A History of the World in 12 Maps

by Jerry Brotton

  In a more light-hearted vein, Aristophanes’ fifth-century comedy The Clouds depicts an Athenian citizen called Strepsiades quizzing a student and his academic paraphernalia. The student tells him, ‘over there we have a map of the entire world. You see there? That’s Athens.’ Strepsiades’ comical response is disbelieving: ‘Don’t be ridiculous,’ he responds. ‘Why, I can’t see even a single lawcourt.’ When the student points out the location of the enemy state of Sparta, Strepsiades tells him, ‘That’s much too close! You’d be well advised to move it further away.’ All these examples imply that as early as the fifth century BC Greek world maps were physical, public objects, used in the arts of warfare and persuasion. They were extremely detailed, inscribed on brass, stone, wood, or even on the ground, and showed a certain level of geographical literacy. But they were also the preserve of the elite: Aristophanes satirizes common ignorance of the representational sophistication of maps, but his jokes only work on the assumption that the audience knows that the map is only a representation of territory, and that it was not possible to simply move countries across it if they seemed uncomfortably close.

  This was the state of Greek geography in the fourth century BC. The military conquests of Alexander the Great propelled mapmaking into a more descriptive direction, based on direct experience and written records of faraway lands, that would ultimately culminate in the creation of Ptolemy’s Geography. Alexander’s conquests were not just significant for the ways in which they expanded Greek knowledge of the known world. Having learnt of the importance of empirical observation from his tutor Aristotle, Alexander appointed a team of scholars to gather data on the flora, fauna, culture, history and geography of the places they visited, and to provide written reports on the army’s daily progress. Uniting the theoretical knowledge of Aristotle and his predecessors with the direct observation and discoveries of Alexander’s campaigns would change how maps were made in the Hellenistic period that followed Alexander’s death.

  Where classical Greek mapping focused on cosmogony and geometry, Hellenistic mapmaking incorporated such approaches in what to us looks like a more scientific approach to mapping the earth. Alexander’s contemporary, Pytheas of Massalia (Marseilles), explored the western and northern coastlines of Europe, travelling along the Iberian, French, English and possibly even the Baltic coastlines. His voyages established Thule (variously identified as Iceland, the Orkneys or even Greenland) as the northernmost limit of the inhabited world, and also correctly established the exact position of the celestial pole (the point at which the extension of the earth’s axis intersects the celestial sphere). But perhaps most importantly for geography, he firmly established the connection between a location’s latitude to the length of its longest day, and went on to project parallels of latitude running right round the globe.31 At about the same time, Aristotle’s pupil Dicaearchus of Messina (fl. c. 326-296 BC) developed a more sophisticated model of the size of the inhabited world, along with some of the earliest known calculations of latitude and longitude. In his lost Circuit of the Earth, Dicaearchus refined Aristotle by arguing that the ratio of the known world’s length in relation to breadth was three to two, and made rudimentary latitudinal calculations by drawing a map with a parallel running from west to east through Gibraltar, Sicily, Rhodes and India, at approximately 36° N. Perpendicular to this parallel was a meridian running north to south through Rhodes.

  Fig. 2 Reconstruction of the world map of Dicaearchus, 3rd century BC.

  Gradually, the inhabited world started to look like an incomplete rectangle, rather than a perfect circle. The Babylonian and early Greek philosophical and geometrical perceptions of the known world had supposed an ideal, abstract sphere, a finite space with a fixed circular boundary (the ocean), with a circumference defined by its centre, a location (Babylon, or Delphi) that defined their own cultures as shaping the world. The ideal early symmetry gives way to an irregular oblong inscribed within a rectangle. Gone is the exact centre of a circle based on geometry and faith, and instead calculations are made from a place like Rhodes simply because it stands at a point where the rudimentary lines of latitude and longitude bisect each other. Implicit in this shift is a changing mentality about the role of mapping. The titles of treatises describing the inhabited earth begin to change: works with titles such as On the Ocean and On Harbours supersede the more traditional Circuit of the Earth. Incremental geographical information slowly alters and expands the rectangular dimensions of the inhabited world, which are no longer perfectly delimited by the geometry of the circle. Conflating geometry with astronomical and terrestrial observation allowed Hellenistic thinkers to embark on a collective enterprise of adding new information on the calculation of latitude, the estimated length of the known world, or the location of a particular city or region. With this cooperative spirit came new ways of seeing maps as repositories of knowledge, encyclopedic compilations of information, or what one classical historian has called ‘a great inventory of everything’.32 A geographical treatise could encompass ideas of creation, astronomy, ethnography, history, botany or just about any other subject related to the natural world. ‘The map’, as Christian Jacob has argued, ‘becomes a device for archiving knowledge about the inhabited world.’33

