64 ME. J. P. JOULE ON THE LIFE AND WHITINGS 



co very of the magnetism of rotation. He showed that a 

 magnetic needle was deflected when a disc, composed of any- 

 kind of substance, was revolved near it. This very interesting 

 phenomenon immediately occupied the attention of the most 

 distinguished physicists, among whom the names of Seebeck, 

 Herschel, Babbage, Christie, and Barlow, may be particularly 

 mentioned. Herschel and Babbage remarked that a slit in 

 the revolving plate materially diminished its action on the 

 needle. Mr. Sturgeon took up the subject in 1832, and after 

 much labour came to the conclusion that the effects were pro- 

 bably owing to a disturbance of the electric fluid by magnetic 

 action. The words he uses are, " It would, however, be no 

 great stretch of the imagination to suppose a disturbance of 

 the electric fluid by magnetic action, as it would be only a 

 kind of re-action to that which takes place in electro-magnet- 

 ism." From the above extract there can be little doubt 

 that Mr. Sturgeon would presently have arrived at the dis- 

 covery of magnetic electricity, had he not been anticipated by 

 Dr. Faraday, who, in November, 1831, communicated to the 

 Royal Society his paper, " On the Evolution of Electricity 

 from Magnetism," which forms the 2nd section of the first 

 of that inimitable series of experimental researches, which 

 has contributed so greatly to the scientific renown of 

 Britain. 



Van Marum and others had shown that a voltaic battery is 

 able to charge coated glass. After repeating their experi- 

 ments, Mr. Sturgeon constructed an apparatus, by means of 

 which a leyden battery in connection with a series of Cruick- 

 shank's voltaic plates is repeatedly charged and discharged, 

 by means of the revolution of a toothed wheel. In this way 

 " the discbarges can be made in such rapid succession as to 

 prevent the sensation of distinct shocks, the effect on the 

 animal economy being similar to that produced by a voltaic 

 battery charged with acid and water. No shock was produced 

 independently of the glass battery." 



