90 



(Figs. 15 and 16). The cores of the arma- 

 ture-coils are of porcelain, and the con- 

 ductor consists, as in the Ferranti ma- 

 chine, of a thin copper strip insulated in 

 a similar manner. The distinguishing 

 feature of this machine is the field. It 

 is of the iron-clad description, and the 

 poles on one side are all of the same 

 sign, whilst those on the other side of the 



Fig. 15 Fig. 16 



armature are of the opposite sign. There 

 is only one coil of exciting wire, C, placed 

 as shown in the diagram. The field may 

 be diagrammatically represented by Fig. 

 4. Each group of conductors is fairly 

 concentrated, and the coefficient k for 

 this machine should, therefore, lie be- 

 tween the values given for cases 1 and 3 

 on p. 22. If the conductors were con 



