KENNELLY AND UPSON— HUMMING TELEPHONE. 



339 



tances between corresponding pairs of breaks in pitch increase as 

 the tube-length is greater, being 4 cm. at A, 9 at B, 11 at C, 13 

 at D, and 15 at E. Although not shown in Fig. 5, owing to limi- 

 tations of space, it was found that these distances between corre- 

 sponding breaks continued to increase until they reached about 20 

 cm., after which they shortened again to commence a new expand- 

 ing series. , 



^O 100 JW JZO I30 NO 



TUBE LENGTH - CENTIMETERS. 



Fig. 6. Humming Cjxles with Cyclic Changes in Tube-length. 



Observation Scries 4. Effect of Alternately Reversing, or Re- 

 ciprocating, the Motion of the Tube. Humming Cycles. — If, when 

 compressing the telescopic tube, and when the note broke from a 

 higher to a lower pitch, the tube was immediately extended again, 

 the note would continue to lower in pitch for a little while, and then 

 break back to a higher pitch. By moving the tube in and out, like 



