706 



ELECTRO-MAGNETS. 



cule. A more correct representation of this state is 

 that in fig. 357 A, which at. the same time exhibits the 

 effect of the current flowing through one of the coils 

 of the spiral (represented by the outer black arrow) in 

 causing the Amperian currents (represented by the 

 small white arrows) to flow all in the same direction 

 and parallel to itself. If we carefully inspect the 

 direction of the currents, first in the central molecule, 

 and then in each of the molecules adjoining it, we 



FIG. 357. 



shall see at once that everywhere the adjacent parts of 

 the current in two adjoining molecules flow in opposite 

 directions. For example, on the right side of the 

 central . molecule the current descends, while on the 

 left side of the adjoining molecule on the right it 

 ascends; in the upper portion of the central molecule 

 the current flows from left to right, in the lower portion 

 of the adjoining molecule above it, it flows from right to 

 left, and so on ; in every two adjoining portions of two 

 molecules the currents oppose one another, and con- 

 sequently cannot exercise any external action. This 

 is not the case with the surface ; there the outer portion 

 of each molecular current is no longer in close vicinity 

 to another opposite current, and its action is therefore 



