Phil. Mag. Ser. 6, Vol. 28, PL IV. 



Fig. 13. 



5000 



3.000 



€> 



2.000 













Cut 



l/£S 



fO/l 



T/l£ 



\ 



L£JV 























M 































s 

 p 





























L 









/^ 





y 























1 

 / 



J, — -» 

























s J 



s 





A-.. 



Lj 



s 

















h\y 



/ ,' 

















/ ■ 

 / 

 / 







'/ 



'/ s T 



-■>< 

























































I 















10 20 30 40 50 60 70 80 CO 100 110 120 130 140 150 



