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( 22 ) projectile itself, and that therefore some material far better than mere ordinary cast iron, must be resorted to; and you will be prepared to hear that steel was selected, even in those early days, when steel manufacture was still in a very backward condition. The difficulty, however, of producing proper projectiles was great; they were either too soft or too hard; they often spent their energy in deforming themselves in the one case, or, in the other case, they broke into pieces on the plate, if indeed they had not failed in the act of hardening and tempering.

Then came the proposition of chilled cast-iron projectiles. I believe that any one who had had experience with chilled metal, would have been disposed to say, "Of all materials this one is the most unlikely, for it is as brittle as the highest tempered steel." This may be true, but it possessed a hardness such as enabled its point to support the vast pressure brought on it by the concentrated energy, without being deformed and blunted, and to bury itself in the iron plate. When once this burying in of the point is effected, a very curious result follows. The brittle shot is bound together by the very plate it is penetrating, and in this manner perforates it, without change of form, although the structure of the shot is so far destroyed, that if the plate were thin enough to allow the shot to pass through, and it struck a second plate behind the first, it would flow away on the surface of this second plate, as the original cast-iron ball, would have flowed over the surface of the first plate.

An analogous instance, is to be found in the impression that may be made in a leaden surface by a sealing-wax seal when laid upon it, and struck a powerful blow; the brittle wax impresses the lead, being held together from dispersion by the lead itself, although in the act of impression the seal is disintegrated.

That the chilled projectile spent its energy in perforating the armour-plate, and not in self-deformation, was clearly proved by the fact, that the fragments from the interior of a chilled projectile were, immediately after impact, cold to the touch,