  Whenever a culture begins to gather and archive its knowledge, it requires a physical location to safely accommodate such knowledge in whatever material form it comes in. For the Hellenistic world this was the Alexandria library, and it is no coincidence that one of its earliest librarians was the figure who, before Ptolemy, summarized Greek geography. Eratosthenes (c. 275–194 BC), a Greek born in Libya, studied in Athens before accepting an invitation from King Ptolemy III to work in Alexandria as tutor to the king’s son and head of the royal library. During this time Eratosthenes wrote two particularly influential books (both lost): the Measurement of the Earth, and the Geographica – the first book to use the term geography as we understand it today, and the first text to plot a geographical projection across a map of the inhabited world.34

  Eratosthenes’ great achievement was to invent a method for calculating the circumference of the earth that united astronomical observation with practical knowledge. Using a gnomon, a part of a sundial that casts a shadow, Eratosthenes made a series of observations in Syene, modern-day Aswan, which he estimated as just over 5,000 stades south of Alexandria. He noticed that at midday on the summer solstice the sun’s rays cast no shadow, and were therefore directly overhead. Taking the same calculation in Alexandria, Eratosthenes measured the angle cast by the gnomon at exactly the same time as one-fiftieth of a circle. Assuming that Alexandria and Syene lay on the same meridian, he calculated that the 5,000 stades between the two places represented one-fiftieth of the earth’s circumference. Multiplying the two figures gave Eratosthenes a total figure for the circumference of the earth, which he estimated at 252,000 stades. Although the exact size of his stadion is unknown, Eratosthenes’ final measurement probably corresponded to somewhere between 39,000 and 46,000 kilometres (most scholars believe it to be nearer the latter figure).35 Considering that the actual circumference of the earth measured at the equator is 40,075 kilometres, Eratosthenes’ calculation was extraordinarily accurate.

  Although Eratosthenes’ calculations were based on some erroneous assumptions – for instance, Alexandria and Syene were not on exactly the same meridian – they allowed him to calculate the circumference of any parallel circle around the earth, and to provide estimates of the length and breadth of the . Strabo tells us that, in his Geographica, Eratosthenes directly addressed the question of how to draw a map of the earth. Like the city from which he drew his knowledge of the world, Eratosthenes envisaged the world as shaped like a Greek chlamys, a rectangle with tapering ends. Drawing on Dicaearchus, he projected a parallel running from east to west from Gibraltar, through Sicily and Rhodes as far as India and the Taurus Mountains (which he placed too far east). Perpendicular to this parallel was a meridian runnin
g from Thule in the north to Meroë (Ethiopia) in the south, bisecting the parallel at Rhodes. Refining Dicaearchus’ estimates, Eratosthenes calculated that from east to west the was 78,000 stades wide, and 38,000 stades from north to south. The width of the known world was, in other words, twice the length of its breadth. This led to some mistaken but tantalizing beliefs. If Eratosthenes’ calculations were correct, the would have extended much too far eastwards, from the west coast of Iberia as far as modern-day Korea, at over 138° of longitude, rather than India, the limit of the Hellenistic world. In a remarkable moment of global imagining, Strabo quotes Eratosthenes maintaining that the earth ‘forms a complete circle, itself meeting itself; so that, if the immensity of the Atlantic Sea did not prevent, we could sail from Iberia to India along one and the same parallel’.36 Although such a claim was based on mistaken assumptions about the size of the earth and its eastward extent, such claims would have a significant impact on Renaissance explorers, including Columbus and Magellan.

  Having made a calculation of the size of the earth and a rudimentary grid of parallels and meridians, Eratosthenes’ final significant geographical innovation was to divide his into geometrical figures which he called sphragides, a term derived from the administrative term for a ‘seal’ or ‘signet’, designating a plot of land.37 Eratosthenes attempted to match the size and shape of different regions to irregular quadrilateral shapes, drawing India as a rhomboid, and eastern Persia as a parallelogram. Although this method sounds like a retrograde step, it remained in line with the prevailing Greek tradition of projecting philosophy, astronomy and geometry onto the physical world. It also showed the unmistakable influence of Eratosthenes’ predecessor as head of the Alexandria library, the Greek mathematician Euclid (fl. 300 BC).

