ELECTRICAL AND MAGNETIC DISCOVEKIES OF FARADAY 639 



Ihivy, when he was twenty-two years old. His attention was first given 

 to chemistry, but was finally attracted to electricity by the discovery of 

 electro-magnetism by Oersted, in 1820. At this period the subject of 

 electrostatics was very far advanced even as compared with modern 

 limes. 



More than 200 years before, Gilbert had commenced the study of 

 electricity, and divided bodies into electrics and non-electrics, accord- 

 ing as they produced or did not produce electricity by friction. Nearly 

 100 years before, Stephen Gray had discovered the difference between 

 conductors and non-conductors, and had shown the means of carrying 

 electrical effects to a distance of several hundred feet by means of a con- 

 ducting thread or wire suspended by non-conducting threads of silk. 

 Otto von Guericke, du Fay and Wilke had shown that there were two 

 kinds of electricity resinous and vitreous. The Leyden jar had been 

 discovered by the Dutch philosophers. Franklin had written his cele- 

 brated series of letters on electricity, explaining the phenomenon of the 

 Leyden jar and induction as clearly as we can do it at present, giving 

 his theory of positive and negative electricity to the world, and demon- 

 strating in the most perfect manner the electrical nature of thunder 

 and lightning. 



Aepinus and Cavendish had applied mathematics to the subject, and 

 the latter had discovered the law of inverse squares, and made for himself 

 a series of graduated condensers, by which he measured the capacity of 

 differently shaped bodies. They had been followed by Laplace, Pois- 

 son and Biot in mathematical electricity. Coulomb had introduced Jiis 

 torsion balance, the first accurate instrument for electrical measure- 

 ment. 



Galvani and Volta had shown how to produce a current of electricity 

 by the galvanic battery. The chemical action of electricity had long 

 been known, and had been forcibly brought before the world by the 

 immortal experiments of Davy only a short time before, and Ritter had 

 discovered polarization and 1he storage battery. 



But, although many persons had suspected that there was some con- 

 nection between electricity and magnetism it was not until Oersted, in 

 1820, discovered the nature of this connection, and Ampere had given 

 the laws of the attraction of currents, that the science of electro-mag- 

 netism became a subject of investigation. This new discovery aroused 

 the attention of the scientific world to another field of research, and 

 especially awakened in Faraday that sublime curiosity with respect to its 

 laws, which finally led him to his first discovery in this subject. 



