Chta-Shun Yth 
where a and a+b are the abscissae of the shore lines. Similarly, 
on multiplying (50) and integrating, we have 
I Pa ae ee eee: ee ke (52) 
where 
Z, 2 2 Z. 
where 
g.py. @ 
pupae // : oe ele 2y dA . (55) 
+ ! ! 
(ore, Eee, pt EP ) 
fo aes ae (56) 
1410 
