so 



DEPTHS IN FATHOM 

 3(> ZO JO 5 Z I. 



Sley 1. — The chart has been checked carefully for 

 changes in slope and the requisite contours drawn in 

 heavily in ink smoothing them off as is consistent with 

 assumption No. 3. 



This chart is then used for all periods and directions 

 without further work. 



Ste-p 2. — A tracing paper overlay is placed on the con- 



tour map and the 



Lave 



is written between each of the 



contours as computed in Table II. This overlay is then 

 good for all directions of approach for a particular period, 

 and can be prepared in a very few minutes. All further 

 work is performed on the overlay. 



Figure 14. 



23 



