ELECTRO-MAGNETISM. 



Electro-Magnetism very recently discovered. — Oersted's Experiments at Copenhagen. — The Law 

 according to which the Needle is deflected. — The Law of Attraction and Repulsion of Electric 

 Currents. — Supposes Electric Currents circulating round the Globe. — Arago shows that the con- 

 ducting Wire has Magnetic Properties. — Needles magnetized by the Electric Current. — The 

 Variation of the Attraction of the Current at different Distances determined. — Laplace reduces 

 this Result to an analytical Formula. — The whole Body of Electro-magnetic Phenomena reduced 

 to analytical Calculation. — Faraday's Researches. — Rotation imparted to Mercury by means of the 

 Magnet and Electric Current. — The Multiplier or Galvanometer. — Its Construction and Applica- 

 tion. — The Earth affects Electric Currents in the same Manner as it affects Magnet-?. — Ampere's 

 Theory of Terrestrial Magnetism. — Researches of M. de la Rive. — Magnetizing Power of the 

 Current at different Distances, and the Law of its Variation. — The Effect produced by transmit- 

 ting it through Metals. — The undulatory Theory of Electricity similar to that of Light. — Tkermo- 

 Electricity. — Thermo-Electric Effects observed by Professer Seebeck. — His Experiment with An- 

 timony and Copper. — Researches of Yelin, Marsh, and Cumming. — Oersted and Fourier construct 

 a Thermo-Electric Pile.— Becquerel decomposes Water with such an Instrument.— Thermo-elec- 

 tric Scale of Metals. 



