ST. JOHN. 



WAVE LENGTHS OP ELECTRICITY. 



227 



secondary disks so near to the plates of the vibrator, so that the wave 

 length found under these conditions is not due to the simple Hertzian 

 vibrator, but to a very heavy complex oscillating system with some- 

 what obscure internal reactions. Lecher calls attention to the change 

 in the sound of the spark when the two parallel wires of the secondary 

 circuit are bridged across by a conductor, and there is a very marked 

 difference in the spark when the secondary circuit is removed entirely, 

 the spark losing much in body and explosive character. The second- 

 ary under these circumstances must exert a strong reaction upon the 

 primary. 



It seemed desirable to devise some arrangement depending more 

 directly upon the principle of electrical resonance, and one whose use 

 would not increase the capacity of the vibrator and whose reaction 

 upon the vibrator would be a minimum. This was accomplished by 

 omitting the secondary disks and using simply one wire, as shown in 

 Figure 3. 



O 



^'59 cm 



p 







R 



S 



Fig 3 



The secondary circuit consisted of the long rectangle P Q R S, 

 which was carefully adjusted to resonance by placing the exploring 

 terminals of the bolometer (described later) at P S, and then cutting 

 off the ends of the wire until the length was found that would give 

 the maximum effect. Such a maximum was found when P Q was 

 859 cm. long. The maximum was sharp and unmistakable, the effect 

 falling off rapidly when the wire was either lengthened or shortened. 

 The result is shown graphically in Figure 4, where, as in all the curves 

 given, distances from Q are used as abscissas and deflections of the 

 galvanometer as ordiuates. 



