﻿of Electrical Waves on Iron Wires. 



443 



capacity of the circuits. This want of isochronism may have 

 been due to irregularities in the hard rubber condensers which 

 I employed. This, however, does not seem probable. The 

 condensers were made of sheets of hard rubber one eighth of 

 an inch in thickness, covered with tinfoil, and the set of 

 condensers in the time circuit did not differ geometrically 

 appreciably from the set in the trial circuit. The electrical 

 disturbance on such a connected system is evidently a com- 

 plicated one when its various reactions are considered, and the 

 statement given by Hertz, which I have quoted, must be 

 modified if there is any capacity in the circuits of the two 

 Ruhmkorf coils which have a common primary. 



The capacity in the time circuit was the same geometrically 

 as that in the circuit which included the wires under examin- 

 ation. A suitable amount of self-induction was placed in the 

 time circuit. To ascertain whether the time circuit could be 

 relied upon, I made many measurements of the ratio of the 

 oscillations in the time circuit to those in the trial circuit, 

 which contained copper wires and the same geometrical 

 capacity. I had no reason to suspect a change in the self- 

 induction in my time circuit ; a change might occur, however, 

 in the capacity of the indiarubber condensers, due possibly to 

 hysteresis from electric strains and deformations. I could not 

 detect, however, such effects. I was dealing with single dis- 

 charges, not repeated ones, such as are employed in obtaining 

 wave-lengths along wires, and the photographs of such single 

 discharges showed no evidence of inconstancy in the capacity 

 of my condensers. If there was any effect of electrical hys- 

 teresis, it affected my time circuit and my trial circuit alike. 



As an example of the degree of accuracy which can be 

 obtained in the measurement of the distances between the 

 oscillations on the negative, the following table is given. 

 The distances between different numbers of oscillations is 

 given in the first column and the average length of the oscil- 

 lations is given in the third column. 



Distance in millim. 



between the first and 



last oscillations. 



Number of oscillations 



included in this 



distance. 



Average length of 

 oscillations in millim. 



22-5 

 26-1 

 300 

 151 



6 



7 

 8 

 4 



375 

 373 



374 

 3-77 



•1 11 ■> 



