143 



Scales in feet 

 ^ 



Depths below surfoce 

 i.e below Z = 33 feet 

 Scole for 



M=2200 lb Z 



(L=68-4ft) ft 



t 2-4 



M= loz< 



Scale for 

 M = 300 lb 

 (L=41-6fr) 



Fiq. 



Colculahons for Z!q = Z 



