PRESIDENTIAL ADDRESS. SECTION A. J/ 



With these differences an equation of the form 

 A (mag. elem.)=a + b AX + c l(p + cf {AXy + e^Wf + fi^ipy- 

 wds formed. The three equations* obtained in this way are : — 



AD^ = —•02199 — -30726 AX + -52533 A^ — -04882 (A\)- + -0;,2966 AX A^ 



- -04264 (A0)2. 

 A9,= —-00779 +-30128 ^^ + "55-47^0 — '04564 (AX)2 + -O4838 AX A.^ 



— -O32003 (A^)-. 

 AII,.= + -28615- I -01442 AX- 3-94215 A^--032lo7 (AX)-- -00254 AX A^ 



+ •001151 (A0)-. 



From these equations the calculated values D,., B,., and H,. were 

 found for the respective mean stations and the differences D^^^ — D 

 taken. 



The results are shown in 



Table No. 4. 



District. 



D,.-D 



0.. — d 



H,.-H 



Finally, Table 5 gives the calculated values for the declina- 

 tion, the dip, and the horizontal intensity, at the intersections 

 of alternate whole degrees of latitude and of longitude. From 

 these figures the respective terrestrial lines have been plotted. 

 Maps I, 2, and 3. 



Table No. q. 



* I. have to thank Mr. Wliittingdale of the Royal Observatory of the Cape 

 •of Good Hope for carrying out the necessary calculations. 



