612 
42 
initially on testing the performance of the tourmaline gage rather than that 
ef the other gages. The recording facilities at Woods Hole were generously 
made available. The overall frequency response of the cable and amplifier 
was good to 300 kilocycles per second. 
PRESSURES IN OPEN WATER 
A welded ring 9 feet in diameter of 1 1/2-inch steel pipe was used 
for the mounting of charges and g&ges; see Figure 25. The charges, which 
Figure 25 - Welded Steel Ring Used for 
Mounting Charges and Pressure Gages 
This ring was used by TMB personnel in tests at 
the Underwater Explosives Research 
Laboratory at Woods Hole. 
ranged from 50 to 250 grams of loose 
tetryl, were placed in the center of 
the steel ring. The gages were 
mounted in the plane of the ring. 36 
inches from the charge. The charge 
and the gages were secured by verti- 
cal and horizontal wires. The wires 
in turn were attached to vertical 
steel rods passed through drilled 
holes in the 9-foot ring. 
Three gages and recording 
channels were ordinarily employed; 
these gave at least two good records 
for each explosion. Two of the 
gages were usually the TMB copper- 
cable tourmaline type, whereas the 
third was a similar tourmaline gage 
mounted on a Belden 8400 rubber- 
sheathed cable; the latter gage was 
supplied by the Underwater Explosives 
Research Laboratory. The tetryl was 
detonated by firing a Number 8 deto- 
nator cap placed in the center of 
the charge. 
Figure 26 shows photograph- 
ic reproductions of some typical rec- 
ords. Table 5 summarizes some of the 
results obtained. Peak pressures re- 
corded by the two types of gages gen- 
erally agreed within 3 per cent. The average deviation of the pressures 
recorded by a single gage was also about 3 per cent. 
After the consistent operation of the tourmaline gages when used 
with charges of this size had been established, it was decided to test their 
