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In this essay we will discuss about the evolution of Roman geography.
Much of the Greek traditions in geography were carried forward into ancient Roman scholarship. The Romans produced little that was new in the field of geography. Writing shortly before the time of Christ, one Marcus Terentius Varro prepared a compendium of geography that dealt with a theory of culture stages that remained almost unchallenged until the nineteenth century.
Varro describes man’s culture as moving through a regular sequence. Originally man derived his food from the things that the virgin Earth produced simultaneously. From this original state, man advanced through a stage of pastoral nomadism, then through an agricultural stage and finally to the stage of contemporary culture.
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Strabo (63 BC-24 AD), a Greek scholar and traveller writing at the height of the Roman Empire, was strongly influenced by the historical topographical tradition of Homer, Hecateaus, and possibly of Aristotle. It is often said that the historical tradition, introduced by the Greek scholars in geographical scholarship was finally summarised by Strabo.
His assertion on the geographer is as follows:
‘Accordingly, just as the man who measures the Earth gets his principles from the astronomer and the astronomer from the physicist, so, too, the geographer must in the same way take his point of departure from the man who has measured the Earth as a whole, having confidence in him and in those in whom he, in his turn, had confidence, and then explain, in the first instance, our inhabited world—its size, shape, and character, and its relation to the Earth as a whole; for this is the peculiar task of the geographer. Then, secondly, he must discuss in a fitting manner the several parts of the inhabited world, both land and sea, noting in passing wherein the subject has been treated inadequately by those of our predecessors whom we have believed to be the best authorities on these matters’.
Strabo accepts Aristotle’s zones of ekumene, as defined by Eratosthenes, and then goes on to assert that the limit of possible human life towards the equator is at latitude 12°-30′ N, but does not explain the basis of his assertion. He also places the northern limit of the habitable Earth, where cold is the limiting factor, only 400 miles north of the Black Sea.
Strabo accepts the calculation of the Earth’s circumference done by Posidonius in about 100 BC. He gives a correct explanation of the floods of the Nile, attributing them to the heavy summer rains in Ethiopia. Drawing from Hipparchus and Posidonius, Strabo concludes the geographer’s need of a sound mathematical base, because that would give him an accurate description of the parts of the ekurnene.
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Strabo wrote a work of 17 volumes called Geographia. This was largely an encyclopaedic description of the known world whose chief value was that it preserved for posterity many writings which he annotated and cited. Geographia also included attempts to explain cultural distinctiveness, types of governments and customs in particular places. The significance of natural condition for cultural development was discussed in relation to a number of places, especially in the description of Italy.
The first two books of Strabo’s work provide historical review of the progress of geography from the days of Homer whom be described as the founder of all geographical knowledge. He also discusses in detail the contributions of Eratosthenes, Hipparchus and Posidonius. He devotes eight books to Europe, six books to Asia, and one book to Africa, most of which deals with Egypt and Ethiopia.
Strabo’s greatest contribution lies in the field of political geography, and in this field he carried forward the Aristotelian tradition. In his Geographia, he examines the pre-requisites for the successful functioning of larger political units and concludes that a strong central government and a single head of state are essential ingredients for success.
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Given the political environment of the times, it is not surprising that Italy, the core of the Roman Empire with its location in the then-known world in the Mediterranean, its ‘ideal’ climatic regime, and its balance of mixed resources, was best suited to fill this role. Again, ethnocentrism coupled with inherited deterministic notions concerning environmental political relationships account for these conclusions.
The period that followed Strabo’s monumental work, Geographia, witnessed the compilation of extensive sailing materials for the guidance of ship captains and described the coastlines and ports with considerable detail and accuracy, such as the Periplus of Scylax for the shores of the Mediterranean and the Periplus of Arrian for the shores of the Euxine (Black Sea).
The most complete work of this kind was an anonymous one that offered a guide for navigators and traders who covered the Red Sea, the east coast of Africa as far as Zanzibar (more than 6 degrees south of the equator), and the northern side of the Indian Ocean as far as the southern end of the Malabar coast in India.
