284 
Transactions of the Boyal Society of SoiUh Africa. 
point, and a table — No. 2 — formed, in which are given the differences in 
longitude (AX), latitude (A^), vertical intensity (AZ), total intensity (AT), 
northerly intensity (AX), and westerly intensity (AY). 
Table 2. 
Mean Station of District. 
I 
II. ., 
III. 
IV. .. 
V 
VI. ., 
VII. ., 
VIII. 
IX. .. 
X 
XII.. 
XIII. 
XIV. 
XV. . 
AX. 
aZ. 
AT. 
aX. 
aY. 
-435' 
+248' 
- 918y 
-892y 
- 664y 
+ 979y 
-323 
+252 
- 321 
-577 
- 837 
+825 
-192 
+238 
+ 258 
- 43 
- 927 
+599 
- 71 
+227 
+ 711 
+275 
- 923 
+384 
+ 140 
+ 121 
+ 1171 
+729 
- 581 
-118 
+259 
+ 5 
+ 1251 
+937 
- 87 
-443 
+231 
-116 
+ 421 
+527 
+ 615 
-535 
+ 97 
-101 
- 17 
+ 163 
+ 560 
-233 
+242 
-219 
- 15 
+426 
+1248 
-683 
+ 104 
-183 
- 335 
+ 72 
+ 920 
-319 
- 53 
+ 120 
+ 340 
+ 123 
- 481 
+261 
-281 
+ 140 
- 625 
-600 
- 443 
+661 
-252 
+ 48 
- 979 
-781 
- 78 
+562 
+ 212 
-345 
- 865 
+ 42 
+ 1973 
-801 
With these differences equations of the form — 
A (mag. elem . ) a + &AX + c A0 + ^^( AX)^ + c AX A0 + /(A^)^ 
were obtained, and the values of the constants a, b, c, d, e, and / deter- 
mined. 
The results " for the four elements were as follows : — 
AZ, = -39009 + 4-59073AX + 4-86998A<^--00106(AX)- 
- •OO13172AXA0 - ■001934(A(^)^ 
AT, = -453O2 + 3-42O2lAX + 2'13O17A0--OOO5825(AX)- 
- •OO1O793AXA0 - •0002655( A^)^" 
AX, = -30017 - •27939AX - 4-84872A0 + •0003224(AX)^ 
- -0020504 AXA(/) + •OO13477(A0)2 
AY„- -66451 - 1-90644AX+ •96844A(^ - •0005363(AX)- 
+ -OOOO6O9AXA0 - •OOO7839(A0)^ 
From these equations the calculated values Z^, T^, X,., Y^, were found 
for the respective mean stations, and the differences between these and 
* I have to thank Mr. Whittingdale of the Royal Observatory of the Cape of Good 
Hope for carrying out the necessary calculations. 
