CHARACTER OE THE ARMOUR-PLATED SHIPS OE THE ROYAL NAVY. 287 
1 
Standard. 
Starboard steering. 
Main deck. 
X 
© 
X 
© 
X 
2) 
Achilles 
T October 
1864 
•822 
+ •121 
•777 
+ •154 
•755 
+ •214 | 
[ December 
1864 
•854 
+ •116 
•819 
+ •137 
•804 
+ •188 | 
'November 
1861 
•716 
+ •145 
Black Prince. < 
September 
April 
1862 
1864 
•783 
•846 
+ •134 
+ •137 
•760 
+ •184 
[November 
1864 
•849 
+ •122 
•881 
+ •144 
f February 
1862 
•822 
+ •122 
•794 
+ •179 
•759 
+ •254 ! 
Defence < 
1 December 
1863 
•853 
+ •122 
•842 
+ •180 
•810 
+ •230 
1 April 
1864 
•857 
+ •112 
•853 
+ •159 
•828 
+ •233 
i 
[October 
1864 
•852 
+ •112 
•830 
•842 
+ •230 
Resistance ... j 
f August 
1862 
•758 
+ •111 
•782 
+ ■244 ! 
[ December 
1863 
•850 
+ •122 
•880 
+ •219 
1 
[" March 
1863 
•861 
+ •047 
Royal Oak ... < 
April 
1863 
•907 
+ •061 
•887 
+ •067 
1 
[ June 
1863 
•907 
+ •055 
•906 
+ •031 
Dromedary... j 
'July 
1862 
•841 
+ •104 
|_ December 
1862 
•861 
+ •097 
These changes, and particularly that in the value of X, seem far too great, far too 
regular, and far too consistent, to be attributed to any cause except some molecular 
change in the structure of the iron which, with the lapse of time, renders it less suscep- 
tible of induced magnetism. Whether this change is accompanied by any change which 
can affect the strength, the liability to oxidation, or any other qualities of the iron, is a 
point on which we are not able to offer any information, but we beg to suggest it as a 
question deserving a careful experimental investigation. 
Heeling Error. 
As the heeling coefficient depends partly on vertical induction in transverse iron, 
partly on the mean vertical force arising from permanent magnetism and vertical induc- 
tion in vertical iron, and as the two conspire when the vertical force of the ship acts 
downwards, or when p is greater than unity, and counteract each other when the ver- 
tical force acts upwards, or when p is less than unity, we may expect great differences 
in the heeling coefficient in different ships. In those which have been built head North, 
we may expect a large heeling error in compasses near the stern, and a smaller one in 
compasses near the bow, and the converse in ships built head South. This we find to 
be the case. 
In these cases the uniformity of the heeling coefficients from transverse iron is remark- 
able, and they are, as might be expected, all of the same sign ; the differences, it will be 
seen, are nearly all in the part which arises from vertical force ; this varies from 1° 6' in 
the Warrior to —1° 9' in the Enterprise. 
It will be seen that in the wood-built iron-plated ships the vertical force is generally 
mdccclxv. 2 R 
