1394 
II. OUTLINE OF SHOOTING PROGRAM 
For the shooting which is here reported, pentolite was 
chosen because of its availability and the ease with which it 
may be cast in spherical molds, Spherical charges were used 
throughout to obtain pressure fields as nearly symmetrical as 
possible, The first series of shots, with 250 gm charges, was 
done in sea water immediately off the Oceanographic Institution 
dock at Woods Hole. A horizontal boom (Fig. 1A) was suspended 
above the surface and from it a vertical rod was projected down 
into the water. On this rod were mounted three piezoelectric 
gauges, 1, 2, and 3 ft below the surface. Farther along the 
boom, a pair of movable spreaders held the charge 2 ft below 
the surface at any desired horizontal distance from the gauges, 
With this rig, shots were fired at horizontal charge~to~gauge 
distances that varied from 4 to 45 ft. 
During this series, the surface of the water was somewhat 
rippled even on the very calmest days, and therefore the depth 
measurements could seldom be made with an accuracy better than 
3 or 4 in. This was one of the reasons that subsequent shooting 
was done at a fresh-water pond on Nonamessett Island. Because 
of the shelter afforded by nearby high ground, a good calm pre- 
vailed on the pond and, except on the windiest days, the ripple 
was less than an inch high. 
At the pond, charges and gauges were mounted on a ring 
(Fig. 1B). Three uprights were bolted to the ring to serve as 
depth indicators. Brightly colored lengths of thin wire were 
strung between the uprights and drawn as tight as possible. 
Gauges and charge were mounted any desired number of inches 
below the wire, and the ring was lowered into the pond until 
the wire just broke the surface. Because the wire was light 
and tightly strung, there was no appreciable sagging, and the 
gauge and charge depths could be measured accurately to within 
one quarter of an inch. 
With this rig, a series of shots was made with charge and 
gauges all at the same depth, with the depth varying from 
4 to.12 in. beneath the surface, and a charge-to-gauge distance 
of 45 in. A second series consisted of shots at the 4 in, depth 
with gauge distances of 30, 45, and 60 in. All of these shots 
were made with 250 gm charges. One group of 500 gm charges 
was also used, at a depth of 5 in. and a gauge distance of 
TOPs 
It. was further desired to observe the pressure directly 
below the explosive source, but this would have required 
extensive revision of the existing set-up. Instead, a vertical 
support was mounted on the ring and extended 3 ft beneath it 
By means of this support a gauge could be mounted off to one 
side and about 30 in. deeper than the charge. 
De 
