Normal-pressure tests were made of 56 rectangular plates with clamped edges and of 5 plates with freely supported edges. Pressure was applied and the center deflection and the permanent set at the center wer measured. For some of the plates, strains and contours were measured in addition.

The observed realtion between center deflection and pressure for the plates with clamped edges was qualitatively in agreement with thoery in that the deflection and then increased more slowly as the membrane stresses became important. Quantitative agreement within plus or minus 10 percent for the linear portion of the deflection-pressure curve was obtained for only about one-fourth of the plate. The deviations for the rest of the plates were ascribed to deviations from the theoretical clamping conditions at the edges.

With the beginnings of permanent set both the total deflection and the permanent set at the center of the plates with clamped edges increased linearly with the pressure for most of the plates. Extreme-fiber strains measured at the center of three square plates were in approximate agreement with calculated values.