4:86 Dr. D. A. Keys on a Piezoelectric 



obtained. Figure 11 shows the carves drawn from one of 

 these plates. A represents the pressure on the first vessel, 

 that on the second, and B the reflected wave from the 

 bottom recorded on the first vessel. The reflected wave 



Fiff. 11. 



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Tfme ?T) Secovds 



recorded by the second vessel was also obtained on some 

 plates. The vessel B was a larger one than A, which 

 accounts for C being greater than A in figure 9. Table III. 

 gives the result obtained in this way. The results show that 

 the velocity varies with the charge. The error in the time 

 measurement is less than 4 per cent., which is the maximum 

 variation found in the alternating current used for the time 

 co-ordinate in these experiments ; but the variation was 

 seldom more than 1 per cent, on any particular day. The 

 frequency was taken before each experiment. 



Table III. 



Plate No. 



141 ... 



142 ... 



148 .., 



149 ... 



150 ... 



Velocity in feet 

 per second XlO~" 



5-0 

 49 



4-6 



5-4 



5-7 



ATerage^S'l 



