IN THE lEON SHIPS OF THE EOTAL NAVY. 
377 
Ship’s head by 
Stand: comp: 
Deviation. 
Head by 
Stand: comp: 
Deviation: 
Head by 
Stand: comp: 
Deviation. 
S.S.E. . . 
O 
2 
6 E. 
S.W. . . . 
O 
6 
30 W. 
W.N.W. . . 
O 
14 
50 W. 
S. by E. . . 
0 
20 E. 
S.W. by W. . 
8 
25 W. 
N.W. by W. 
14 
15 W. 
South . 
1 
40 W. 
W.S.W. . . 
10 
15 W. 
N.W. . . . 
12 
50 W. 
S. by W. . . 
3 
40 W. 
W. by S. . . 
12 
0 W. 
N.W. by N. 
10 
10 W. 
S.S.W. . . 
4 
45 W. 
West . 
13 
0 W. 
N.N.W. |W. 
8 
0 w. 
S.W. byS. . 
5 
30 W. 
W.byN. . . 
14 
20 W. 
It was necessary to deduce from these results the probable values for the remaining 
points of the compass ; this appeared to be obtained with sufficient accuracy by trials of 
the coefficients B, C, D, with various assumed values, adopting those, the deviations 
resulting from which should approximate most closely to the actual observed deviations 
on the sixteen and a half determined points. The coefficients A and E were, under the 
circumstances, assumed as O'. 
The resulting values for B of -j-lS® 30', C-f-l® 40', D-}-4° 20', afforded a satisfactory 
approximation ; from whence the ship’s force in direction and amount are respectively 
7° and 0’235, the earth’s horizontal magnetic force being considered, as at the other 
ports, 1-000. 
A recapitulation of the Great Eastern’s total magnetic force at each place of observa- 
tion is herewith appended, as also a Table of deviations, which brings practically to view 
the change in the deviation of the mariners compass in a newly launched iron vessel, 
amounting in this special case to a decrease of 12° on some points of the compass in the 
first five days, 19° in seven weeks, and nearly three points, or 32° 10' in the first nine 
months of service afloat. 
Angle of force 
from ship’s head. 
Total force. 
Earth’s horizontal 
force. 
1859. 
September 7, Eiver Thames . 
O 
47 
0-585 
1-000 
9) 
„ 10 — 12, Portland . . 
37 
0-480 
?? 
99 
Oct. 22— 24, Holyhead . . 
32 
0-390 
99 
1860. 
June 13 — 15, Southampton . 
7 
0-235 
99 
3 E 
MDCCCLX. 
Deviations 
