196 



was that the development of lines, taking 

 place as circular magnetism around the 

 primary conductors, was carried out with 

 great speed to the lodgment of the lines 

 in the iron shell or core. Thus all parts 

 of the secondary conductor were cut at 

 almost the same instant, by each line 

 evolved, in its passage to the iron core, 

 the same actions being repeated at each 

 alternation. The great speed at which 

 the lines passed the conductor in such 

 cases, in going to the iron core, left no 

 time during which differences of electro- 

 motive force in parts of the conductor 

 might act to induce eddy-currents. Now, 

 when a coil without an iron core passed 

 through a field, the speed of cutting did 

 not exceed the speed of motion, so that 

 if the lines being cut by a conductor 

 were denser at one point than at another, 

 eddy- currents resulted. Provide the 

 coil with an iron core and the lines re- 

 main in the core until dragged out, as it 

 were, by the movement given to it in 

 front of the field-cores, at which time the 

 lines move through the space between 



