164 ONTOLOGY. 



the direction of the meridian deviates from the earth's 

 axis in accordance with these masses. 



786. The magnetic needle can therefore assume a 

 different direction on every part of the earth, according 

 as its relative position is varied between two principal 

 masses of metals, and even as is indicated by the move- 

 ment of the compass with the change of geographical 

 longitudes, it is removed from one metallic mass, 

 approaches another, and by this becomes more powerfully 

 attracted. Upon the whole, however, the direction 

 must tend toward the poles. Such are the phenomena 

 of declination of the magnetic needle ; and we can now 

 comprehend why this is present. 



787. But there must be also spots upon the earth, 

 where the needle points straight to the north, probably, 

 when it is between two metallic masses, or stands at a 

 certain angle to them. These are the lines without 

 declination, of which there are many as is well known, 

 but which have not as yet been reduced to any law. 

 Nor can they ever be so, because we shall never become 

 acquainted with the metallic beds. 



788. As the solid land, so far as it projects out of the 

 water, forms a horse-shoe figure, of which the two 

 Americas represent one leg, Europe with Asia and Africa 

 the other leg, the sea being interposed between them ; so 

 must the lines without declination fall principally in the 

 ocean, between the earth's crura. Moreover as both 

 these crura of the earth are unequal in size, so must the 

 one influence the needle more than the other, and in 

 this respect also there can be therefore no regularity 

 in the lines without declination. Thus everything 

 co-operates, to the effect of rendering the direction 

 of the magnetic needle unequal ; such as the distribution 

 of metalliferous mountains, of masses of iron, of the 

 earth's hemispheres, of the earth's crura, and inversely 

 the earth has probably obtained this horse-shoe form 

 through magnetism. The cavities of the earth probably 

 do not fall in there, because the ground, namely 

 the mountains, is supported by metallic plates. On 



