steel ellipsoidal shells. The solid line, therefore, represents the upper 

 bound of experimental results, and the broken line represents the lower 

 bound for tests of shells with various initial imperfections. It can be 

 seen from Figure 2 that spherical glass shells should always be considerably 

 more efficient than long cylindrical shells and should also be more 

 efficient than stiffened cylindrical shells for a considerable portion of 

 the ocean depth. Tests of spherical glass shells are required to verify 

 these calculations. 



Many unknowns must be determined before glass may seriously be con- 

 sidered as a hull or float material. Specif icaJ-ly, tests must be conducted 

 to study cyclic strength, creep strength, impact strength, and the combined 

 effects of marine atmosphere, interior flaws in the glass, and surface 

 imperfections. Tlie present study demonstrates, however, that in addition to its 

 excellent transparency properties, glass has a very high strength-weight 

 ratio when under favorable compressive static loads, as created in a 

 cylinder under external- hydrostatic pressure. 



RECOMMENDATIONS 



The utilization of glass spheres imbedded in a plastic matrix as 

 float material and appendages should be studied. 



ACKNOWLEDGMENTS 



The author wishes to express his appreciation to Mr. Eo E. Johnson, 

 Head, Ship Structures Division, for his initial and continued interest in 

 this project and to Mr. L. J. Ginffreda for conducting the hydrostatic 

 tests . 



