27 
I D 
о 
F H Z 
nT 
1 
69.2 
69.0 
68.8 
68.6 
68.4 
68.2 
68.0 
67.8 L -6 
-1 
-2 
- -3 
1930 1940 1950 1960 1970 1980 1990 
Fig. 3: Wmgst Epoch Values I, D, F, H and Z 
Fig. 3: 
Wingst Epoch values I, D, F, H and Z