QUARTZ CRYSTAL PLATES 



525 



are slightly different in character. The curves for this case are 

 illustrated by Fig. 9 which shows the wave-lengths of this system as 

 a function of the tuning of circuit group No. 2. Fig. 10 shows the 

 wave-lengths at which a parallel cut plate will oscillate plotted as a 

 function of the width. The similarity between this experimentally 



TUNIKir. CtP NO. I 



Fig. 8 — Wave-lengths of the system of coupled circuits of Fig. 7 as a function of the 

 tuning of circuit No. 1, the tuning of circuit group No. 2 being fixed. 



determined curve and Fig. 9 is at once apparent. There is one 

 anomalous segment of a curve between the 7th and 8th harmonics, 

 the Hne AB\ but it is possible that this is caused by the coupling of 

 some third free period which has not been considered, perhaps a high 

 order harmonic of a flexural vibration. In general, however, the 

 curves of wave-length versus thickness for these crystal plates are of 



