MAPS AND MAP-MAKING BEFORE MERC AT OR. 485 



care the works of his predecessors, collected all the information that 

 was procurable from travelers and mariners, and produced a geograph- 

 ical work far beyond anything that had preceded it, illustrated by 

 maps which were covered with a network of parallel and meridian 

 lines, cutting each other at right angles, under which the different 

 places were indicated according to their direction and distance from 

 each other. His object was to put an end to the uncertainty about 

 the position of countries and cities, by assigning to every locality or 

 place its approximate latitude and longitude. He divided the globe 

 into sections, each having an astronomical extent of fifteen degrees, 

 and the places falling within these limits he put together in what he 

 supposed to be their relative position to each other. He drew a line 

 due east from the Fortunate Islands, and arranged countries and places 

 in what he regarded as their proper position north and south of this 

 line, so as to bring them alike under the proper zone or climate, as 

 well as under the astronomical section he had devised. 



Marinus was probably the first who undertook to combine system- 

 atically the results of astronomical observations with those of travel- 

 ers and mariners in determining geographical positions. There being 

 no delicate instruments to indicate direction, altitude, or time, the lati- 

 tudes and longitudes ascertained were at first, of course, erroneous. 

 Marinus corrected earlier errors, and accumulated much new material 

 for the preparation of a geographical work which premature death 

 prevented him from perfecting. 



The geography of his immediate successor, Ptolemy, which has 

 fortunately come down to us, was written at least within half a century 

 afterward, and, as Ptolemy himself says, was based upon the work of 

 Marinus. 



Ptolemy's labor was what in this day we should call editing a new 

 and revised edition of an existing work. Ptolemy was a much better 

 mathematician and astronomer, but evidently very inferior as a geog- 

 rapher to his predecessor. He undertook to correct Marinus's chief 

 error by reducing his projection of the earth, from east to west, from 

 225° to 180°. In making this geometrical correction, however, he fell 

 into a multitude of errors which, had he been a better geogi'apher, he 

 would readily have detected. 



A period of twelve hundred years elapses from the time of Ptolemy 

 to the inauguration, by Prince Henry the Navigator, of Portugal, of 

 the spirit of maritime enterprise which led to the circumnavigation of 

 Africa, and the discovery of the Continent of America. This long 

 interval is marked by the decline in Europe of everything in the form 

 of geographical knowledge, until a state of ignorance was reached in 

 which little interest was felt in any branch of human learning. For 

 the purposes of our inquiry it may be divided into three periods. The 

 first Avas one of long-continued and nearlv incessant wars, during which 



