Artifacts #2: Maps & State Secrets


This is the so-called Cantino Map, a chart stolen by an agent of an Italian Duke from the Portuguese Crown in 1502. It provides an interesting follow-up to our discussion of the first map of the continent of Africa from Friday.

TPM Reader HT wrote in arguing that this was in fact the first map of the continent rather than the one by Sebastian Münster published in 1554. I told HT it was mainly a semantic argument. Münster produced separate maps of each of the four continents he knew and it was also an attempt to take stock, albeit it sometimes comically to our eyes, the interior of the continent. See the argument for firstness here.

But wherever we come down on that question there are several fascinating points about the Cantino Map tied to its origins and where it’s placed in the history of cartography. First is something that seems mainly alien to us today: the extent to which maps were treated as state secrets by the colonizing powers of the day, particularly Portugal and Spain during the early 16th century. Both powers had a master royal map which was updated with new data from each successive early voyage, the secrecy of which was closely guarded. I can’t find a reference online at the moment but my recollection is that captains and pilots checked the maps out soon before departure and had to surrender them back to authorities on their return.

As you can see, Portuguese navigators knew dramatically more about the contours of the globe in 1502 than some of the most advanced scholars in Central Europe half a century later. Note too on the left the first data on Brazil which, amazingly, Cabral had only discovered two years before this map was stolen. See too the rough outline of Columbus’s islands in the Caribbean.

But here’s another aspect of this map. As I said, this was not the work of scholars but sailors and government bureaucrats trying to provide as clear a data as possible about where things actually were. And if you look closely at the map it seems to follow in the tradition of the so-called Portolan Charts that sailors had used in the Mediterranean for centuries. As the name implies, these were port maps, given sailors details about which ports were where, what they were called, a rough sense of distance between them and sometimes information about depths and other safety obstacles.

You can get more sense of this from this detail of the same map showing the eastern Mediterranean. As you can see, relatively detailed information about coasts and city names but then an almost total lack of interest and detail about what’s inland. Jerusalem is represented by that massive castle which extends almost all the way to Iran, while that crescent banner signals that Asia Minor is the heartland of the Ottoman Empire.

By way of comparison here is a Portolan Map from the middle of the 15th century, roughly 50 years earlier.

The Atlantic is at the top, Jerusalem at the bottom. Again, the dense thicket of port names making up a reasonably accurate representation of the coastlines of the Mediterranean and the Black Sea.

Here’s another from 1586, almost a century and a half later (again Atlantic and the top, Jerusalem at the bottom). More accuracy and detail and the beginnings of something more like modern mapping. But still a navigation document.

What’s striking about the Portolans, for all their shortcomings, is their remarkable accuracy about the basic shape of the Mediterranean coast. Here’s some more discussion about just where and how they arose and how this remarkable degree of accuracy was possible.

[Portolan Charts from the Beinecke Rare Book and Manuscript Library, Yale University]