microphone, but can you hear me? Is that okay? Yep, all good? Testing, testing, one, one.
Yep, okay, great. Okay, yes, so thank you very much for having me here. Those of you who know
me will may well know me as mainly sort of an infrastructure kind of a guy with projects like
Pelagios and Google Engine Places, but this presentation will be something entirely different
because I'm going to hopefully show the use of digital humanities to answer a question.
There's been a lot of debate about whether digital humanities should be answering new
questions. This one is an old question. In fact, it's about 700 years old. So the alternative
title for my talk is new perspectives on the prehistory of the map. What do I mean by that?
Well, I want to start with a map that many of you will know. The Waldseemuller map of 1507,
often referred to as the birth certificate of America. It's the most expensive map in the world,
and the reason for its fame and its price tag is over here on the left-hand side because it's the
first map which at least ostensibly shows America as a new continent, as a new island rather than
the West Indies as it had previously been thought of. But it interests me for a different reason,
and it interests me for the title, and names are an important thing here. We think of this
as the Waldseemuller map or the birth certificate, but its official title is the Universal Cosmography
according to the traditions of Ptolemy and the voyages of Amerigo Vespucci and others.
The reason that it's called that is Waldseemuller was working in Germany. Clearly he didn't have
time to go gallivanting around the world, and if you're in the business of producing world maps,
then you've got to get your data from somewhere. The data that he got was from the relatively
recently rediscovered Ptolemy's geography, which first reemerges in 1295 in Byzantium,
takes a century to get through to Western Europe, and indeed almost the entire center of his map,
the coordinates, the geographic coordinates for those are from Ptolemy's map with new
contemporary place names assigned. Over to the west he's got details from Amerigo Vespucci's,
travels over to the east from Marco Polo and others. The question that I'm interested in
is one that if we put ourselves in a parallel universe, let's imagine that since 1500,
all of Ptolemy's works have been lost to us. All of Amerigo Vespucci's letters about the new world
have been lost to us. All of the Marco Polo's travels and others have been lost to us.
To what degree could we, by looking at the map, figure out which of this stuff is Ptolemy, which
of this stuff is Amerigo Vespucci, and what if it belongs to other people? And the reason I'm
interested in that is because Ptolemy is precisely that situation. In fact, we could think of
Ptolemy's geography as having the title of the universal cosmography according to a tradition
of Merinos, a chap we're going to come to in a moment, the voyages of Alexandros and others,
see Ptolemy 150 AD. So who's called Ptolemy and why is he interesting? Well, he's interesting
because he's unquestionably one of the most significant figures in the history of science.
We can't think of contemporary astronomy today without thinking about Ptolemy and again
contemporary geography, as we'll see, and particular geographic information systems
are also pretty much inconceivable without thinking about Ptolemy.
He also wrote some very influential treaties on astrology, which was a very strong interest of his,
optics, harmonics, and a variety of other things. However, we have a tendency to think of Ptolemy
as being some kind of polymath, somebody who is interested in this whole wide variety of things.
In contrast, Ptolemy probably thought of himself not as some kind of polymath doing lots of different
stuff, but as more or less a single role of a cosmographer, as a cosmologist, somebody who is
thinking about the universe as a whole, and in particular, and we can this overhearism is a much
later diagram representing the Ptolemaic universe, that there were very strong interactions between
what's taking place in the astronomical and the celestial sphere, in the impact of the sun, the
moon, and the stars on what's going on on Earth, and that can help you with the effects of those
cores, can help you learn a whole bunch of stuff about predicting future events, about guessing
what the weather's going to be like, and about understanding why it is that Greece is full of
beautiful, intelligent, cultured people, and everybody else is a bunch of barbaric savages.
