as well have been given the length of the record and the statistical 
reliability of the analysis. Stated another way, to prove that the 
spectrum is actually as irregular as shown a very much longer 
stationary record would be needed. 
The upper and lower dash-dot curves might represent the 90% con- 
fidence limits of the analysis, and if the record is related to the 
Square root of the power spectrum then rough computations suggest 
that the number of degrees of freedom of the analysis lies between 
4 and 20 and that it is most likely about 9. Thus the individual 
peaks and troughs are extremely unreliable. 
Nevertheless the analysis shows that there are important contri- 
butions to the entire spectrum from » equal to 27/20 to # equal to 
or/7. The record is undoubtedly that of a pressure filtered "sea" 
record, and the sea surface would best be represented by a spectrum 
covering a wide band with possibly important contributions even for 
periods below seven seconds. 
Spectrum number two is from the paper by Klebba [1949]. It was 
taken in 78 feet of water on 15 September 1946 at 0650 EST off Cutty- 
hunk. Spectral components with a six second period would begin to 
show in the spectrum if they were present and certainly important ten 
second components would be evident. They are not present; the highest 
important value of » is at 27/11 and the lowest is at 27/15. Since 
the dashed curve could represent the spectrum just as accurately as 
the one shown, (and since the dash-dot curves again suggest the degrees 
of freedom of the analysis), it would appear that this record is a 
clear cut example of a power spectrum such as those predicted in 
Chapters 7 and 10. The record must have been a "swell" record with a 
aa 
