100 rEURESTRIAL 



the northern hemisphere (14*21 and 13*30), yet the mag- 

 netic force of the one hemisphere is not to be regarded as 

 greater on the whole than that of the other." 



It is quite otherwise, however, if we divide the earth into 

 an eastern and a western hemisphere by a great circle 

 formed by the meridians of 100 and 280 E. long., so 

 that the eastern (and the more continental) hemisphere shall 

 comprehend South America, the Atlantic Ocean, Europe, 

 Africa, and Asia almost to Lake Baikal ; and the western 

 (which is the more oceanic and insular) shall contain 

 almost the whole of North America, the Pacific Ocean, 

 New Holland, and the eastern part of Asia. These meri- 

 dians are, the one about 4 west of Singapore, the other 

 13 west of Cape Horn; the latter being also the meridian 

 of Guayaquil. In this division all four foci of maximum 

 magnetic lorce, and even the two magnetic poles themselves, 

 all belong to the western and more oceanic hemisphere. ( 103 ) 



Adolph Erman's important observation of the least or 

 minimum magnetic force in the Atlantic Ocean, on the 

 east side of the Province of Espiritu Santo in Brazil (lat. 

 20 S., long. 35 02' W.), has been already referred to in 

 Vol. i.( 10 *). He found in the relative scale 0-706 ; in the 

 absolute, 5 "35. This region of weakest intensity was also 

 crossed twice by the Antarctic Expedition of Sir James 

 lloss,( 105 ) between latitudes 19 and 21 S., and by Lieute- 

 nant Sulivan and Mr. Dunlop, on the passage from England 

 to the Falkland Islands. ( 106 ) Sabine has represented the 

 curve of least magnetic force [corresponding to the year 

 1840], which Eoss terms "the equator of least intensity/' 

 on the isodynamic map of the whole Atlantic Ocean, draw- 

 ing it from shore to shore. It cuts the west coast of Africa 



