Chta-Shun Yth 
am 
iH] 
—" 
tanh ax coth ymx 
which demands 
' 
— 
(69) 
Thus 
d = m F (70) 
2 
Since m is real, \ must be positive. Equations (68), (69) and 
(70) give 
so that 
and a= (71) 
The dispersion relation is given by the free-surface condition (47), 
which in this case can be written as 
q 6, See Nh een (72) 
(73) 
