806 
a Gh 
(f) Repeat test - firing against cable. 
This was similar to test 1(1), except that the end of the cable 
(a different sample) immersed in the water was sealed with a paraffin-wax 
vaseline insulator. The resylt on firing however was the same. The 
cable again proved itsolf immune to signals as a result of pressure changes 
in the wator. 
EXPERIMENTAL WORK: PART 4. 
When this stago of the experimental work had been reached, the 
method of construction desoribed in Appendix 2 had been evolved. Briefly 
this consists in sintering silver at a high tenporaturo onto the orystal 
faces, soldcring small conncoting copper tags to the faces and enveloping 
the whole gauge in a very thin film of speoial rubberoid wax. The space 
between the cable ond and the basc of the gaugo is filled with this wax, 
and the whole gauge aftor dipping in natural latex is oured at a modoratoly 
low temperature. 
Rosults with single=ply }' e x 4" thick. 
Plate 8, Records 1 and 2 are typical face-on and edge-on records 
of the prossuro pulse of the explosion wave. The only point to emphasise 
is the overshoot of the peak pressure in the face-on direction which 
amounts to about 65% of the true peak pressure for this relative large 
thiokness of gauge. 
(b) (i) Results with single-ply 3" gauge x 4" thiok. 
Typical face-on and edge-on records are shown on Plate 8, Reoords 
3 and 4, and attention is again draw to the overshoot on the face-on 
record, which now amounts to about 20% only. 
(ii) Amplificr changes. 
Further face=-on signatures are shown on Plate8, Records 5 and 6. 
In Record 5, a change was made in the amplifier, reducing the flatness of 
its high frcequenoy response from 550 kc/s to about 300 ko/s, whercas in 
Record’ 6, the response was flat up to about 20 kc/s only. 
An overshoot of about 15% is still present in Record 5; not only 
also is the peak rounded very considerably in Record 6, but tho time of 
rise of the wave front is lengthened. 
These records confirm that to avoid a reduction in the recording of 
peak pressures, the amplifier must havo a suitably high frequenoy response; 
and, for faithful determination of peak pressures the gauge must not be 
direoted face-on to the prossure wave. 
(c) Results with single-ply 3" gauge x 1/16" thiok. 
Typical face-on and edge-on records are shown in Plate 9, Records 
{1 and 2 respectively. 
(4) (i) Results with single-ply 3" gauge x x" thick from 
yarious G ATZES+ 
On Plate Reoords 3, 4 and 5 indicate the pressure-time ses 
for a standard 4£’ 1d. T.N. 1.  blook oharge in its areal case, aaatanuare 
15 lb. T.N.T, blook ae charge without its case, and a 14 oz. P.E. 
spherioal bare charge (fired without a primer) respectively. The gauge 
was direoted faco-on to tho charges in all three cascs. It will be 
observed that the tail of the signature is a little smoother for the 
spherical P.E. charge than for the T.NeT, charges, the bare T.N.T. oharge 
being slightly smoother than the standard cased charge. 
(G:))) CGEDY Gudoc 
