566 BELL SYSTEM TECHNICAL JOURNAL 



purposes to deal only with the cases where hs/h^ is either small or 

 large compared with unit\% and to use the following approximations: 



(1) (hi/h-^ small compared with unity. 



P=C(.v=) + 5(.r=), 

 <7 = C(.v=)-5(.v=), 

 .v=(i'/2/^2)^ 

 t' = t-B'{oi). 



(2) (hs/hi) large compared n'ith unity. 



P=-\+fjA{y)dy, 



a = 0, 



y={2/^Y'\t'/h,). 



