76 
MR. AIRY ON THE OBSERVED DEVIATIONS OF THE COMPASS 
Horizontal Force. 
Vertical Force. 
7. 
Constantinople 
• 
5-63 
• 
. -P 7-34 
8. 
Piraeus . . . 
• 
5-85 
. • 
. + 6-85 
9. 
Plymouth . 
• 
3'82 
• 
. + 9-67 
10. 
Lisbon . . 
4*62 
* 
. + 919 
11. 
Piraeus . . . 
. 
5-85 
« • 
. + 6-85 
12. 
Greenhithe . . 
. • 
3'79 
• 
. + 9'66 
13. 
Malta . . . 
• • 
5'74 
• 
. + 7*03 
14. 
Plymouth . . 
• 
3'82 
. + 9-67 
15. 
Auckland . . 
• • 
6-32 
• * 
. -11*32 
16. 
Sheerness . . 
• 
3'78 
. • 
. + 9*67 
17. 
Simon’s Bay . 
• 
4-46 
• • 
. — 6*19 
18. 
Plymouth . . 
3-82 
• • 
. + 9-67 
19. 
Valparaiso . . 
7-17 
. 
. — 5*23 
20. 
Portsmouth 
• • 
3*83 
• • 
. -f 9*63 
21. 
St. Catherine’s 
• • 
6-48 
• 4 
. - 2*54 
22. 
Sheerness . . 
• « 
3'78 
• 
. + 9*67 
23. 
St. Paul’s Loando 
• • 
5-57 
. — 3*09 
24. 
Greenhithe . . 
• • 
3'79 
• • 
. + 9-66 
25. 
Rio de Janeiro 
. * 
6-49 
* . 
. — 1*49 
26. 
Portsmouth 
» • 
3-83 
• • 
. + 9*63 
27. 
Simon’s Bay . 
* 
4'46 
• 
. — 6*19 
28. 
Portsmouth 
. 
3'83 
• 
. + 9-63 
29. 
Simon’s Town . 
. 
4-46 
. . 
. — 6*19 
From these, with the starboard angle and the modulus, the resolved polar-magnet- 
force in the two directions of “ headward” and “ starboard” are formed by the rules 
given above. It will be remembered that H is the ship’s subpermanent magnetism 
headward, 8 the subpermanent magnetism to the starboard side, and N a constant 
of capacity for induced magnetism peculiar to each ship. As the total directive force 
at Greenhithe is 3*79, a, change of disturbing force represented by-^, or '066 nearly. 
Avould produce at Greenhithe a change of disturbance whose maximum is 1° nearly; 
and so, mutatis mutandis, at other places. 
1 . Wood-built Sailing Ships. 
The Erebus. 
1. 
H + Nx 
9*94 = + 0'261 
S= + 0-020 
2. 
H + Nx 
6-38= +0-202 
S= +0-037 
3. 
H-Nx 
1-97= +0-043 
S=+o-oi7 
4. 
H-Nx 
608= -0-090 
S=+0-018 
5. 
H — Nx 10-68 = — 0*262 - 
S=+0'0I0 
