Electrical Oscillations in Air. 



333 



other ; so that if an error was made in the setting of the cross- 

 hair on the image of one discharge — for example, making the 

 measurement of that oscillation large — a corresponding 

 amount would be deducted from the measurement of the next 

 oscillation. The result of this would be that if the apparent 

 variations were due to errors in measurement, the periods 

 of discharge would be alternately large and small, or at least 

 as often and as far below the theoretical value as above it. 

 But this is conspicuously not the case. 



A consideration of the curves which represent our results 

 shows that with quick oscillations which result from the em- 

 ployment of a small air condenser, the air dielectric did not 

 have time to recover completely, in the time of one oscillation, 

 from the strain to which it was subjected. With the larger 

 air condenser, the oscillations being slower, more time was 

 given for this recovery, and hence the periodicity which we 

 have discovered was not so marked. It seems, therefore, that 

 not only should an electrical resonator be turned for capacity 

 and self-induction, but also for a certain periodicity of strain 

 in the dielectric. 



In the case of glass, we should not expect to obtain evidence 

 of this periodical recovery from a quick strain, since it is 

 well known that the recovery from strain is so slow that the 

 discharge from a Leyden-jar is incomplete after a discharge 

 lasting a second. The curve we give for glass (fig. 7) shows 



j. 7. 



that this periodical recovery is too slow to manifest itself 

 during the time of quick oscillation. 



It is perhaps unnecessary to call attention to the fact that 

 the capacity of a dielectric for rapid discharges is very diffe- 

 rent from its capacity for slow discharges. In the paper of 

 Lorenz, already cited, the value of the dielectric capacity of 

 glass was determined by slow methods, and used to test an 

 equation in which the capacity of glass appears under very 

 rapid charging and discharging. 



Phil. Mag. S. 5. Vol. 30. No. 85. Oct. 1890. 2 A 



