MAGNETIC ACTION PKODUCED BY GALVANISM. 209 



each plate, the qualities of the two currents being differ- 

 ent: and we shall sometimes, for convenience of language, 

 speak of a "zinc current" and a "graphite current." 

 Mechanically, the effects of such currents passing in 

 the same direction may be considered as + and : but 

 when (as when originating from opposite ends of one 

 wire) their directions are opposed, their effects are 

 added together. 



The simplest magnetic action produced by a gal- 

 vanic current is the following. The current as in 

 Figure 64 will deflect the red end of the needle from 



Fig. 64. 



the reader's eye. The current as in Figure 65 will 



Fig. 65. 



deflect the red end towards the reader's eye. The 



14 



