CH. v.] DIRECT PROCESS 55 



coil T, whose terminals lead respectively to the 

 cathode C and to a ring-anode A. 



Ley den jars I and J can be excited by a Ruhm- 

 korff coil, or in any ordinary manner, and they 

 discharge across the spark-gap G. Thereby a sub- 

 sidiary oscillating circuit, of very high frequency, 

 characterised by the condensers H and K, and 

 limited t6 the region above the spark-gap G, is 

 set in action ; and an oscillatory discharge is con- 

 veyed to the symmetrical terminals PQ, whence it 

 can pass round a pair of wire loops in parallel, MN 



S 



FIG. 7. Enlarged portion of fig. 6, showing the vibration of the 

 cathode rays by an alternating circuit and the adjustment of their range 

 of excursion by a fixed magnet. 



and M'N'. The effect of the alternating field, thus 

 generated in the loop MN (fig. 7) is to wave the 

 cathode rays rapidly to and fro, so that only in the 

 middle of their path will they pass through the 

 aperture in the disk B the effect on the distant 

 phosphorescent screen being then quite faint. But 

 if a permanent magnet D is applied to them, the 

 oscillation is deflected, and can be limited to the 

 region between the centre and the circumference of 

 the disk as illustrated by the figure; thereby a 

 greater number of rays get through, and the screen 

 becomes more luminous than when the magnet is not 

 applied, because the aperture will now be at the 

 -extremity of the swing of the oscillating rays. If 



