"The second of these two errors emphasizes the need to re- 
consider the basic theory which does not agree with experiment. 
Every observer who has simultaneously measured the surface waves 
and the subsurface pressure fluctuations has *.: 4d the theo- 
retical response factor determined from equativ” 2a to be too 
small. Ten random measurements made at the Waterways Experiment 
Station (Folsom, 1947) indicated an average correction of 1.07 
should be applied to equation 1. Seventeen laboratory measure- 
ments at the University of California, Berkeley, indicated an 
average correction of 1.10 (1949). Field data reported by the 
Woods Hole Oceanographic Institute (Admirality Research Labo- 
ratory, 19473; Seiwell, 1947) indicated a correction factor in 
excess of 1.20 while the three sets of field data obtained at 
the University of California (Folsom, 1946) indicated values of 
1.06, 1.00, and Lelde” 
The basic fallacy occurs at the very beginning of the material 
quoted when the statement is made that "The following basic defi- 
nitons have been accepted" and that the "wave period is the time 
interval between the appearance at a fixed point of successive wave 
crests." What is measured are the time intervals between success- 
ive relative maxima of a non-periodic* function. These time intervals 
have absolutely nothing to do with the time intervals between success- 
ive crests of a pure sine wave such as in equation (2.19). From the 
measurement of this quantity, the error is compounded by averaging 
a number of such measured quantities and calling the result the 
"characteristic wave period." From then on, the "characteristic 
wave period" is applied to the wave record as if it were actually 
the true period of the wave record and as if the wave record had 
one discrete spectral component. All wave records are thus treated 
as if they were the one special case given in example one of Chapter 
9. All of the subsequent formulas quoted are also based upon this 
assumption. 
*See the correct mathematical definition of period in Chapter 2 
(equation (2.11) for a pure sine wave). 
58 
