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Geographical Knowledge: Roger Bacon

Geographical Knowledge: Roger Bacon


Influence . The geographical research of the English philosopher and scientist Roger Bacon in many ways anticipated by one century the new geography of the Renaissance. Although he did not invent map projection, his demand for a new mathematical way for making maps with the use of astronomical instruments certainly contributed to its development. Bacon’s account on geography is found in his Opus Maius (Major Work, circa 1267) and in the Opus Tertium (Third Work, circa 1267). It is based on traditional sources such as Aethicus Ister’s Cosmographia, Aristotle’s De cáelo et mundo and Meteorologia, Sallust’s De bello jugurthino, Seneca’s Naturales questiones, Pliny’s Naturalis historia, Ptolemy’s Almagest, Saint Jerome’s De situ et nominibus locorum Hebraicorum, Paulus Orosius’s Historia adversus paganos, Saint Isidore’s Etymologiae and De natura rerum, the works of Al-Fraganus, Avicenna, and other Islamic writers, and the Bible and biblical commentaries. Bacon saw himself as providing the intelligent reader with a “summary” of the geographic knowledge handed down from antiquity. He omitted discussions of Northwestern Europe and Southern Europe because they were so well known.

Ideological Foundation . Bacon drew much information from the Travel Account (1256) of friar William of Ruysbroeck who journeyed in 1253-1255 to the Mongol or Tatar kingdom on behalf of the French King Louis IX. For example, he learned from this work that the Caspian Sea was not an arm of the circular Ocean surrounding the world but was rather a large inland sea. In many respects Bacon’s account of world geography may be compared with that of Albertus Magnus; indeed, with the exception of the material taken from William of Ruysbroeck’s account, it differs little from what is found in the German scholar’s De natura locorum. Still, Bacon’s account has a definite ideological foundation.

Ultimate Goal . Bacon was interested in geography as far as it could help Christian missionaries. Furthermore, he believed the use of mathematics in geography was important since it led to a greater knowledge of the heavens and the earth. This approach allowed his readers to gain natural knowledge which could serve as a basis for the symbolic knowledge found in sacred scripture. David Woodward and Herbert M. Howe point to Bacon’s singular contribution to knowledge of geography in the Middle Ages: “What sets Bacon aside from his contemporaries, however, is his insistence on the need for a systematic, mathematical way of positioning places on the earth for the practical needs of government, both to understand history and to predict from where in the world threats to Christianity are likely to come.”

Links with Columbus. One passage from the geography section of the Opus Maius has been linked to the voyage of Christopher Columbus in 1492. What is clear is that Columbus owned a copy of the Imago Mundi by the French theologian Pierre D’Ailly, and this work contained a long section of Bacon’s geographical writing.

The Inhabitable World. It is in his description of the various latitudinal zones (climates) of the inhabitable world that Bacon offers his most original geographical contribution, “the allusion to a systematic map of the inhabited world.” Bacon wrote:

Since these climata and their famous cities cannot well be described by words alone, a map must be used to make them clear to our senses. I shall, therefore, first present a map of our quadrant, and on it I shall label the important cities, each in its own place, with the distance from the equator—what we call the latitude—of the city or the region. I shall also label them according to their distance from east to west, what we call the place’s longitude. In my assigning of climata and likewise of latitude and longitude, I shall make use of the prestige and experience of the wisest scholars. To locate each city in its proper place [on this map] by its longitude and latitude, which have already been discovered by my authorities, I shall use a method by which their positions may be shown by their distances north and south, east and west. The device is this: parallel to the equator (already drawn on a plane surface), a straight line [i.e. a parallel of latitude] is drawn. This intersects another straight line [a meridian], from the point corresponding to the number of degrees of latitude of the place. This point is also marked on the colure (the quarter of the great circle that passes from the equator to the pole of the universe), and is, in fact, an arc of the colure. This procedure is both easier and better [than anything now in use], and a map drawn in this way is quite capable of representing to the senses the location of any point in the world.

Coordinate System. In this manner, using the “Toledo” or “Alphonsine” Tables, Bacon provided a coordinate system based on parallels and meridians. These tables provided a better estimate of the Mediterranean than those of Ptolemy. Bacon’s original map has been lost but it was clearly different from the common medieval Mappamundi such as the Hereford Map of circa 1290. Unlike those maps which were focused on the East and Jerusalem, Bacon’s map was focused on the North, and used the structural base which only became common in the fifteenth century.


Roger Bacon, Opus Mains, translated by Robert Belle Burke (Philadelphia: University of Pennsylvania Press, 1928).

Stewart C. Easton, Roger Bacon and His Search for a Universal Science (New York: Columbia University Press, 1952).

Paul D. A. Harvey, Medieval Maps (London: British Library, 1991).

George H. T. Kimble, Geography in the Middle Ages (New York: Russell & Russell, 1968).

David Woodward and Herbert M. Howe, “Roger Bacon on Geography and Cartography,” in Roger Bacon and the Sciences: Commemorative Essays, edited by Jeremiah Hackett (Leiden St New York: Koln, Brill, 1997), pp. 199-222.

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