124 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 195G 



the left hand side (l.h.s.) of (2.28) in this area we first see how the point 

 k^ = f = 1^ can be approached so that the l.h.s. remains finite. If we 

 put k^ = H + £ and a' = ^ + ce and expand the first two dominant 

 terms of (2.28), then adjust c to keep the result finite as f -^ we find 



= 1 3^' - 5 

 ^ ~ 4 32^ + 1 



c varies from — % to \i as z goes from to c» , changing sign at 2^ = %. 

 Every curve for which the l.h.s. is constant makes quadratic contact with 

 the Jine 5" — V3 = c(/v" — ]i) at Jc' = 5' = I/3. If we remember that 

 the l.h.s. is positive for A;' = 0, < 5" < 1 and for A;^ = 1, < 5^ < 1, 



3 



3 



Fig. 6B 



