Sentence:  Together they also developed a new form of voltaic cell in which the wooden trough was replaced by one of <WSD>copper</WSD> , thereby producing stronger currents . 
Meaning of the word marked with <WSD> tags:  a ductile malleable reddish-brown corrosion-resistant diamagnetic metallic element; occurs in various minerals but is the only metal that occurs abundantly in large masses; used as an electrical and thermal conductor