504 
(1) Cathode ray circuit 
(2) Pressure switch circuit 
(3)  Piezo-electric gauge and testing circuits 
(4) Calibration circuits:- 
(i) Pressure calibration circuits ~ a.c,, Rotating potentiometer, 
and inductive time base methods. 
(ii) Time calibration circuits. 
(e) An estimation is made of the mechanical and electrical lags in the piezo-electric gauge 
and its associated circuits. 
(f) Explosive Charges. 
Much of the preliminary work of the investigation (testing gauges, pressure switches, electrical 
circuits etc. etc.) was carried out by means of small gun cotton Charges either 24 1b. primer tins of Dry 
G.C. or 164 1D. tins of wet G.c. primed with 24 1b. tins of dry G.c. when larger charges were required 
for test purposes 300 1b. amatol depth charges were used, In the main part of the investigation a special 
series of T.N.T, charges was employed, these charges being filled, to Vernon 'mM' instructions, at Woolwich. 
These special T.N.T. charges were ‘poured’ fillings from the same 'melting' of T.N.T. to ensure uniformity 
of composition and density. The charges were made up In ‘similar’ cylindrical cases (length - diameter) 
to the fol¥owing approximate weights:-— 20, 60, 100, 150, 250, 500, 750, 1000 and 2000 Ibs. A certain 
number cf block-filled 100 1b. T.N.T. Charges were fired also for comparison with the 100 1b. poured-filted 
Charges. The T.N.T. Charges were primed with C.£. pellets and a standard detonator was used. 
1n order to compare different method of priming and detonating some of the 100 1b. T.N.T. Charges 
were detonated near one end of the cylinder wnilst inthe other the detonation was initiated centrally. 
The small gun cotton charges were found extremely useful also in examining certain theories of 
explosion pressure and the behaviour of the p.e. gauge under different conditions. Measurements of the 
time of rise of pressure, velocity of pressure wave, surface and bottom reflections werc made with these 
gun cotton charges. 
The 24 1b. Dry Gun Cotton Charge - consists of 4 cylindrical slabs of dry gun cotton, each 9 ozs. 
packed in cylindrical watertight containers 104 inches long, 34 inches diameter and .02 inches thick in the 
wall. Two No. 9 Service detonators are fitted in parallel at one end and a watertight gland serves to seal 
the tin and bring out the firing leads. See Figure 38. Charge No. (14). 
The 182 1b. G.C. charge - consists of 164 1bs. of wet gun cotton (with 20% added water) packed in a 
cylindrical container (nett weight 13 lbs.) 104 inches diameter x 194 inches long, having two cylindrical 
holes into one of which (the axial hole) is fitted a 24 1b. dry G.C. primer, the other hole being left open 
to the sea. The primer is fired as beforewith 2 No. 9 service detonators in parallel. The thickness of 
the outer wall of the charge is as inches. Reference to the diagram No. (13) in Figure 8 shows that the 
charge case is only partly filled with wet gun cotton the spaces between the cylindrical slabs being filled 
with air. 
Depth Charges. These are of the stangard service pattern shown in Figure B No. (11) containing 
300 lbs. of 40/60 Amatol. For the purposes of the present experiments they were prepared for electrical 
firing being fitted with C.E. primers and standard detonators. These charges are practically free from 
air cavities. 
Hi Id seunee 
