THE ROYAL ARTILLERY INSTITUTION. 
33 
These bars however are not suited for ships of war, as it is by no means 
an economical form (as regards weight) of disposing the iron for defence. 
The weakest parts of an armour-plated ship are the joints of the plates : 
it follows then that the more these joints are multiplied, the weaker the 
structure becomes. To obtain, therefore, similar resistance with plates and 
bars, the latter must be considerably thicker than the former,—a most 
serious objection where weight is of such great importance. 
The Committee appointed at the beginning of last year to continue the 
inquiry on the subject of iron defences, obtained the opinion of most of 
the principal iron manufacturers in the country as to the best quality and 
manufacture of iron to resist shot. The great diversity of opinion among 
so many practical men could only be accounted for by the fact that none 
of these gentlemen had ever had an opportunity of witnessing the effect of 
a shot on an iron plate, and this in some measure explains the very small 
progress that had, up to a recent period, been made in their manufacture. 
In consequence, plates of various qualities and manufactures were ordered 
for experiment, and the makers were requested either to be present them¬ 
selves at the experiment, or to send some one in whom they placed 
confidence. They all most gladly availed themselves of this permission, 
and at the conclusion of the experiment they expressed themselves confident 
of being able to overcome all difficulties of manufacture, and of pro¬ 
ducing plates capable of resisting shot. Practical knowledge of great value 
was by this means afforded to those manufacturers who proposed to devote 
themselves to this branch of the iron trade; and a spirit of emulation raised 
among the different iron-masters which cannot fail to have a most beneficial 
effect in bringing the question (as far as qualities and manufacture are 
concerned) to a satisfactory solution. 
The advantage of having allowed the iron manufacturers to be present at 
the different experiments is already becoming apparent in the improvement 
of the plates supplied for trial; and the time is not far distant when the 
more general use of mechanical means, to move the large masses while being 
forged, will reduce the price per ton to more reasonable limits. 
These preliminary experiments determined the following points:—* 
(1) That steely iron, commonly known as homogeneous iron, puddled 
steel, &c., when in large masses, is inapplicable for defensive purposes; 
although in the thinner plates this metal offered great comparative resistance, 
it became brittle when in large masses, and readily cracked when struck by 
a shot. 
(2) That plates of a hard crystalline structure are inferior to those of 
a soft fibrous nature. 
(3) That the great fault and primary cause of weakness in all forged 
plates is unsoundness in welding the different piles of which the plate is 
composed. This defect was invariable in all (except the homogeneous iron 
plates); it was more apparent in the rolled than in the hammered plates, but 
this was compensated for by the hammered plates being harder and more 
crystalline than those forged under the rolls; and this led to the conclusion 
that there is but little choice between the two processes if both are properly 
worked out with efficient machinery. 
5 
[VOL. III.] 
