22 MAPS AND THEIR MAKERS 



Upon the scientific basis, his influence promoted cartographical 

 progress. On the other hand, in several ways his ideas hindered 

 the development of an accurate map of the world. One of his 

 principal mistakes was the adoption of a value for the length 

 of a degree equivalent to 56 J miles, in contrast to Eratos- 

 thenes' more accurate value. Thus when transforming distances 

 into degrees, he obtained greatly exaggerated figures, an 

 exaggeration intensified by the common tendency of travellers 

 to overestimate distances covered. The longitudinal extent of 

 the Mediterranean, for example, he fixed at 62°, instead of 

 42°, and in the same way he exaggerated the easterly extension 

 of Asia, placing its eastern shores some 50° too far east. This 

 was however a reduction of 45° on the figure adopted by 

 Marinus. He also incorporated erroneous conceptions on the 

 configuration of the old world: for example, he greatly over- 

 estimated the size of Taprobana (Ceylon) and overlooked the 

 peninsular form of the Indian sub-continent, or perhaps 

 confused it with Ceylon; he conceived the Indian Ocean to be 

 a land-locked sea, extending the south-eastern African coast- 

 line eastwards to meet a southerly extension of what he probably 

 intended to represent the Malay peninsula. Another con- 

 spicuous error is the easterly direction he gave to Scotland, 

 probably due to a mistake in joining two sectional maps 

 together. His representation of the hydrography of northern 

 Africa, which showed a great eastward-flowing river, perhaps 

 the Niger, ending in a central swamp, was sometimes followed 

 until the early nineteenth century. Less erroneous was his 

 delineation of the Nile, rising from lakes at the foot of the 

 Mountains of the Moon, some degrees north of the Equator. It 

 is useful to keep these misrepresentations in mind when study- 

 ing the maps of the Renaissance and to note their gradual 

 elimination as exploration progressed. 



The Romans seem to have been singularly unconcerned 

 with Greek achievements in scientific cartography. For them 

 a map remained a practical aid to the journeys of their officials 

 and the campaigns of their legions. If we were to judge from 

 the sole surviving example of any size, we would conclude that 

 they were little more than graphical renderings of written 

 itineraries. This example, and in a very late copy at that, is 



