181 Dr. D. A. Keys on a Piezoelectric 



that reflected from the bottom. Many oscillations were 

 present as shown by the dotted lines, the position and number 

 varying with the charge and particular detecting vessel used. 

 The cause of these oscillations was not definitely settled, but 

 the general nature of the wave is the same in each case. In 

 figure 9 is shown the tvpe of wave produced by the explosion 

 of a small charge of T.N.T. There are signs of oscillations 



Fig. 9. 



•001 -002 -Oil -012 -013 -014 -0/5 -016 -017 

 T/'/r>e, Seconds, 



Time-Pressure Curve for Explosion of 2\ lb. of T.N.T. 

 One cm. displacement = 1600 Ib./sq. inch. 



in this case too, though they are not so marked. The pres- 

 sure is not sustained so long with T.N.T. as with guncotton, 

 but the maximum pressure is greater. As before, A is the 

 direct wave and B the reflected wave, the charge being 

 12 feet from the detecting vessel in both cases. 



As an example of how the individual explosions agree 

 among themselves, a few readings of the maximum pressures 

 are given in Table II. Figure 10 represents the relations 

 between distance and maximum pressure for equal charges 

 of dry guncotton. The pressure appears to fall off in- 

 versely as the distance from the explosion within the range 

 examined. 



