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MINUTES OF PEOCEEDINGS OF 
(4) Tongueing and grooving not only weakens each particular plate when struck 
by shot, but assists in damaging the adjoining plates. 
(5) Combinations of bars are inferior to solid plates of the same thickness or 
weight of metal. 
(6) A series of thin plates superimposed offers less resistance to projectiles than 
one solid plate of equal weight and area. 
(7) In all trials which have been made with a view of testing combined sub¬ 
stances in comparison with a solid iron plate of the same weight, the solid plate has 
been found in every instance to offer the greater resistance. 
(8) No advantage is gained by opposing iron plates to rifled projectiles of good 
quality at an angle, where, by doing so, the plate must be made thinner to compen¬ 
sate for a more extended area. 
(9) The more rigid the backing, the greater is the support of the plate ; but, on 
the other hand, a soft backing has the advantages of yielding, in some degree, to the 
distortion of the plate; of distributing the effect of the blow over a larger area ; of 
diminishing the damage to the general structure; and of retaining the broken 
fragments in case of fracture. 
(10) Tor these reasons it is not desirable, as far as the experiments have yet 
shown, to construct any ships for war purposes without a wooden backing in rear of 
the armour plates. 
(11) A facing of wood, or other soft substance upon armour plates, affords a 
considerable amount of protection from solid shot, but is soon destroyed by shell. 
(12) Experiments have shown that a good shield for coast batteries can be 
obtained at a reasonable cost, by the use of two layers of plates, or rather “ planks ” 
of wrought-iron, crossing each other, and secured through their centres with screw 
bolts. 
In conclusion, I think it may be interesting to give a few of the results 
which have been obtained in America, both from practical experience in war 
and from experiments against iron armour. The information on this subject, 
which will be found in Appendix A, C, and D is extracted from the Annual 
Report of the Secretary of the United States Navy, and from Mr Holley's 
book on “ Ordnance and Armour." 
