Cannon-balls and iron plates struggled for supremacy, the former getting larger as the latter got thicker.

Ships armed with formidable guns went into the fire under shelter of their invulnerable armour.

The Merrimac, Monitor, ram Tennessee, and Wechhausen shot enormous projectiles after having made themselves proof against the projectiles of other ships.

They did to others what they would not have others do to them, an immoral principle upon which the whole art of war is based.
Now Barbicane was a great caster of projectiles, and Nicholl was an equally great forger of plate-armour.

The one cast night and day at Baltimore, the other forged day and night at Philadelphia.