3bb VOLTA-ELECTKIC INDUCTION. [SECT, xxxin. 



ing needles, of passing through a small extent of fluid, and, 

 when charcoal points were interposed in the current of the 

 induced helix, a minute spark was perceived as often as the 

 contacts were made or broken, but neither chemical action 

 nor any other electric effects were obtained. A deviation 

 of the needle of the galvanometer took place when common 

 magnets were employed instead of the Voltaic current ; so 

 that the magnetic and electric fluids are identical in their 

 effects in this experiment. Again, when a helix formed of 

 220 feet of copper wire, into which a cylinder of soft iron 

 was introduced, was placed between the north and south 

 poles of two bar magnets, and connected with the galvano- 

 meter by means of wires from each extremity, as often 

 as the magnets were brought into contact with the iron 

 cylinder, it became magnetic by induction, and produced a 

 deflection in the needle of the galvanometer. On continuing 

 the contact, the needle resumed its natural position, and, 

 when the contact was broken, deflection took place in the 

 opposite direction; when the magnetic contacts were re- 

 versed, the deflection was reversed also. With strong 

 magnets, so powerful was the action, that the needle of the 

 galvanometer whirled round several times successively ; and 

 similar effects were produced by the mere approximation or 

 removal of the helix to the poles of the magnets. Thus it 

 was proved that magnets produce the very same effects on 

 the galvanometer that electricity does. Though at that 

 time no chemical decomposition was effected by these 

 momentary currents which emanate from the magnets, they 

 agitated the limbs of a frog ; and Dr. Faraday justly ob- 

 serves, that "an agent which is conducted along metallic 

 wires in the manner described, which, whilst so passing, 

 possesses the peculiar magnetic actions and force of a cur- 

 rent of electricity, which can agitate and convulse the limbs 

 of a frog, and which finally can produce a spark by its dis- 

 charge through charcoal, can only be electricity." Hence 

 it appears that electrical currents are evolved by magnets, 



