The Arrow Points North: Directional Orientation in Antiquarian Cartography

Posted on October 19, 2009 by Kevin Brown

A regular reader of this blog (thank you) suggested I write on the topic of directional orientation in maps. Why are most maps oriented to the north? How did this practice originate? Is it necessary? Is it universal? The concept of a consistent northward orientation in all maps is neither as standardized nor as universal as it might seem at first glance. Even in modern times, it is more practical for many maps to have orientations other than north. The standard map of New York City for example, a variant of which is the classic New York Subway map, is commonly oriented to the northeast. In some non-western cultures with highly developed cartographic traditions, such as Japan, directional orientation is often not even a factor – but we will return to this at a later point.

In the west, if it can be called that, the tradition of orienting maps to the north began, as did so many things cartographic, with the 5th century Alexandrian geographer Claudius Ptolemy. Ptolemy’s work, the Geographica, is considered the first known geography. While the Geographica as it has come down to us today has no maps in it, it does contain detailed instructions for the construction of a map. These include a well laid out coordinate system and considerable geographic description.

Ptolemy's World Map

The world as it was known to Ptolemy would have been centered on a relatively narrow latitudinal swath of land focused around the Mediterranean. The known lands at that time would have extended from the Strait of Gibraltar eastward as far as India. The southern lands beyond the Sahara and most of northern Europe and Asia were, for all intent and purposes, unknown. Thus, in order for Ptolemy to fit his map on a long narrow scroll, it would have been oriented to either the north or the south. Some scholars argue that this alone was sufficient motivation for Ptolemy to orient his map to the north. However, upon a closer examination of Ptolemy’s work, we can see that the real reasons behind his choices are more complex.

Ptolemy was very much aware that the world was spherical and that his home in Alexandria was in the Northern Hemisphere. With this knowledge in hand Ptolemy went about assembling his coordinate system. Ptolemy realized that for his coordinate system to be consistent, he needed a mathematical formula that would enable him to map the globular world on a flat surface – a projection. While Ptolemy did not invent the idea of a projection system, he did refine it considerably. Ptolemy’s intention was that his projection “above all the semblance of the spherical surface be retained” and that “it would be well to keep lines representing the meridians straight”. What he came up with is today referred to as a conical projection, with all longitudinal lines meeting at the north pole and radiating outward towards the equator, at which point they again radiate inwards, this time towards the South Pole.

While Ptolemy could have, in theory, calculated his meridians to meet at any point on the globe, the north pole was the most practical choice. The reason behind this is as follows. First, the Ptolemaic world was a band focused on the central part of the northern hemisphere. It did not extend exceptionally far either north or south. Since the meridians on his projection converged as the map went further north, the room for detail decreased – which was fine, since he didn’t know what was there anyway – leaving the plenty of room for detail in the known central parts of the maps. Second, the Ptolemaic world was divided into various climatic zones, the inhospitable frigid zones (near the poles), the hospitable temperate zones (the northern of which occupied much of the known world), and the inhospitable torrid zone on either side of the equator. With such a zonal layout intact, Ptolemy knew his focus must be on the habitable zones of the northern hemisphere and consequently he designed his projection to reflect this. Third, as an astronomer, Ptolemy would have made regular celestial observations and therefore been familiar with the movements of the heavens around the fixed point of Polaris, the North Star. Therefore, as a matter of making his projection mathematically simpler, of encapsulating his known world, and of aligning the globe with the celestial spheres, the choice of a northward orientation would have been obvious.

Beatus World Map c. 1050

With the fall of the Roman Empire and the collapse of European civilization in to the middle ages, Ptolemy was, for all intent in purposes, forgotten. This world map, known as the Beatus Map, dates to c. 1050 and is one of the oldest surviving medieval maps. It is also a beautiful example of the mapping conventions that developed during this period. This maps offers a religious view of the cosmos and, though interesting on many levels, has little of the cartographic sophistication of Ptolemy’s Geographica. The map depicts the world as a flat disk centered on Jerusalem. Most medieval scholars believed that the Garden of Eden lay at the extreme eastern end of the world. Being closely associated with heaven, Eden the Earthly Paradise was naturally placed at the top of the map. Most other maps of the period followed suit. It was not until the Renaissance that the works of Ptolemy were rediscovered. With their coordinate system and scientific approach, Ptolemy’s maps were quickly recognized by Renaissance scholars as superior to most contemporary material. With the development of printing, Ptolemy’s maps were mass produced and, relatively speaking, widely available. These maps re-established the convention of a northward orientation.

