A Case of Mistaken Identity and Severe Historical Confusion

Update 10 March 2022: another example of the confusion!

It is de rigueur to complain about Wikipedia’s flaws and shortcomings as a source for information. Teachers warn of the traps it lays for the unwary student, of its intellectual pitfalls and actively curated biases. And, to be honest, I find the Wikipedia pages concerning maps and map history to be in dire need of correction, expansion, and balance. But even I use Wikipedia, and digital-born students flock to it. And I must admit that the Wikipedia entry on Gerardus Mercator is actually quite good. Indeed, it is stunningly good by comparison to an online piece on the great renaissance cosmographer, which a student found on no less an authoritative website than the “Resource Library” provided by the National Geographical Society. Here’s a screen shot of the beginning (click through to the NGS page itself):

Screen shot from National Geographical Society, last updated 15 January 2020. Click on image to see entire entry.

While I really dislike this essay, for reasons I will explain, it is exactly the kind of bad history that reveals how people think about maps, mapping, and their history. It was written by a committee—its credits list six individuals in addition to the author, the NGS itself—for a target audience of 5th–8th graders (11–14 year olds), It encapsulates what a group of professional educators and writers think are the key factoids about Mercator and maps. Shame it’s mostly wrong and that when it is technically correct, it is nonetheless quite misleading.

Misrepresenting Gerardus Mercator

The overall issue is made plain by the entry’s hook, directly below the title:

Gerardus Mercator
If you have ever seen a map of the world in a classroom or in an atlas, chances are you have seen a version of a “Mercator projection.” You may not, however, be familiar with its creator, Gerardus Mercator.

The entry “sees” GM almost entirely through the lens of map projections, and in particular through the lens of the projection he devised for his large 1569 world map ad usum navigantium, “for the use of navigation.” The fact of this projection, its inherent distortions, and its continuing ubiquity together form a great, warped mirror that distorts everything in this short article.

Consider the summary statement in the initial box, shown above, that needs to be considered sentence by sentence:

Geradus Mercator's world maps flattened the spherical planet to make it easier to display.

Yes, GM’s world maps flattened the spherical plant to make it easier to display, a statement that neatly reinforces students’ knowledge of the technical nature and function of map projections. The specification of “GM’s world maps,” however, suggests that only GM had figured out how to project the globe onto a plane or that other geographers' world maps were ineffective in some way. Not also the conflation throughout this entry of “projection” with “world map.”

Displays of the landmasses are not necessarily proportional to their actual size, especially toward the poles.

This sentence is also technically correct, proportionality of areas being a function only of specifically “equal area” map projections, and the map shown does indeed distort areas towards the poles. Yet the complaint about poleward distortions is of course a standard comment concerning Mercator’s 1569 projection, much less so of the map depicted. (Has any reader actually read any criticism of the distortions of the projection behind the map shown here?) Again, the 1569 map is the lens through which GM’s work is seen.

Despite these distortions, his maps are still in heavy use.

This cliché again refers to GM’s 1569 projection and world map. The world map and its projection shown here is not in heavy use. And, to be clear, the conflation of map projection with world map bugs me no end: GM’s “maps” are not still in heavy use; the maps that he had a direct hand in are rare. Finally, the coup de grace:

Though Mercator is best known for his cylindrical maps, he created various map types, like this spherical map.

How many ways is this statement wrong?

• its implication is that Mercator made “various map types” in addition to his “cylindrical map.” How many is “various” and what is meant by “map types”? Given the emphasis throughout on world maps as conflated with map projections, we might translate the question into “how many different world map projections did GM make"?” Answer, excluding the globes he made in 1544 (which are not really map projections), just two:

1) 1538 double-hemisphere world map projecting northern and southern hemispheres in a cordiform manner;

2) 1569 rectangular world map in 18 sheets.

GM did not make many world maps nor did he design many world map projections. Such work was not the be-all and end-all of his work, as this entry suggests. He did not make the map that is illustrated.

• GM is not credited with making the map that is reproduced in this entry. That is the work of GM’s son, Rumold. In fact, I find it possible, because of the cosmographical connotations of this world map—each hemisphere is projected using the transverse aspect of the azimuthal stereographic projection, used since antiquity for mapping the heavens; also, the armillary sphere set between the hemispheres indicates the integration of the earth into the cosmos, perhaps further symbolized by the fretwork pattern—that the old cosmographer himself had a hand in designing the world map. Yet Rumold might equally well have worked in homage to his father. I have not encountered a map historian who has provided any evidence that Rumold only published a map already prepared by his father. Overall, if GM is known today for his “cylindrical map,” why not show that map rather than a map he did not make?

• technically, the reference to the 1569 map projection as a “cylindrical map” is valid, because its “developable surface” is a cylinder, onto which the earth is projected and then opened out to make the flat, rectangular plane of the map. Yet the parallel concept of “spherical map” is meaningless. It seems to be a coinage by the NGS authorial committee that draws a distinction between the distorting world map and other world maps.

So, throughout this entry, NGS sees GM above all as a designer of world map projections. The entry does note his coinage of “atlas” for a systematic collection of maps (although really for the first volume of the much larger cosmographical project under that name that GM intended but did not complete) and briefly notes his maps of other regions, which were his major map work. But the hegemonic image of maps on the 1569 projection has led NGS to completely reconfigure GM’s life around map projections, to the point where NGS actively distorts the empirical record, puffing up GM’s work in map projections and attributing to him works that he is not known to have designed or produced.

Misrepresenting Maps

To be fair to NGS, map historians have had a habit of saying that Rumold Mercator’s map is a “reduced version of GM’s world map” (I paraphrase) and thereby conflating the two maps. You can see GM’s excessively rare map at the Bibliothèque nationale de France, and Rumold’s much more common map at many sites, including the Osher Map Library. The issue is that Rumold copied the geographical content of his father’s map, reducing it down from a large wall map that measures 200 x 133 cm to hemispheres measuring 11 cm in diameter. That’s a reduction from 26,600 square centimeters of map area to just 760 square centimeters.

Such a degree of reduction (to just one thirty-fifth of the area of the wall map) requires active manipulation of the content. Rumold further used a different projection, giving it decoration that had contemporary significance. How significant? Rodney Shirley, in his huge bibliography of European printed world maps before 1700 included 45 world map as being on the 1569 projection, but 259 on the double-hemisphere stereographic, of which Rumold’s was the first! Rumold’s was a seriously important intervention that must not be downplayed.

The older presumption that Rumold’s map is factually equivalent to his father’s effectively argues that geographical mapping is essentially algorithmic. The map is defined by the content; the reduction of the archive of geographical information to the map is a straightforward process.

So, NGS permits a hero-worshipping entry in their apparently authoritative resources for teachers and students that reduces Gerardus Mercator’s work to a single point that can then be promoted as his life’s work which is then hopelessly exaggerated by the claim that he created “various [world] maps.” Yet maps are not defined by the creator of their data, but are the work of designers and engravers and printers who create the thing. The choice of the double-hemisphere stereographic was utterly innovative! No one else had previously used it!!

Update 10 March 2022

A piece about Gerardus Mercator on his birthday provides another instance of the confusion between Mercator father and son and their maps:

The caption to this digital image is telling: Rumold published the map in 1587, and then used it to complete his father’s Atlas in 1595; and while Rumold took the content from his father’s wall map of 1569, it cannot be said that this double-hemisphere map was “after” the large wall map.