574 



h^-'n[i-f' (8.1) 



where Aw^ = maximum radius for n-th oscillation (ft) 

 ff = charge weight (lb) 

 Zq = H + 33, where H is the depth of the charge in ft. 



The values of J-j_ are shown in the last coliomn of the tables. 



TABLE XVI 



FIRST MAXIMUM BUBBLE RADIUS, PRESSED TETRYL 



Charge Weight: 0.0558 lb 



Shot Number Depth Aj., 



(£t) (in.) 



E15 380 



E16 380 



E17 196 



E18 33U 



E19 3U 



E20 347 



E22 205 



E23 207 



Average 12.8+0.25 



B. Radii Close to a Free Surface . Photographs of the bubbles from 

 25 gm tetryl charges described under period mea3\irements (Sec, 5) were 

 measured, and radius-tirae c\u:-ves drawn. Tne resulting niaxlmum radii are 

 given in Table XVII together with the values of Jj^. 



The precision of measurement is less for these shots than for the 

 previoi:is ones despite the superior definition of the bubble surface 

 occasioned by back lighting in this instance. The scale used was a 

 12 in. transparent ruler, with the 1 in. squares on the ends blackened. 

 This was rather Indistinct in the photographs, and checks of the 12 in. 

 against the 10 in. distance often disagreed by as much as 2-4$. Another 

 indication of possible errors appeared when a check of the bubble radius 

 was made from the optical characteristics of the system euid differed from 

 the above measurement by 2-3/K. The overall accviracy in the radius measure- 

 ment is probably no better than 3-4$. The greatest difficulty comes from 

 the fact that only part of the circumference of the bubble is visible in 



-18- 



