GEOGRAPHICAL LATITUDE. 759 



gfeography reaches it highest point of development.^ He not only 

 possessed all the available knowledge of his time bearing upon the 

 subject, but based his work so thoroughly on scientific principles that 

 its revival in modern times gave the starting point to many of the im- 

 provements of the new geography. That his maps were but improve- 

 ments on those of Eratosthenes^ and Hipparchus,"* and not absolutely 

 new, is not matterof censure. He recognized the justness of their prin- 

 ciples and simply added thereto what his talent and the better facili- 

 ties for obtaining knowledge afforded by his time and circumstances 

 rendered possible. He not only wrote the principles of map-drawing, 

 but put the same into practice, producing a very fair representation 

 of the then known world, and he added thereto special maps on alarger 

 scale to the number of twenty-six.* Here it is not in place to go deeply 

 into the details of Ptolemy's projection, which however is interesting.^ 

 The ground-plan is that of an open fan, the radii forming the meridians 

 of longitude, the lines parallel to the outermost curve representing 

 the parallels of latitude. Of these there were four principal ones, 

 the outermost being the supposed southern limit of the habitable zone. 

 From the center of this line to the point forming the pivot of the fan 

 was a line to be divided into one-hundred and thirty-one equal parts. 

 Starting from the south, sixteen of those parts bring us to the equa- 

 tor, on which 180 degrees of longitude were marked, forming the ex- 

 treme limits east and west of the known world. Counting then thirty- 

 six parts toward the north, came Rhodes, whose parallel was the most 

 imiiortant line of ancient geography. Twenty-seven parts more bring 

 us to the parallel of Thule, the limit to the north of the habitable world. 

 The other parallels were those of important places, without an attempt 

 to make equal divisions, as is done with the meridians, although at one 

 side the parallels are marked at distances of 10 degrees. At the other 

 side an unequal division into climates is indicated. Theoretically, 

 however, Ptolemy advocates the division into equal parts by parallels 

 of latitude. He gives also rules for another kind of projection in 

 which the meridians should be curved lines, as this would better rep- 

 resent the middle latitudes. At the same time he says that this pro- 

 jection is much more difficult to draw." Here we have the best pro- 



' Mannert, i. U>'.i : ''Nacli lUolcniiius wagtc sicli niciiiand weiter an dio Verbesser- 

 mig (ler Geof^rajthio. Anstatt nianclie soinor Angaben zn bericbtigen, iiahm niau 

 dessen Werk fiir das iion j)lnii ultra der Wissonscbaft, imd liielt es fast fur Siinde eine 

 seiner Beliauptungeu nicbt gclten lassen zu wollen ; und desto mebr, da eiii grosser 

 Theil der spiitern Gelehrten die Griindederselbcn nicht verstundeu." 



2 Mannert, i. 9G. 



' Berger, 80, Note 1. " Es (das Verfabreu des Ptolemiius) giebt fast die gauze Hip- 

 parcbiscbe Lebre wieder." 



"* Zacb remarks tbat tbe special maps are not drawn according to Ptolemy's own 

 proposition (Mon. Cor. Jnn., 1805, p. 504). 



* Ptolemiius, Geograpbica, lib. i. cap. xxiii. 



«Tbo first maps based on tbis projection were drawn by Nikolaus Donis (1482). 

 (Mannert, 1. 178, 179). 



