SCIENCE OF THE ROMAN PERIOD 



cern us here, being rather an elaboration of the doc- 

 trines to which we have already sufficiently referred. 

 None of Ptolemy's original manuscripts has come 

 down to us, but there is an alleged fifth-century manu- 

 script attributed to Agathadamon of Alexandria which 

 has peculiar interest because it contains a series of 

 twenty-seven elaborately colored maps that are sup- 

 posed to be derived from maps drawn up by Ptolemy 

 himself. In these maps the sea is colored green, the 

 mountains red or dark yellow, and the land white. 

 Ptolemy assumed that a degree at the equator was 

 500 stadia instead of 604 stadia in length. We are not 

 informed as to the grounds on which this assumption 

 was made, but it has been suggested that the error was 

 at least partially instrumental in leading to one very 

 curious result. "Taking the parallel of Rhodes," says 

 Donaldson, 5 "he calculated the longitudes from the 

 Fortunate Islands to Cattigara or the west coast of 

 Borneo at 180, conceiving this to be one-half the cir- 

 cumference of the globe. The real distance is only 125 

 or 127, so that his measurement is wrong by one- 

 third of the whole, one-sixth for the error in the meas- 

 urement of a degree and one -sixth for the errors in 

 measuring the distance geometrically. These errors, 

 owing to the authority attributed to the geography of 

 Ptolemy in the Middle Ages, produced a consequence 

 of the greatest importance. They really led to the dis- 

 covery of America. For the design of Columbus to sail 

 from the west of Europe to the east of Asia was founded 

 on the supposition that the distance was less by one- 

 third than it really was." This view is perhaps a trifle 

 fanciful, since there is nothing to suggest that the cour- 



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