CURVES OF EQUAL DIP AND EQUAL HORIZONTAL FORCE. 97 



distance at about 318 east longitude, or 50 from 

 the same node. The inclination of the Magnetic 

 Equator to the geographical equator is greater near 

 the west coast of Africa than in any other part. Pro- 

 ceeding to the neighbouring lines, it will be seen that 

 the increase of dip is nearly double of the increase 

 of latitude; and upon this circumstance was founded 

 the conjectural law, tan. Dip = 2 tan. distance from 

 magnetic equator; to which we shall advert in the 

 next Section. Nearer to the Magnetic Poles the 

 curves are oval, or rather pear-shaped; but the major 

 axes of the northern curves, and those of the southern 

 curves, are not in the same direction. The North 

 Magnetic Pole (in longitude 265) and the South 

 Magnetic Pole (in longitude 152) are not opposite 

 each other. These remarks show that the Earth's 

 magnetism cannot be represented as the power of one 

 magnet, and that the distribution of magnetism about 

 the Earth is unsymmetrical. 



The curves of equal Horizontal Force, Figures 28 

 and 29, are still more strange. The greatest values 

 are 3733 at the geographical equator in longitude 

 259, and 3'673 in 14 north latitude, longitude 103. 

 Proceeding along an equatoreal belt, one minimum 

 of 3'039 is reached in longitude 345, north latitude 3, 

 and another 3'408, in longitude 156, south latitude 

 13. Proceeding in either direction, north or south, 

 from this equatoreal belt, the Horizontal Force gradu- 

 ally diminishes to at each pole. The north pole is in 

 the north of Baffin's Bay: the south in South Victoria. 



7 



