256 PECULIARITIES IN THE MAGNETISM 
employed, it seemed prudent to augment the 
polarizing force still further. I therefore nearly 
doubled the polarizing force last used, in some 
subsequent experiments, but in no case could 
magnetic action be detected when the iron as- 
sumed a high red heat. 
102. I next subjected cylindrical bars of 
wrought iron, highly heated, to the action of 
powerful electric currents, from a voltaic battery 
consisting of eight pairs of cast iron jars and 
amalgamated zinc plates, arranged in a series of 
four double pairs, and excited by a strong solu- 
tion of sulphuric acid. The iron bars were 
placed in a brass tube enclosed in a spiral con- 
ductor, from which it was insulated by interven- 
ing stout brown paper. But, although the iron 
bars, when cold, would display a powerful attrac- 
tive force by virtue of the electro-magnetic action 
of similar currents, not a trace of magnetic 
action on a delicately suspended magnetic needle, 
beyond that due to the spiral, could be discovered 
when the iron was at a high red heat. But in 
these experiments, as in the former, the iron 
gradually. resumed its magnetic functions as it 
cooled down towards blackness. 