  In the thirteen books of his great mathematical treatise, the Elements, Euclid established the a priori principles, or ‘elements’, of geometry and mathematics. Explaining the basic rules of the theory of numbers and geometry, Euclid enabled thinkers like Eratosthenes to understand how anything (and everything) worked, based on the irreducible mathematical truths and reality of the universe. Beginning with the definitions of a point (‘which has no part’), line (‘breadthless length’) and surface (‘which has length and breadth only’), Euclid proceeded to the principles of plane and solid geometry. This posited a series of truths that still inform most secondary school geometry, such as that the sum of the angles in any triangle is 180°, or the Pythagorean theorem that in any right-angled triangle the area of the square whose side is the hypotenuse equals the total area of the squares of the two sides of the triangle that meet at right angles. Euclid’s principles established a world shaped by the basic laws of nature as geometry. Although Euclid synthesized much earlier Greek thinking on the subject, taken together his Elements provided a perception of space that would endure for nearly two millennia, to Einstein’s theory of relativity and the creation of a non-Euclidean geometry. For Euclid, space was empty, homogenous, flat, uniform in all directions, and reducible to a series of circles, triangles, parallels and perpendicular lines. The impact of such a perception of space on mapmaking was extremely important. It manifested itself initially in Eratosthenes’ rather clumsy attempt to reduce all terrestrial space to a series of triangular calculations and quadrilateral shapes, but it then also allowed subsequent mapmakers to process empirical geographical data in completely new ways. All terrestrial space could, in theory, now be measured and defined according to enduring geometrical principles, and projected onto a frame made up of a mathematical grid of lines and points that represented the world. Euclidean geometry would thus form not only all subsequent Greek geography from Eratosthenes onwards, but also the Western geographical tradition until the twentieth century.

  The Hellenistic response to Eratosthenes’ astronomical and geographical calculations was shaped by a shift in the political world throughout the third and second centuries BC. The rise of the Roman Republic, including its victories in the Punic and Macedonian wars, signalled the decline of the Hellenistic empires and ultimately the destruction of the Ptolemaic dynasty in Alexandria. It is one of the great puzzles of cartographic history that hardly any world maps survive from either the Roman Republic or Empire. Although it is dangerous to extrapolate from the limited evidence of Roman cartography that does survive in the form of stone and bronze cadastral (or land-surveying) maps, floor mosaics, engineering plans, topographical drawings, written itineraries and road maps imply a relative indifference towards the more abstract preoccupations of Hellenistic geography. Instead, the Romans favoured the more practical use of maps in military campaigns, colonization, land division, engineering and architecture.38

  However, this apparent division between a more theoretical, abstract Hellenistic mapping tradition and a practical, organizational Roman geography is to some extent illusory, especially as the two traditions met and fused from the second century BC. Other centres of learning in the Hellenistic world were by then starting to challenge Alexandria’s cultural pre-eminence. By 150 BC the Attalid dynasty, closely allied to the rise of Rome and with its capital in Pergamon, established a library second only to its Ptolemaic rival, run by the renowned philosopher and geographer Crates of Mallos. Strabo tells us that Crates constructed a terrestrial globe (since lost) with four symmetrical inhabited continents, separated by a vast cross of ocean running east to west across the equator and north to south through the Atlantic. The northern hemisphere featured the but also the perioikoi (‘near dwellers’) to the west, with the antoikoi (‘opposite dwellers’) and antipodes (‘those with feet opposite’) in the southern hemisphere.39 Crates’ globe was a fascinating combination of established traditions of Greek geometry with the developing ethnography of the Roman Republic, formalizing the geography of the antipodes and anticipating later Renaissance voyages to discover the ‘fourth part’ of the world.

