Thus we see that the sufficiency of armor-plate must, other things being equal, inevitably depend upon insufficiency in range and penetrating power of the gun to which it is opposed. An unarmored vessel, with guns capable of penetrating the armor-plate of an opponent having shorter-range guns, needs only to have superior speed in order to choose a position out of range of the armor-clad's guns, and, atmospheric conditions being favorable, to destroy it without itself being exposed to any danger whatsoever. But there are other conditions which prevent the gun, however long its range and however great its power of penetration, from being a complete defense in the absence of armored protection. These conditions are--the limit of vision due to the rotundity of the earth, even in clear weather, the limitation of vision, at much nearer distances, in thick or hazy weather, and, of course, the greatly increased difficulty of hitting at extreme ranges. Also, it is necessary to be able to observe, from the fighting-tops, where trial shots strike, in order to get the correct range, and lay the guns exactly upon the target. In the recent North Sea fight, firing began at more than 17,000 yards, or about ten miles; 12-inch and 13-inch shells from the British ships struck the _Bluecher_ before more than the upper works of the _Bluecher_ could be seen from the decks of the British ships. Only by the fire-control officers, a hundred feet above the decks, could her whole hull be seen. When the first huge shells came plunging down out of the sky upon the _Bluecher_, her gunners could not see the ships from which they came. It is true that with much more powerful guns than those of her enemy, an unarmored vessel would be able to shoot right through any armored protection opposed to them. But there is the danger that an armored ship of an enemy may emerge from the fog or haze, or from out of the darkness at night, and then neither speed nor weight of gun-fire might save the unarmored ship. The unarmored vessel would not be able with her small guns, if she carried them, materially to injure her armored enemy, whereas the enemy, with its secondary batteries, firing with enormous rapidity and faster than the speed of the heavier guns, would be able to riddle her in a few moments. Consequently, it is considered wise to employ sufficient armor to afford protection against the rapid-fire guns of smaller caliber. Such armor also at longer ranges affords considerable protection against the big guns, for it must be expected that not all projectiles will strike the plate at right angles. They strike at all angles, and sometimes at very sharp angles, and glance off, in which case armor of moderate thickness may save a ship by diverting the shots, while, if she were wholly unarmored, she might be destroyed.