_Ordnance and Targets_.--The Admiralty having erected a new target, representing a portion of the side of the _Hercules_, experiments were made at Shoeburyness which proved that a thickness of armor casing had been attained which afforded perfect security against even the largest guns recently constructed. The target has a facing of {138} 9-inch armor-plates, and contains altogether eleven inches thickness of iron. Against this three 12-ton shunt guns were fired, at a distance of only 200 yards, with charges varying from 45 lbs. to 60 lbs. of powder. One steel shot, of 300 lbs. weight, 10-1/2 inches in diameter, fired with 60 lbs. of powder, at a velocity of 1,450 feet per second, barely broke through the armor, without injuring the backing. Sir William Armstrong has expressed his conviction, in the _Times_, that the 600-pounder gun will be unable to penetrate this target, and that it will, in fact, require a gun carrying 120 lbs. of powder and steel shot to pierce this massive shield. Mr. W. C. Unwin has pointed out, in a letter to the _Engineer_, that for similar guns with shot of similar form, and charges in a constant ratio to the weight of the shot, the velocity is nearly constant. Then, assuming the resistance of the plates to be as the squares of their thicknesses, it follows that when the diameter of the shot increases, as well as the thickness of the armor, the maximum thickness perforated will (by theory) vary as the cube root of the weight of the shot, or, in other words, as the calibre of the gun; and the weight of the shot necessary to penetrate different thicknesses of armor will be as the cubes of those thicknesses. The ratio deduced from the Shoeburyness experiments is somewhat less than this, being as the 2.5 power and the 5.2 power respectively. Practical formula deduced from experiments are given, which agree with Sir William Armstrong's conclusion, and prove that a gun which can effectively burn a charge of at least 100 lbs. of powder will be required to effectually penetrate the side of the _Hercules_.