This paper describes early cartographers' concepts of the world and its polar regions. Some comments on the relationships of astronomy to cartography are made (inclusion of Ptolemaic thought) and of the importance of technical method in cartography. Most of the paper is devoted to a description of medieval cartography and cosmology

Pognon, Edmond

English

University of Calgary Journal Hosting

ARCTIC VOL. 37,  NO. 4 (DECEMBER 1384) P. 334-340 Cosmology ,and Cartography EDMOND  ‘POGNON* Cosmology and cartography: immense subjects, the general compass of  which gives me the perilous honour of contributing the first communication of this congress. It  is; indeed, a sub- ject which touches  only  indirectly  on the problems of’the Arc- tic  regions  which are our concern. Cosmology is defined in almost the same  terms by Larousse and.Linr6as “the science of the general laws,which  govern  the physical world”, and its  influence  on  cartography is evident. The shape of the  Earth  and  its  relationship to the rest of the cosmos, or more  exactly to the celestial bodies, are the very basis of cartography. To define them, or in other words  to es- tablish astronomy, is historically  the first priority of cosmol- ogy;  and  at  least  since  Newton i t  has  been clear that  this first step is of crucial importance to all other problems of cosmology. All historical cognizable or even imaginable cosmologies may be placed in ‘one of two. categories: they -are either scientific or irrational. Our own, in particular our astronomy, is scientific. We observe as exactly as possible. the greatest possible  number of phenomena,  and we  reason logically  and mathematically from these data without  reference  to.  anything else. It  is  hardly necessary to recall  that  in  applying this method we are merely following, -although with incomparably. more effective means,  the  example first set in.the  sixthcentury B.C. by the  Greek “physicists” of the Ionian  school.  It  is  equally well  known  that  the  concept  inaugurated by .these great minds culminated, for astronomy, in the- Ptolemaic system which dates  from the second  century A.D. The stages of these eight centuries of progress are described in many books;  however, since they concern the relationship of astronomy to carto- graphy, there are some  comments  which should-be made. The Ptolemaic system has all the astronomical elements which are still used  today  in  map-making:  meridians  and parallels  of the celestial sphere projected onto the. terrestrial sphere which is at its oentre, polar circles and tropics deduced from the inclination of the terrestrial axis to the ecliptic, divi- sion of the circumference into 360”; the “compass rose” or mariner’s  compass. Of course, .we  no longer accept the Ptolemaic system - we no longer believe in the geocentric universe, .and  we  have  known since Copernieus thavthe Earth is a planet which orbits the Sun.. Nevertheless,.  Copernicus’ revolutionary  work in astronomy, which  had  tremendous repercussions  on  cosmology as a whole, had no effect what- soever on cartography. The astronomical observations which determine.  the.  latitude  and  longitude of a point  on the surface of the earth (its coordinates) are in  no  way influenced; nor, in- deed,  are the- operations of the navigator  who  takes a bearing which is, in fact, the  same thing. As Thomas S. Kuhn  writes in his  remarkable work me Copernican Revolution: “most treatises on aerial or maritime  navigation  open  with a sentence such  as .‘For our present purpose,. we shall  assume that the Earth .is a small stationary sphere at the centre of a larger celestial sphere which is imrotation.’ ” Although  since  the  time  of  Ptolemy  and even before, there has  existed a theoretical  idea of the  Earth  and its place’  in the Universe which was perfectly  suited  to cartographical work, the practical means of using it were hopelessly inadequate. Latitude was determined by  using the old  Egyptian gnomon, a vertical pylon, the Iength of  whose  shadow at noon gave the in- clination of the sun. ,The lack, of precision in this method  is ,clear, and  it  could  only  be  applied  at a few points. As for long- itude, it  could  only be measured by comparing  the exact time at several locations - impossible  .with a, sundial, or even  with a clepsydra or sand-glass, which  were  much  too  inaccurate  and not  easily portable. It  was  only in the seventeenth  century  that a satisfactory solution was found via the invention of the chronometer. So much for the  technical  methods of cartography in the An- cient  World. To these impediments  was added, .of course, ig- norance of the  major  part of the Earth’s surface; Knowledge was  limited to those-regions which  had  been  reached by travel- lers, navigators,, and explorers. Thus  it  happened that. astro- nomical  theory  engendered.  