1453 
disturbance should reach the gauge for r = 26.3, that is for 
34.4" under the test condition. This corresponds to Wr = 0.56 
which is marked in Fig. 7B and is in fair agreement with the ex- 
perimental results. 
A much better check of the calculations is possible if 
the following experimental result is considered which was pre- 
sented in Ref. 4 and which is repeated in Fig. 8. A spherical 
shockwave propagates from the lower side of the picture. A plate 
out of plastic material, hard sponge ebonite with cellular con- 
struction containing air bubbles and an overall density < 0.l, 
is arranged above the charge (see Fig. 8). When the spherical 
shockwave hits the plate, a sudden disturbance (attenuation) is 
produced in the shockfront which should propagate according to 
the theory described above. 
The observed wavefronts at that test are drawn as thin lines 
in Fig. 7; they are no longer circles but are additionally curved 
near the material presenting the surface. The attenuation propa- 
gates along the wavefront decreasing the peak pressure, thus de- 
creasing the speed of propagation. The evaluation of these wave- 
fronts results in the curves of equal peak pressure, which are 
dravn on Fig. 8 as solid lines. They show that a range of dis- 
tortion exists which increases with increasing distance from the 
charge. 
With the undistorted peak pressure known for different 
distances by the spherical behavior of the undistorted curves of 
25 
