CHARACTER OF THE ARMOUR-PLATED SHIPS OF THE ROYAL NAVY. 285 
Warrior. 
Black 
Prince. 
Achilles. 
Defence. 
Resist- 
ance. 
Hector. 
Valiant. 
Royal Oak 
(wood- 
built). 
q, , i / From fore-and-aft induction. . . 
" [ From transverse induction ... 
+ 06 
- I 4 
- 2 45 
- 2 42 
- 5 55 
- 3 51 
- 2 14 
— 1 19 
+ 8 24 
+ 11 42 
+ 9 40 
+ 9 44 
+ 12 21 
+ 9 15 
+ 7 11 
+ 4 32 
Starboard f From fore-and-aft induction. . . 
+ 0 14 
- 3 47 
- 3 47 
- 2 17 
- 7 53 
- 3 23 
- 2 59 
- 2 7 
Steering . . . \ From transverse induction . . . 
+ 11 46 
+ 14 28 
+ 12 43 
+ 12 35 
+ 16 33 
+ 11 49 
+ 9 54 
+ 3 51 
-w- • -j-. ,f From fore-and-aft induction... 
am ec y jr rom transverse induction . . . 
- 2 35 
- 3 9 
- 2 10 
- 1 02 
- 5 58 
- 6 56 
- 3 51 
+15 58 
+ 15 36 
+ 16 58 
+ 15 11 
+ 15 54 
+ 15 14 
+ 5 20 
Standard .. | g 
+ 002 
-112 
-079 
-•078 
-158 
-109 
-•068 
-043 
-■256 
-•322 
-•277 
-•278 
-•326 
-•263 
-•214 
-143 
Starboard fa . 
+ ■006 
-100 
-•103 
-•064 
— 193 
-093 
-•085 
-•066 
Steering . . . \ e 
-•340 
-■380 
-•343 
-■348 
- 401 
-•325 
- 281 
-122 
fa 
-•068 
-•083 
-048 
-027 
-151 
— •176 
— 116 
Main Deck •! 
-•418 
-•407 
— •434 
-•409 
-■397 
-•380 
-160 
The conclusions we have drawn will be seen to be supported by this separation. Thus 
we see that the Warrior is the only vessel which has a -\-a and a -J-D from fore-and-aft 
iron. In the Hector and Valiant the D is comparatively small, because the — a is large, 
the — e small. 
In the Resistance the two parts, the difference of which makes up the D, are very 
much larger than in the Defence, though the resulting value of D is less. 
The comparison of the values of D and of a and e in the compasses of the Royal 
Oak with those in the compasses of the Hector and Valiant is very instructive. These 
ships are nearly alike in dimension, in the arrangement of the iron-plating, and the posi- 
tion of the compasses. The Royal Oak has an iron upper deck, but is otherwise wood- 
built. The Hector and Valiant are entirely iron-built. 
A first inspection of the Table might lead us to infer that the large value of D in the 
iron-plated ships is due to the armour-plating at the sides, but the comparison with the 
Royal Oak shows this not to be the case. In fact a little consideration will show that, 
as regards longitudinal induction, the effect of armour-plating continued from end to end 
is to produce a — a ; that, as regards transverse induction, the effect of the parts which 
run fore and aft is to produce a small -\-e, and the effect of the transverse parts near 
the extremities of the ship to produce a small — e, so that on the whole the tendency is 
probably rather to diminish than to increase D. The large value of D in the iron ships 
is evidently attributable to the increased amount of transverse iron in decks, bulkheads, 
iron beams, and the iron bottom of the ship, the magnetism of which is, as it were, con- 
ducted upwards by the iron sides. 
X. 
The value of X is so closely connected with that of D that it is desirable to consider 
them together. In the earlier built iron vessels X was very nearly equal to 1. In the 
Rainbow, at four stations distributed along nearly the whole length of the ship, X ranged 
from - 972 to T003. In the Ironsides, the first iron-built sailing ship, it was ‘917 at 