logical ideas, which  1ater.discover- ies  revealed to be false. For example, it  was understood  that the more  perpendicular  the  sun’s rays, the greater-the heating effect. .From Ehis it .was deduced that the zone between the tropics‘would be  too  .fiery to be habitable. There was .much  de- bate  as to whether the, unknown lands of the-southern temper- ate  zone were inhabited. As for the  regions  circumscribed by the polar circles, where the rays of the sun fall very  obliquely - and here is  the  indirect  link  mentioned at the beginning - theory declared  them  uninhabitable  because of the cold. But  it wa5 known,  even if not universally  believed,  that at about  the time of the death of- Aristotle (222 B.C.), Pytheas,  .the explorer from Marseille, on his return from a daring voyage in the Atlantic,  claimed ‘to have reached. a northern  land  which  he called Thule, where there was abundant  ice  and  where  the  sun .did not set at.  the  summer solstice. .Rolemy, of course, was‘ also a geographer, but he could describe only  that  portion of the earth’s surface known  in  his time  (which  was  called the oecumn), using  only  very  approxi- mate coordinates almost,  always  determined ‘by .the distances in stadia  between  the  points o be fixed from a reference  meridian *Conservateur en chef honoraire du d6partement  des Canes et Plans de la BiblioWxpe natienale.de  Paris, 24 rue de la Faisanderie, 751 16 Paris, FranCe COSMOLOGY AND CARTOGRAPHY and parallel, in practice those  which cross at Rhodes. These dubious coordinates, some 8000 of  them,  were  listed by him  in tables which fill six  volumes  of  his Geugraphy. Ptolemy  him- self, or more probably a cartographer named Agathodemon who lived three centuries later, extracted from this data 26 regional  maps  and  one  map  of the oecumen. They are drawn up according to the systems of projection described in the eighth  book. To allow for the  roundness of the earth, he con- structed  the  regional  maps  (Figs. 1,2) on  parallels  which  were arcs of concentric circles, crossed by rectilinear meridians. For  the maps  of the oecumen, in effect a flat map  of the world (or  at  least  of  the  part  he  knew), the rectilinear meridians  were no longer suitable. This map  claimed to represent  the terres- trial sphere from latitude 26’5 to 65 ON, and  in  longitude,  from the  Atlantic Ocean to China. The further north one goes from the  latitude  of  Rhodes, the more  untenable  becomes the altera- tion in lengths produced by rectilinear meridians. ptolemy provided for this by constructing curves of constant  length on the concentric parallels on both sides of the Rhodes meridian, which  was  kept rectilinear. He  called this projection  “homeo- teric”, which  means “very similar”. The map  thus  obtained was named “the cloak-shaped map” because  of its appearance (Fig. 3). Since  Ptolemy’s  world  map  included nothing north  of 65 ON, it  did  not  even  extend to the polar circle. Indeed, the peripheral regions of the  map  could  only offer imaginary configurations. 335 FIG. I .  Ptolemy (1842), Geography. “Prima Europae Tabula”. The most nor- therly  regional  map of the work. Note  the  inscription  “Oceanus iperboreus”. None of this diminishes the achievement of this great geo- grapher and astronomer, who  indisputably  extracted  the  maxi- mum from the theoretical  and  practical data at his  disposal  and who  based  his cartographical work  rigorously  on his cosmology. This is perhaps ,the place to observe that the smaller the area covered by the map, the less the cartographer is  limited  by the shape he  assumes for  the Earth, and  in general by his  cosmol- 336 E. POGNON ogy. Even today, for topog aphical maps, the processes of horizontal  sighting - and  no I I aerial photography - are more effective  and  more  used  than geodesy, from  which we demand only an overall skeleton  map. For plans, surveying is the  pro- per  technique. At the other extreme, flat maps  of the Earth are the most directly influenced by the  cosmology of the carto- grapher. Abundant  proof  of these statements is provided by the world maps drawn in the early centuries of the Middle  Ages.  Never- theless, they were preceded by a cartography which can be said to have  been  independeht of any  cosmology.  