348 



KENNELLY AND UPSON— HUiMMING TELEPHONE. 



[July 20, 



from 200 to 80 cm. Curves 2 represent the corresponding behavior 

 when the diaphragm was loaded. The primary currents were all 

 unusually large, probably owing to the imperfect adjustment of the 

 transmitter. 



60 80 100 ISO ItO 160 JSO ZOO 



TUBE LENGTH - CENTIMETERS. 



Fig. II. Test of a Transmitter with its Diaphragm Loaded and Unloaded. 



It will be observed that the loading did not appreciably alter the 

 ascending intersections of the pitch lines with the G"S mean- 

 frequency line, which occur in conformity with the series 20 -\-<\om 

 cm. The loading seems to have somewhat lowered the range of 

 pitch as a whole ; or to have modified the conditions at breaking, 

 without materially affecting the conditions at mean-frequency 



(825-). 



A number of trials with further modifications of the transmitter 

 diaphragm substantiated the above stated results. In one case, a 

 new experimental diaphragm of tinned sheet iron, 0.38 mm. thick 



