1908.1 



KENNELLY AND UPSON— HUMMING TELEPHONE. 



345 



steadily reduced from 260 to 70 cm., with batteries of 3, 4 and 5 

 storage cells, respectively, in the primary circuit (6.5, 8.5 and 10.5 

 volts). The transmitter, induction coil, receiver and transmitter 

 were all as in Figs, i to 6. It will be seen that the primary cur- 

 rents have their respective maxima and minima in substantial agree- 

 ment, the range of variation being naturally greatest for the largest 

 battery, and least for the smallest. The ascending intersections of 

 the frequency line with the mean-frequency line of 825 — are the 

 same throughout, and conform to the series 30 -{- 4o;;z cm., in agree- 

 ment with line / of Fig. 2. The breaks in pitch do not all coincide ; 

 but the differences in this respect are not great, nor can it be said 



80 100 120 IW /60 ISO ZOO 220 ZtO Z60 



TUBE LENGTH - CENTIMETERS. 

 Fig. 9. Frequencies and Primary Current Strengths for Dififerent Condensers 

 in Secondary Circuit. 



that the biggest battery always produced the most retarded break. 

 Moreover, excepting perhaps the break at 240 cm., the variations 

 in breaking points are within the limits of variation obtained in suc- 

 cessive series with one and the same battery. 



Observation Series 7. Effect of a Condenser in the Secondary 

 Circuit. — It was found that a certain magnitude of condenser 

 capacity inserted in series in the secondary circuit had a marked 

 effect on the behavior of the humming telephone. The results are 



