MAGNETISM. 



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 Macrnets observed. Construction of artificial 

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

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

 Method. Dnhamers 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 Pari* Advancement of Magnetic Geography. Magnetic Equator. Mag- 

 netic Poles. 



