Smithionian Report, 1964. — Field 



PLATE 2 





/mm 



1. Fractures produced on glass by the impact of a liquid cylinder at 2,400 feet per second. 

 This impact gives a short but intense pulse of pressure which initiates the many short 

 circumferential cracks. These cracks are not found under static or slow impact condi- 

 tions. (Magnification X 13.5.) 



2. The short fractures along the top edge of the glass plate are initiated by the Rayleigh 

 Surface wave caused by the impact of the lead slug. The interval between frames is 2 

 microseconds. 



