92 



ever, for greater convenience of manufact- 

 ure, arranged in two halves, C C. Fig. 

 19 shows diagrammatically the relative 

 position of armature-coils and field-poles 

 straightened out. It will be seen that 

 the lines of force, which are shown dotted, 

 have an oblique course, and that only 

 one-half of the wire in the armature-coil 

 is at any time in the position of greatest 

 activity. The width of the field, when 

 making due allowance for the fringe of 

 lines which surrounds the actual contour 

 of the pole-piece, is somewhat greater 

 than the pitch ; whilst the proportion of 

 space on the armature, occupied by the 

 winding, varies with the radial distance 

 at which it is measured. On the inside 

 of the armature nearly the whole space 

 is so filled, whilst on the outside a little 

 less than half the space is occupied by 

 the coils. For the outside of the arma- 

 ture the coefficient k will, therefore, be 

 nearly that corresponding to case 3 on 

 p. 22, and for the inside it will be rather 

 less than that of case 2. The actual 

 mean value of the coefficient should 



