Chta-Shun Yth 
But from (16), on making kz =k , , we have 
2 
ge% 2eG (26) 
dk 
Since 
dc 
Ce = (ap Ko - 
0 <4 (ee << Cc ’ (27) 
which means that the magnitude of c, is always less than the magni- 
tude of c, whether or not c is positive. 
For superposed layers, each of which is homogeneous within 
itself, (23) and (26) are obtained in much the same way. All we need 
to do is to apply the same procedure to each of the layers, and then 
apply the interfacial condition (11) at each interface. 
IV. THE DIFFERENTIAL SYSTEM FOR A CONTINUOUSLY STRATI- 
FIED FLUID 
If the fluid is continuously stratified, we shall denote the 
density of the fluid when it is undisturbed by pg, which is a function 
of y alone. The density perturbation will be denoted by p , so that 
the total density is po +p. The mean pressure pg is related to 
po by the hydrostatic equation 
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