334 KENNELLY AND UPSON-HUMMING TELEPHONE. [July 20, 



merely to observational error, but also to variations in the behavior 

 of the transmitter. 



The zig-zag pitch line PORST is found to be somewhat irregu- 

 lar. The slants are by no means regularly parallel. The breaks 

 QTIV are neither regularly elevated, nor regularly spaced. The 

 only substantial regularity is in the spacing along the pitch line 

 G"# of 825 r-'. The intersections of the ascending branches with 

 this line lie approximately 40 cm. apart, at no, 150, 190, 230 and 

 270 cm., or in accordance with the series 30 -f- 40/;; cm., where w 

 is any positive integer. 



As regards the current curve pqrst, its points of minima p, r, 

 V, etc., correspond fairly well to the ascending intersections of the 

 pitch line with the line of G"S 825 ^. The points of maxima q, t, x, 

 etc., occur near to the breaks in the pitch 0, T, W , etc. Minimum 

 primary current was noticed to be associated with maximum micro- 

 phonic activity of vibration. Feeble action in the microphone, on 

 the other hand, was found to be associated ordinarily with increase 

 of primary current. 



Observation Series 2. Effect of Shortening the Tube with Re- 

 versed Receiver Terminals. — Curves //, in Fig. 2, represent the 

 behavior of note pitch and primary current, as the tube was short- 

 ened from 265 cm. to 80 cm., with the terminals of the receiver 

 reversed. Their general characters are similar to those of curves /. 

 The two sets of curves indicate the effect which would be produced 

 by reversing the receiver terminals at any particular tube-length 

 within the above range. Thus, at S, or 220 cm., a reversal would 

 lower the pitch from 870 '—' on curve / to K, at 810 >—', on curve //. 

 On the other hand, a reversal made on curve /, at V, of 825 '—', 

 would raise the pitch to N of 900 —' on curve //, so that whether 

 the reversal produces a rise or fall of pitch depends, in general, 

 upon whether the reversal is effected above or below the mean pitch 

 of G"t, 825 ^. 



The only apparent regularity in the pitch line // lies in the 

 spacing of the ascending intersections with the line of mean pitch 

 G"ff (825 — ■). These occur near to 90, 130, 170, 210 and 250 cm. 

 of tube-length, or according to the series 10 -f- 40?» cm. On the 

 mean-pitch line, the ascending intersections of one curve lie ap- 