The geography is just part of a whole toolkit of treaties that he produces, and again, the title,
and we again, we think of it of these days as the geography of the Geographia, but the actual title
of it is the Geographica Hypagesis, a manual for producing a map of the world. It's got a much more
kind of pedestrian kind of title, it's something that's useful that you can use, it's not so much
kind of a theoretical work, although of course it is full of theory, and that's precisely why it's so
exciting and so interesting for us. So for those of you who aren't intimately familiar with it,
it breaks down into about three separate components. So the first book is theory,
he talks to some degree about where his sources are coming from, including Marinos. He also very
importantly talks about a theory of projections, the problem of how can we describe places on the
spherical earth and project those into a planar system, and he gives us a series of different
projections that we can use. The central portion is a catalog, and it runs through several books,
and it contains several thousand locations, about half of, about eight thousand locations, about
half of which have coordinates assigned to them, and that's the catalog. And by associating those
two things together, you can produce a variety in a different series of maps. So any of those of you
who work with GAS will know that these are effectively the basic principles of a geographic
information system, okay? Here are our coordinates, here are our projections, we can reduce different
kinds of visualizations by combining those two things together. In the third section of this,
halfway through book seven and finishing with book eight, there's a more theory and a series of
captions to be associated with both world maps and also regional maps as well. But we don't know,
we're not sure about, some of the manuscripts that have come to us do seem to have maps associated
with them, they seem to date from antiquity, but there's been some debate about whether these
originate with Ptolemy or whether they originate later, somebody else producing these maps based
on Ptolemy's work. So thinking a little bit, so returning to a question and the nature of what it
is that he's trying to do, at the very, very beginning of the work, Ptolemy distinguishes
between two different traditions of mapping in antiquity and he uses the terms choreography and
geography and these are going to be very important terms for us. Although these terms are used by
other people, the manner in which they use is not particularly regular. So to a certain degree,
I'm going here by Ptolemy's distinction, that doesn't necessarily mean that other people using
these terms, choreography and geography, were always using those things in the same sense.
But he makes a very clear distinction. So choreography is regional mapping, if you like,
and geography is world mapping, it's global mapping, it's mapping associated with the earth
itself. And the distinction that he makes are that choreography presents the minute features,
as geography presents the grosser features of the world. Choreography requires landscape drawing,
okay, it has a lot of visual impact. Geography in contrast, we can represent merely through lines
and through labels. Choreography has no particular need for mathematical method. In geography, it
takes absolute precedence. Choreography represents the qualities rather than the quantities of things
and geography is the quantities rather than the qualities and indeed, in particular considerations,
the proportionality of distance. Choreography, and I think ultimately this is the most important
distinction of all, choreography sets out the individual localities, harvest towns and districts,
but geography shows the known world as a single and continuous entity and that's something that
again we're going to come back to as an issue. He then goes on to say we're going to look at
geography and he never mentions choreography again, okay, so he distinguishes between these
two apparently completely different traditions and then he parks choreography and so, you know,
as far as we could tell, that's the end of his interest in that particular tradition.
He then moves on to talk about his primary source, a chap called Marinos of Tyre,
who we presume comes from Tyre. Unfortunately, we don't know an awful lot more about him other than
what it is that the Marinos says, sorry, what Ptolemy says, but there are some important things
that he does say about him. So most of all, of course, he's the latest person at the time of
Ptolemy to have undertaken this subject of geography and he's done it with absolute
diligence, okay, he's the greatest thing since sliced bread more or less and that more or less
is crucial because he then spends the next bunch of chapters telling us all the reasons why
Marinos is wrong and indeed why he needs to correct them and incorporate a whole range of things.
He then moves on to say that we have then taken on a two-fold task. The first is to preserve
Marinos' opinions expressed throughout the whole of his compilation, Marinos' compilation,
except for those things that need some correcting, and second, to see that the things he didn't make
clear will be inscribed so that they should be so far as possible using the researches of people
who visited those places or their positions in the more accurate maps. So to be a little bit more
specific about the question I first asked, the issues I'm interested in, well, what was it the
Marinos didn't make clear and what are the more accurate maps that Ptolemy is using to kind of
fill in those gaps? Straight away we start to run into a problem when we think about Marinos.
So this is the question that's been plagued people ever since the rediscovery of Ptolemy's
geography. It tends to lead to a lot of hand waving about, you know, well, maybe he was sort of more
locations like this or maybe he was mainly Marinos with some kind of some tweaks, but there
are some real issues. So the two key issues to bring up with Marinos here, a quote from the
geographic hypergesis 118, when putting the cities in their positions, it might have been easier
labeling those on the coast if we're using Marinos' notes, since in general some indication
of position is noted for them, but that's not so for the inland ones, okay, since the relative
position with respect to each other or with respect to the cities on the coast is not indicated,
and with few exceptions, and in these instances sometimes only the longitude and sometimes only
the latitude, and that seems pretty weird if Marinos was drawing a map which he's copying,
but that's okay because that's clarified by a statement in 117 that Marinos did not have time
to draw a map. So straight away we have to ask ourselves, well, where on earth is he getting this
information from if Marinos is not giving a lot of the kind of coordinates or at least half an
ordinate for these things, and there's no visual representation from it. We can start to break this
data down, fortunately because the University of Bern has released a database of coordinates from
Ptolemy's geography, which we can map out and we can start to play with this data spatially
typologically, and when we go through the text of the data, one of the things that becomes very
clear is that Ptolemy distinguishes very clearly as he goes through across the earth, starting in
the northwest, moving down towards the southeast, but region by region he divides very clearly
between four different types of data. So he always starts by delineating the region that
he's interested in, with the boundaries, predominantly coastlines, but also some
terrestrial boundaries as well. He then moves on to geophysical features, principally mountains.