Astronomy was still  at  the  stage  where Fltolemy  had left  it 150 years after his death, when Christianity.triumphéd in the  Roman  Empire with  the  famous  Edict of Constantine of A.D. 313. The utilitar- ian and  empirical spirit of tlk Romans, which  dominated this period, sterilized the theoretical  reflection which  had  been so fruitful  among  the  Greeks  and their immediate successors, the Alexandrians. As for cartography, it seemed to lose  all  rela- tionship to astronomy. The new masters of the  world  did  not need  the general  shape of the Earth, only  convenient  routes. It is probable  that  even  the “Description of the World”, ordered by Caesar  and  completed - by four engineers led by Agrippa - 25 years later under  Augustus,  paid little heed to the  exam- ple  of  Ptolemy. The only  sample  of  this  cartography  which  we  have is,the map  prepared by a certain Castorius, probably  in the third cen- tury, and  known  only by a thirteenth-century copy, called after the collector who  owned  it, “Tabula Peutingeria” (Fig. 4). It is a strip 0.34 m high  and 6.80 m long, on  which itineraries that are in  reality oriented in all directions are shown  to be par- allel. It is clearly a schematic diagram, designed to be  drawn on  an  easily transportable scroll. Such a map - if the  word  can be applied to it - obviously  has  no  connection  with  cosmology or astronomy. The sudden eclipse of astronomical  research after Ptolemy has  an intrinsic cause. His world  system  gave a satisfactory  ac- count of astronomical  phenomena insofar as they could be ob- served  with the rudimentary  means of the epoch. All  seemed to be “finished”: there was felt to be  no  need to complete or perfect astronomy, and no idea of how to do it. Rolemy’s COSMOLOGY AND CARTOGRAPHY authority was definitive. Never quite forgotten, restored  intact in the thirteenth century (or at least in that epoch), reintro- duced  by Saint  Thomas  Aquinas  (with  Aristotelian  philosophy, of  which the world  system was fundamentally  the same), and widely  recognized before the  nd  of  the  Middle  Ages, Ptolemy’s astronomy, with allowances made for the refine- ments made necessary by progress in astronomical observa- tion, dominated without question until Copernicus, and long resisted  the  strongest attacks. However, at the  beginning of the  Middle  Ages,  Ptolemy was virtually  dismissed by Christianity. Infinitely  more structured than  pagan  mythologies,  its  unyielding  adherents  were  directly persuaded  that  the entire truth of the  world  was  contained in the  Bible. Any assertion  which  seemed to contradict  the letter of the sacred text could only be false. Above all, for the Church, which  was  only concerned with the salvation of souls in the  next world, all objective knowledge of the visible  world was irrelevant. The greatest of the Fathers of the Church, Saint  Augustine,  who had studied  Greek  science  passionately before his conversion, wrote in his handbook for the use of Christians: “Thus, when  we are asked our religious beliefs, it is  not necessary  to  examine  the nature of things, as did  those whom the Greeks  called physici .... It  is  enough for the Chris- tian to believe  that the only  cause  of  all  created things, ter- restrial or celestial, visible or invisible, lies in the goodness of the Creator, the  only true God; and  that  nothing exists, except for Him, which does not draw  its  existence  from Him.” From such a mental attitude; no cosmology could arise. However, the desire to denigrate pagan science produced a criticism of the world system which it had engendered, and consequently  the need to replace  it. This criticism and  substitu- tion  owed  almost  nothing  to  observation  of  the  visible  world, drawing  its  arguments  from sacred texts. In the time of Constantine, Lactantius, preceptor of the em- peror’s son, drew  attention  to the fact  that if the  Earth  were spherical, there would  be  sky  above  and  below; as the sky  is above, this  cannot be so. Later in the fourth century, the  bis- hop  of Gabala  proved  that  the  sky  is  not  spherical  because  God “stretcheth out  the  heavens  as a  curtain, and  spreadeth  them out as  a tent to dwell in” (Isaiah  XL:22).  Genesis (I:7) tells  us that  there is water  above  the  firmament  and  the  Earth  is flat. Two centuries later, a man from Alexandria named Cosmas 331 (also known  as Indicopleust&s, meaning “seafarer in India”), who seems  to  have  travelled a great deal on  the  Red Sea, the Indian Ocean, and  the  Persian Gulf, set  up a complete  cosmol- ogy inspired by the Scriptures. His  universe had the form of the  tabernacle  which  the  Lord ordered Moses  to  construct in the desert: a flat base, vertical sides, and semi-cylindrical roof. The Earth, “the footstool of the Lord”, became a plane twice as long as it was wide,  and  rested on the  flat  bottom of the  universe (Fig. 5) .  