Arguments without end are found in favor of this or that type, varying between the two limits. The truth is, however, that there is scarcely any choice between these extremes. Experiment has fully proved that inclining armor at any angle less than 50° is of itself no advantage as regards preventing penetration. Beyond this angle the great increase of weight necessary to make up the vertical space required necessitates a curtailment in extent of armor entirely neutralizing all the benefits of the inclination. There is left then no choice between the vertical complete protection and the horizontal or armored-deck system giving none whatever. In the vertical protection the question of distribution presents itself anew, varying between the long rectangle and the circular turret. The minimum turret diameter may be safely taken at 20 feet inside. Here the greatest economy of room is attained, but this economy involves a reduction in the number of guns, a limitation in the position, and, unless the French barbette turret be used, the possibility of disabling at one blow the greater part of the offensive power of the ship by jamming the turret. With the same amount of armor that is used in a turret of 20 feet, the broadside may be well covered for a length of from 15 to 18 feet, giving protection to double the number of guns. This advantage, however, is purchased at the expense of a more unfavorable disposition of weight and a complication of upper-work framing. These points bear directly upon the service for which the vessel is intended, and are so intimately connected with the whole general type of the vessel that it becomes the most complete absurdity to assert that turrets alone or armored broadsides alone shall be used. As weight of armor increases, the extent of its protection becomes one of the most serious of questions. In ten years from the date of its introduction it became impossible to completely protect the hull of the frigate, and in fifteen years we find it necessary to commence to strip the turreted vessel with her minimum of freeboard. If the greatest architects of the world find themselves almost at a loss to retain the effectiveness of the armor carried whilst keeping within proper bounds in weight, it is certainly idle for those who barely appreciate the necessity for covering battery and steering-gear to assert that armor should be carried thus and so. The application of horizontal armor presents problems equally abstruse; more so in fact to the designer who does not fully appreciate all the obstacles to be surmounted and the real advantages which are to be obtained. A vessel having a heavy steel deck that shall fully protect her under-water sections and yet permit of such a division of above-water spaces as to permit her to be pierced with impunity whilst that space is left available for the many necessities of circulation and storage, is a consummation of architectural skill the most difficult of attainment.