CHAFFEE. — IMPACT EXCITATION OF ELECTRIC OSCILLATIONS. 273 



spectrum appears with an occasional weak flashing-up of a few of the 

 ahiminum lines. Plate lb gives the discharge spectrum with an 

 aluminum comparison spectrum. The nature of the discharge will be 

 considered more in detail in Part II, but it is evident from the figure 

 that the metals are not vaporized, and the indications are that the 

 conduction is entirely by gaseous ionization. 



140 



180 



100 



80 



60 



5 40 



iij 

 < 



UJ 



a: 



O 



X 



20 



LENGTH OF GAP 



Figure 4. Effect of Changing Length of Gap. 



lo = .335 ampere. 

 \o = 106 meters. 

 C\= 112 X 10-5 M./. 

 C2= 60 X 10-5 m/. 



When the secondary oscillations are examined by means of a wave 

 meter, but one wave with exceedingly sharp tuning is observed. On 

 account of the steadiness of the oscilliations it is often difficult to set 

 the wave meter — which makes use of a telephone receiver as the de- 

 tecting device — without the use of a chopper or interrupter in the 

 wave meter circuit. 



• The change in wave length of the secondary oscillations with chang- 

 ing supply current is very much less than is observed with the Poulsen 

 and Lepel generators. This point is, however, more profitably con- 

 sidered later, after a better understanding of the action of the gap has 

 been gained. 



In order to show the effect on the intensity of the secondary oscilla- 

 tions of varying the length of the gap, the curve shown in Figure 4 

 was taken. It is seen that the intensity of the secondary current, as 

 measured by the hot-wire ammeter, does, to some extent, depend upon 

 the length of the gap, but not to the extent that might be expected. 

 At 0.19 mm. the secondary current is a maximum, but at about this 



VOL. XLVII. — 18 