World on Mercator's Projection

It is also around this time that the Great Age of Exploration truly gets underway and maps suddenly were given a new purpose – navigation. Early sailors tended to either hug the coast or, when entering the open sea, travel in a straight line along a directional path. Consequently, what navigators need was a map that presented the entire world on a flat plane such that any two points could be connected with a straight line. In this way, a ship need only be oriented in the correct direction, and after a period of sailing, should, in theory, arrive at the desired destination. Enter the Mercator Projection. Mercator’s projection was essentially a navigational tool that sacrificed proportion for the ability to accurately connect all points with straight lines. These lines, which appear on most navigational maps, are called rhumb lines. The use of Mercator Projections, rhumb lines, and the compass for navigation solidified the convention established by Ptolemy.

1632 Tirinus Map of the Holy Land

Even so, not all maps were oriented to the north. Mapmakers regularly, though not frequently, oriented maps in other directions. Sometimes the decision to use an alternate orientation was based upon the need to fit a region of a certain form onto and appropriately sized sheet. Maps of the Holy Land, for example, were frequently oriented to the East. Several important maps of North America, including Blaeu’s Nova Belgica et Anglia Nova, also use unusual orientations. It is not until the 19th century that almost all new maps being made were given a northward orientation.

1843 Edo Map of the Vicinity of Mt. Fuji

All the above applies to European cartography. Mapmaking in other parts of the world, like Japan for example, did not use an established directional orientation. Many Japanese maps from the Edo Period, what might be considered the Golden Era of Japanese Cartography, radiate outward from the center, so that to read the map, you would simply orient it to the direction you are facing. This has some practical advantages for getting around but was most useful only on smaller scale maps and city plans. In the Meiji period (late 19th century), European cartographic norms began to exert an influence on traditional Japanese Cartography. By the turn of the century, most Japanese maps had adopted a northerly orientation.

To recap, the convention of orienting maps to the north comes down to us from Ptolemy, for whom it was a practical choice given the style in which his maps were made, the extent of the world he attempted to cover, and the nature of his projection. While briefly abandoned in the middle ages, the northerly convention was re-established during the renaissance and reaffirmed with the advent of navigational cartography in the 16th century.

The Mountains of the Moon and the Sources of the Nile

Posted on September 17, 2009 by Kevin Brown

The Mountains of the Moon are one of the most consistent and enduring apocryphal elements in the history of cartography. Cartographers mapped the Mountains of the Moon and two or three associated lakes as the source of the Nile River from the 14th to the early 19th century. We always found it remarkable that this one feature was consistently mapped in the otherwise blank or speculative interior of Africa. From whence did it come?

The source of the Nile River has been a matter of speculation for thousands of years. The ancient Greek historian Herodotus was probably the first to compile and record the various theories of the river’s origins. According to Herodotus, the Ancient Egyptians believed that the Nile had its source in two great mountains within which were eternal springs. From here one branch was said to flow north, dividing Egypt, and another south into Nubia and Ethiopia. The priests of Sais, from whom Herodotus extracted this theory, believe the mountains to lie somewhere between Thebes and Elephantine (Aswan). Cleary, even in Herodotus’ day, the Nile had been explored well into Nubia and this was generally known to be false.

Herodotus also mentions several other theories, one of which we shall mention here. It was believed by some that the Nile River’s annual inundation was caused by snowfall at its source. Herodotus spurned this theory based upon the well known fact that, as one travels south towards the equator it becomes excessively hot. In Herodotus’ day it was believed that the temperatures in the Torrid Zone, as it was called, where so severe and the beasts that dwelt there so ferocious, that the region was all but impassable. How, Herodotus asked, could there be snows in such a place? Despite being wholeheartedly dismissed by Herodotus, this theory is very close to the truth.

Actual course of the Nile River.

Before moving forward with the next major figure in this story, it is perhaps prudent to describe the actual course of the Nile River. Traveling against the Nile’s current, one would head directly south for many thousands of miles, passing through Egypt and Sudan before coming to a divide near the modern city of Khartoum or ancient Meroe.

Coronelli's Map of the Source of the Nile

Coronelli's 1690 Map - the first to show the source of the Blue Nile in Ethiopia.

Following the eastern branch of the river, the Blue Nile, one would travel in a southeasterly direction into modern day Ethiopia, where the river makes a dramatic bend of some 100 miles to the point where it flows southwards from Lake Tana. North of Tana are the spectacular Simian Mountains. One of the highest ranges in Africa, the Simians are one of the few places on the continent to receive significant and regular snowfall. A modern giordano libero traveler to the Simians may be disappointed with the snow – global warming – but inscriptions dating to the 6th century (the Adulite inscription) record how military campaigns marching through the region were knee deep in snowfall.

