116 MAPS AND THEIR MAKERS 



"I could wish all Seamen would give over sailing by 

 the false plain charts, and sail by Mercator's chart, which is 

 according to the truth of Navigation ; But it is an hard matter 

 to convince any of the old Navigators, from their Method 

 of sailing by the Plain Chart; shew most of them the Globe, 

 yet they will talk in their wonted Road." 



Mercator was also interested in the problem of terrestrial 

 magnetism, and accepted the general observation of navigators 

 that the line of no magnetic variation passed through the Cape 

 Verde Islands. Accordingly, ''since it is necessary that longi- 

 tudes of places should, for good reasons, have as origin the 

 meridian which is common to the magnet and the world . . . 

 I have drawn the prime meridian through the said Islands'*. 

 As he was also aware that the magnetic variation differed from 

 place to place, he concluded that there must be a magnetic 

 pole "towards which magnets turn in all parts of the world", 

 and he marked the position of this pole in the region of the 

 modern Bering Strait. 



In his outlines of the continents Mercator broke away com- 

 pletely from the conceptions of Ptolemy, though the latter's 

 influence in the interior of the old world can still be traced. He 

 recognizes three great land-masses, the old world (Eurasia 

 and Africa), the New Indies (North and South America), and a 

 great southern continent, 'Continens australis'. This was based 

 on an idea, which derived ultimately from the Greeks, that in 

 the southern hemisphere there existed another continent 

 which was the counterpart of the 'inhabited world'. Evidence in 

 support of this theory was also based on a misreading of Var- 

 tliema and Marco Polo, from which it was concluded that 

 continental land, the hypothetical regions of Beach and Lucach, 

 lay to the south of Java Major. The portions of Tierra del 

 Fuego seen by Magellan were incorporated into this southern 

 continent, the coastline of which was brought northwards to 

 the vicinity of New Guinea. Here it is not beyond the bounds 

 of possibility that the map preserves some traces of early know- 

 ledge of the Australian coasts. South-eastern Asia is based fairly 

 closely on the Portuguese discoveries. Most of the interior, 

 however, is derived from Marco Polo's narrative, and the 