He then moves on to describe the cities of the interior, and those are universally cities that
he's describing there, and then finally he moves on and discusses the islands. So over here,
and you can see how neat that distinction is, just so we can take every region, divide it into,
if you like, four blocks, always following that same order with about one exception,
and you can see very clearly that we have coastlines in blue, green we have the internal
cities, the blue dots in the middle here, those are the origins of rivers, so they're still
associated with the river mountains which are on the coastline, brown is the mountains and
purple here as the islands. That turns out to be interesting for further reason.
If we look at other geographers, other people with geographic writings associating places
with plate with the latitude and longitude on the earth's surface, then we see precisely that same
kind of ratio that Tollemy was talking about. Now we have to be clear that in the case of
Aretosthenes and Hipparchus here, we're dealing with fragments of information, we don't actually
have the full text themselves, but nonetheless, if we look at the places they refer to, we do see
that predominantly they're talking about places on coastlines or places which are in terms of
important terrestrial boundaries, and the numbers of interior cities, settlements which are some
inland, if you like, are very few and far between in comparison to those other ones,
and that's particularly weird because when we look at Tollemy, it's a completely different
picture. As you saw, there is a huge number of interior cities, but he's already told us that
he can't get it from Rhinos. It also seems to be the case that he can't get them from Aretosthenes,
Hipparchus, plenty of others. What's going on? Where is this magical data emerging from when it
seems that he's not getting it from somewhere else? And the problem gets even worse than that.
Let's suppose that maybe somebody's dropped out of history who has created
the Ur map for Tollemy with all of these coordinates in it. Here's the reason why I think
that's unlikely. Stravo says that if you're creating a world map, then you're going to need
a pretty large thing to put it on. So if you're going to have a large globe, then it shouldn't
have a diameter of less than ten feet, and if you can't produce a globe of that size,
then you should go for a plain service of about seven feet. Unfortunately, I wasn't able to bring
a ten-foot globe with me to demonstrate this hypothesis, but luckily I came across a seven-foot
globe only the other day, which hopefully will give you some indication of the problem that I'm
referring to. So this is a seven-foot globe. Here is somebody very kindly standing there to provide
some kind of a scale. Over at the top, we have Europe. If you look over on the west side, you
can, of course, see the Iberian Peninsula. Now, the Iberian Peninsula on this seven-foot globe,
ten-foot globe, is probably about the size of a human hand, but Ptolemy has something like 570
separate coordinates for cities within the Iberian Peninsula. The question is, how can you possibly
fit that? What kind of a map would have that many locations pegged into such a tiny size and yet
still be visible or usable by anybody at all? It seems extraordinarily unlikely that there was some
kind of geographic map that contained that density of information. The question then we
need to ask ourselves is Ptolemy using choreographic information to fill out that data?
Well, there are various clues that we can use to help us answer that particular question. So one of
those is the level of precision that he uses. Clearly, he doesn't pay everything to a specific
degree. He or he, to get a final level of granularity, he has to use fractions of a degree.
Now, although we have some levels of conflation between these fractions, so these are all the
points which are on a degree, these are all the points which are on a half degree, these are on a
quarter and three quarters and so on, and the lowest level of granularity is one-twelfth of a
degree. And you can see that there are a few of them, but not enough. It's not an even distribution.
And if we map those out, we see that there is a very specific spatial correlation with those high
precision coordinates. So maybe he's getting better data from somewhere, and that's different
from the data that's through on the periphery. However, is that data because we've got roman
surveyors who are going out there, they're astronomically figuring out, okay, here's the
latitude at least, longitude, of course, is famously much harder to measure. Is that what's
going on? Well, this image here should show us that that's not what's going on, because places
like Sardinia are horribly, horribly wrong, horribly out of joint with where they physically
are, despite the fact that you could go out with a stick, take this on a shadow and figure out where
you were latitudinally. That precision has got nothing to do with scientific accuracy, it is
entirely a product of the way that this information has come together. However, there's another clue
about it, because the places that Ptolemy refers to along here are along a very special parallel,
known as the parallel of roads, which, if you like, conceptually divides the Mediterranean.