This was the famous Periplus of the Erythraean Sea, which Bunbury dates as some 10 years after the death of Pliny in 79 AD. The merchants and sailors of the first century after Christ, who had no access to the accounts of Aristotle, Posidonius, or Strabo, were happily not conscious of the horrible fate that would come to those who ventured within 120 of the equator or the impossibility of maintaining life in this central part of the Torrid Zone.
The mathematical tradition in ancient geographical scholarship, a heritage that the Greek scholars carried forward into the successive periods of academic innovations since Thales, really comes to an end with the monumental work of Ptolemy. Much of his geography, which he claims to be a science of the art of map-making, seems to have been borrowed from the earlier works of Aristotle, Hipparchus, Posidonius and his teacher, Marinus of Tyre.
Ptolemy tried to rationalise the earlier Greek geographical and astronomical ideas into organised categories preparing them in a scientific manner. His great work on classical astronomy— the Almagest—which long remained the standard reference work on the movements of celestial bodies, reveals his indebtedness to Aristotle, Hipparchus and Posidonius.
Ptolemy’s concept of the universe is a mere reflection of Aristotle’s tradition that the Earth was a sphere that remained stationary in the centre, while the celestial bodies moved around it in circular motions. This remained the accepted notion until the time of Copernicus in the seventeenth century. He adopted the grid of latitude and longitude lines developed by Hipparchus, based on the division of the circle into 360 parts.
Every place, therefore, could be given a precise location in mathematical terms. His biggest mistake was to underestimate the size of the Earth, rejecting almost correct estimate of Eratosthenes in favour of Posidonius who recalculated the circumference of the Earth.
The calculation of longitude in those days was only possible by estimating the length of journeys from one place to another and many of Ptolemy’s locations of places were found to be incorrect. Therefore, each listing of latitude and longitude was, in fact, only a selection among estimates.
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Ptolemy not only favoured a smaller estimate of the Earth’s circumference, but also erroneously increased the eastward extension of the land area. Because calculations of longitude had to be based on rather unreliable travel distances, his otherwise accurate map of the then world included too many degrees of longitude. The map extended from a prime meridian in the Canary Islands to a 180 degree meridian which crossed inner China. Ptolemy followed Marinus in taking his prime meridian a north-south line.
In the art of map making, the great contribution made by Ptolemy was his modification and improvement over the previously drawn maps and this he did by adopting a projection for the world map showing the graticule of latitudes and longitudes. He was, in fact, far ahead of his predecessors with regard to the mathematical construction of projections.
He represented the equator and the latitudes by parallel curves, and the meridians as straight lines, cutting the equator at right angles that converge at a point (pole) situated beyond the limits of the map. Subsequently, he reduced the meridians also to a curved form, so as to make them correspond more nearly with reality. The map on which graticule of longitudes and latitudes were drawn was not a perfect hemisphere.
After the completion of the Almagest, Ptolemy produced a Guide to Geography, consisting of eight volumes. The first was a discussion of map projections together with a few corrections of the data from Marinus based on actual astronomical observation which he had himself done.
Books II through VII contained tables of latitude and longitude. Book VIII contained maps of different parts of the world based on the gazetteer. Ptolemy rejected the hypothesis of Hecateaus, Herodotus and Strabo who believed that there was an ocean to the east of Asia.
Strabo who pointed out that Sera and Sine (in China) were merely the most easterly points in Asia, just as Agisyamba was the most southerly. He also indicated on his map that the Indian Ocean was closed by land on the south, an idea he probably borrowed from Hipparchus.
However, Ptolemy accepted Aristotle’s concept that the parts of the Earth near the equator were uninhabitable due to heat. It is interesting to note that Ptolemy accepted the incorrect estimate of the circumference of the Earth done by Posidonius, but he failed to appreciate Posidonius correct belief concerning the habitability of the equatorial region.
James and Martin have rightly observed:
‘With the death of Ptolemy the geographical horizons that had been widened both physically and intellectually by the Greeks closed in again. It was many centuries before the effort to describe and explain the face of the Earth as the home of man again attracted the attention of scholars’.