MOTION OF THE GAS SPHERE 



S47 



ward velocity of 180 ft. /sec. during the contraction and shortly later 

 came in contact with the boat. 



The most spectacular result of all was obtained when the charges 

 were fired midway between steel plates. If these were twenty-four 

 inches apart, the bubble was not affected appreciably. For a twelve 

 inch separation, the bubble expanded spherically, but as the contraction 

 phase set in, it began to stretch out toward each vertical plate, and two 



DISTANCE FROM WALL (inches) 



Fig. 8.23 Migration of the bubble from a detonator placed nine inches from 



a vertical wall. 



or three milliseconds before its maximum contraction divided rapidly 

 in two globes, one for each rigid surface, so to speak. The two globes 

 contracted separately and moved rapidly toward the two plates where 

 they expanded in contact and flattened out again. This bubble division 

 was found to be critical to charge position, deviations of one-quarter of 

 an inch from exact centering causing the bubble to move intact toward 

 the nearer plate. This result is not surprising in view of the strongly 

 distant-dependent nature of the phenomenon. 



Although Campbell's results give a beautiful confirmation of the 

 predicted effects of surfaces on bubble displacements, they are not well 

 suited to comparison with theory owing to the very small size and un- 



