Discharge in a Magnetic Field. 



249 



The phenomena were the same whether the alternate 

 current from an induction-coil, or the alternate current pro- 

 duced by the alternator, was used, so far as the visible effects 

 were concerned. 



When a tube, as shown in fig. 2, 300 millims. long and 25 



Fio:. 2. 



»^u 



^ 



millims. in diameter, containing brush electrodes at each end, 

 is placed between the poles of the unexcited large magnet (see 

 fig. 3) and has a very small alternate current traversing it, 



Fiff. 3. 



rfk\ 



M/> 



the bands are produced in the usual way. Now excite the 

 magnet, the switches having been so adjusted that one pole is 

 N. and one S., a great change is now observed within the 

 tube, If the E.M.F. of the current is very small, the bands 