So in the Greco-Roman world, this is an important boundary on the earth, which
psychologically as much separates between Libya and Europe. And that in turn gives us a clue,
because that is not the only important traditional boundary. There are a very large number, sorry,
there are, Ptolemy uses a separate gratitude based on time, which he overlays in that series
of angular coordinates that's based on time. So these are longitudinally, effectively he uses
time zones, which are divided into three, so segments of 20 minutes. And north to the south,
in terms of latitude, he uses time based on length of longest day. Unfortunately, length of longest
day is not a regular feature, and he has to subdivide parts of that into halves and quarters,
and that means that running north to south you have a very uneven grid, whereas east to west you
have an even grid. Does that help? Are things pegged, if you like, to that particular gratitude?
Well, if we look at Hellas here, then we can start to see that, yes, indeed, there seems to be some
very curious aspects to which the west side of Hellas is running perfectly along one side,
the center of Hellas on another of these traditional longitudinal meridians,
and the same thing for the east. But we can also think, because we have these coordinates,
of this not merely as a map, but as a text, and we can look at the running order in which Ptolemy
lists his coordinates, and indeed, in the way that he breaks down all the affiliations of his
locations with specific tribes. And what it turns out is that, again, in terms of the coastline,
we can see very clearly that pegging to this traditional parallel, whereas in terms of tribes
very frequently, we can see the interiors seem to be pegged to these angular coordinates,
which he has superimposed. So there seem to be two different kinds of data associated here.
However, if we use that same approach, we ask, is this the case all over? We take the same
approach over here in the Levant and Mesopotamia, and we can see that within some of his areas,
he continues those tribal divisions. In other areas, there's no tribal division at all,
and in fact, he uses a very regularized, effectively running along parallels of angular
coordinates with no tribal affiliation, i.e., the nature of the data over here in Syria is
entirely different from the nature of the data over here in Mesopotamia, and if we overlay that
with those precision coordinates that we saw earlier, then hey, presto, it turns out that there
is a perfect correlation, so those precision coordinates are used as a way of distinguishing
between these different tribal affiliations. Can we prove this statistically that that's
going on? Well, yes, we can. If we look over here, so we can count all of the places on boundaries
that are associated with a traditional meridian over here, and you can see that there's
significantly more of those than those boundary locations that fall on a particular degree.
We can't... One minute left, almost done, so we're good. We can't quite play the same trick
when it comes to latitude, because as we saw, the latitudinal parallels did not fall evenly
in terms of angular coordinates, so we expect some kind of distortion here.
What we would expect at purely random on the left-hand side would be about 2%.
We, in fact, get slightly more than that for inland settlements, but that's not conclusive.
What we can see is that a great deal more boundary locations proportionately fall
on these latitudinal, traditional latitudinal parallels than on the angular latitudes
that Ptolemy is introducing. If we take all that stuff together, if we look at all of these things,
we can actually see that there are distinct regions of the map. Over here in the Mediterranean,
we have that kind of precision, the tribal affiliations. In Britannia, Gaul, North Africa,
and most interestingly of all, India, we have tribal affiliations, but in a kind of coarser
distinctions. The green areas are where we get those very linear features, which you can see,
with no tribal affiliation, and frankly, the blue stuff is pretty much guesswork on Ptolemy's part,
so far as we can tell. So, to wrap up, because we're out of time, potentially a new prehistory
of tolling. The key thing to bear in mind here, and we can discuss this later if you want, but the
purpose of the geographical hypagesis is to set terrestrial localities within a wider cosmological
setting. It's not about navigation. It's not about projecting the imperial power of Rome.
It's not many of the other things that we typically think about when we think about mapping
in antiquity, and indeed, later on. But the problem for Ptolemy is that neither geography
or choreography are individually sufficient. Geography is too sparse, and choreography is
unrelated to the surface, and therefore, you can't associate it with astronomical phenomena.
It seems, therefore, that Ptolemy is producing an entirely original composition by pegging those
choreographic content to a sparse geotemporal framework for marinos, and furthermore, the
traces of those materials might still be identifiable and provide a new window on the prehistory of
mapping. Great. Thank you very much for listening, and thank you very much for this.
Thank you very much.