the use of Table 1. In Table 1, after the envelope has traveled 
29.6 kilometers in 1.87 hours, the envelope is 0.5 units high, 
107 seconds before its maximum value of 0.8 and 107 seconds after 
its maximum value. Then in Table 5 at the time t = Be - 107 
seconds, the apparent local period is 5.04 seconds and at the time 
t= t. + 107 seconds, the apparent local period is 4.96 seconds. 
Thus the first waves to arrive at the point of observation have 
the longest apparent local period. 
Tables 5 through 13 combined with equation (4.20) show 
that the larger the values of o and T, the more rapidly the 
value of T* departs from T as the wave group travels away from 
x = 0. In Table 8, for example, after the group has traveled 
only 10.9 kilometers, the apparent local period for the waves 
which arrive first is 5.42 seconds and for those which arrive 
last, 4.64 seconds. In Table 5, after the group has traveled 
612 kilometers, the apparent local period is 5.08 for the waves 
which arrive first and 4.92 seconds for those which arrive last. 
The dispersive effects of the various spectra graphed in figure 
1 are evident. 
The overall variation of equation (4.9) at a fixed point 
as a function of time can now be described. A wave height re- 
corder at some distance xy from the origin would not detect any 
Significant variations in height until a time corresponding to 
t. had elapsed. At a time in seconds before and after t. cor- 
responding to t' waves of the amplitude given in the tables with 
an apparent local veriod given in the tables would be recorded. 
For times much greater than too the sea surface would be essentially 
- 57 - 
