326 



CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. 



not as satisfactory as in the case of the other experiments; a slight dif- 

 ference in the intensity of two shocks could not be appreciated with 

 perfect certainty. 



SECTION TI. 



The production of induced Currents of the different Orders from 



ordinary Electricity. 



98. Dr Faraday, in the ninth series of his researches, remarks, that 

 "the effect produced at the commencement and the end of a current 

 (which are separated by an interval of time when that current is sup- 

 plied from a voltaic apparatus) must occur at the same moment when 

 a common electrical discharge is passed through a long wire. Whe- 

 ther if it happen accurately at the same moment they would entirely 

 neutralize each other, or whether they would not still give some defi- 

 nite peculiarity to the discharge, is a matter remaining to be exa- 

 mined." 



99. The discovery of the fact that the secondary current, which 

 exists but for a moment, could induce another current of considerable 

 energy, gave some indication that similar effects might be produced by 

 a discharge of ordinary electricity, provided a sufficiently perfect insu- 

 lation could be obtained. 



100. To test this a hollow glass cylinder. Fig. 11, of about six 



inches in diameter, was pre- 

 pared with a narrow riband of 

 tinfoil, about thirty feet long, 

 pasted spirally around the out- 

 side, and a similar riband of 

 the same length, pasted on the 

 inside ; so that the correspond- 

 ing spires of the two were di- 



ffl glass cylinder, h Leyden jar, c magnetizing spiral. TCCtly OppOSitC Cach Othcr. The 



ends of the inner spiral passed out of the cylinder through a glass tube, 

 to prevent all direct communication between the two. When the 

 ends of the inner riband were joined by the magnetizing spiral (11), 

 containing a needle, and a discharge from a half gallon jar sent through 



