From keithp@MINN.NET Fri Apr  3 11:47:43 1998
Date: Mon, 23 Mar 1998 19:11:18 PST
From: Keith Pickering 
Reply-To: Map History Discussion List 
To: Multiple recipients of list MAPHIST 
Subject: Re: tordesillas line

There are two ambiguous points in the Treaty of Tordesillas that make a firm answer impossible: 1) from which point in the Cape Verde Islands do we measure? and 2) what is the length of a league?

The league would have been almost certainly the Portuguese Maritime League, which was also in common use among Spanish sailors of the day. But this does not solve the problem since various sources give the length of this league between 3.18 and 3.22 nautical miles.

The most likely place for the measurement to begin would have been the westernmost point of the Islands, which is also the westernmost point of Santo Antao, which my rough measurement places at about 17 10 N, 25 22 W.

Using this point, and the mean league length of the PML (3.2 nmi), the line would be 1184 nmi west of the starting point. Measured along the 17 10 parallel, that would become (roughly) 18 degrees 51 minutes west of the starting point, or 44 d 13 m West of Greenwich.

The question of where the Spanish Crown placed the line in _degrees_ is somewhat of an oxymoron: there was no way to measure longitude in degrees in the 15th century. This was the reason that the line was specified in this manner to begin with. We should note, however, that Santo Antao is the northwesternmost island in the Cape Verdes. Moving to a starting point more southerly or more easterly would give the Spanish more territory in South America and less in the Spice Islands.

I highly recommend W.G.L. Randles, "Spanish and Portuguese Attempts to Measure Longitude in the 16th Century," _The Mariner's Mirror_ 81:4 (November 1995), 402-408, which deals extensively with attempts to determine the Tordesillas antimeridian in the Pacific.

Keith Pickering
keithp@minn.net

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----------
Wendy,
>
> thanks for your response.
>
> But I think my goal may be futile. Naturally, mapmakers and chroniclers
> all
> placed La Linea between Brazil and the rest of South America; but the
> tolerance of that line was far too wide for my purposes, and they were
> guessing anyway. I am trying to calibrate longitude error in the Pacific
> by some early Spanish voyages, which were gauged from the Line rather
> than their point of departure. To do this, I would need to know where
> the Spanish crown itself placed the line, not in term of leagues, but
> rather in degrees longtitude from some specific point (the Cape Verde
> Island would suffice, but Seville or true point of departure would be
> better, since it would eliminate the small variable between the two).
>
> Cheers,
>
> Tom S.
>
> __________________________________________
>
>
> Wendy Waters wrote:
> >
> > At 10:23 AM 23/03/98 -0500, you wrote:
> > >Two questions which perhaps someone out there can help me with :
> > >>
> > >2. Is there any reliable figure for what the real-world longitude
(based
> > >on Greenwich) would have been of the Line of Demarcation as established
> > >by the 1494 Treaty of Tordesillas (i.e., 370 leagues west of the Cape
> > >Verde Islands)? I know this is a more complicated issue than simply
> > >translating leagues into degrees and resetting it from Greenwich, but
is
> > >there a trustworthy narrow range of figures?
> > >
> >
> > I don't know if this will help but I've noticed in several latin
american
> > history text books a line consistently drawn on maps of south america
that
> > roughly could be extended from Sao Paulo in a straight line north and
> > south.  Thus it bisects modern-day brazil.   One place where a rough
map is
> > is in the skidmore and smith _Modern Latin America_ text.  Also,
although I
> > don't have it I would suggest looking in Bradford Burn's _History of
> > Brazil_ for a lead on the politics and measuring of this line.
> >
> > The line was constantly in dispute then, and my recollection from grad
> > school courses on this era is that no one today is precisely sure what a
> > league was (or league had differnet meanings in different regions, thus
we
> > have to be sure we're talking about the right league), so you may find
> > several arguments for the placement of the line today as in the 15th and
> > 16th centuries.
> >
> > If you do not get other help, you could ask the editors of H-Latam
> > (h-latam@h-net.msu.edu)--a Latin America history discussion list-- if
they
> > will post your query.

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