FIFTEENTH-CENTURY WORLD MAPS 55 



East. This departure from orthodox practice clearly worried 

 the friar, and he excuses himself thus: 



"Jerusalem is indeed the centre of the inhabited world 

 latitudinally, though longitudinally it is somewhat to the 

 west, but since the western portion is more thickly populated 

 by reason of Europe, therefore Jerusalem is also the centre 

 longitudinally if we regard not empty space but the density 

 of population." 



It is clear from numerous legends that Fra Mauro was 

 very much aware of the great deference then paid to the cosmo- 

 graphical conceptions of Ptolemy, and the likelihood of severe 

 criticism for any map which ignored them. Nevertheless, in 

 general, he stands by contemporary ideas and forestalls criticism 

 thus: \ 



"I do not think it derogatory to Ptolemy if I do not 

 follow his Cosmografia, because, to have observed his 

 meridians or parallels or degrees, it would be necessary in 

 respect to the setting out of the known parts of this circum- 

 ference, to leave out many provinces not mentioned by 

 Ptolemy. But principally in latitude, that is from south to 

 north, he has much 'terra incognita', because in his time it 

 was unknown." 



If Fra Mauro's basis was less scientific than it might have 

 been, he did at least point to the necessity for modifying 

 Ptolemy's ideas in the light of more recent knowledge. In one 

 major modification, the opening of the 'Sea of India' to the 

 circumfluent ocean, he was in accord with all his contem- 

 poraries. Ptolemy, he writes, like all cosmographers, could not 

 personally verify everything that he entered on his map and 

 with the lapse of time more accurate reports will become avail- 

 able. He claimed for himself to have done his best to establish 

 the truth. 



"In my time I have striven to verify the writings by 

 experience, through many years' investigation, and inter- 



