69 



lOOCy 



_9oo- 



QOO 



~loo- 



LoCh 



£00 



^0- 



500 ■ 



Boo 



i'H- /-^ /<3 rj IS i'9 ^o ^1 P'2 23 i-^ ^S 



Orr-iS. 



Fig. 6. 



