Electric Waves along Wires. 



657 



The amount of demagnetization of the detector-needle was 

 observed for different positions of the bridge along the parallel 

 wires. Alternate readings were taken without a bridge, so 

 that any variation in the intensity of sparking could be cor- 

 rected for. 



The corrections were, however, very small. 



Fig. 3 shows the curve obtained by plotting positions of 

 the movable bridge measured from A and A' as abscissae, and 

 amounts of demagnetization of the detector-needle for those 

 positions of the bridge as ordinates. 



a. -=< 

 a eg 

 3 S 



% a 



















Fig. 



3. 























1 





























































































































































:t 













: 

































.. 



1 

























30 





















1 









































/ 





\ 





/ 



V 



A 







/ 



i 



| 



\ 









/ 



15 





\ 



/ 



V; 



* \ 





t^u ^ 



/ 



L. 



J 



V 



\/ 





^y 



/ 



























V 



\r* 







100 



200 



300 400 500 600 



Distances of the bridge from A (fig. 1) in centimetres. 



700 



It was found that there was a maximum of demagnetiza- 

 tion when the bridge BB' w r as in such a position that the 

 lengths of the two circuits SABB'A'S' and BKRK'B' (giving 

 the capacities at S and S' and the portions of wire SA and 

 S'A' an equivalent length along the parallel wires) were in 

 the ratios of small odd to even numbers. The movable bridge 

 BB' was included in both circuits. 



The equivalent length of the capacity and wires SA and 

 S'A' was obtained from the observation of the position of the 

 most sharply-defined maximum which corresponded to the 

 simplest possible ratio 1 : 2. 



The total length of the circuit BKRK'B' being known, 

 that of the circuit equivalent to SABB'A'S' was determined 

 by this ratio of the lengths, and hence the equivalent value of 

 the capacity and curved portion of the wire w T as obtained. 



