We will mention three distinct forms of couples which 

 will help us to understand the subject 



ut an at c from a sheet of 20 gauge sheet 



Iron (Fig. 2), say 2% inches high by 3^ to 4 inches long, 







and 3/16 to j inch wide. Take the bottom cm! ami tv 

 into a coil (Fig. 3) ; pour the Zinc-antimony into it, and 

 have the two metals in combination. 



. 3. 



