811 
= (ei 3 
now record faithfully the pressure changes in open water as a result of an 
underwater explosion. Moreover it is confidently expected that the effect 
of changes brought about by the presence of water-backed and air-backed 
targets in the vicinity of exploding charges can be determined. 
The simple theory of pressure measurement with a tourmaline gauge is 
given in Appendix 1, together with the theoretical effect of cable signal. 
A reference to the natural frequency oscillations set up in tourmaline 
discs is also given. 
Work, involving exploration of the pressure field as near an underwater 
exploding charge as possible is now proceeding with the finalised type of 
miniature gauge described herein, 
REFERENCE 
(4) The electric potentials produced in the conductors of a submerged 
cable by underwater explosions. A.H. Bebb and R.V. Bundy. 
