The effect of hardening projectiles is probably much greater than is generally supposed, that is, the amount of work gained is much greater than the increase of strength of the projectile. It is well known that a very small force may under certain circumstances determine the per formance or non-performance of a very large amount of work. In like manner a very slight addition to the rigidity of a projectile, by hardening or otherwise, may determine whether a very large amount of work shall be wasted upon the projectile or expended upon the plate. Another means of increasing the work done upon the armor plate in comparison with that done upon the projectile is by increasing the velocity of the latter. That is, a projectile moving at a low velocity may be smashed up or flattened against the plate, while the same projectile fired at a higher velocity may go through the same plate almost uninjured. On this principle a lead shot may be fired through iron ron plate, or a tallow candle through a pine board.
Numerous trials have shown a superiority of steel projectiles over those made of chilled cast-iron; and although the former are some what more expensive than the latter, it would be misplaced economy to leave any means =availed of to increase the penetrating power of projectiles. The quality of chilled pro
jectiles, from the nature of their manufacture, is necessarily unreliable; whereas this is not the case with hammered cast-steel, or at least not to the same extent by far, even when large masses are produced, and the difficulty of manufacture increases with the calibre. The most essential difference in the behavior of steel and chilled projectiles on striking the target consists in the reaction on the projectile showing itself in the latter by breaking up, while the former are only set up. As the breaking up of the chilled shells may take place before the bursting-charge conies into opera tion, whereby the rending effect is considerably prejudiced, this material appears far less adapted for shells than steel. The superiority of steel in this respect is still further increased by the fact that the steel shell can have thinner walls, consequently a larger chamber, and can thus hold a larger bursting-charge than the chilled metal. SEE ARMOR PLATE; PROJECTILES.