Sentence:  Beccaria had almost stumbled on a lead to the relationship between electricity and magnetism when a discharge from a Leyden jar was sent transversally through a piece of watch spring <WSD>steel</WSD> making its ends magnetic . 
Meaning of the word marked with <WSD> tags:  an alloy of iron with small amounts of carbon; widely used in construction; mechanical properties can be varied over a wide range