Mapping the Magnetic Field. 



379 



disc magnet shown in fig. 8. The leakage indicated by the 

 lines at the right of the figure is due to the iron base upon 

 which the fields were mounted. 



,A1 



Fig. 8. Disc Magnet. 



Figure 10 is the field of a small motor of the common horse- 

 shoe type. 



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Both figures 9 and 10 were obtained by removing the arma- 

 ture and one bearing so as to make it possible to place the 

 plate within a short distance of the field, at right angles to the 

 armature shaft. 



