CHAFFEE. — IMPACT EXCITATION OF ELECTRIC OSCILLATIONS. 305 



tions in one train or the damping can be varied at will. The damping 

 is evidently exponential in fulfilment of the familiar theory. 



Cuts c-f of Plate 5 and cut a of Plate 6 are the results of adding to. 

 the arrangement of circuits just considered, a second secondary cir- 

 cuit, excited by the primary discharge and with its deflecting coil 

 placed parallel to that of the first secondary. There results, therefore, 

 a doubly-periodic secondary system having two secondary circuits 

 inductively coupled together. The doubly-periodic secondary oscilla- 

 tion gives the beats and curious figures shown. Cuts c and d are due 

 to the addition of two oscillations differing widely in frequency. As 

 will be seen from the description of the figures, the second oscillation 

 is m one case over twice and in the other case almost three times the 

 frequency of the main secondary oscillation. 



Cut a of Plate 6 shows beats taken with almost undamped oscilla- 

 tions. The wave lengths are not recorded but they were probably of 

 the magnitude of 100 meters. 



(6) Damping in a Circuit Containing a Spark Gap. 



When the dissipation of energy in an oscillatory circuit is propor- 

 tional to the square of the current, as is the case in a constant resist- 

 ance, the damping is exponential. If, however, the resistance is a 

 function of the current the energy dissipation is no longer proportional 

 to the square of the current, and the damping no longer exponential. 

 For instance, the resistance of a spark gap or arc is a function of the 

 current, the resistance being greater the smaller the current through 

 the gap. 



Richarz and Ziegler* in 1900 observed, in a revolving mirror, the 

 straight line deflection which is produced in a Braun tube when a con- 

 denser is rapidly discharged across a spark gap and through the de- 

 flecting coil. The frequency of the oscillations was very low. On 

 account of the impossibility of taking a photograph, we have only their 

 description of the phenomenon as seen in the revolving mirror. In 

 appearance the figure resembled the backbone of a fish, or, in other 

 words, a long straight line, due to the undeflected spot, and at intervals 

 along the line pairs of equally inclined short straight lines, as one 

 would indicate an arrow point. The short lines were due to the more 

 intense maximum deflections during a train of oscillations, the separate 

 oscillations being entirely undiscernible. The results showed that the 

 damping due to a spark gap is not exponential but approximately 

 linear. 



9 F. Richarz u. W. Ziegler, Ann. d. Phys., 1, 468, 1900. 

 VOL. XL VII. — 20 



