' of Iron and Bismuth. SI 



and it will not only immediately be thrown into action itself, 

 but all the inactive wires in the series after it will turn active 

 also, the needle being strongly deflected; but if it should 

 happen, as it sometimes, but rarely, does, that one termi- 

 nation retains its peculiar state, then there will be no disturb- 

 ance of the needle^ which is an additional and irresistible 

 proof of the utter incapacity of the iron in that state to con- 

 duct weak current electricity. It will be found impossible to 

 render either end of the connecting wires inactive by com- 

 pleting the circuit by dipping into the platina glass Jirst ; nei- 

 ther can the terminal iron wire connected with the galvano- 

 meter be brought into the same state unless both ends of both 

 connecting wires are undergoing chemical action, it being 

 absolutely necessary that there should be a free passage for 

 the slight current which the needle shows to be produced the 

 moment the wire dips into the acid, and on isohich current the 

 development of the peculiar state depends. 



Again, supposing the terminal iron wire, or one end ofone or 

 of both the connecting wires to be inactive, if the platina ter- 

 minal wire is removed from its glass, and a wire of any other 

 metal on which the liquid exerts chemical action substituted 

 for it, the counter current which that metal calls forth through 

 the liquid instantly destroys the peculiar state of ail the wires 

 in the arrangement : the brown oxide appears as if by magic, 

 and the needle is deflected. 



From these experiments it appears to me quite clear, that 

 the inactive state of iron is occasioned by a voltaic current 

 of a certain intensity passing through it in a certain direction ; 

 and as it is impossii3le to induce such a state on wire after its 

 surface has been abraded or previously wetted with acid, it is 

 evident that the state of surface over which the current passes 

 is closely connected with the phaenomenon ; it seems that it 

 must bear a certain relation to oxygen, or, in the happy lan- 

 guage of Dr. Faraday, be in a state equivalent to an oxidation. 



That a current does pass from it previously to its acquiring 

 the peculiar state, is evident from the slight motion of the 

 needle at the moment the wire first touches the acid ; that it 

 afterwards stops the passage of a current altogether, is shown 

 by the subsequent stillness of the instrument even when con- 

 tact with its cups is rapidly broken and renewed ; and that a 

 slight counter current is sufficient to destroy the, inactive state 

 altogether, is shown by touching it at a single point for a mo- 

 ment with any metal on which the diluted acid exerts an 

 action, and in a still more interesting manner by making the 

 extreme platina and iron wire change places. 



With regard to the " Chemical peculiarity of Bismuth," I 



H2 



