BELIEF IN ASIA 65 



Map to Illustrate These Geographical 

 Ideas 



We may now attempt to construct a map embody- 

 ing the ideas that were familiar to Columbus. The 

 accompanying map (PL II) is based upon a com- 

 parison of Ptolemy, Behaim's globe, the Bartholo- 

 mew Columbus maps, and the writings of Columbus. 

 The configuration of Ptolemy (Fig. 3) is used for the 

 southern coast of Asia, stretched in longitude, how- 

 ever, to conform to Marinus of Tyre, with whose 

 views as to the eastward extension of Asia Columbus 

 agreed, as we have seen (p. 29). This stretching is 

 only necessary east of the crossing of the Euphrates 

 at Hieropolis, 72° east of Ptolemy's prime meridian 

 (Fig. 3; beyond the border of PL II), as west of this 

 point Ptolemy accepted the longitudes of Marinus of 

 Tyre.^^ Longitudes east of the Euphrates are ob- 

 tained by subtracting 72° from the Ptolemaic longi- 

 tude to obtain a base, then multiplying the remainder 

 by 17/12 so as to place Cattigara 225° east of the 

 prime meridian (Marinus' conception) instead of 

 180° (Ptolemy's conception). ^^ (To convert these 

 longitudes to longitudes from Greenwich, 1 7 y^ should 

 be subtracted, this being the difference between Green- 

 wich and the conventional meridian of Ferro, the 



18 Vignaud, Histoire critique, Vol. i, p. 256; Nordenskiold, Facsimile- 

 Atlas, p. 4. 



19 17/12 = ratio of 225 — 72 to 180 — 72. 



