1485 
The bottom of Vineyard Soud in this region is of firmly 
packed sand and is relatively smooth. Fathometer traverses show 
fairly gradual rise and fall of the order of 5 to 10 ft. over 
horizontal distances of the order of a few hundred feet. 
The range, or horizontal distance between charge and 
gauges, was obtained by timing the interval between charge 
Getonation and arrival of the primary shock wave at the gauge 
position. This time interval was then converted to distance by 
using the value of sound velocity in sea water of the salinity 
and temperature obtaining at the time of the experiment. 
3.2 Sample experimental records for a variety of conditions are 
shown in Figures 2 and 3. The first event on all of these records 
is the incident exponential shock wave; the subsequent distur- 
bances are reflections of successively higher order. In Figure 
3, the emphasis is placed upon the comparison of theoretical and 
experimental curves for the first bottom reflection, denoted by 
BR, for various angles of incidence. It is believed that the 
critical angle for total reflection Ue) is about 58° for these 
experiments. Taking the density ratio fa /P, to be about 2.7%, 
the velocity ratio Co/Cy appears to be roughly 1.15. 
The theoretical curves in Figure 3b are plotted at 15° 
intervals of the angle E€ . The adjacent experimental curves 
% 
Information supplied by Dr. Henry Stetson of the Woods Hole 
Oceanographic Institution. 
