142 Prof. Faraday on Rulunkorff^s Apparatus. [June 8, 1855. 



moment of induction, is discharged back again at the same place the 

 instant the induction is over ; the first discharge heats and prepares 

 the air there for the second discharge, and the two are so nearly 

 simultaneous as to produce the appearance of a single spark to the 

 unaided eye. 



Reference was then made to the hopes raised by this instrument, 

 of advance in the investigation of the magneto-electric power, 

 by means of the great aid which it seems competent to supply. 

 The results obtained by Grove* apparently referable to polarization 

 were adverted to ; as also the remarkable transverse bands presented 

 in the recurring discharge across very rarified airf ; and, founded 

 as the instrument is by its core and its wires upon the joint effects 

 of electro-dynamic and magneto-electric induction, it was observed 

 that it gave great promise of aid in the investigation of that condi- 

 tion of either the space or the ether which is about magnets, and 

 around every discharge of electricity, whether in good or bad 

 conductors, and which is expressed by the terms (themselves syn- 

 onymous) of the magnetic or the electrotonic state. 



[M. F.] 



* Phil. Trans. 1852, p. 93, &c. f Phil. Mag. 1852, iv, p. 514. 



