CHARACTER OF THE ARMOUR-PLATED SHIPS OF THE ROYAL NAVY. 283 
Quadrantal Deviation, D sin 2£'+E cos 2£\ 
Mean force to North XH. 
The Tables show that the values of E when the ship is upright and the compass in 
the midship line, give no certain indication of any real value. The more accurate the 
instrument, and the more careful the observations, the smaller E generally is. 
When the compass is not in the midship line the case is different ; an E may then 
have a considerable value. Instances of this will be seen in the deviations of the Royal 
Sovereign, the peculiar construction and fittings of which ship made it necessary to 
place compasses considerably out of the midship line, and with gun turrets placed 
diagonally to them. 
At the steering wheel on upper deck . 
At the steering wheel in captain’s cabin 
(Port side 
Forward on lower deck 
(Starboard side 
. E= — 9 14 
. E= — 5 10 
. E=+4 38 
. E= — 4 42 
It will easily be seen that a +E would be caused by a gun turret in the first and 
third quadrant relatively to the compass, and a — E by a turret in the second and 
fourth. The close agreement of the numerical value of E in the two last examples, 
with the difference in their signs, is striking. 
The value of the E introduced by the ship heeling by an angle i to starboard being 
£±£ ? - 
2A 
and both c and g being generally positive, we should expect a — E when the ship heels 
to starboard, a +E when she heels to port, and this is the case in the few instances 
we have in the Tables. 
E. 
Warrior. — Standard Compass . . 
Black Prince. — Standard Compass . 
Defence. — Standard Compass 
o o 
\n 
to 
starboard 
-0 
45 
m 
to 
port . . 
+o 
59 
m 
to 
starboard 
-1 
25 
to 
port . 
+ 1 
50 
n 
to 
starboard 
-0 
05 
.7* 
to 
port . . 
+ 1 
50 
D. 
As regards D, the most important point is its magnitude in different positions in ships 
of different classes. 
The usual or average value of D has greatly increased since the publication of the 
Paper in 1860. In that paper it was observed that a value for this coefficient not 
exceeding 4° and ranging between that amount and 2°, might be assumed to represent 
