184 
Tj^ansactions of the Boyal Society of South Africa. 
change is found in the south-western part of the continent ; in the neigh- 
bourhood of Cape Town it amounts to an increase of southerly dip of 8' 
per year ; the annual increase becomes less towards the east, and off the 
coast of Natal is between 4' and 5' per year ; the line of no change 
passes through Madagascar, and east of that the change is a decrease of 
southerly dip. Lines of equal annual change have been drawn. 
In Fig. 2 the change in dip is shown for the whole period at a number 
of places. 
,/$90 fS93 /S9ff. ■ fSal i90B ./90S. .I9U .19 1* 
Fig. 2. 
The annual change in the horizontal intensity at various places is 
shown in Plate III. No attempt has been made to draw the lines of equal 
annual change. Generally it may be stated that the decrease amounts 
to approximately 90y over the southern part of the continent, and that a 
pronounced decrease in this value is shown towards the north in Ehodesia. 
