12 



KENT AND TAYLOR. 



E 



Y 



b 



c 



1 



!^ 



I 23^66789 10 



I 23H56789 



Fig. 8. 



Fig. 9. 



Fig. 7. 



Figure 7. Case I: Echelon in double order 

 condition and a grid maximum coincident with 

 the jirimarv maximum. 



Figure 8. Case II : Echelon in double order 

 condition and a grid minimum coincident with the 

 primary maximum. 



Figure 9. Case III: Echelon in single order 

 condition and a grid maximum coincident with 

 the primary maximum. 



