Bessho 



where Zir/k is the wavelength. 



Assuming a surface disturbance of the form, 



^ = b + c cos kx + d cos 2kx, (B. 3) 



and integrating the expressions for M, T, and V, we have 



2 



-U = trcaL 1 + k(b + |) + ^(c^ + 4b^ + 2d^ + 4bd)] , 



2 



i T = ^ [ 1 + 2kb + k^c^ + 2b^ + d^ + k'c^2b + d)] , (B. 4) 



i V = ^ (c" + d' + 2bV 

 p 2k 



Differentiating P with respect to a, b, c and d, and equating 

 the derivatives to zero (by the principle (3,16)), we obtain the follow- 

 ing stationary values, neglecting higher order terms: 



5 2 2^ 

 c = a(i +-5- k a ), 



b •= O(k') , 

 d = -y ka , 



(B.5) 



2 2 



g/k = 1 - k a% 



^V^^c^l t^k^c^). (B.6) 



These expressions agree with other well-known resxilts. [1,2] 



570 



