198 



to the incoming core, producing a weak 

 field between the two composed of few 

 lines moving at great speeds. Figs. 42 

 and 43 represented the two conditions 

 comparatively. Fig. 42 showed a coil 

 without core cutting lines between N and 

 S ; and Fig. 43 the progressive move- 

 ment of coils with iron cores through 

 the field. The rapid movement of the 

 lines backward across the space between 

 the iron armature-cores, or projections, 

 II, Fig. 43, as the armature moved for- 

 ward, pointed also to the necessity for 

 lamination of the field-poles when such 

 cores or projections were used. The 

 turns of armature-conductor nearest the 

 enclosed iron core would be subject to 

 eddy-currents, on account of the field 

 density being made more irregular by 

 the bending of the lines leaving the iron. 

 He was of opinion that the use of "horns " 

 on pole-pieces was not akin to the effects 

 just mentioned, excepting in so far as the 

 entering and leaving field was more 

 spread out or graduated in density, and 

 so placed the parts of a large section 