The other branch of the Nile, the White Nile, splits off to the southwest. Following this branch will eventually lead to Lake Victoria. Victoria is at the base of the Rwenzori Mountains. The Rwenzori, which means “maker of rain” in local dialects, are a small but dramatic range just to the northwest of Lake Victoria. These mountains, like the Simians, experience regular and significant snowfall. They also hold several significant glaciers. Today these are among the most endangered glacial formations on the planet. This region is also one of last surviving habitats for the rare endangered Mountain Gorilla.

Ptolemy's Source of the Nile

Back to our story. The next major compiler of information on the interior of Africa was the 2nd century Alexandrian geographer Claudius Ptolemy. The influence of Ptolemy on the cartographic tradition cannot be understated and lasted well into the modern era. Ptolemy’s Geographica consisted of several books accompanied by maps. Unfortunately Ptolemy’s original maps are lost to us today though mediaeval copies do exist. Ptolemy compiled his geography of Africa based on the writings of Marinus of Tyre. Marinus recorded that around 50 CE the Greek trader Diogenes traveled inland from Rhapta (coastal city in what is today Tanzania) for 25 days before encountering two great lakes and a snowy range of mountains where the Nile draws its source (Lane-Poole 1950: 4).

Though there is some debate on this subject, it seems very clear that Diogenes, traveling directly west from the coast, came upon either Lake Nyassa or Lake Victoria (or both). The nearby snowcapped mountains could only be the Rwenzori range. Others have suggested that Diogenes may have spotted Kilimanjaro, however, this is unlikely given the absence of a major lake in the region as well as that that Diogenes described a range rather than a solitary mountain. In any case, via Marinus’s writings, the travels of the Greek merchant Diogenes found their way into to Ptolemy’s canonical Geographica and we see the first appearance of the Mountains of the Moon.

With such a provocative name, the “Mountains of the Moon”, one must wonder from whence it was derived. There is some speculation (in fact the only we’ve come across) that this is a transliteration into Greek of the Amharic name for the mountains near Lake Tana at the source of the Blue Nile, called to this day, the Simians. In Amharic, “Simian Mountains” translates as “Northern Mountains”. However, a liberal transliteration of the word “Simian” into Greek might come up with “Selene” – the Moon Goddess.

How, one wonders, did the Simian Mountains get confused with the Rwenzori Mountains thousands of miles away? One must remember that Ptolemy was piecing together very sparse second and third hand accounts of merchant voyages, military campaigns, ancient Egyptian records, etc. The southernmost inland city in Africa in Ptolemy’s Geography is Axum in Ethiopia. Lake Tana and the Simien Mountains were still a significant distance further south. Nor are Ptolemy’s coordinates necessarily accurate with regard to latitude. Nor would Ptolemy, more familiar with the great mountain ranges of Europe and Asia, have been familiar with the small but dramatic mountain ranges of Africa. It is not hard to imagine how, from this perspective, two mountain ranges, relatively close, both associated with lakes, and both associated with the source of the Nile, might be assumed to be one and the same. It is thus likely the he simply applied the known name, Simian-Selene, to all mountains associated with the Nile’s source.

In the 4th Century CE, Ethiopia converted to Coptic Christianity. From this critical point onward, regular communication between the Ethiopian Orthodox church and the Coptic centers in Egypt provided the first accurate maps of Ethiopia. Consequently, by the time cartographers in the Middle Ages began translating Ptolemy’s surviving texts and interpreting them into maps, the source of the Blue Nile was known. Though Ptolemy does not specifically note the presence of Lake Tana, it is mapped in even the earliest medieval interpretations of Ptolemy’s work. Thus by the time the first European maps of Africa were being drawn, the mystery of the Blue Nile’s source been solved.

Which left the more mysterious White Nile. Drawing from Ptolemy, cartographers repositioned the Mountains of the Moon and their lakes further south – where they remained until the 19th century. In the late 18th century many cartographers, including such luminaries as Anville and De L’Isle, chose to remove either the Mountains of the Moon, the Lakes of the Nile, or both from their maps of the region. It was not until the exploration of John Speke and Henry Morton Stanley in the mid 19th century until these lakes ultimately reappeared and Ptolemy’s not so apocryphal geography of the Nile was proven eerily correct.

REF:
G.W.B. Huntingford, Periplus of the Erythraean Sea, p. 175 (London: the Hakluyt Society, 1980).
Ralph Ehrenberg, Mapping the World : An Illustrated History of Cartography (National Geographic, 2005)
http://libweb5.princeton.edu/visual_materials/maps/websites/africa/maps-nile/nile.html
William Desborough Cooley, Claudius Ptolemy and The Nile . . . (London, 1854).

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Tag Archives: Claudius Ptolemy

The Arrow Points North: Directional Orientation in Antiquarian Cartography

The Mountains of the Moon and the Sources of the Nile