74 
MR. AIRY ON THE OBSERVED DEVIATIONS OF THE COMPASS 
I shall first proceed to consider the qnadrantal deviations in these ships. It will 
be remembered that, according to theory, the coefficient of qnadrantal deviation in 
each ship ought to be sensibly the same in all localities ; but that the coefficient in 
one ship may differ in any degree from that in another ship. 
Coefficients of Quadrantal Deviation. 
1. Wood-built sailing-ships. 
In the Erebus, at 
. Gillingham (No. 1) . . . . 
+ 0 23 
Porto Piaya (No. 2) . . . . 
+ 0 28 
St. Helena (No. 3) . . . . 
H-O 34 
Cape of Good Hope (No. 4) . 
+0 35 
Kerguelen’s Land (No. 5) . . 
+ 0 38 
In the Pandora, at 
Plymouth (No. 14) . . . . 
-fO 38 
Auckland (No. 15) . . . . 
+ 0 30 
In the Mseander, at 
. Sheerness (No. 16) .... 
— 0 12 
Simon’s Bay (No. 17) . . . 
— 0 11 
In the Spy, at . . 
. Sheerness (No. 22) .... 
-1-0 46 
St. Paul’s Loando (No. 23) 
— 0 14 
The accordance of the numbers in the three first instances 
is 
very remarkable ; 
and the more so because the compound polar magnetism has changed considerably. 
In the Spy there is a discordance, but not important in nautical experiments. It 
will be seen, on referring to the columns of Residual Error for the Spy, that there is 
general irregularity. 
2. Wood-built steamers. 
In the Virago, at . 
. Plymouth (No. 18) .... 
O i 
+ 1 9 
Valparaiso (No. 19) . . . . 
• 
-1-1 44 
In the Plumper, at 
. Portsmouth (No. 20) . . . 
• 
-fl 3 0 
St. Catherine’s (No. 21) . . 
• 
-fl 42 
The agreement is sufficiently close. 
3. Iron-built steamers. 
In the Bloodhound, at Plymouth (No. 6) . . . 
O t 
+3 48 
Constantinople (No. 7) • • 
+ 3 27 
Piraeus (No. 8) 
-1-3 59 
In the Jackal, at . 
. Plymouth (No. 9) .... 
-1-4 14 
Lisbon (No. 10) 
-f4 11 
Piraeus (No. 1 1) 
-1-3 32 
