MAGIETISM. 



Magnetic Attraction and Polarity. Magnetic Meridian, Variation. Dip of the Magnetic Needle. 

 Magnetic Attraction known to the Ancients. Invention of the Mariner's Compass of uncertain 

 Date. Discovery of the Variation. Tables of Variation constructed. Robert Norman discovers 

 the Dip. Invention of the Dipping Needle. The Variation of the Variation discovered. Influ- 

 ence of Magnets on soft Iron observed. Polarity of Magnets observed. Construction of artificial 

 Magnets. Magnetism imparted to Iron by the Earth. Laws of Magnetic Attraction discovered 

 by Coulomb. Methods of making artificial Magnets consequent Points. Knight's improved 

 Method. Duhamel's Improvement. Coulomb's Researches on artificial Magnets. Influence of 

 Heat on Magnetism. Local and periodical Changes of the Variation. Diurnal Variation. Cas- 

 sini's Observations at Paris. Advancement of Magnetic Geography. Magnetic Equator. Mag- 

 netic Poles. 



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