 45 degrees 30 minutes West. This is
approximately the longitude of Sa~o Paulo, far enough west to
make Portuguese one of the official languages of this mailing
list, but well to the east of any Caribbean islands. (In fact
the Portuguese cheated a few degrees. The easternmost former
Spanish possession in the New World is Uruguay, starting at
around 53 degrees west longitude, and the westernmost point of
Brazil is around 73 degrees.)
At this point I run out of data and cannot draw any further
conclusions.
> ...as clearly the [longitude of the] 4th trip would have been
> established by a trained navigator
But Columbus was a "trained navigator", one of the best of his
day and age. Unless Columbus were guilty of psychological errors
in his eclipse sights, it is difficult to argue that any
contemporary could have found a more accurate longitude.
Circa 1500 there were exactly two ways to find longitude: by
eclipses of the moon and by dead reckoning. Columbus's dead
reckoning was remarkably good (Morison page 56 quotes one source
as that Columbus "made an average 9 per cent overestimate of
distance". This means that his dead reckoning placed the
Caribbean about 5 degrees, rather than 23 degrees, west of its
true longitude. He did not correct his lunar observation by his
dead reckoning, but then "everybody knows" that eclipse
observations are more accurate than dead reckoning!)
> I thank James for citing the thoughts of Colon's son Fernando,
> someone that was clearly off base, related to the best navigator
> minds of Spain that monitored Colon's work.
I gave only a partial quote of Fernando's dubious description of
the commission that examined Columbus's plan. Some more:
"As there were not so many geographers then as now, the members
of the commission were not so well informed as the business
required...[Some members] who based their opinions on geography,
claimed that the world was so large that it would take more than
three years to reach the end of India, whither the Admiral wished
to sail. In support of this, they cited Seneca, who discusses
the question in one of his books, saying that many scholars
disagreed astowhether the Ocean was infinite ornot, and doubted
that men could ever sail across it..." (Landstro"m pp 38-39). I
agree that Fernando was "clearly off base", having the bias of
wanting to promote his father's reputation.
James A. Landau