AGNETISM. 



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 £oulomb. — 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. 



