THE BEGINNINGS OF GEOGRAPHICAL SCIENCE. 245 



10 -0 Sd 4i) oJ GO TO 8J 90 100 110 liiO 13 1 14J loO UO lit) 

 PTOLEMY'S MAP OF THE WORLD. 



only authority foi* more than thirteen centuries. Happily it has 

 come down to us entire, though the different manuscript copies 

 vary considerably among themselves. Through the generosity of 

 the Emperor of Russia, fac-simile copies have been made of the old- 

 est extant Greek MS., written about the year 1200 a. d., and now 

 at Mount Athos ; and these copies are in the more important libra- 

 ries of the world. The method of projection which Ptolemy used in 

 his maps had been slow of practical realization. Ilipparchus's work 

 had not gained a circulation. Marin of Tyre had had but poor 

 success in attempting it, so that Ptolemy's approach to success seems 

 the more commendable. We present a map drawm upon his system. 

 In it are to be noticed two great errors. We have spoken of Posido- 

 nius as the originator of an error. Dissatisfied with Eratosthenes's mea- 

 surement of the earth, he had measured it anew. To do this he had 

 observed by a star the arc between Alexandria and Rhodes, and had 

 ascertained the distance as nearly as he could from the number of 

 days' sail between the cities. But soon becoming dissatisfied in regard 

 to the distance he had employed, he adopted Eratosthenes's distance, 

 which the latter had obtained by computing the arc at 700 stadia to 



