and the results are thus to be expected. The reader, though, would 
have been perfectly justified in objecting at that point in Chapter 
7 where a transition zone wave record and transition zone pressure 
records were used to prove the Gaussian property, and then the 
Gaussian property was tacitly assumed for deep water waves. These 
results now show that given that the waves have the Gaussian property 
in deep water, it then follows that they have the Gaussian property 
in the transition zone (and conversely since the wave refraction pro- 
cess can be theoretically reversed). 
From equations (11.3), (12.41), (12.18), and (12.21), it then 
follows that the pressure record which will be recorded at the bot- 
tom by a pressure guage at the point of observation in the transition 
zone is given by equation (12.42). The pressure record is therefore 
Gaussian. The power spectrum of the pressure record is related to 
the power spectrum of the waves passing overhead by equation (12.43). 
Given [Ap py ie the power spectrum for the surface record can be 
computed from equation (12.43), and conversely. For those pressure 
recorders which respond to different periods in different ways, the 
calibration curve appropriately modified must be inserted as another 
function at this point. An instrument with a completely flat response 
curve is assumed in this derivation. 
Ewing and Press [1949] are of course correct in their statement 
of the problem of pressure record analysis. These formulas simply 
formalize the procedures to be employed. 
Equations (12.42) and (12.43) are extremely important to the 
practical engineer. Nearly all of the wave records being taken at 
the present time in the United States are made with a pressure recorder 
54 
