352 
MAGNETIC SURVEY OF A PART OF THE SOUTHERN HEMISPHERE. 
“ 4 3. Using the deviations observed on the eight principal points only, we have 
A= 
g{' y 0 + ’ s 4 + ' s 8 • 
(26.) 
B=-1768(iog=l-24742)K-^ 28 + % -5 20 }, 
+4{ 6 ’8 — %} 
C = 4 { 5 o~ 5 16)> 
.... ( 27 .) 
-f*l / 68 (log = 1 ’24742) {•s 4 +.s 28 '—.? 12 ■%)}• 
.... (28.) 
= 4 { ^*4 ^28 ,9 12 - 1 - ' s 2o} 
.... (29.) 
E=— {^0+^16 $8 ^ 24 } 
.... (30.) 
c Having found A, B, C, D, E by any of the above methods, a table of the deviations 
on all the points may then be computed. The computation will be facilitated by 
using the following Table : — 
“ ‘ Let B l3 B 2 .... B 7 , C l5 C 2 . . . . C 7 represent the values of B and C multiplied 
by sin 1 1° 15', sin 22° 30', and let D 2 , D 4 , D 6 , E 2 , E 4 , E 6 represent the values of D and 
E multiplied by sin 22° 30', sin 45°, and sin 67' 30°, we have then 
sin =A-f C+E 
sin c) 16 =A — C-fE 
sin e5 4 =A-f B 1 +C 7 +D 2 +E 6 
sin ^ 1 =A-B 1 +C 7 -D 2 +E 6 
sin A-^B^ — C 7 — D 2 - I-L 0 
sin & 17 =A— B 4 — C 7 +D 2 +E 6 
sin ^ 2 =A+B 2 +C 6 +D 4 +E 4 
sin ^ 0 =A— B 2 +C 6 — D 4 -{-E 4 
sin £ 14 = A-j-B 2 — C 6 — D 4 d-E 4 
sin § 18 =A— B 2 — C 6 +D 4 +E 4 
sin =A+B 3 +C 5 +D 6 +E 2 
sin § 29 = A — Bg-j- Cg — D 6 +E 2 
sini 13 =A+ B 3 — C 5 — D 6 +E 2 
sin c) 19 =A — B 3 — C 5 -J-D 6 +E 2 
sin& 4 — A-{-B 4 +C 4 -|-D 
sin h 28 = A— B 4 +C 4 - D 
sin c$ 12 = A+B 4 — C 4 — D 
sinS 20 =A— B 4 — C 4 +D 
