with a 1-1/2-inch plate in front, and held together by alternate rivets and screws 8 inches apart, was completely punched; and a 10-inch target, similarly constructed, was greatly bulged and broken at the back by the 68-pounder (8 inch) smooth-bore especially, and the 100-pounder rifle at 200 yards,—­guns that do not greatly injure the best solid 4-1/2-inch plates at the same range.  On the contrary, a 124-pounder (10 inch) round-shot, having about the same penetrating power, as calculated by the ordinary rule, fired by Mr. Stevens in 1854, but slightly indented, and did not break at the back, a 6-5/8-inch target similarly composed.  All the experiments of Mr. Stevens go to show the superiority of laminated armor.  Within a few months, official American experiments have confirmed this theory, although the practice in the construction of ships is divided.  The Roanoke’s plates are solid; those of the Monitor class are laminated.  Solid plates, generally 4-1/2 inches thick and backed by 18 inches of teak, are exclusively used in Europe.  Now the resistance of plates to punching in a machine is directly as the sheared area, that is to say, as the depth and the diameter of the hole.  But, the argument is, in this case, and in the case of laminated armor, the hole is cylindrical, while in the case of a thick armor-plate it is conical,—­about the size of the shot, in front, and very much larger in the rear,—­so that the sheared or fractured area is much greater.  Again, forged plates, although made with innumerable welds from scrap which cannot be homogeneous, are, as compared with rolled plates made with few welds from equally good material, notoriously stronger, because the laminae composing the latter are not thoroughly welded to each other, and they are therefore a series of thin plates.  On the whole, the facts are not complete enough to warrant a conclusion.  It is probable that the heavy English machinery produces better-worked thick plates than have been tested in America, and that American iron, which is well worked in the thin plate used for laminated armor, is better than English iron; while the comparatively high velocities of shot used in England are more trying to thin plates, and the comparatively heavy shot in America prove most destructive to solid plates.  So that there is as yet no common ground of comparison.  The cost of laminated armor is less than half that of solid plates.  Thin plates, breaking joints, and bolted to or through the backing, form a continuous girder and add vastly to the strength of a vessel, while solid blocks add no such strength, but are a source of strain and weakness.  In the experiments mentioned, there was no wooden backing behind the armor.  It is hardly possible,—­in fact, it is nowhere urged,—­that elastic wooden backing prevents injury to the armor in any considerable degree.  Indeed, the English experiments of 1861 prove that a rigid backing of masonry—­in other words, more armor—­increases the endurance of the plates struck.  Elastic backing, however, deadens the blow upon the structure behind it, and catches the iron splinters; it is, therefore, indispensable in ships.