12 



KENT AND TAYLOR. 



Fig. 8. 



Fig. 9. 



Fig. 7. 



Figure 7. Case I: Echelon in double order 

 condition and a grid maximum coincident with 

 the primary 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. , 



