where 6 is some small value. But as c -> <*>, 



and from equation (275) 



tanh 



4jS 



c R* 



n 2 d S 

 c R g * 



(276) 



n 2 d* 

 2 S 



(277) 



2 _ (R P 



2 J* r * 



S p 



(278) 



From equation (265) , noting, that for c 



tanh 



n 2 d* 



r* c 

 L P 



n 2 d< 



r* c 



P 



(279) 



it is found that 



n 2 d* 



= 1 



(280) 



Substituting the value of r* from equation (278), and noting that for 

 a uniform slope 



d* = d* + (r* - R*) S (281) 



S p S 2 



equation (280) is then 



n^ [d* R* S 9 - (d*) 2 ] - n 2 (R*) 2 S, + (R*) 2 - (282) 



Equation (282) is a quadratic equation for n 2 which provides minimum 

 and maximum values given by 



(nj 



l J min r* s - d* 

 si s 



(283) 



(R*) 2 S 2 



(n 9 ) 



2 max R* s - d* 



S 2 S 



(284) 



121 



