[ISHMap-List] 'Cartographic innovations by the early portolan chartmakers'

Tony Campbell tonycampbellockendon at gmail.com
Thu Jan 12 16:34:11 CET 2017


I will respond briefly to your latest post.  Given the distance between 
our two positions I think it unlikely we will be able to find much 
agreement, and I question how long this exchange can usefully continue.

First of all, though, thank you for pointing out the internal 
contradiction in my text about the nature of the increase in the number 
of compass lines through the centre of his later charts. I have removed 
the careless and incorrect statements about '64 directions'.

I now comment only on what I consider to be one or two major issues.

The first is your supposed conviction that portolan chart historians 
assume a medieval origin. I don't think most of us are committed to that 
view.  We have looked for whatever evidence there might be, whether 
documentary or in the charts, but have found no convincing evidence for 
an earlier origin. Nor I think have you, beyond extrapolation from 
cartometric findings.

Where I would argue that there *is* a 'departure point' is in your 
dismissal of the possibility that the medieval mind and its technology 
were capable of creating the portolan chart. It is surely unwise, given 
examples from indigenous wayfinding and mapping techniques, to place a 
theoretical limit on what less advanced societies were capable of. 
History depends on documentation, and we would not expect to find a 
description of the devising and construction of a portolan chart.

What we *do have* is actual evidence of the process of creation in the 
charts themselves, although it is dismissed by you thus in a Delphic 
sentence :

"Regarding the Atlantic coastlines; these innovations are unsuitable for 
distinguishing between the hypothesis of a medieval and the one of a 
non-medieval origin, because both can provide an explanation for the 

On the contrary, I consider this to be crucial evidence because we here 
see - by degrees, involving different chartmakers and presumably 
different informants - the gradual emergence of a recognisable coastline 
from Cape St Vincent to Bruges, along with a parallel expansion in the 
toponomy. All this occurred between perhaps c.1280 and c.1320. If the 
sailors of that period were capable of such an achievement, why not 
those from a century before?

The general assumption that seems to have been made - perhaps there are 
exceptions - is that the portolan charts are the result of some kind of 
surveying operations (or of a process we can recognise as that).  Where 
is the evidence for that?  As you know, in Lisbon I asked that 
consideration be given to the hypothesis that the charts might never 
have been consciously 'mapped' at all, but rather have emerged from the 
sharing and adjustment of the mental maps that any experienced mariner 
must have had in their head. The Black Cab drivers' mental map of every 
London street, and the ability to get between any pair of those, is a 
far more impressive feat.

  I do not think that two related questions have ever been properly 
asked - and if you have done so please accept my apologies and point me 
to the relevant part of your book. How did mariners find their way 
around and across the Mediterranean for millennia before the appearance 
of the portolan charts; and what advantage did the charts offer them?  I 
am not sure how cartometric analysis can help here.

Best regards,


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