CLASSICAL AND EARLY MEDIEVAL HERITAGE 17 



succeed each other from east to west. One meridian was taken 

 to run down the Nile, and through the Cilician Gates and 

 Sinope to the mouth of the Ister (Danube). Since these lines 

 were far from 'straight', the distortion introduced into the 

 map was considerable. In this way also an east-west axis for 

 the Mediterranean was established; since, in coasting along 

 considerable stretches, the west coast of Italy and the south 

 coast of France, for example, the change in direction was gradual 

 and not easily perceptible, these portions tended to be shown 

 as parallel to the east- west axis. The Mediterranean was thus 

 narrowed in proportion to its length. A general principle which 

 governed much Greek thinking then entered into the delinea- 

 tion of the map — namely, the symmetry of nature. Features 

 north of the axis must be balanced by similar features to the 

 south; the Pyrenees by the Atlas mountains, the Adriatic by 

 the Gulf of Syrtes, Greece by the Cyrenaica promontory, and 

 so forth. This principle was applied further afield; the Nile 

 being thought to flow in its upper course from west to east, the 

 unknown upper course of the Ister was made to do likewise. 

 Emphasis on this point is necessary, for it strongly influenced 

 later ideas on the earth's configuration. Ptolemy probably 

 conceived his enclosed Indian Ocean as a counterpart of the 

 Mediterranean. The frame of the world map continued to be 

 circular, and, for the Greeks, centred at Delphi — assumptions 

 which the philosophers often derided. 



Meanwhile the progress of science was revolutionizing 

 conceptions of the earth, and suggesting much more precise 

 methods of fixing position on its surface. The idea that the 

 earth w^as a sphere, and not a flat disc, was first advanced by 

 philosophers of Pythagoras' school, and brought to general 

 attention through the v/ritings of Plato. When the spherical 

 character of the earth was recognized, and later the obliquity 

 of the ecliptic, astronomers were able to deduce latitudes from 

 the proportions between the lengths of the shadow and the 

 pointer of the sun dial. This was the forerunner of the modern 

 method of obtaining latitude by observing the altitude of the 

 sun at midday and applying the necessary correction from 

 tables in the Nautical Almanac. 



Thus alongside the 'mapping' of relatively small areas for 



B 



