FURTHER STUDIES OF GLASS FRACTURE WITH HIGH-SPEED PHOTOGRAPHY*

Photoelastic photographs, with exposures of approximately one-millionth of a second, were taken of transient stresses in glass before, during, and after fracture. The longitudinal and transverse waves in glass have been photographed and their velocities measured (18,000 and 11,000 ft. per sec, respectively). It was also found that under special conditions cracks may travel slower than .5000 ft. per sec, the value previously given as the crack propagation velocity.