15 MARGH 1945 
1600 9000 
16 MARCH 1945 
800 16 
\7 MARCH 1945 
00 0000 800 1600 
OBSERVED AND COMPUTED WAVE PERIODS 
LEGEND 
dL 
OBSERVED 
OBSERVED 
COMPUTED 
PERIOD AT PENDEEN, OUTER BAND 
PERIOD AT PENDEEN, INNER BAND 
PERIOD AT PENDEEN, Tp 
TRAVEL TIME, to 
PERIOD AT END OF FETCH, Tr 
COMPUTED 
COMPUTED 
a 
WAVE PERIOD IN SECONDS 
5 
OBSERVED 
AND COMPUTED WAVE HEIGHTS 
3 4 
LEGEND 
OBSERVED WAVE HEIGHT 
AT PENDEEN, UNSMOOTHED 
OBSERVED WAVE HEIGHT 
AT PENDEEN, SMOOTHED 
COMPUTED WAVE HEIGHT 
AT PENDEEN, SMOOTHED 
45 = COMPUTED TRAVEL TIME, to 
O + COMPUTED WAVE HEIGHT 
AT PENDEEN, INDIVIDUAL POINTS 
COMPUTED WAVE HEIGHT IN FEET 
w 
) 
31v9S ANVHLIGUY ‘LHDIZH 3AVM O3AN3SEO 
1600 0000 
800 
1600 
15 MARCH 1945 
0000 
800 
16 MARCH 1945 
1600 0000 800 1600 
17 MARCH 1945 
Figure 14.—Observed and computed wave periods and wave heights at Pendeen, England, March 14 to 17, 
1945. For explanation see text. 
region of decay has long been a controversial 
subject. According to the classical theory waves 
should proceed with constant velocity into the 
area of calm as long as the depth to the bottom 
remains greater than about one-half the wave 
length. In recent years Cornish (1934) has 
emphasized that such is the case. He has quoted 
a number of examples to show that the periods 
of swell observed on coasts were in agreement with 
periods which might have been produced by strong 
winds over the adjacent ocean. However, in the 
discussion dealing with observations of wave 
33 
velocities and wind velocities Cornish has over- 
estimated wave periods in the generating area 
since he has paid attention only to the maximum 
wind velocity. He has omitted any discussion 
of the length of time the strong wind blew in a 
uniform direction, as well as any estimate of the 
fetch of the wind. Since these factors are of 
great importance, Cornish’s arguments lose much 
of their weight. 
Kriimmel (1911) compiled considerable evidence 
to show that the swell has longer periods than the 
originally produced waves and therefore, corre- 
