1. This paper is the result of a portion of a research program carried out at the Massachusetts Institute of Technology for the Bureau of Ordnance, Navy Department. Approval for the release of this information has been received from the Chief of the Bureau of Ordnance. Statements expressed are those of the authors and should in no way be construed as the opinion of the United States Navy.
2. Professor of Applied Mechanics, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.
3. Assistant Professor of Mechanical Engineering, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.
4. Instructor, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.
5. P. W. Bridgman, Watertown Arsenal Laboratory Report Number WAL 111∕7-3, October 8, 1943.