  But not everyone accepted Eratosthenes. The astronomer Hipparchus of Nicaea (c. 190–120 BC) wrote a series of treatises in Rhodes, including three books entitled Against Eratosthenes, in which he criticized his predecessor’s use of astronomical observations in drawing maps. ‘Hipparchus’, Strabo tells us, ‘shows that it is impossible for any man, whether layman or scholar, to attain to the requisite knowledge of geography without a determination of the heavenly bodies and of the eclipses which have been observed.’40 Hipparchus’ detailed astronomical observations of more than 850 stars allowed him to point out the inaccuracies of Eratosthenes’ calculation of latitude, as well as acknowledging the problems of measuring distances from east to west – lines of longitude – other than through precise comparative observations of eclipses of the sun and moon. This was a problem that would only be satisfactorily resolved in the eighteenth century by means of the chronometer and the accurate measurement of seaborne time, but Hipparchus offered his own rudimentary calculations of both latitude and longitude in the first known astronomical tables.

  Those who challenged Eratosthenes were not always right. One of the most influential revisionist geographers was the Syrian mathematician, philosopher and historian Posidonius (c. 135–50 BC). As well as running a school in Rhodes, he was befriended by distinguished Romans like Pompey and Cicero, and wrote several treatises (all lost) refining and revising various elements of Hellenistic geography. He proposed seven climatic zones running around the earth rather than Aristotle’s five, based on astronomical and ethnographic observations, which included some of the most detailed information on the inhabitants of Spain, France and Germany drawn from the recent Roman conquests of these regions. More controversially, Posidonius questioned Eratosthenes’ method of calculating the circumference of the earth. Starting from his adopted home of Rhodes, Posidonius argued that it was on the same meridian as Alexandria, and at a distance of just 3,750 stades (a serious underestimation, whatever his value of a stadion). He then observed the height of Canopus, in the Carina constellation, and claimed it was exactly on the horizon at Rhodes, but rose
7½° or one-forty-eighth of a circle at Alexandria. Multiplying the figure of 3,750 stades by forty-eight, Posidonius estimated the earth’s circumference as 180,000 stades. Unfortunately, his estimate of the angle of inclination between the two places was wrong, as well as his calculation of the distance between Rhodes and Alexandria. His calculations provided a gross underestimation of the size of the earth, but they would prove to be remarkably enduring.

  Historically, Posidonius represented the moment when Hellenistic and Roman mapping traditions came together. It was a development that reached its climax in Strabo’s Geography, written between AD 7 and 18. The seventeen books of Strabo’s Geography, most of which still survive, encapsulate the ambiguous state of geography and mapmaking prior to Ptolemy, as the Roman Empire came to dominate the Mediterranean, and the Hellenistic world went into its long decline. Strabo, a native of Pontus (in modern Turkey), was intellectually influenced by Hellenism, but politically shaped by Roman imperialism. Although generally following Eratosthenes’ calculations, Strabo reduced the size of the , giving it a latitudinal range of less than 30,000 stades, and a longitudinal breadth of 70,000 stades. He sidestepped the problem of projecting the earth onto a plane surface by recommending the creation of ‘a large globe’, at least 3 metres in diameter. If this also proved impossible he accepted drawing a flat map with a rectangular grid of parallels and meridians, claiming rather breezily that ‘it will make only a slight difference if we draw straight lines to represent the circles’, because ‘our imagination can easily transfer to the globular and spherical surface the figure or magnitude seen by the eye on a plane surface’.41

  Strabo’s Geography acknowledged the importance of philosophy, geometry and astronomy in the study of geography, while also praising ‘the utility of geography’ for ‘the activities of statesmen and commanders’. For Strabo, ‘there is need of encyclopedic learning for the study of geography’, of everything from astronomy and philosophy to economics, ethnography and what he called ‘terrestrial history’. In keeping with Roman attitudes, Strabo’s version of the subject was a highly political version of human geography, and of how the earth is appropriated by mankind. This was practical knowledge concerned with political action, as it allowed rulers to govern more effectively, or, as Strabo put it, if ‘political philosophy deals chiefly with the rulers, and if geography supplies the needs of those rulers, then geography would seem to have some advantage over political science’.42 Strabo was no mapmaker, but his work marks an important change between Hellenistic and Roman geography. The Hellenistic world had established geography as the philosophical and geometrical study of the , the ‘living space’ of the known world; the Romans now perceived geography as a practical tool to comprehend their version of it: the orbis terrarum, or ‘circle of lands’, a space regarded from the period of Emperor Augustus onwards as coextensive with Rome as imperium orbis terrarum, or ‘empire of the world’.43 In one of the earliest and most daring syntheses of geography and imperialism, the orbis terrarum came to define the world and Rome as one and the same thing.