ARMOUR AND ITS ATTACK BY ORDNANCE. 
49 
Terrible plates. The plate in question was a most excellent one, 
measuring 4 feet x 4 feet x 9 inches, and weighing about 2*64 tons. 
It resisted the attack of three steel projectiles tired from a 16 cxn (6‘3- 
inch) gun, weighing 45 Kg. (99*2 lbs.), each with a striking velocity 
of 468 m (1535 f.s.), without allowing the points of the projectiles to 
come through and without cracking apparently. The theoretical per¬ 
foration of the shot is 9*3 inches of iron or 7*4 inches of steel. It 
ought not, therefore, to perforate. Its energy is 1622 foot-tons or 614 
foot-tons per ton of plate. The resistance to cracking was then very 
remarkable, but it is to be observed that while the Cammed plate is a 
singularly unfortunate specimen, perhaps the worst known, that selected 
by Schneider is probably the best he had to produce, and it is remark¬ 
able that, writing in 1889, he selected a plate of the date 1880. 
In a letter he wrote to the Engineer,” M. Schneider said, “We 
admit that the hard steel of the compound plates breaks projectiles 
of medium quality more easily than the less hard solid steel plates, 
because the fire only acts on the exterior layer. The compound plate 
when well backed then, as is the case in the Cammed plate instanced—• 
which is the perfection of the type—ought to have the superiority. 
This would be absolutely exhibited with ordinary cast-iron projectiles. 
But when this hard exterior layer is powerless to break the projectile 
immediately ; when it allows of penetration, either because of its 
small thickness in relation to the calibre, or because of the quality of 
the projectile, the compound plate is necessarily inferior to the solid 
steel plate, which continues through its entire thickness to oppose 
penetration energetically. This is proved incontestably to any impar¬ 
tial person by the rounds on these plates—up to 10 or 12 cm —with 
chided cast-iron projectiles of 16 and above, which will not break on 
these thin plates, and the blows with chrome projectiles of ad calibres 
of the kind. Consequently the French Navy have adopted for proof 
trials of these projectiles, of solid steel plates exclusively.” 
About this date M. Weyl 1 wrote on this question in the “ Gfenie M. Weyi on 
Civil.” “ Soon after these Spezia trials, occurred an incident which armouiv 
the manufacturers of compound metal sought to make the most of. 
Pressed by the Navy to increase the resistance and penetration ” (or 
rather resistance to penetration) “ of their plates, the Creusot firm, in 
their search for the best, had gone too far in the direction of hard 
steel. At the opening of the manufacture of the Terrible plates a very 
hard steel had been employed, and as there had not been yet sufficient 
experience with this quality of metal it happened that the factory, as 
wed as the naval control, allowed to be sent to Brest three plates which 
presented small cracks — ( tapures. ? The flaws appeared at Brest visible 
in the bottom of the bolt holes, without which nothing could have 
revealed their existence at the factory. Creusot made then a slight 
retrograde step in the hardness of its steel, and simply exchanged the 
cracked plates, although they had been passed. Since that time no 
port has had to say that they have received cracked plates In fact, it 
was merely a simple accident in manufacture which was easily rectified 
1 See “ Engineer,” August 9th, 1889. 
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