The Sun  did  not  pass  beneath  the Earth at night  but  hid  behind  an  immense  mountain  which  stood in the north. This northern  mountain  is  the  only  equivalent in Cosmas’s  system  to what  we  call the arctic regions. The Church  never  officially  adopted  Cosmas’s  cosmology, nor  did it censure  those of  its  members - for all  the  intellec- tuals  belonged  to  the  Church - who,  like  Isodore of Seville in his  encyclopedic work Etymologies or Origins, retained - in- sofar  as  the  destruction or loss of countless  texts  allowed - some fragments of ancient knowledge. There were always some  who  knew  that  the  Earth  was  spherical  and  who  situated it  at  the centre of  the universe. At the  end of the  tenth century, a future pope named Gerbert d’Aurillac who  held  this  opinion constructed  celestial spheres. As for cartography in the early centuries of the Middle Ages, it  produced  only  world  maps;  no  regional  maps,  and  no topographical  maps.  Until  the  Renaissance  these  types of  maps were rare. Nor is there any textual  mention of maps, with the exception of plans of  Rome  and  Constantinople  engraved  on asilver table  (and  thus no doubt  converted  sooner or later  into denarii) which,  according  to Eginhard, was  owned by Charle- magne.  It  must  be  said  in  passing  that  it  is  surprising  that  peo- ple who spent their lives arguing over  and  dividing territory should  have  dispensed so easily with a visual  aid  which  seems so necessary to us. There is a temptation  to  imagine  that they had an intuitive perception of surrounding or even distant space  which  escapes  us  today. Among the world  maps  of  this  period there are some  which are of special  interest here: those  which,  reflecting traces of 338 E. POGNON COSMOLOGY AND CARTOGRAPHY 339 E. POGNON centered on the Mediterranean and not one approaches the glacial zones. .But they are not:  without links with cosmology, as their creation depended on the  bearings to be maintained in navigating from one point to another. -These bearings were maintained  at  sea  thanks to the  compass  introduced  to  the West in the twelfth .century - a compass. that ind.icates a North which. differs from astronomical. N o d .  The draughtsmen of portuluns, the.most ancient.of which-is  the “Pisan Chart” in the Bibliotheque Nationale. de Paris, which appears to .date from around 1300, seem to have considered only magnetic North, and drew their charts not on lines of latitude and longitude; but  on several compass roses (mariner’s compasses) placed  in the  sea -at  given  positions  -whence radiated, straight lines indicating the various. azimuths, These-  are known as “rhumbs”. To find  his heading,& navigator-drew a straight line- between his point of departure and. his destination and observed to which  rhumb-line  it  was.paralle1. Paradox.ically , this. rhumb-line  mapping .led  tor a representa- tion of the Mediterranean  noticeably  more accurate than  would then  have  been  obtained  .using .meridians .and parallels, as the degree of longitude inherited from Rolemy . was .greatly overestimated..The first “scientific” rnaps,.which  appeared in the sixteenth century and, which were. believed then to be closer to.reality; were, for this reason, much  less accurate than the  old porculuns. They ,attributed a greatly  exaggerated  .width to  the  Mediterranean. FIG. to. World map .from Sallustvs Bcllwn Jugurrhinum twelfth century. (BibliotMque-nationale f. 52v.). The  T-O.structure allows a  relatively  rich is or.iented  with  the North to the right rather than the divide the earth .in .the same way. Such. representations are almost  exclusively  inspired.by an  irrational  cosmology,  which owes practically nothing to concrete knowledge. .Naturally, during the  Middle,  Ages - which  lasted  s1000’years.  and  were in-.no way the  long  period of ignorance  and “obscurantism” alleged’ by ’ detractors .- cartography  made  noticeable pro- gress. Eleventh-century  world maps are found.  on.  which  the still very inexact-configurations of. the terrestrial surface are ’ much  more detailed, and  which; little by little,.escape from  the T-O scheme (Fig. 10). Before  concluding, we must note :at least  briefly the medieval nautical charts known as.portulans. They are actu- ally outside the scope  of  this congress, because they are 

Cosmology and Cartography

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Cosmology and Cartography

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